在 Android 中旋转可绘制对象

Question

从资源加载的Drawable 在绘制时如何旋转？比如我想画一个箭头，画的时候可以旋转到不同的方向？

Answer 1

你需要使用Bitmap和Canvas Class函数来准备drawable：

Bitmap bmpOriginal = BitmapFactory.decodeResource(this.getResources(), R.drawable.image2);
Bitmap bmResult = Bitmap.createBitmap(bmpOriginal.getWidth(), bmpOriginal.getHeight(), Bitmap.Config.ARGB_8888);
Canvas tempCanvas = new Canvas(bmResult); 
tempCanvas.rotate(90, bmpOriginal.getWidth()/2, bmpOriginal.getHeight()/2);
tempCanvas.drawBitmap(bmpOriginal, 0, 0, null);

mImageView.setImageBitmap(bmResult);

在此代码示例中，图像中心发生 90 度旋转。

Answer 2

基本上可以归结为：做一个（n 逆）画布变换而不是变换可绘制对象

private BitmapDrawable drawable; // or Drawable

protected void onDraw(Canvas canvas) { // inherited from View 
  //...
  canvas.save();
  canvas.rotate(degrees, pivotX, pivotY);
  drawable.draw(canvas);
  canvas.restore();
  //...
}

如果您有 BitmapDrawable，可能需要通过设置抗锯齿来提高输出质量

drawable.setAntialias(true);

Answer 3

接受的答案对我不起作用。我有非方形图像，所以我稍微更改了他的代码。

private Bitmap rotateDrawable(@DrawableRes int resId) {
    Bitmap bmpOriginal = BitmapFactory.decodeResource(getResources(), resId);
    Bitmap bmpResult = Bitmap.createBitmap(bmpOriginal.getHeight(), bmpOriginal.getWidth(), Bitmap.Config.ARGB_8888);
    Canvas tempCanvas = new Canvas(bmpResult);
    int pivot = bmpOriginal.getHeight() / 2;
    tempCanvas.rotate(90, pivot, pivot);
    tempCanvas.drawBitmap(bmpOriginal, 0, 0, null);
    return bmpResult;
}

mImageView.setImageBitmap(rotateDrawable(R.drawable.some_image));

Answer 4

基本上是这样的：

ImageView spaceshipImage = (ImageView) findViewById(R.id.spaceshipImage);
Animation hyperspaceJumpAnimation = AnimationUtils.loadAnimation(this, R.anim.hyperspace_jump);
spaceshipImage.startAnimation(hyperspaceJumpAnimation);

来源链接：

http://developer.android.com/guide/topics/graphics/2d-graphics.html#tween-animation