如何保存重绘时先前绘制到画布上的对象? [英] How to save objects previously drawn to the Canvas on a redraw?

问题描述

每次重新绘制SurfaceView时，都会删除以前绘制的内容.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?

Every time a SurfaceView is redrawn, things that were previously drawn are erased. How do I save their state so that my loop will add new objects to the screen without erasing the old ones?

推荐答案

使用Bitmap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);

In that way, "mDrawBitmap" will always contain the currently drawn state. If you want to, you can clear it by calling mBitmapCanvas.drawColor(Color.WHITE);

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