package com.loper7.date_time_picker.number_picker;
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/*
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* Copyright (C) 2006 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import android.content.Context;
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import android.hardware.SensorManager;
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import android.os.Build;
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import android.view.ViewConfiguration;
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import android.view.animation.AnimationUtils;
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import android.view.animation.Interpolator;
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/**
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* <p>This class encapsulates scrolling. You can use scrollers ({@link Scroller}
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* to collect the data you need to produce a scrolling animation—for
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* example, in response to a fling gesture. Scrollers track scroll offsets
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* for you over time, but they don't automatically apply those positions
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* to your view. It's your responsibility to get and apply new coordinates
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* at a rate that will make the scrolling animation look smooth.</p>
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*
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* <p>Here is a simple example:</p>
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*
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* <pre> private Scroller mScroller = new Scroller(context);
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* ...
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* public void zoomIn() {
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* // Revert any animation currently in progress
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* mScroller.forceFinished(true);
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* // Start scrolling by providing a starting point and
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* // the distance to travel
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* mScroller.startScroll(0, 0, 100, 0);
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* // Invalidate to request a redraw
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* invalidate();
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* }</pre>
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*
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* <p>To track the changing positions of the x/y coordinates, use
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* {@link #computeScrollOffset}. The method returns a boolean to indicate
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* whether the scroller is finished. If it isn't, it means that a fling or
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* programmatic pan operation is still in progress. You can use this method to
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* find the current offsets of the x and y coordinates, for example:</p>
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*
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* <pre>if (mScroller.computeScrollOffset()) {
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* // Get current x and y positions
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* int currX = mScroller.getCurrX();
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* int currY = mScroller.getCurrY();
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* ...
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* }</pre>
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*/
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public class Scroller {
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private final Interpolator mInterpolator;
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private int mMode;
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private int mStartX;
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private int mStartY;
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private int mFinalX;
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private int mFinalY;
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private int mMinX;
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private int mMaxX;
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private int mMinY;
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private int mMaxY;
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private int mCurrX;
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private int mCurrY;
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private long mStartTime;
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private int mDuration;
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private float mDurationReciprocal;
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private float mDeltaX;
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private float mDeltaY;
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private boolean mFinished;
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private boolean mFlywheel;
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private float mVelocity;
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private float mCurrVelocity;
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private int mDistance;
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private float mFlingFriction = ViewConfiguration.getScrollFriction();
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private static final int DEFAULT_DURATION = 250;
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private static final int SCROLL_MODE = 0;
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private static final int FLING_MODE = 1;
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private static float DECELERATION_RATE = (float) (Math.log(0.78) / Math.log(0.9));
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private static final float INFLEXION = 0.35f; // Tension lines cross at (INFLEXION, 1)
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private static final float START_TENSION = 0.5f;
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private static final float END_TENSION = 1.0f;
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private static final float P1 = START_TENSION * INFLEXION;
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private static final float P2 = 1.0f - END_TENSION * (1.0f - INFLEXION);
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private static final int NB_SAMPLES = 100;
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private static final float[] SPLINE_POSITION = new float[NB_SAMPLES + 1];
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private static final float[] SPLINE_TIME = new float[NB_SAMPLES + 1];
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private float mDeceleration;
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private final float mPpi;
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// A context-specific coefficient adjusted to physical values.
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private float mPhysicalCoeff;
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static {
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float x_min = 0.0f;
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float y_min = 0.0f;
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for (int i = 0; i < NB_SAMPLES; i++) {
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final float alpha = (float) i / NB_SAMPLES;
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float x_max = 1.0f;
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float x, tx, coef;
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while (true) {
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x = x_min + (x_max - x_min) / 2.0f;
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coef = 3.0f * x * (1.0f - x);
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tx = coef * ((1.0f - x) * P1 + x * P2) + x * x * x;
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if (Math.abs(tx - alpha) < 1E-5) break;
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if (tx > alpha) x_max = x;
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else x_min = x;
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}
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SPLINE_POSITION[i] = coef * ((1.0f - x) * START_TENSION + x) + x * x * x;
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float y_max = 1.0f;
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float y, dy;
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while (true) {
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y = y_min + (y_max - y_min) / 2.0f;
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coef = 3.0f * y * (1.0f - y);
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dy = coef * ((1.0f - y) * START_TENSION + y) + y * y * y;
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if (Math.abs(dy - alpha) < 1E-5) break;
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if (dy > alpha) y_max = y;
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else y_min = y;
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}
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SPLINE_TIME[i] = coef * ((1.0f - y) * P1 + y * P2) + y * y * y;
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}
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SPLINE_POSITION[NB_SAMPLES] = SPLINE_TIME[NB_SAMPLES] = 1.0f;
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}
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/**
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* Create a Scroller with the default duration and interpolator.
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*/
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public Scroller(Context context) {
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this(context, null);
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}
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/**
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* Create a Scroller with the specified interpolator. If the interpolator is
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* null, the default (viscous) interpolator will be used. "Flywheel" behavior will
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* be in effect for apps targeting Honeycomb or newer.
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*/
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public Scroller(Context context, Interpolator interpolator) {
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this(context, interpolator,
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context.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.HONEYCOMB);
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}
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/**
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* Create a Scroller with the specified interpolator. If the interpolator is
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* null, the default (viscous) interpolator will be used. Specify whether or
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* not to support progressive "flywheel" behavior in flinging.
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*/
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public Scroller(Context context, Interpolator interpolator, boolean flywheel) {
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mFinished = true;
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if (interpolator == null) {
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mInterpolator = new ViscousFluidInterpolator();
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} else {
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mInterpolator = interpolator;
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}
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mPpi = context.getResources().getDisplayMetrics().density * 160.0f;
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mDeceleration = computeDeceleration(ViewConfiguration.getScrollFriction());
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mFlywheel = flywheel;
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mPhysicalCoeff = computeDeceleration(0.84f); // look and feel tuning
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}
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/**
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* The amount of friction applied to flings. The default value
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* is {@link ViewConfiguration#getScrollFriction}.
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*
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* @param friction A scalar dimension-less value representing the coefficient of
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* friction.
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*/
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public final void setFriction(float friction) {
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mDeceleration = computeDeceleration(friction);
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mFlingFriction = friction;
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}
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private float computeDeceleration(float friction) {
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return SensorManager.GRAVITY_EARTH // g (m/s^2)
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* 39.37f // inch/meter
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* mPpi // pixels per inch
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* friction;
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}
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/**
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*
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* Returns whether the scroller has finished scrolling.
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*
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* @return True if the scroller has finished scrolling, false otherwise.
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*/
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public final boolean isFinished() {
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return mFinished;
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}
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/**
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* Force the finished field to a particular value.
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*
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* @param finished The new finished value.
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*/
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public final void forceFinished(boolean finished) {
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mFinished = finished;
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}
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/**
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* Returns how long the scroll event will take, in milliseconds.
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*
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* @return The duration of the scroll in milliseconds.
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*/
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public final int getDuration() {
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return mDuration;
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}
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/**
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* Returns the current X offset in the scroll.
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*
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* @return The new X offset as an absolute distance from the origin.
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*/
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public final int getCurrX() {
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return mCurrX;
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}
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/**
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* Returns the current Y offset in the scroll.
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*
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* @return The new Y offset as an absolute distance from the origin.
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*/
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public final int getCurrY() {
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return mCurrY;
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}
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/**
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* Returns the current velocity.
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*
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* @return The original velocity less the deceleration. Result may be
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* negative.
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*/
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public float getCurrVelocity() {
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return mMode == FLING_MODE ?
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mCurrVelocity : mVelocity - mDeceleration * timePassed() / 2000.0f;
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}
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/**
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* Returns the start X offset in the scroll.
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*
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* @return The start X offset as an absolute distance from the origin.
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*/
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public final int getStartX() {
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return mStartX;
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}
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/**
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* Returns the start Y offset in the scroll.
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*
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* @return The start Y offset as an absolute distance from the origin.
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*/
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public final int getStartY() {
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return mStartY;
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}
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/**
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* Returns where the scroll will end. Valid only for "fling" scrolls.
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*
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* @return The final X offset as an absolute distance from the origin.
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*/
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public final int getFinalX() {
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return mFinalX;
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}
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/**
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* Returns where the scroll will end. Valid only for "fling" scrolls.
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*
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* @return The final Y offset as an absolute distance from the origin.
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*/
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public final int getFinalY() {
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return mFinalY;
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}
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/**
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* Call this when you want to know the new location. If it returns true,
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* the animation is not yet finished.
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*/
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public boolean computeScrollOffset() {
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if (mFinished) {
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return false;
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}
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int timePassed = (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);
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if (timePassed < mDuration) {
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switch (mMode) {
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case SCROLL_MODE:
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final float x = mInterpolator.getInterpolation(timePassed * mDurationReciprocal);
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mCurrX = mStartX + Math.round(x * mDeltaX);
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mCurrY = mStartY + Math.round(x * mDeltaY);
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break;
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case FLING_MODE:
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final float t = (float) timePassed / mDuration;
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final int index = (int) (NB_SAMPLES * t);
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float distanceCoef = 1.f;
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float velocityCoef = 0.f;
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if (index < NB_SAMPLES) {
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final float t_inf = (float) index / NB_SAMPLES;
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final float t_sup = (float) (index + 1) / NB_SAMPLES;
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final float d_inf = SPLINE_POSITION[index];
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final float d_sup = SPLINE_POSITION[index + 1];
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velocityCoef = (d_sup - d_inf) / (t_sup - t_inf);
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distanceCoef = d_inf + (t - t_inf) * velocityCoef;
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}
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mCurrVelocity = velocityCoef * mDistance / mDuration * 1000.0f;
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mCurrX = mStartX + Math.round(distanceCoef * (mFinalX - mStartX));
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// Pin to mMinX <= mCurrX <= mMaxX
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mCurrX = Math.min(mCurrX, mMaxX);
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mCurrX = Math.max(mCurrX, mMinX);
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mCurrY = mStartY + Math.round(distanceCoef * (mFinalY - mStartY));
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// Pin to mMinY <= mCurrY <= mMaxY
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mCurrY = Math.min(mCurrY, mMaxY);
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mCurrY = Math.max(mCurrY, mMinY);
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if (mCurrX == mFinalX && mCurrY == mFinalY) {
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mFinished = true;
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}
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break;
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}
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}
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else {
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mCurrX = mFinalX;
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mCurrY = mFinalY;
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mFinished = true;
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}
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return true;
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}
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/**
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* Start scrolling by providing a starting point and the distance to travel.
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* The scroll will use the default value of 250 milliseconds for the
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* duration.
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*
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* @param startX Starting horizontal scroll offset in pixels. Positive
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* numbers will scroll the content to the left.
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* @param startY Starting vertical scroll offset in pixels. Positive numbers
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* will scroll the content up.
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* @param dx Horizontal distance to travel. Positive numbers will scroll the
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* content to the left.
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* @param dy Vertical distance to travel. Positive numbers will scroll the
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* content up.
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*/
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public void startScroll(int startX, int startY, int dx, int dy) {
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startScroll(startX, startY, dx, dy, DEFAULT_DURATION);
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}
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/**
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* Start scrolling by providing a starting point, the distance to travel,
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* and the duration of the scroll.
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*
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* @param startX Starting horizontal scroll offset in pixels. Positive
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* numbers will scroll the content to the left.
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* @param startY Starting vertical scroll offset in pixels. Positive numbers
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* will scroll the content up.
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* @param dx Horizontal distance to travel. Positive numbers will scroll the
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* content to the left.
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* @param dy Vertical distance to travel. Positive numbers will scroll the
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* content up.
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* @param duration Duration of the scroll in milliseconds.
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*/
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public void startScroll(int startX, int startY, int dx, int dy, int duration) {
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mMode = SCROLL_MODE;
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mFinished = false;
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mDuration = duration;
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mStartTime = AnimationUtils.currentAnimationTimeMillis();
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mStartX = startX;
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mStartY = startY;
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mFinalX = startX + dx;
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mFinalY = startY + dy;
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mDeltaX = dx;
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mDeltaY = dy;
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mDurationReciprocal = 1.0f / (float) mDuration;
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}
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/**
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* Start scrolling based on a fling gesture. The distance travelled will
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* depend on the initial velocity of the fling.
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*
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* @param startX Starting point of the scroll (X)
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* @param startY Starting point of the scroll (Y)
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* @param velocityX Initial velocity of the fling (X) measured in pixels per
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* second.
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* @param velocityY Initial velocity of the fling (Y) measured in pixels per
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* second
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* @param minX Minimum X value. The scroller will not scroll past this
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* point.
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* @param maxX Maximum X value. The scroller will not scroll past this
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* point.
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* @param minY Minimum Y value. The scroller will not scroll past this
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* point.
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* @param maxY Maximum Y value. The scroller will not scroll past this
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* point.
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*/
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public void fling(int startX, int startY, int velocityX, int velocityY,
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int minX, int maxX, int minY, int maxY) {
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// Continue a scroll or fling in progress
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if (mFlywheel && !mFinished) {
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float oldVel = getCurrVelocity();
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float dx = (float) (mFinalX - mStartX);
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float dy = (float) (mFinalY - mStartY);
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float hyp = (float) Math.hypot(dx, dy);
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float ndx = dx / hyp;
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float ndy = dy / hyp;
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float oldVelocityX = ndx * oldVel;
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float oldVelocityY = ndy * oldVel;
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if (Math.signum(velocityX) == Math.signum(oldVelocityX) &&
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Math.signum(velocityY) == Math.signum(oldVelocityY)) {
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velocityX += oldVelocityX;
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velocityY += oldVelocityY;
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}
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}
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mMode = FLING_MODE;
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mFinished = false;
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float velocity = (float) Math.hypot(velocityX, velocityY);
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mVelocity = velocity;
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mDuration = getSplineFlingDuration(velocity);
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mStartTime = AnimationUtils.currentAnimationTimeMillis();
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mStartX = startX;
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mStartY = startY;
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float coeffX = velocity == 0 ? 1.0f : velocityX / velocity;
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float coeffY = velocity == 0 ? 1.0f : velocityY / velocity;
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double totalDistance = getSplineFlingDistance(velocity);
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mDistance = (int) (totalDistance * Math.signum(velocity));
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mMinX = minX;
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mMaxX = maxX;
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mMinY = minY;
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mMaxY = maxY;
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mFinalX = startX + (int) Math.round(totalDistance * coeffX);
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// Pin to mMinX <= mFinalX <= mMaxX
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mFinalX = Math.min(mFinalX, mMaxX);
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mFinalX = Math.max(mFinalX, mMinX);
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mFinalY = startY + (int) Math.round(totalDistance * coeffY);
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// Pin to mMinY <= mFinalY <= mMaxY
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mFinalY = Math.min(mFinalY, mMaxY);
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mFinalY = Math.max(mFinalY, mMinY);
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}
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private double getSplineDeceleration(float velocity) {
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return Math.log(INFLEXION * Math.abs(velocity) / (mFlingFriction * mPhysicalCoeff));
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}
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private int getSplineFlingDuration(float velocity) {
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final double l = getSplineDeceleration(velocity);
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final double decelMinusOne = DECELERATION_RATE - 1.0;
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return (int) (1000.0 * Math.exp(l / decelMinusOne));
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}
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private double getSplineFlingDistance(float velocity) {
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final double l = getSplineDeceleration(velocity);
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final double decelMinusOne = DECELERATION_RATE - 1.0;
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return mFlingFriction * mPhysicalCoeff * Math.exp(DECELERATION_RATE / decelMinusOne * l);
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}
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/**
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* Stops the animation. Contrary to {@link #forceFinished(boolean)},
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* aborting the animating cause the scroller to move to the final x and y
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* position
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*
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* @see #forceFinished(boolean)
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*/
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public void abortAnimation() {
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mCurrX = mFinalX;
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mCurrY = mFinalY;
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mFinished = true;
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}
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/**
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* Extend the scroll animation. This allows a running animation to scroll
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* further and longer, when used with {@link #setFinalX(int)} or {@link #setFinalY(int)}.
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*
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* @param extend Additional time to scroll in milliseconds.
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* @see #setFinalX(int)
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* @see #setFinalY(int)
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*/
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public void extendDuration(int extend) {
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int passed = timePassed();
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mDuration = passed + extend;
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mDurationReciprocal = 1.0f / mDuration;
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mFinished = false;
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}
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/**
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* Returns the time elapsed since the beginning of the scrolling.
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*
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* @return The elapsed time in milliseconds.
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*/
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public int timePassed() {
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return (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);
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}
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/**
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* Sets the final position (X) for this scroller.
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*
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* @param newX The new X offset as an absolute distance from the origin.
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* @see #extendDuration(int)
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* @see #setFinalY(int)
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*/
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public void setFinalX(int newX) {
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mFinalX = newX;
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mDeltaX = mFinalX - mStartX;
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mFinished = false;
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}
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/**
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* Sets the final position (Y) for this scroller.
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*
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* @param newY The new Y offset as an absolute distance from the origin.
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* @see #extendDuration(int)
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* @see #setFinalX(int)
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*/
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public void setFinalY(int newY) {
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mFinalY = newY;
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mDeltaY = mFinalY - mStartY;
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mFinished = false;
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}
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/**
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* @hide
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*/
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public boolean isScrollingInDirection(float xvel, float yvel) {
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return !mFinished && Math.signum(xvel) == Math.signum(mFinalX - mStartX) &&
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Math.signum(yvel) == Math.signum(mFinalY - mStartY);
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}
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static class ViscousFluidInterpolator implements Interpolator {
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/** Controls the viscous fluid effect (how much of it). */
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private static final float VISCOUS_FLUID_SCALE = 8.0f;
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private static final float VISCOUS_FLUID_NORMALIZE;
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private static final float VISCOUS_FLUID_OFFSET;
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static {
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// must be set to 1.0 (used in viscousFluid())
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VISCOUS_FLUID_NORMALIZE = 1.0f / viscousFluid(1.0f);
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// account for very small floating-point error
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VISCOUS_FLUID_OFFSET = 1.0f - VISCOUS_FLUID_NORMALIZE * viscousFluid(1.0f);
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}
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private static float viscousFluid(float x) {
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x *= VISCOUS_FLUID_SCALE;
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if (x < 1.0f) {
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x -= (1.0f - (float)Math.exp(-x));
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} else {
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float start = 0.36787944117f; // 1/e == exp(-1)
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x = 1.0f - (float)Math.exp(1.0f - x);
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x = start + x * (1.0f - start);
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}
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return x;
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}
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@Override
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public float getInterpolation(float input) {
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final float interpolated = VISCOUS_FLUID_NORMALIZE * viscousFluid(input);
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if (interpolated > 0) {
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return interpolated + VISCOUS_FLUID_OFFSET;
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}
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return interpolated;
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}
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}
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}
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