Android

Question

我有以下有效的代码：

protected void onDraw(Canvas canvas) {    
    canvas.drawRect(undoButtonRectF, buttonPaint);
    canvas.drawPath(undoButtonArrow, buttonArrowPaint);

无论如何，当我将其与以下内容交换时：

protected void onDraw(Canvas canvas) {        
        undoButtonBitmap = Bitmap.createBitmap((int) undoButtonRectF.width(), (int) undoButtonRectF.height(), Bitmap.Config.ARGB_8888);

        Canvas ca = new Canvas(undoButtonBitmap);

        ca.drawRect(undoButtonRectF, buttonPaint);
        ca.drawPath(undoButtonArrow, buttonArrowPaint);

        canvas.drawBitmap(undoButtonBitmap, undoButtonRectF.left, undoButtonRectF.top, buttonPaint);

什么都没画。这怎么会发生？我以错误的方式使用位图吗？请帮帮我！！！

Answer 1

我想是协调器出错了。

错误是 undoButtonRectF 包含 "canvas" 的偏移量，而不是 "ca" 的偏移量，您应该在调用

之前调整或删除 top/left 偏移量

 ca.drawRect(undoButtonRectF, buttonPaint);
 ca.drawPath(undoButtonArrow, buttonArrowPaint);

对吗？

Android - 无法在 canvas 中绘制位图

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