CustomAnalogClock.java 文件源码

private void drawBackgroundArc(Canvas canvas, float centerX, float centerY, int radius, double angle) {
    if (decoration != Decoration.MINUTE_HAND) return;
    canvas.save();
    paint.setAlpha(70);
    paint.setColorFilter(customColorFilter);
    final int[] colors = {Color.TRANSPARENT, Color.WHITE};
    final float[] positions = {0.5f, 1.f};
    Shader gradient = new SweepGradient(centerX, centerY, colors, positions);
    float rotate = (float) radiansToDegrees(angle);
    Matrix gradientMatrix = new Matrix();
    gradientMatrix.preRotate(rotate, centerX, centerY);
    gradient.setLocalMatrix(gradientMatrix);

    paint.setShader(gradient);
    paint.setStyle(Paint.Style.FILL_AND_STROKE);
    canvas.drawCircle(centerX, centerY, handLengthMinutes * radius, paint);
    paint.setShader(null);
    canvas.restore();
}