Android开发实现ImageView宽度顶边显示，高度保持比例的方法

<ImageView
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:paddingLeft="5dp"
  android:paddingRight="2.5dp"
  android:layout_weight="1"
  android:scaleType="fitXY"
  android:adjustViewBounds="true"
  android:src="@drawable/default_wallpaper_collection_cover"/>

public class MImageView extends ImageView {
  public MImageView(Context context) {
    super(context);
  }
  public MImageView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }
  public MImageView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
  }
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    Drawable drawable = getDrawable();
    if (drawable != null) {
      int width = MeasureSpec.getSize(widthMeasureSpec);
      int height = (int) Math.ceil((float) width * (float) drawable.getIntrinsicHeight() / (float) drawable.getIntrinsicWidth());
      setMeasuredDimension(width, height);
    } else {
      super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }
  }
}