Android Open Source - customhellochartdemo Zoomer Compat

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License

The source code is released under:

Apache License

Java Source Code

/*
 * Copyright 2013 The Android Open Source Project
 */*from ww  w .  ja  va  2s.c o m*/
 * 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 lecho.lib.hellocharts.gesture;

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 ZoomerCompat {
  private static final int DEFAULT_SHORT_ANIMATION_DURATION = 200;
  /**
   * The interpolator, used for making zooms animate 'naturally.'
   */
  private Interpolator mInterpolator;

  /**
   * The total animation duration for a zoom.
   */
  private long 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 ZoomerCompat(Context context) {
    mInterpolator = new DecelerateInterpolator();
    // TODO: use constant
    mAnimationDurationMillis = DEFAULT_SHORT_ANIMATION_DURATION;
  }

  /**
   * 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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