Question

我正在尝试动画片段的进入和退出。 setEnterTransition工作正常，但如果我使用setExitTransition，则会抛出nullPointerException。如果我使用setReturnTransition，它就不会显示任何动画。

这就是我所拥有的。

private void showFragment() {
    Fragment fragment = JoinGroupFragment.newInstance();
    FragmentTransaction ft = getFragmentManager().beginTransaction()
            .add(R.id.fragment_container, fragment, JOIN_GROUP_FRAGMENT_TAG);


    if (Build.VERSION.SDK_INT >= 21) {
        Log.i(TAG, "set enter transition");
        fragment.setEnterTransition(new Slide(Gravity.TOP));
//      fragment.setExitTransition(new Slide(Gravity.BOTTOM));
    }

    ft.commit();
}

private void dismissFragment() {
    Fragment joinGroupFragment = getFragmentManager().findFragmentByTag(JOIN_GROUP_FRAGMENT_TAG);
    if (joinGroupFragment != null) {
        FragmentTransaction ft = getFragmentManager().beginTransaction();
//      ft.hide(joinGroupFragment);
        ft.remove(joinGroupFragment);
        ft.commit();
    }
}

现在，如果我使用setExitTransition，我会收到以下错误。

java.lang.NullPointerException：尝试从字段＆＃39; int中读取 android.app.Fragment.mContainerId＆＃39;在null对象引用上在android.app.BackStackRecord $ 1.onPreDraw（BackStackRecord.java:1131）在android.view.ViewTreeObserver.dispatchOnPreDraw（ViewTreeObserver.java:944）在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:1970）在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1061）在android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:5885）在android.view.Choreographer $ CallbackRecord.run（Choreographer.java:767）在android.view.Choreographer.doCallbacks（Choreographer.java:580）在android.view.Choreographer.doFrame（Choreographer.java:550）在android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:753）在android.os.Handler.handleCallback（Handler.java:739）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:135）在android.app.ActivityThread.main（ActivityThread.java:5254） at java.lang.reflect.Method.invoke（Native Method）在java.lang.reflect.Method.invoke（Method.java:372）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:903）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:698）

我环顾四周，发现有关于此的错误。 https://code.google.com/p/android/issues/detail?id=82832

已发布解决方法。我尝试了同样的事情，但使用FragmentManager而不是supportFragmentManager，但我仍然面临同样的问题。

我尝试过的解决方法

// This is in onCreate().
getFragmentManager().beginTransaction().add(R.id.fragment_container, new Fragment())
                    .addToBackStack("dummy")
                    .commit();

private void showFragment() {
    Fragment fragment = JoinGroupFragment.newInstance();
    FragmentTransaction ft = getFragmentManager().beginTransaction()
            .replace(R.id.fragment_container, fragment, JOIN_GROUP_FRAGMENT_TAG);

    ft.addToBackStack(null);
    // ft.addToBackStack("dummy");
    // ft.addToBackStack("my_backstack); // none of these work
    ft.commit();


    if (Build.VERSION.SDK_INT >= 21) {
        Log.i(TAG, "set enter transition");
        fragment.setEnterTransition(new Slide(Gravity.TOP));
        fragment.setExitTransition(new Slide(Gravity.BOTTOM));
    }

    ft.commit();
}

private void dismissFragment() {
    Fragment joinGroupFragment = getFragmentManager().findFragmentByTag(JOIN_GROUP_FRAGMENT_TAG);
    if (joinGroupFragment != null) {
        FragmentTransaction ft = getFragmentManager().beginTransaction();
//      ft.hide(joinGroupFragment);
        ft.remove(joinGroupFragment);
        ft.commit();
    }
}

我知道在Backstack中没有任何片段用于转换，但添加虚拟片段也没有帮助。有没有解决方法呢？

更新

我使用相同的片段而不是虚拟片段。

getFragmentManager().beginTransaction().add(R.id.fragment_container, JoinGroupFragment.newInstance())
                        .addToBackStack("dummy")
                        .commit();

private void showFragment() {
    Fragment fragment = JoinGroupFragment.newInstance();
    FragmentTransaction ft = getFragmentManager().beginTransaction()
            .replace(R.id.fragment_container, fragment, JOIN_GROUP_FRAGMENT_TAG);

    ft.addToBackStack("dummy");
    ft.commit();


    if (Build.VERSION.SDK_INT >= 21) {
        Log.i(TAG, "set enter transition");
        fragment.setEnterTransition(new Slide(Gravity.TOP));
        fragment.setExitTransition(new Slide(Gravity.BOTTOM));
    }

    ft.commit();
}

private void dismissFragment() {
    Fragment joinGroupFragment = getFragmentManager().findFragmentByTag(JOIN_GROUP_FRAGMENT_TAG);
    if (joinGroupFragment != null) {
        FragmentTransaction ft = getFragmentManager().beginTransaction();
//      ft.hide(joinGroupFragment);
        ft.remove(joinGroupFragment);
        ft.commit();
    }
}

如果我这样做，当我第一次调用showFragment（）时，先前添加的（在onCreate（）中）片段显示退出转换，新的片段显示输入转换，但是当我调用dismissFragment()时，它仍然会抛出同样的错误。我一直使用getBackStackEntryCount()记录后台堆栈计数，并在删除片段时显示2，但仍然是错误。

但我不明白第一个片段是如何显示退出过渡的。

我也试过了。

getFragmentManager().beginTransaction().add(R.id.fragment_container, new Fragment())
                        .addToBackStack("dummy")
                        .commit();

private void showFragment() {
    Fragment fragment = JoinGroupFragment.newInstance();
    FragmentTransaction ft = getFragmentManager().beginTransaction()
            .replace(R.id.fragment_container, fragment, JOIN_GROUP_FRAGMENT_TAG);

    ft.addToBackStack("dummy");
    ft.commit();


    if (Build.VERSION.SDK_INT >= 21) {
        Log.i(TAG, "set enter transition");
        fragment.setEnterTransition(new Slide(Gravity.TOP));
        fragment.setExitTransition(new Slide(Gravity.BOTTOM));
    }

    ft.commit();
}

private void dismissFragment() {
    Fragment joinGroupFragment = getFragmentManager().findFragmentByTag(JOIN_GROUP_FRAGMENT_TAG);
    if (joinGroupFragment != null) {
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        ft.replace(R.id.fragment_container, new Fragment());
        ft.remove(joinGroupFragment);
        ft.commit();
    }
}

这很好用并显示退出转换。但BackStackEntryCount尽管remove调用增加了已用内存，但仍在不断增加。

Answer 1

So it turns out that I do not understand FragmentManager's backstack yet. What I was trying to do could be done without backstack. It is simple.

For Transition, I need to replace the fragment with some other fragment, otherwise it is not a transition.

$(".ui-watermark").css("background-color", "red");

This is working well. I'll try it with backstack also and post later.

将setExitTransition用于Fragment时出现NullPointerException

更新

1 个答案: