当转换到其他Activity过早调用时,ActivityTransitionCoordinator中的ViewRootImpl.setPausedForTransition(boolean)NullPointerException

Question

在我的Android应用程序中,我有一个启动画面,我在其中进行一些设置和加载.我的应用程序使用默认值explode作为a windowEnterTransition和a windowExitTransition和changeImageTransformplus changeBounds转换设置为windowSharedElementEnterTransition和windowSharedElementExitTransition.为方便起见,我Activity使用静态方法开始下一个方法,其中我将当前Activity作为a Context和共享元素传递.该帖子的第二部分提供了该代码.

其中一个场景是没有任何东西可以加载,所以应用程序几乎会立即触发下一个Activity.问题是,在这种情况下,应用程序以某种方式神秘地崩溃,ActivityTransitionCoordinator并在本文的下一部分中给出了一个堆栈.对内部的调试表明,ViewRootImpl实现的是null,并且没有空检查,因此调用viewRoot.setPausedForTransition(false)抛出a NullPointerException.你可以在下面的代码中找到这个不吉利的地方.

为了关注这个失败的场景,让我们假设一个逻辑决定没有任何东西可以加载而下一个Activity应该立即启动,这很简单,可以简化为刚开始提到的活动.

没有区别,如果第二的开始Activity被调用中onCreate(),onResume()或onEnterAnimationComplete()方法.我甚至尝试在通过调用获取的Transition上添加一个侦听器,getWindow().getSharedElementEnterTransition()并在转换完成时getWindow().getEnterTransition()允许启动下一个侦听器Activity.给定Transitions的不是null,但app永远不会进入附加的侦听器的方法.

我现在使用的解决方法是安排一个Runnable调用下一个Activity延迟的.

我想知道这是否是Android(一个SupportLibrary更具体的)问题,或者我错过了什么.有谁遇到过类似的问题？

堆栈跟踪:

08-12 00:35:32.550 26453-26453/com.faver.mkoslacz.faverdemo E/AndroidRuntime: FATAL EXCEPTION: main
                                                                              Process: com.faver.mkoslacz.faverdemo, PID: 26453
                                                                              java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.ViewRootImpl.setPausedForTransition(boolean)' on a null object reference
                                                                                  at android.app.ActivityTransitionCoordinator.startInputWhenTransitionsComplete(ActivityTransitionCoordinator.java:897)
                                                                                  at android.app.ActivityTransitionCoordinator.viewsTransitionComplete(ActivityTransitionCoordinator.java:885)
                                                                                  at android.app.ExitTransitionCoordinator.getExitTransition(ExitTransitionCoordinator.java:318)
                                                                                  at android.app.ExitTransitionCoordinator.beginTransitions(ExitTransitionCoordinator.java:365)
                                                                                  at android.app.ExitTransitionCoordinator.-wrap0(ExitTransitionCoordinator.java)
                                                                                  at android.app.ExitTransitionCoordinator$4.run(ExitTransitionCoordinator.java:216)
                                                                                  at android.app.ActivityTransitionCoordinator.startTransition(ActivityTransitionCoordinator.java:773)
                                                                                  at android.app.ExitTransitionCoordinator.startExit(ExitTransitionCoordinator.java:213)
                                                                                  at android.app.ActivityTransitionState.startExitOutTransition(ActivityTransitionState.java:317)
                                                                                  at android.app.Activity.cancelInputsAndStartExitTransition(Activity.java:3960)
                                                                                  at android.app.Activity.startActivityForResult(Activity.java:3936)
                                                                                  at android.support.v4.app.BaseFragmentActivityJB.startActivityForResult(BaseFragmentActivityJB.java:48)
                                                                                  at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:75)
                                                                                  at android.app.Activity.startActivity(Activity.java:4196)
                                                                                  at com.faver.mkoslacz.faverdemo.activity.AuthorizationActivity.startWithTransiton(AuthorizationActivity.java:45)
                                                                                  at com.faver.mkoslacz.faverdemo.activity.SplashActivity.onEnterAnimationComplete(SplashActivity.java:27)
                                                                                  at android.app.Activity.dispatchEnterAnimationComplete(Activity.java:5852)
                                                                                  at android.app.ActivityThread.handleEnterAnimationComplete(ActivityThread.java:2668)
                                                                                  at android.app.ActivityThread.-wrap10(ActivityThread.java)
                                                                                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1558)
                                                                                  at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                  at android.os.Looper.loop(Looper.java:148)
                                                                                  at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                                  at java.lang.reflect.Method.invoke(Native Method)
                                                                                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

代码失败ActivityTransitionAnimator:

private void startInputWhenTransitionsComplete() {
    if (mViewsTransitionComplete && mSharedElementTransitionComplete) {
        final View decor = getDecor();
        if (decor != null) {
            final ViewRootImpl viewRoot = decor.getViewRootImpl(); // it's null
            viewRoot.setPausedForTransition(false); // crashes here
        }
        onTransitionsComplete();
    }
}

一个方法开始下一个Activity:

public static void startWithTransiton(Activity activity, android.view.View logo) {
    Intent intent = new Intent(activity, AuthorizationActivity.class);
    ActivityOptionsCompat options = ActivityOptionsCompat
            .makeSceneTransitionAnimation(
                    activity,
                    logo,
                    activity.getString(R.string.logoTransfer));
    activity.startActivity(intent, options.toBundle());
}

启动Activity内容(简化):

public class SplashActivity extends AppCompatActivity {

    private static final String TAG = "SplashActivity";

    private View logo;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash);
        logo = findViewById(R.id.logo);

//        AuthorizationActivity.startWithTransiton(this, logo); // will fail

        new Handler().postDelayed(() -> {
            AuthorizationActivity.startWithTransiton(this, logo); // executes flawlessly
        }, 300);

        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
            Transition sharedElementEnterTransition = getWindow().getSharedElementEnterTransition();
            if (sharedElementEnterTransition != null) {
                sharedElementEnterTransition.addListener(new Transition.TransitionListener() {
                    @Override
                    public void onTransitionStart(Transition transition) {
                        Log.d(TAG, "onTransitionStart: never executes");
                    }

                    @Override
                    public void onTransitionEnd(Transition transition) {
                        Log.d(TAG, "onTransitionEnd: never executes");
                    }

                    @Override
                    public void onTransitionCancel(Transition transition) {
                        Log.d(TAG, "onTransitionCancel: never executes");
                    }

                    @Override
                    public void onTransitionPause(Transition transition) {
                        Log.d(TAG, "onTransitionPause: never executes");
                    }

                    @Override
                    public void onTransitionResume(Transition transition) {
                        Log.d(TAG, "onTransitionResume: never executes");
                    }
                });
            }

            Transition enterTransition = getWindow().getEnterTransition();
            if (enterTransition != null) {
                enterTransition.addListener(new Transition.TransitionListener() {
                    @Override
                    public void onTransitionStart(Transition transition) {
                        Log.d(TAG, "onTransitionStart: never executes");
                    }

                    @Override
                    public void onTransitionEnd(Transition transition) {
                        Log.d(TAG, "onTransitionEnd: never executes");
                    }

                    @Override
                    public void onTransitionCancel(Transition transition) {
                        Log.d(TAG, "onTransitionCancel: never executes");
                    }

                    @Override
                    public void onTransitionPause(Transition transition) {
                        Log.d(TAG, "onTransitionPause: never executes");
                    }

                    @Override
                    public void onTransitionResume(Transition transition) {
                        Log.d(TAG, "onTransitionResume: never executes");
                    }
                });
            }
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
//        AuthorizationActivity.startWithTransiton(this, logo); // will fail
    }

    @Override
    public void onEnterAnimationComplete() {
        super.onEnterAnimationComplete();
//        AuthorizationActivity.startWithTransiton(this, logo); // will fail
    }
}

Answer 1

在使用“爆炸活动”过渡时，我也遇到相同的问题，我发现此代码在Lollipop版本中正常运行，但在Lollipop之上崩溃。甚至我也找不到崩溃的原因。但我以另一种方式解决它。只是推迟活动过渡。我在下面给出了我的代码

public class SplashActivity extends AppCompatActivity {

final Handler handler = new Handler();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_splash);
    handler.postDelayed(new Runnable() {
        @Override
        public void run() {
            navigate();
        }
    },500);
}

private void navigate() {
    ActivityOptions options = ActivityOptions.makeSceneTransitionAnimation(this);
    Intent intent = new Intent(SplashActivity.this, MainActivity.class);
    startActivity(intent, options.toBundle());
}}

添加后，此版本在所有版本中均正常运行。