如何從正方形customview android中刪除部分畫布？

Question

我一直在試圖繪製一個圓弧頂部填充顏色的圓弧，並刪除customview矩形中圓弧的底部部分。我經歷了很多stackoverflow問題，但它不起作用。畫布中的白色區域需要從下面的截圖中移除。這裏顯示了customview的代碼。請幫我解決這個問題。由於

代碼：

@Override 
protected void onDraw(Canvas canvas) { 
    float size = Math.min(getWidth(), getWidth()); 
    RectF rectRectF = new RectF(0, 0, getWidth(), getHeight()); 
    Path rectPath = new Path(); 
    rectPath.addRect(rectRectF, Path.Direction.CCW); 
    Paint bgPaint = new Paint(); 
    bgPaint.setColor(Color.RED); 
    canvas.drawPath(rectPath, bgPaint); 
    RectF rectF = new RectF(0, 0, 2 * getWidth(), 2 * getWidth()); 
    Paint transparentPaint = new Paint(); 
    transparentPaint.setColor(Color.WHITE); 
    transparentPaint.setAntiAlias(true); 
    canvas.drawArc(rectF, 180, 90, true, transparentPaint); 

} 

Answer 1

使用

private Canvas bitMapCanvas; 
    private Bitmap frameBitmap; 
    private Paint paint; 
    private PorterDuffXfermode porterDuffXfermode; 
    @Override 
     protected void onSizeChanged(int w, int h, int oldw, int oldh) { 
     // first time setup 
     if (bitMapCanvas == null) { 
      bitMapCanvas = new Canvas(); 
      frameBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888); 
      bitMapCanvas.setBitmap(frameBitmap); 
    porterDuffXfermode = new PorterDuffXfermode(PorterDuff.Mode.CLEAR); 

     } 
     super.onSizeChanged(w, h, oldw, oldh); 
     } 

@Override 
    protected void onDraw(Canvas canvas) { 
..... 
.... 
    paint.setXfermode(porterDuffXfermode); 
    bitMapCanvas.drawArc(rectF, 180, 90, true, paint); 
canvas.drawBitmap(frameBitmap, 0, 0, null); 
    } 

這可以幫助你。它會清除你的顏色並使其透明