android 菱形布局,Android 设计一个菱形形状的Imageview组件.

使用PorterDuffXfermode, 可以看看图像合成Xfermode和任意形状ImageView

public class RectImageView extends ImageView {

private Paint mPaint;

private Xfermode mXfermode;

private Bitmap mRectMask;

public RectImageView(Context context) {

this(context, null);

}

public RectImageView(Context context, AttributeSet attrs) {

this(context, attrs, 0);

}

public RectImageView(Context context, AttributeSet attrs, int defStyleAttr) {

super(context, attrs, defStyleAttr);

mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);

mPaint.setColor(Color.RED);

// 关键方法

mXfermode = new PorterDuffXfermode(PorterDuff.Mode.DST_IN);

}

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

super.onMeasure(widthMeasureSpec, heightMeasureSpec);

createMask();

}

private void createMask() {

if (mRectMask == null) {

int maskWidth = getMeasuredWidth();

int maskHeight = getMeasuredHeight();

mRectMask = Bitmap.createBitmap(maskWidth, maskHeight, Bitmap.Config.ARGB_8888);

Canvas canvas = new Canvas(mRectMask);

canvas.translate(maskWidth / 2, 0);

canvas.rotate(45);

int rectSize = (int) (maskWidth / 2 / Math.sin(Math.toRadians(45)));

canvas.drawRect(0, 0, rectSize, rectSize, mPaint);

}

}

@Override

protected void onDraw(Canvas canvas) {

int id = canvas.saveLayer(0, 0, canvas.getWidth(), canvas.getHeight(), null, Canvas.ALL_SAVE_FLAG);

super.onDraw(canvas);

// 关键方法

mPaint.setXfermode(mXfermode);

canvas.drawBitmap(mRectMask, 0, 0, mPaint);

mPaint.setXfermode(null);

canvas.restoreToCount(id);

}

}

效果如下

总结

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