java - 如何在重绘时保存先前绘制到 Canvas 上的对象？

Question

每次重绘 SurfaceView 时，之前绘制的内容都会被删除。如何保存它们的状态，以便我的循环将新对象添加到屏幕上而不删除旧对象？

Answer 1

使用位图绘制:

Bitmap mDrawBitmap;
Canvas mBitmapCanvas;
Paint mDrawPaint = new Paint();

@Override
public void onDraw(Canvas canvas) {

    if (mDrawBitmap == null) {
        mDrawBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
        mBitmapCanvas = new Canvas(mDrawBitmap);
    }

    // draw on the btimapCanvas
    //... and more
    mBitmapCanvas.drawWhatever(...);

    // after drawing with the bitmapcanvas,
    //all drawn information is stored in the Bitmap       

    // draw everything to the screen
    canvas.drawBitmap(mDrawBitmap, 0, 0, mDrawPaint);
}

这样，“mDrawBitmap”将始终包含当前绘制的状态。如果需要，可以通过调用mBitmapCanvas.drawColor(Color.WHITE);

来清除它