AspectRatioFrameLayout.java

/*
 * Copyright (C) 2014 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.google.android.exoplayer;

import android.content.Context;
import android.util.AttributeSet;
import android.widget.FrameLayout;

/**
 * A {@link FrameLayout} that resizes itself to match a specified aspect ratio.
 */
public final class AspectRatioFrameLayout extends FrameLayout {

  /**
   * The {@link FrameLayout} will not resize itself if the fractional difference between its natural
   * aspect ratio and the requested aspect ratio falls below this threshold.
   * <p>
   * This tolerance allows the view to occupy the whole of the screen when the requested aspect
   * ratio is very close, but not exactly equal to, the aspect ratio of the screen. This may reduce
   * the number of view layers that need to be composited by the underlying system, which can help
   * to reduce power consumption.
   */
  private static final float MAX_ASPECT_RATIO_DEFORMATION_FRACTION = 0.01f;

  private float videoAspectRatio;

  public AspectRatioFrameLayout(Context context) {
    super(context);
  }

  public AspectRatioFrameLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  /**
   * Set the aspect ratio that this view should satisfy.
   *
   * @param widthHeightRatio The width to height ratio.
   */
  public void setAspectRatio(float widthHeightRatio) {
    if (this.videoAspectRatio != widthHeightRatio) {
      this.videoAspectRatio = widthHeightRatio;
      requestLayout();
    }
  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    if (videoAspectRatio == 0) {
      // Aspect ratio not set.
      return;
    }

    int width = getMeasuredWidth();
    int height = getMeasuredHeight();
    float viewAspectRatio = (float) width / height;
    float aspectDeformation = videoAspectRatio / viewAspectRatio - 1;
    if (Math.abs(aspectDeformation) <= MAX_ASPECT_RATIO_DEFORMATION_FRACTION) {
      // We're within the allowed tolerance.
      return;
    }

    if (aspectDeformation > 0) {
      height = (int) (width / videoAspectRatio);
    } else {
      width = (int) (height * videoAspectRatio);
    }
    super.onMeasure(MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY),
        MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY));
  }

}