左侧是在 Android P 测试版上截取的屏幕截图,右侧是在 Android 26 上截取的屏幕截图 。Xfermode 在 Android P 测试版上的工作方式似乎不一致。
下面是对应的代码。
public class CropView extends View {
private Paint paint;
private Path clipPath;
private int arcHeight;
public CropView(Context context) {
super(context);
init();
}
public CropView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public CropView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init() {
paint = new Paint();
paint.setAntiAlias(true);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
arcHeight = getResources().getDimensionPixelOffset(R.dimen.row_size);
setLayerType();
}
private void setLayerType() {
if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.KITKAT) {
// looks like this is happening in some devices with lollipop and kitkat
// trying to fix https://github.com/lifesum/bugs/issues/7040
setLayerType(View.LAYER_TYPE_SOFTWARE, null);
} else {
setLayerType(LAYER_TYPE_HARDWARE, null);
}
}
private Path createClipPath(int height, int width) {
final Path path = new Path();
path.moveTo(0, 0);
path.lineTo(0, height);
path.quadTo(width / 2, height + arcHeight, width, height - arcHeight);
path.lineTo(width, 0);
path.close();
return path;
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
if (changed) {
int height = getMeasuredHeight();
int width = getMeasuredWidth();
clipPath = createClipPath(height, width);
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (clipPath != null) {
canvas.drawPath(clipPath, paint);
}
}
}
以下是运行来自 android 示例的Apidemos时的屏幕截图