Fragment.onCreateAnimator(int, boolean, int) 的完整文档方法由以下文本组成:

"Called when a fragment loads an animation."

就是这样。参数不做说明。

参数是什么意思？ Even the source code doesn't reveal much.

最佳答案

onCreateAnimator 方法很奇怪。 我看到的原型(prototype)是这样的:

public Animator onCreateAnimator(int transit, boolean enter, int nextAnim)

int transit - 过渡类型，正如上面sandrstar所说的

boolean enter - 如果'进入'则为真，否则为假

int nextAnim - 即将播放动画的资源ID。

例如，如果您尝试翻转卡片，from the documentation :

// Create and commit a new fragment transaction that adds the fragment for the back of
// the card, uses custom animations, and is part of the fragment manager's back stack.
BackOfCardFragment backFragment = new BackOfCardFragment();

getFragmentManager()
    .beginTransaction()

    // Replace the default fragment animations with animator resources representing
    // rotations when switching to the back of the card, as well as animator
    // resources representing rotations when flipping back to the front (e.g. when
    // the system Back button is pressed).
    .setCustomAnimations(
         R.animator.card_flip_right_in, R.animator.card_flip_right_out,
         R.animator.card_flip_left_in, R.animator.card_flip_left_out)

    // Replace any fragments currently in the container view with a fragment
    // representing the next page (indicated by the just-incremented currentPage
    // variable).
    .replace(R.id.container_view, backFragment)

    // Add this transaction to the back stack, allowing users to press Back
    // to get to the front of the card.
    .addToBackStack(null)

    // Commit the transaction.
    .commit();

注意:上例中的 R.id.container_view 是包含您要替换的现有 fragment 的 ViewGroup 的 ID。

当执行上述代码时，会调用 onCreateAnimator 方法，nextAnim 参数将是传入 setCustomAnimations 的四个动画 ID 之一() 函数，即R.animator.card_flip_right_in、R.animator.card_flip_right_out...等

一开始这似乎并没有立竿见影的效果，因为它没有为您提供可以附加监听器的实际 Animator 对象的引用。但奇怪的是，您可以直接从 nextAnim 资源中为另一个 Animator 充气，然后将监听器附加到该资源上，奇怪的是，这会在正确的时间触发所有被覆盖的回调:

@Override
public Animator onCreateAnimator(int transit, boolean enter, int nextAnim) {
    Animator animator = null;
    // In this example, i want to add a listener when the card_flip_right_in animation
    // is about to happen.
    if (nextAnim == R.animator.card_flip_right_in) {
        animator = AnimatorInflater.loadAnimator(getActivity(), nextAnim);
        // * Sometimes onCreateAnimator will be called and nextAnim will be 0, 
        //   causing animator to be null.
        // * I wanted to add a listener when the fragment was entering - 
        //   your use case may be different.
        if (animator != null && enter) {

            animator.addListener(new Animator.AnimatorListener() {
                @Override
                public void onAnimationStart(Animator animation) {
                   // Do something when the card flip animation begins
                }

                @Override
                public void onAnimationEnd(Animator animation) {
                   // Do something as soon as the card flip animation is over
                }

                @Override
                public void onAnimationCancel(Animator animation) {
                }

                @Override
                public void onAnimationRepeat(Animator animation) {
                }
            });
        }
    }
    return animator;
}

通过这种方式，您应该能够将监听器添加到 fragment 转换动画器中，就像您自己创建它们一样。

关于android - Fragment.onCreateAnimator() 的文档在哪里？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/16910510/