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/*
* Copyright 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.interactivechart;
import android.content.Context;
import android.os.SystemClock;
import android.view.animation.DecelerateInterpolator;
import android.view.animation.Interpolator;
/**
* A simple class that animates double-touch zoom gestures. Functionally similar to a {@link
* android.widget.Scroller}.
*/
public class Zoomer {
/**
* The interpolator, used for making zooms animate 'naturally.'
*/
private Interpolator mInterpolator;
/**
* The total animation duration for a zoom.
*/
private int mAnimationDurationMillis;
/**
* Whether or not the current zoom has finished.
*/
private boolean mFinished = true;
/**
* The current zoom value; computed by {@link #computeZoom()}.
*/
private float mCurrentZoom;
/**
* The time the zoom started, computed using {@link android.os.SystemClock#elapsedRealtime()}.
*/
private long mStartRTC;
/**
* The destination zoom factor.
*/
private float mEndZoom;
public Zoomer(Context context) {
mInterpolator = new DecelerateInterpolator();
mAnimationDurationMillis = context.getResources().getInteger(
android.R.integer.config_shortAnimTime);
}
/**
* Forces the zoom finished state to the given value. Unlike {@link #abortAnimation()}, the
* current zoom value isn't set to the ending value.
*
* @see android.widget.Scroller#forceFinished(boolean)
*/
public void forceFinished(boolean finished) {
mFinished = finished;
}
/**
* Aborts the animation, setting the current zoom value to the ending value.
*
* @see android.widget.Scroller#abortAnimation()
*/
public void abortAnimation() {
mFinished = true;
mCurrentZoom = mEndZoom;
}
/**
* Starts a zoom from 1.0 to (1.0 + endZoom). That is, to zoom from 100% to 125%, endZoom should
* by 0.25f.
*
* @see android.widget.Scroller#startScroll(int, int, int, int)
*/
public void startZoom(float endZoom) {
mStartRTC = SystemClock.elapsedRealtime();
mEndZoom = endZoom;
mFinished = false;
mCurrentZoom = 1f;
}
/**
* Computes the current zoom level, returning true if the zoom is still active and false if the
* zoom has finished.
*
* @see android.widget.Scroller#computeScrollOffset()
*/
public boolean computeZoom() {
if (mFinished) {
return false;
}
long tRTC = SystemClock.elapsedRealtime() - mStartRTC;
if (tRTC >= mAnimationDurationMillis) {
mFinished = true;
mCurrentZoom = mEndZoom;
return false;
}
float t = tRTC * 1f / mAnimationDurationMillis;
mCurrentZoom = mEndZoom * mInterpolator.getInterpolation(t);
return true;
}
/**
* Returns the current zoom level.
*
* @see android.widget.Scroller#getCurrX()
*/
public float getCurrZoom() {
return mCurrentZoom;
}
}
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