尝试在后台/前景中运行时应用程序崩溃，但适用于其他手机

Question

While using android studio and firebase, my app (in the background or foreground) crashes on an API 26 device when notification is clicked. Whereas when I use an API 23 device, the app crashes when the app is closed and notification is clicked but can still process the notification when app is in the background/foreground. I don't understand the problem and any help is appreciated.

NOTIFICATION SERVICE

import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.support.v4.app.NotificationCompat;

import com.google.firebase.messaging.RemoteMessage;

public class FirebaseMessagingService extends com.google.firebase.messaging.FirebaseMessagingService {


    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        super.onMessageReceived(remoteMessage);

        String notification_title = remoteMessage.getNotification().getTitle();
        String notification_message = remoteMessage.getNotification().getBody();

        String click_action = remoteMessage.getNotification().getClickAction();

        String from_user_id = remoteMessage.getData().get("from_user_id");

        NotificationCompat.Builder mBuilder =
                new NotificationCompat.Builder(FirebaseMessagingService.this, "default")
                        .setSmallIcon(R.mipmap.ic_launcher)
                        .setContentTitle(notification_title)
                        .setContentText(notification_message);


        Intent resultIntent = new Intent(click_action);
        resultIntent.putExtra("user_id", from_user_id);


        PendingIntent resultPendingIntent =
                PendingIntent.getActivity(
                        FirebaseMessagingService.this,
                        0,
                        resultIntent,
                        PendingIntent.FLAG_UPDATE_CURRENT
                );

        mBuilder.setContentIntent(resultPendingIntent);




        int mNotificationId = (int) System.currentTimeMillis();

        NotificationManager mNotifyMgr =
                (NotificationManager) getSystemService(NOTIFICATION_SERVICE);


        mNotifyMgr.notify(mNotificationId, mBuilder.build());


    }
}

USERS ACTIVITY

import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.firebase.ui.database.FirebaseRecyclerOptions;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
import com.squareup.picasso.Picasso;

import de.hdodenhof.circleimageview.CircleImageView;


public class UsersActivity extends AppCompatActivity {

    private Toolbar mToolbar;
    private RecyclerView mUsersList;
    private DatabaseReference mUsersDatabase;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_users);
        mToolbar=(Toolbar)findViewById(R.id.users_appBar);
        setSupportActionBar(mToolbar);
        getSupportActionBar().setTitle("All Users");
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        mUsersDatabase= FirebaseDatabase.getInstance().getReference().child("Users");
        mUsersDatabase.keepSynced(true);
        mUsersList=(RecyclerView)findViewById(R.id.users_list);
        mUsersList.setHasFixedSize(true);
        mUsersList.setLayoutManager(new LinearLayoutManager(this));


    }

    @Override
    protected void onStart() {
        super.onStart();
        startListening();

    }
    public void startListening(){
        Query query = FirebaseDatabase.getInstance()
                .getReference()
                .child("Users")
                .limitToLast(50);

        FirebaseRecyclerOptions<Users> options =
                new FirebaseRecyclerOptions.Builder<Users>()
                        .setQuery(query, Users.class)
                        .build();
        FirebaseRecyclerAdapter<Users, UserViewHolder> adapter = new FirebaseRecyclerAdapter<Users, UserViewHolder>(options) {

            @Override
            public UserViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                // Create a new instance of the ViewHolder, in this case we are using a custom
                // layout called R.layout.message for each item
                View view = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.users_single_layout, parent, false);

                return new UserViewHolder(view);
            }

            @Override
            protected void onBindViewHolder(UserViewHolder holder, int position, Users model) {
                // Bind the Chat object to the ChatHolder
                holder.setName(model.name);
                holder.setStatus(model.status);
                holder.setUserImage(model.getThumb_image());
                final String user_id= getRef(position).getKey();

                holder.mView.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent profileIntent = new Intent(UsersActivity.this, ProfileActivity.class);
                        if (user_id != null) {
                            profileIntent.putExtra("user_id", user_id);
                            startActivity(profileIntent);
                        }
                    }
                });
            }


        };
        mUsersList.setAdapter(adapter);
        adapter.startListening();
    }

    public static class UserViewHolder extends RecyclerView.ViewHolder {
        View mView;
        public UserViewHolder(View itemView) {
            super(itemView);
            mView = itemView;
        }
        public void setName(String name){
            TextView userNameView = (TextView) mView.findViewById(R.id.user_single_name);
            userNameView.setText(name);
        }

        public void setStatus(String status){
            TextView userStatusView= (TextView) mView.findViewById(R.id.user_single_status);
            userStatusView.setText(status);
        }

        public void setUserImage(String thumb_image){
            CircleImageView userImageView = (CircleImageView) mView.findViewById(R.id.user_single_image);
            Picasso.get().load(thumb_image).placeholder(R.drawable.accountpicture).into(userImageView);
        }

    }
}

PROFILE ACTIVITY

import android.app.ProgressDialog;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.squareup.picasso.Callback;
import com.squareup.picasso.NetworkPolicy;
import com.squareup.picasso.Picasso;

import java.text.DateFormat;
import java.util.Date;
import java.util.HashMap;


public class ProfileActivity extends AppCompatActivity {

    private ImageView mProfileImage;
    private TextView mProfileName, mProfileStatus, mProfileFriendsCount;
    private Button mProfileSendReqBtn;
    private DatabaseReference mUserDatabase;
    private Button declineRequest;
    private FirebaseUser mCurrent_user;
    private ProgressDialog mProgressDialog;
    private DatabaseReference mFriendRequestDatabase;
    private DatabaseReference mFriendDatabase;
    private String mCurrent_state;
    private DatabaseReference mNotificationDatabase;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_profile);
        final String user_id = getIntent().getStringExtra("user_id");
        mUserDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(user_id);
        mFriendRequestDatabase = FirebaseDatabase.getInstance().getReference().child("Friend_req");
        mCurrent_user= FirebaseAuth.getInstance().getCurrentUser();
        mFriendDatabase= FirebaseDatabase.getInstance().getReference().child("Friends");
        mNotificationDatabase= FirebaseDatabase.getInstance().getReference().child("notifications");
        mProfileImage = (ImageView) findViewById(R.id.profile_image);
        mProfileName = (TextView) findViewById(R.id.profile_profileName);
        mProfileStatus = (TextView) findViewById(R.id.profile_status);
        mProfileFriendsCount = (TextView) findViewById(R.id.profile_totalFriends);
        mProfileSendReqBtn = (Button) findViewById(R.id.profile_send_req_btn);
        declineRequest= (Button)findViewById(R.id.profile_decline_btn);
        mCurrent_state = "not_friends";
        mProgressDialog = new ProgressDialog(this);
        mProgressDialog.setTitle("Loading User Data");
        mProgressDialog.setMessage("Please wait...");
        mProgressDialog.setCanceledOnTouchOutside(false);
        mProgressDialog.show();
        mUserDatabase.keepSynced(true);
        mFriendDatabase.keepSynced(true);
        mFriendRequestDatabase.keepSynced(true);
        declineRequest.setVisibility(View.INVISIBLE);

        if(mCurrent_user.getUid().equals(user_id)){
            mProfileSendReqBtn.setVisibility(View.INVISIBLE);
        }

        mUserDatabase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                String diplay_name = dataSnapshot.child("name").getValue().toString();
                String status = dataSnapshot.child("status").getValue().toString();
                final String image = dataSnapshot.child("image").getValue().toString();
                mProfileName.setText(diplay_name);
                mProfileStatus.setText(status);
                Picasso.get().load(image).networkPolicy(NetworkPolicy.OFFLINE).placeholder(R.drawable.accountpicture).into(mProfileImage, new Callback() {
                    @Override
                    public void onSuccess() {

                    }

                    @Override
                    public void onError(Exception e) {
                        Picasso.get().load(image).placeholder(R.drawable.accountpicture).into(mProfileImage);
                    }
                });

                mFriendRequestDatabase.child(mCurrent_user.getUid()).addListenerForSingleValueEvent(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                        if(dataSnapshot.hasChild(user_id)){
                            String req_type= dataSnapshot.child(user_id).child("request_type").getValue().toString();
                            if(req_type.equals("received")){
                                mCurrent_state= "req_received";
                                mProfileSendReqBtn.setText("Accept Friend Request");
                                declineRequest.setVisibility(View.VISIBLE);
                                mUserDatabase.keepSynced(true);
                                mFriendDatabase.keepSynced(true);
                                mFriendRequestDatabase.keepSynced(true);
                            }
                            else if(req_type.equals("sent")){
                                mCurrent_state="req_sent";
                                mProfileSendReqBtn.setText("Cancel Friend Request");
                                mUserDatabase.keepSynced(true);
                                mFriendDatabase.keepSynced(true);
                                mFriendRequestDatabase.keepSynced(true);
                            }
                            else if(req_type.equals("req_sent")){
                                mCurrent_state= "not_friends";
                                mProfileSendReqBtn.setText("Send Friend Request");
                                mUserDatabase.keepSynced(true);
                                mFriendDatabase.keepSynced(true);
                                mFriendRequestDatabase.keepSynced(true);
                            }
                            mProgressDialog.dismiss();
                        }
                        else{

                            mFriendDatabase.child(mCurrent_user.getUid()).addListenerForSingleValueEvent(new ValueEventListener() {
                                @Override
                                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                                    if(dataSnapshot.hasChild(user_id)){
                                        mCurrent_state= "friends";
                                        mProfileSendReqBtn.setText("Unfriend User");
                                        mProfileSendReqBtn.setEnabled(true);
                                        mUserDatabase.keepSynced(true);
                                        mFriendDatabase.keepSynced(true);
                                        mFriendRequestDatabase.keepSynced(true);
                                    }
                                    mProgressDialog.dismiss();
                                }

                                @Override
                                public void onCancelled(@NonNull DatabaseError databaseError) {
                                    mProgressDialog.dismiss();

                                }
                            });
                        }


                    }

                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {

                    }
                });


            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });



            mProfileSendReqBtn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    mProfileSendReqBtn.setEnabled(false);
                    if (user_id.equals(mCurrent_user.getUid())) {
                        Toast.makeText(ProfileActivity.this, "Cannot send friend request to yourself!", Toast.LENGTH_LONG).show();
                        declineRequest.setVisibility(View.INVISIBLE);
                    } else {
                        if (mCurrent_state.equals("not_friends")) {
                            mFriendRequestDatabase.child(mCurrent_user.getUid()).child(user_id).child("request_type").setValue("sent").addOnCompleteListener(new OnCompleteListener<Void>() {
                                @Override
                                public void onComplete(@NonNull Task<Void> task) {
                                    if (task.isSuccessful()) {
                                        mFriendRequestDatabase.child(user_id).child(mCurrent_user.getUid()).child("request_type").setValue("received").addOnSuccessListener(new OnSuccessListener<Void>() {
                                            @Override
                                            public void onSuccess(Void aVoid) {


                                                HashMap<String, String> notificationData= new HashMap<>();
                                                notificationData.put("from", mCurrent_user.getUid());
                                                notificationData.put("type", "request");

                                                mNotificationDatabase.child(user_id).push().setValue(notificationData).addOnSuccessListener(new OnSuccessListener<Void>() {
                                                    @Override
                                                    public void onSuccess(Void aVoid) {
                                                        mCurrent_state = "req_sent";
                                                        mProfileSendReqBtn.setText("Cancel Friend Request");
                                                        mUserDatabase.keepSynced(true);
                                                        mFriendDatabase.keepSynced(true);
                                                        mFriendRequestDatabase.keepSynced(true);
                                                    }
                                                });


                                            }
                                        });
                                    } else {
                                        Toast.makeText(ProfileActivity.this, "Error", Toast.LENGTH_LONG).show();
                                    }
                                    mProfileSendReqBtn.setEnabled(true);
                                }
                            });
                        }


                        if (mCurrent_state.equals("req_sent")) {
                            mProfileSendReqBtn.setEnabled(true);
                            mFriendRequestDatabase.child(mCurrent_user.getUid()).child(user_id).removeValue().addOnSuccessListener(new OnSuccessListener<Void>() {
                                @Override
                                public void onSuccess(Void aVoid) {
                                    mFriendRequestDatabase.child(user_id).child(mCurrent_user.getUid()).removeValue().addOnSuccessListener(new OnSuccessListener<Void>() {
                                        @Override
                                        public void onSuccess(Void aVoid) {
                                            mCurrent_state = "req_sent";
                                            mProfileSendReqBtn.setText("Send Friend Request");
                                            mCurrent_state = "not_friends";
                                            mUserDatabase.keepSynced(true);
                                            mFriendDatabase.keepSynced(true);
                                            mFriendRequestDatabase.keepSynced(true);

                                        }

                                    });

                                }
                            });

                        }


                        if (mCurrent_state.equals("req_received")) {
                            declineRequest.setVisibility(View.INVISIBLE);
                            mProfileSendReqBtn.setEnabled(true);
                            final String currentDate = DateFormat.getDateTimeInstance().format(new Date());
                            mFriendDatabase.child(mCurrent_user.getUid()).child(user_id).setValue(currentDate).addOnSuccessListener(new OnSuccessListener<Void>() {
                                @Override
                                public void onSuccess(Void aVoid) {
                                    mFriendDatabase.child(user_id).child(mCurrent_user.getUid()).setValue(currentDate).addOnSuccessListener(new OnSuccessListener<Void>() {
                                        @Override
                                        public void onSuccess(Void aVoid) {
                                            mFriendRequestDatabase.child(mCurrent_user.getUid()).child(user_id).removeValue().addOnSuccessListener(new OnSuccessListener<Void>() {
                                                @Override
                                                public void onSuccess(Void aVoid) {
                                                    mFriendRequestDatabase.child(user_id).child(mCurrent_user.getUid()).removeValue().addOnSuccessListener(new OnSuccessListener<Void>() {
                                                        @Override
                                                        public void onSuccess(Void aVoid) {
                                                            mCurrent_state = "friends";
                                                            mProfileSendReqBtn.setText("Unfriend User");
                                                            mUserDatabase.keepSynced(true);
                                                            mFriendDatabase.keepSynced(true);
                                                            mFriendRequestDatabase.keepSynced(true);

                                                        }

                                                    });

                                                }
                                            });

                                        }
                                    });
                                }
                            });
                        }


                    }
                }


            });

        declineRequest.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                declineRequest.setVisibility(View.INVISIBLE);
                mFriendRequestDatabase.child(mCurrent_user.getUid()).child(user_id).removeValue().addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        mFriendRequestDatabase.child(user_id).child(mCurrent_user.getUid()).removeValue().addOnSuccessListener(new OnSuccessListener<Void>() {
                            @Override
                            public void onSuccess(Void aVoid) {
                                mCurrent_state= "not_friends";
                                mProfileSendReqBtn.setText("Send Friend Request");
                                mUserDatabase.keepSynced(true);
                                mFriendDatabase.keepSynced(true);
                                mFriendRequestDatabase.keepSynced(true);
                            }

                        });

                    }
                });
            }
        });


    }


}

INDEX.JS FILE

'use strict'

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);


/*
 * 'OnWrite' works as 'addValueEventListener' for android. It will fire the function
 * everytime there is some item added, removed or changed from the provided 'database.ref'
 * 'sendNotification' is the name of the function, which can be changed according to
 * your requirement
 */

exports.sendNotification = functions.database.ref('/notifications/{user_id}/{notification_id}').onWrite((change, context) => {


  /*
   * You can store values as variables from the 'database.ref'
   * Just like here, I've done for 'user_id' and 'notification'
   */

  const user_id = context.params.user_id;
  const notification_id = context.params.notification_id;

  console.log('We have a notification from : ', user_id);

  /*
   * Stops proceeding to the rest of the function if the entry is deleted from database.
   * If you want to work with what should happen when an entry is deleted, you can replace the
   * line from "return console.log.... "
   */

  if(!change.after.val()){

    return console.log('A Notification has been deleted from the database : ', notification_id);

  }

  /*
   * 'fromUser' query retreives the ID of the user who sent the notification
   */

  const fromUser = admin.database().ref(`/notifications/${user_id}/${notification_id}`).once('value');

  return fromUser.then(fromUserResult => {

    const from_user_id = fromUserResult.val().from;

    console.log('You have new notification from  : ', from_user_id);

    /*
     * The we run two queries at a time using Firebase 'Promise'.
     * One to get the name of the user who sent the notification
     * another one to get the devicetoken to the device we want to send notification to
     */

    const userQuery = admin.database().ref(`Users/${from_user_id}/name`).once('value');
    const deviceToken = admin.database().ref(`/Users/${user_id}/device_token`).once('value');

    return Promise.all([userQuery, deviceToken]).then(result => {

      const userName = result[0].val();
      const token_id = result[1].val();

      /*
       * We are creating a 'payload' to create a notification to be sent.
       */

      const payload = {
        notification: {
          title : "New Friend Request",
          body: `${userName} has sent you a request`,
          icon: "default",
          click_action : "com.example.****.chattingapp_TARGET_NOTIFICATION"
        },
        data : {
          from_user_id : from_user_id
        }
      };

      /*
       * Then using admin.messaging() we are sending the payload notification to the token_id of
       * the device we retreived.
       */

      return admin.messaging().sendToDevice(token_id, payload).then(response => {

        return console.log('This was the notification Feature');

      });

    });

  });

});

ERROR I GET

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.****.chattingapp, PID: *****
                  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.****.chattingapp/com.example.****.chattingapp.ProfileActivity}: java.lang.NullPointerException: Can't pass null for argument 'pathString' in child()
                      at com.example.****.chattingapp.ProfileActivity.onCreate(ProfileActivity.java:53)

DATABASE VALUES

Answer 1

You removed most of the important rows of the Error. However you have to look at it very well and even decode it. It was saying that: there is a problem on "ProfileActivity.onCreate()" method when it calls a "Firebase.....child()" method . There are few rows where you call a "child()" method using a Variable (and not a fixed String), so one of them (please check the Error Log and find the line of that "child()" warning) is the real problem.

Answer 2

So I figured out I needed

 final String user_id;
    String data = getIntent().getStringExtra("user_id");
    if (data == null) {
        user_id = getIntent().getStringExtra("from_user_id");
    } else {
        user_id = getIntent().getStringExtra("user_id");
    }

I wasn't check what string I was getting from my intents, hence the null exceptions.