Android 绕其中心旋转的 Drawable

Question

我使用以下代码得到奇怪的结果：

iv = (ImageView) findViewById(R.id.iv);
        iv.setImageResource(R.drawable.spinner_white_76);

        Animation a = new RotateAnimation(0.0f, 360.0f,
                Animation.RELATIVE_TO_SELF, iv.getDrawable()
                        .getIntrinsicWidth() / 2, Animation.RELATIVE_TO_SELF,
                iv.getDrawable().getIntrinsicHeight() / 2);
        a.setRepeatCount(-1);
        a.setDuration(1000);

        iv.startAnimation(a);

Whats the right way to指定轴点（可绘制的中心）？

Answer 1

感觉自己很蠢！花了一些时间仔细阅读文档后让它开始工作：

Animation a = new RotateAnimation(0.0f, 360.0f,
                Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,
                0.5f);
        a.setRepeatCount(-1);
        a.setDuration(1000);

Answer 2

请注意，如果您的对象具有不对称内边距（例如，左内边距为 5 像素，右内边距为 0 像素），则此方法将不起作用，因为内边距被视为对象的一部分。这意味着计算的中心将发生偏移。

解决此问题的一种方法是，如果出于布局原因而使用填充，则使用边距而不是填充。正如 API 关于边距的说法：“该空间超出了该视图的边界。” (ViewGroup.MarginLayoutParams)

这意味着边距不会像填充那样旋转。

Answer 3

由于这个问题的标题是Drawable围绕其中心旋转（我正在精确地搜索它，没有找到它并且必须自己实现它）想发布我的解决方案/答案。

我最终编写了自定义可绘制对象，它可以包装任何可绘制对象并允许其旋转。这是代码：

public class RotatableDrawable extends DrawableWrapper {

    private float rotation;
    private Rect bounds;
    private ObjectAnimator animator;
    private long defaultAnimationDuration;

    public RotatableDrawable(Resources resources, Drawable drawable) {
        super(vectorToBitmapDrawableIfNeeded(resources, drawable));
        bounds = new Rect();
        defaultAnimationDuration = resources.getInteger(android.R.integer.config_mediumAnimTime);
    }

    @Override
    public void draw(Canvas canvas) {
        copyBounds(bounds);
        canvas.save();
        canvas.rotate(rotation, bounds.centerX(), bounds.centerY());
        super.draw(canvas);
        canvas.restore();
    }

    public void rotate(float degrees) {
        rotate(degrees, defaultAnimationDuration);
    }

    public void rotate(float degrees, long millis) {
        if (null != animator && animator.isStarted()) {
            animator.end();
        } else if (null == animator) {
            animator = ObjectAnimator.ofFloat(this, "rotation", 0, 0);
            animator.setInterpolator(new AccelerateDecelerateInterpolator());
        }
        animator.setFloatValues(rotation, degrees);
        animator.setDuration(millis).start();
    }

    @AnimatorSetter
    public void setRotation(float degrees) {
        this.rotation = degrees % 360;
        invalidateSelf();
    }

    /**
     * Workaround for issues related to vector drawables rotation and scaling:
     * https://code.google.com/p/android/issues/detail?id=192413
     * https://code.google.com/p/android/issues/detail?id=208453
     */
    private static Drawable vectorToBitmapDrawableIfNeeded(Resources resources, Drawable drawable) {
        if (drawable instanceof VectorDrawable) {
            Bitmap b = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
            Canvas c = new Canvas(b);
            drawable.setBounds(0, 0, c.getWidth(), c.getHeight());
            drawable.draw(c);
            drawable = new BitmapDrawable(resources, b);
        }
        return drawable;
    }
}