使用硬件加速的`drawTextOnPath()`的奇怪行为

Question

在硬件加速自定义中View添加ScrollView或ListView以下两个代码片段产生相同的结果:( 请忽略最佳实践一秒)

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas); 
    // centering stuff
    float centerX = getWidth() / 2f;
    float centerY = getHeight() / 2f;
    float size = 80;
    float halfSize = size / 2f;
    float left = centerX - halfSize;
    float top = centerY - halfSize;

    RectF oval = new RectF(left, top, left + size, top + size);

    Path path = new Path();
    path.addArc(oval, 160, 359);

    Paint paint = new Paint();
    paint.setTextSize(30);
    paint.setStyle(Style.STROKE);

    canvas.drawTextOnPath("Hello world", path, 0, 0, paint); //<--- line A
    canvas.drawCircle(centerX, centerY, 10, paint);          //<--- line B
}

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@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas); 
    // centering stuff
    float centerX = getWidth() / 2f;
    float centerY = getHeight() / 2f;
    float size = 80;
    float halfSize = size / 2f;
    float left = centerX - halfSize;
    float top = centerY - halfSize;

    RectF oval = new RectF(left, top, left + size, top + size);

    Path path = new Path();
    path.addArc(oval, 160, 359);

    Paint paint = new Paint();
    paint.setTextSize(30);
    paint.setStyle(Style.STROKE);

    canvas.drawCircle(centerX, centerY, 10, paint);          //<--- line B
    canvas.drawTextOnPath("Hello world", path, 0, 0, paint); //<--- line A
}

相同的结果:

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但是对于后来的代码片段,只要你滚动ScrollView (我有隐形假人View,我可以滚动)和helloworld触摸ActionBar,就会发生一些非常有趣的事情,你会看到智能人类曾经在旧的Windows操作系统中看到的东西.

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我知道drawTextOnPath()硬件加速模式不支持,但是如果你先调用它,为什么它可以工作？

Answer 1

drawTextOnPath()Android 4.1 之后由硬件加速支持这在这里正式提到： https: //code.google.com/p/android/issues/detail ?id=37925 但下一条评论似乎以某种方式表明了你的问题，所以可能是漏洞。

当然，对于 4.1 之前的版本，不要让它使用 HW accel - 通过调用在视图上设置软件层类型，View.setLayerType(View.LAYER_TYPE_SOFTWARE, null)并尝试在性能与错误之间进行权衡