爲什麼畫布上的位圖出現在背景可繪製的下方？

Question

我有一個SurfaceView這裏我設置背景顏色和像這樣的圖像：

BitmapDrawable tiledBackground = new BitmapDrawable(BitmapFactory.decodeResource(getResources(), R.drawable.background)); 
tiledBackground.setTileModeX(Shader.TileMode.REPEAT); 
tiledBackground.setColorFilter(0xaacceeff, PorterDuff.Mode.DST_OVER); 
this.setBackgroundDrawable(tiledBackground); 

我也有一個動畫線程在那裏我畫的圖像（連續的調整它的x座標，使其顯示移動到左側）。背景圖像是透明的PNG，因此它的某些部分是透明的。看來我正在從線程繪製的圖像出現在以下可在SurfaceView上繪製的背景。我如何讓它出現在背景之上？我繪製的圖像，像這樣：

private void doDraw(Canvas canvas) { 
    canvas.drawColor(Color.BLACK); 
    canvas.drawBitmap(missile, x, getHeight() - 95, paint); 
    canvas.restore(); 
} 

missile和paint在線程的構造函數初始化：

missile = Bitmap.createBitmap(BitmapFactory.decodeResource(getResources(), R.drawable.missile)); 
paint = new Paint(); 

Answer 1

到doDraw每次調用應吸引你想要的一切顯示，包括的背景。

// Add to initializer 
tiledBackground = new BitmapDrawable(BitmapFactory.decodeResource(getResources(), R.drawable.background)); 
tiledBackground.setTileModeX(Shader.TileMode.REPEAT); 
tiledBackground.setColorFilter(0xaacceeff, PorterDuff.Mode.DST_OVER); 

private void doDraw(Canvas canvas) { 
    canvas.drawColor(Color.BLACK); 
    // Create a rectangle (just holds top/bottom/left/right info) 
    Rect drawRect = new Rect(); 

    // Populate the rectangle that we just created with the drawing area of the canvas. 
    canvas.getClipBounds(drawRect); 

    // Make the height of the background drawing area equal to the height of the background bitmap 
    drawRect.bottom = drawRect.top + tiledBackground.getBitmap().getHeight(); 

    // Set the drawing area for the background. 
    tiledBackground.setBounds(drawRect); 

    tiledBackground.draw(canvas); 
    canvas.drawBitmap(missile, x, getHeight() - 95, paint); 
    canvas.restore(); 
}