CircularBorderDrawable.java 文件源码

/**
 * Creates a vertical {@link LinearGradient}
 * @return
 */
private Shader createGradientShader() {
  final Rect rect = mRect;
  copyBounds(rect);

  final float borderRatio = mBorderWidth / rect.height();

  final int[] colors = new int[6];
  colors[0] = ColorUtils.compositeColors(mTopOuterStrokeColor, mCurrentBorderTintColor);
  colors[1] = ColorUtils.compositeColors(mTopInnerStrokeColor, mCurrentBorderTintColor);
      colors[2] = ColorUtils.compositeColors(
          ColorUtils.setAlphaComponent(mTopInnerStrokeColor, 0), mCurrentBorderTintColor);
      colors[3] = ColorUtils.compositeColors(
          ColorUtils.setAlphaComponent(mBottomInnerStrokeColor, 0), mCurrentBorderTintColor);
  colors[4] = ColorUtils.compositeColors(mBottomInnerStrokeColor, mCurrentBorderTintColor);
  colors[5] = ColorUtils.compositeColors(mBottomOuterStrokeColor, mCurrentBorderTintColor);

  final float[] positions = new float[6];
  positions[0] = 0f;
  positions[1] = borderRatio;
  positions[2] = 0.5f;
  positions[3] = 0.5f;
  positions[4] = 1f - borderRatio;
  positions[5] = 1f;

  return new LinearGradient(
              0, rect.top,
              0, rect.bottom,
              colors, positions,
              Shader.TileMode.CLAMP);
}