通知中的意图未正确发送到其他活动

编程问答 2022-05-06

问题描述

我正在尝试在通知的 Intent 中添加额外内容，以便打开 ChatActivity 并与向我发送消息的用户进行对话。我在 NotificationsListener 上传递的用户不为空。问题是我一直收到这个错误，无论我尝试什么其他调整：

2021-04-27 21:46:57.679 13553-13553/com.example.videomeeting E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.videomeeting,PID: 13553
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.videomeeting/com.example.videomeeting.activities.ChatActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.videomeeting.models.User.getUserName()' on a null object reference
        at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:3431)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7660)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.videomeeting.models.User.getUserName()' on a null object reference
        at com.example.videomeeting.activities.ChatActivity.onCreate(ChatActivity.java:108)
        at android.app.Activity.performCreate(Activity.java:8000)
        at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:3404)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:223) 
        at android.app.ActivityThread.main(ActivityThread.java:7660) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 

代码如下：

NotificationsListener.java

@Override
    public void onMessageReceived(@NonNull RemoteMessage remoteMessage) {
        super.onMessageReceived(remoteMessage);
        Intent activityIntent = new Intent(this,ChatActivity.class);
            FirebaseDatabase.getInstance().getReference(KEY_COLLECTION_USERS)
                    .child(remoteMessage.getData().get(KEY_USER_ID))
                    .addValueEventListener(new ValueEventListener() {
                        @Override
                        public void onDataChange(@NonNull DataSnapshot snapshot) {
                            user = snapshot.getValue(User.class);
                        }

                        @Override
                        public void onCancelled(@NonNull DatabaseError error) { }
                    });
            activityIntent.putExtra(Constants.INTENT_USER,user);
            activityIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK |Intent.FLAG_ACTIVITY_CLEAR_TASK);
            PendingIntent contentIntent = PendingIntent.getActivity(
                    this,activityIntent,FLAG_UPDATE_CURRENT
            );

ChatActivity.java

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chat);

        processExTradata();

        //Toolbar
        Toolbar toolbar = findViewById(R.id.toolbar);
        toolbar.setTitle("");
        setSupportActionBar(toolbar);

        TextView usernameTV = findViewById(R.id.usernameTV);
        usernameTV.setText(remoteUser.getUserName()); //ERROR LINE

@Override
    protected void onResume() {
        super.onResume();
        processExTradata();
    }

    @Override
    public void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
        setIntent(intent);
        processExTradata();
    }

    private void processExTradata(){
        remoteUser = (User) getIntent().getSerializableExtra(INTENT_USER);
    }

我已经检查过来自 NotificationsListener 的 Intent 的额外内容是否为空，而事实并非如此。一定有我没有看到的细节。感谢您抽出宝贵时间。

解决方法

错误信息明确指出 remoteUser 尚未初始化或为空，您需要检查 processExtraData() 方法正在接收哪些数据和

如果 (User) getIntent().getSerializableExtra(INTENT_USER) 没有返回用户，那么问题出在 NotificationsListener 类中

,

首先，确保您传递给活动的用户不为空。我认为 onDataChange 在您将用户作为额外传递后会触发。我认为它可能对您有所帮助，如果没有，请查看 this 和 this。

,

谢谢你们，我只是在 onDataChange 中跟踪用户的值，由于他的异步性，这是不正确的。我做了这个修复以避免空值：

while(!isFound) {
      FirebaseDatabase.getInstance().getReference(KEY_COLLECTION_USERS)
              .child(remoteMessage.getData().get(KEY_USER_ID))
              .addValueEventListener(new ValueEventListener() {
                      @Override
                      public void onDataChange(@NonNull DataSnapshot snapshot) {
                           user = snapshot.getValue(User.class);
                           isFound = true;
                      }

                      @Override
                      public void onCancelled(@NonNull DatabaseError error) {
                      }
             });
}

再次感谢。真的很感谢?

androidandroidandroid-intentandroid-pendingintentnotifications