Android Open Source - android-plotter Pinch Zoom Tracker

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License

The source code is released under:

Apache License

Java Source Code

package org.solovyev.android.plotter;
//from  w w  w.  ja va  2  s.com
import android.graphics.PointF;

import javax.annotation.Nonnull;

final class PinchZoomTracker {

  private static final float EPS = 1.5f;
  // todo serso: dpi!!!
  private static final float MIN_DISTANCE = distance(0f, 25f);

  @Nonnull
  private final PointF distance = new PointF();

  @Nonnull
  private final ZoomLevels current = new ZoomLevels();

  void reset(float x1, float y1,
         float x2, float y2) {
    distance.x = distance(x1, x2);
    distance.y = distance(y1, y2);
  }

  @Nonnull
  ZoomLevels update(float x1, float y1, float x2, float y2) {
    current.reset();

    if (distance.x > MIN_DISTANCE) {
      final float dx = distance(x1, x2);
      if (dx > EPS) {
        current.x = distance.x / dx;
      }
    }

    if (distance.y > MIN_DISTANCE) {
      final float dy = distance(y1, y2);
      if (dy > EPS) {
        current.y = distance.y / dy;
      }
    }

    current.adjust();
    return current;
  }

  private static float distance(float x1, float x2) {
    final float dx = x1 - x2;
    return dx * dx;
  }
}

Java Source Code List

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