与setnextanim崩溃？

Question

我一直收到setnextanim崩溃,但没有跟踪我的代码中的确切位置.这是我使用nextanim的唯一地方:

@Override
    public Animation onCreateAnimation(int transit, boolean enter, int nextAnim) {
        Animation defaultAnimation = super.onCreateAnimation(transit, enter, nextAnim);

        if (defaultAnimation == null && nextAnim != 0) {
            defaultAnimation = AnimationUtils.loadAnimation(getActivity(), nextAnim);
        }

        if (defaultAnimation != null) {
            if (getView() != null) {
                getView().setLayerType(View.LAYER_TYPE_HARDWARE, null);
            }

            defaultAnimation.setAnimationListener(new Animation.AnimationListener() {
                @Override
                public void onAnimationStart(Animation animation) {
                }

                public void onAnimationEnd(Animation animation) {
                    if (getView() != null) {
                        getView().setLayerType(View.LAYER_TYPE_NONE, null);
                    }
                }

                @Override
                public void onAnimationRepeat(Animation animation) {
                }
            });
        }

        return defaultAnimation;
    }

这是我能找到的痕迹:

FATAL EXCEPTION: main
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.Fragment.setNextAnim(int)' on a null object reference
    at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:765)
    at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580)
    at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)
    at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2229)
    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:700)
    at android.os.Handler.handleCallback(Handler.java:751)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:6119)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

知道我做错了什么可能会引发这次崩溃吗？

Answer 1

看一下例外:

java.lang.NullPointerException:尝试在空对象引用上调用虚方法'void android.support.v4.app.Fragment.setNextAnim(int)'

并且堆栈跟踪不包含对代码的引用这一事实,我认为假设它与代码的这一部分无关是合理的.

相反,它可能与某些视图在某个地方被垃圾收集/清空然后尝试使用它,然后在空对象上调用show/hide或类似物有关.见这个讨论.

Answer 2

在我的情况下,我null从堆栈中删除了一个片段:

val fragment = getSelectedFragment() // null
supportFragmentManager?.beginTransaction()
    ?.remove(fragment)
    ?.commit()