当我运行该应用程序时，我没有收到错误消息，但一切正常，但是当我单击“发送消息”按钮时，该应用程序崩溃了，但消息仍然被发送。下面是我的chatActivity和logcat消息的代码
package com.paddi.paddi.paddi;
public class ChatActivity extends AppCompatActivity
{
private String messageReceiverId;
private String messageReceiverName;
// private Toolbar ChatToolBar;
private TextView userNameTitle;
private TextView userLastSeen;
private CircleImageView userChatProfileImage;
private ImageButton SendMessageButton;
// private ImageButton SelectImageButton;
private EditText InputMessageText;
FirebaseUser fuser;
DatabaseReference rootRef;
private FirebaseAuth mAuth;
private String messageSenderId;
private RecyclerView userMessagesList;
private final List<Messages> messageList = new ArrayList<>();
private LinearLayoutManager linearLayoutManager;
private MessageAdapter messageAdapter;
private static int Gallery_Pick = 1;
private StorageReference MessageImageStorageRef;
private ProgressDialog loadingBar;
private String downloadImageUrl;
Intent intent;
ValueEventListener seenListener;
String userid;
APIServiceFragment apiService;
boolean notify = false;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_chat);
rootRef = FirebaseDatabase.getInstance().getReference();
mAuth = FirebaseAuth.getInstance();
messageSenderId = mAuth.getCurrentUser().getUid();
messageReceiverId = getIntent().getExtras().get("visit_user_id").toString();
messageReceiverName = getIntent().getExtras().get("user_name").toString();
MessageImageStorageRef = FirebaseStorage.getInstance().getReference().child("Messages_Pictures");
apiService = Client.getClient("https://fcm.googleapis.com/").create(APIServiceFragment.class);
// ChatToolBar = (Toolbar) findViewById(R.id.chat_bar_layout);
// setSupportActionBar(ChatToolBar);
loadingBar = new ProgressDialog(this);
ActionBar actionBar = getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setDisplayShowCustomEnabled(true);
LayoutInflater layoutInflater = (LayoutInflater)
this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View action_bar_view = layoutInflater.inflate(R.layout.chat_custom_bar, null);
actionBar.setCustomView(action_bar_view);
userNameTitle = (TextView) findViewById(R.id.custom_profile_name);
userLastSeen = (TextView) findViewById(R.id.custom_user_last_seen);
userChatProfileImage = (CircleImageView) findViewById(R.id.custom_profile_image_last_seen);
SendMessageButton = (ImageButton) findViewById(R.id.send_message_btn);
// SelectImageButton = (ImageButton) findViewById(R.id.select_image);
InputMessageText = (EditText) findViewById(R.id.input_message);
messageAdapter = new MessageAdapter(messageList);
userMessagesList = (RecyclerView) findViewById(R.id.messages_list_of_users);
linearLayoutManager = new LinearLayoutManager(this);
userMessagesList.setHasFixedSize(true);
userMessagesList.setLayoutManager(linearLayoutManager);
userMessagesList.setAdapter(messageAdapter);
FetchMessages();
userNameTitle.setText(messageReceiverName);
rootRef.child("Users").child(messageReceiverId).addValueEventListener(new ValueEventListener()
{
@Override
public void onDataChange(DataSnapshot dataSnapshot)
{
final String online = dataSnapshot.child("online").getValue().toString();
final String userThumb = dataSnapshot.child("user_thumb_image").getValue().toString();
Picasso.with(ChatActivity.this).load(userThumb).fit().centerInside().networkPolicy(NetworkPolicy.OFFLINE).placeholder(R.drawable.default_profile)
.into(userChatProfileImage, new Callback() {
@Override
public void onSuccess()
{
}
@Override
public void onError()
{
Picasso.with(ChatActivity.this).load(userThumb).fit().centerInside().placeholder(R.drawable.default_profile).into(userChatProfileImage);
}
});
if (online != null) {
if (online.equals("true"))
{
userLastSeen.setText("online");
}
else
{
LastSeenTime getTime = new LastSeenTime();
long last_seen = Long.parseLong(online);
//problem with last seen time here
String lastSeenDisplayTime = getTime.getTimeAgo(last_seen, getApplicationContext()).toString();
userLastSeen.setText(lastSeenDisplayTime);
}
}
}
@Override
public void onCancelled(DatabaseError databaseError)
{
}
});
SendMessageButton.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View view)
{
SendMessage();
}
});
// SelectImageButton.setOnClickListener(new View.OnClickListener() {
// @Override
// public void onClick(View v)
// {
// Intent galleryIntent = new Intent();
// galleryIntent.setAction(Intent.ACTION_GET_CONTENT);
// galleryIntent.setType("image/*");
// startActivityForResult(galleryIntent, Gallery_Pick);
//}
//});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
super.onActivityResult(requestCode, resultCode, data);
if(requestCode==Gallery_Pick && resultCode==RESULT_OK &&data!=null)
{
loadingBar.setTitle("Sending Image");
loadingBar.setMessage("Please Wait");
loadingBar.show();
Uri ImageUri = data.getData();
final String message_sender_ref = "Messages/" + messageSenderId + "/" + messageReceiverId;
final String message_receiver_ref = "Messages/" + messageReceiverId + "/" + messageSenderId;
DatabaseReference user_message_key = rootRef.child("Messages").child(messageSenderId)
.child(messageReceiverId).push();
final String message_push_id = user_message_key.getKey();
final StorageReference filePath = MessageImageStorageRef.child(message_push_id + ".jpg");
final StorageTask<UploadTask.TaskSnapshot> taskSnapshotStorageTask = filePath.putFile(ImageUri).addOnCompleteListener(new OnCompleteListener<UploadTask.TaskSnapshot>() {
@Override
public void onComplete(@NonNull Task<UploadTask.TaskSnapshot> task) {
if (task.isSuccessful()) {
downloadImageUrl = filePath.getDownloadUrl().toString();
// return filePath.getDownloadUrl();
Map messageTextBody = new HashMap();
messageTextBody.put("message", downloadImageUrl);
messageTextBody.put("isseen", true);
messageTextBody.put("type", "image");
messageTextBody.put("time", ServerValue.TIMESTAMP);
messageTextBody.put("from", messageSenderId);
messageTextBody.put("to", messageReceiverId);
Map messageBodyDetails = new HashMap();
messageBodyDetails.put(message_sender_ref + "/" + message_push_id, messageTextBody);
messageBodyDetails.put(message_receiver_ref + "/" + message_push_id, messageTextBody);
rootRef.updateChildren(messageBodyDetails, new DatabaseReference.CompletionListener() {
@Override
public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) {
if (databaseError != null) {
Log.d("Chat_Log", databaseError.getMessage().toString());
}
InputMessageText.setText("");
loadingBar.dismiss();
}
});
Toast.makeText(ChatActivity.this, "Picture Sent Successfully.", Toast.LENGTH_SHORT).show();
loadingBar.dismiss();
} else {
Toast.makeText(ChatActivity.this, "Picture not sent, Try again", Toast.LENGTH_SHORT).show();
loadingBar.dismiss();
}
}
});
}
}
private void FetchMessages()
{
rootRef.child("Messages").child(messageSenderId).child(messageReceiverId)
.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s)
{
if (dataSnapshot.exists())
{
Messages messages = dataSnapshot.getValue(Messages.class);
messageList.add(messages);
messageAdapter.notifyDataSetChanged();
userMessagesList.smoothScrollToPosition(userMessagesList.getAdapter().getItemCount());
}
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s)
{
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot)
{
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s)
{
}
@Override
public void onCancelled(DatabaseError databaseError)
{
}
});
// seenMessage(userid);
}
private void seenMessage(final String userid) //add String and userid
{
rootRef = FirebaseDatabase.getInstance().getReference("Messages");
seenListener = rootRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot)
{
for (DataSnapshot snapshot : dataSnapshot.getChildren())
{
Messages messages = snapshot.getValue(Messages.class);
if (messages.getTo().equals(fuser.getUid()) && messages.getFrom().equals(ChatActivity.this.userid))//change messages to userid
{
Map messageTextBody = new HashMap();
messageTextBody.put("isseen", true);
snapshot.getRef().updateChildren(messageTextBody);
}
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
private void SendMessage()
{
notify = true;
String messageText = InputMessageText.getText().toString();
if (TextUtils.isEmpty(messageText))
{
Toast.makeText(ChatActivity.this,
"Input message", Toast.LENGTH_SHORT).show();
}
else
{
String message_sender_ref = "Messages/" + messageSenderId + "/" + messageReceiverId;
final String message_receiver_ref = "Messages/" + messageReceiverId + "/" + messageSenderId;
DatabaseReference user_message_key = rootRef.child("Messages").child(messageSenderId)
.child(messageReceiverId).push();
String message_push_id = user_message_key.getKey();
Map messageTextBody = new HashMap();
messageTextBody.put("message", messageText);
messageTextBody.put("isseen", false);
messageTextBody.put("type", "text");
messageTextBody.put("time", ServerValue.TIMESTAMP);
messageTextBody.put("from", messageSenderId);
messageTextBody.put("to", messageReceiverId);
Map messageBodyDetails = new HashMap();
messageBodyDetails.put(message_sender_ref + "/" + message_push_id, messageTextBody);
messageBodyDetails.put(message_receiver_ref + "/" + message_push_id, messageTextBody);
rootRef.updateChildren(messageBodyDetails).addOnCompleteListener(new OnCompleteListener() {
@Override
public void onComplete(@NonNull Task task)
{
if (task.isSuccessful())
{
Toast.makeText(ChatActivity.this, "Message Sent", Toast.LENGTH_SHORT).show();
InputMessageText.setText("");
}
else
{
String message = task.getException().getMessage();
Toast.makeText(ChatActivity.this, "Error:" + message, Toast.LENGTH_SHORT).show();
InputMessageText.setText("");
}
}
});
**i tried sending chat notification with the code below
这就是引发错误的原因，该错误仍然会发送消息，但应用程序崩溃并自行重启。**
final String msg = messageText;
rootRef = FirebaseDatabase.getInstance().getReference("Users").child(fuser.getUid());
rootRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot)
{
User user = dataSnapshot.getValue(User.class);
if (notify) {
sendNotification(message_receiver_ref, user.getUsername(), msg);
}
notify = false;
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
}
private void sendNotification(String message_receiver_ref, final String username, final String message)
{
DatabaseReference tokens = FirebaseDatabase.getInstance().getReference("Tokens");
Query query = tokens.orderByKey().equalTo(message_receiver_ref);
query.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot)
{
for (DataSnapshot snapshot: dataSnapshot.getChildren())
{
Token token = snapshot.getValue(Token.class);
Data data = new Data(fuser.getUid(), R.mipmap.app_icon, username+": "+message, "New Message",
userid);
Sender sender = new Sender(data, token.getToken());
apiService.sendNotification(sender)
.enqueue(new retrofit2.Callback<MyResponse>() {
@Override
public void onResponse(Call<MyResponse> call, Response<MyResponse> response)
{
if (response.code() == 200)
{
if (response.body().success != 1)
{
Toast.makeText(ChatActivity.this, "Failed!", Toast.LENGTH_SHORT).show();
}
}
}
@Override
public void onFailure(Call<MyResponse> call, Throwable t)
{
}
});
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
{
}
});
}
}
这是下面的日志
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference
at com.paddi.paddi.paddi.ChatActivity.SendMessage(ChatActivity.java:504)
at com.paddi.paddi.paddi.ChatActivity.access$200(ChatActivity.java:58)
at com.paddi.paddi.paddi.ChatActivity$2.onClick(ChatActivity.java:251)
at android.view.View.performClick(View.java:5274)
at android.view.View$PerformClick.run(View.java:21543)
at android.os.Handler.handleCallback(Handler.java:815)
at android.os.Handler.dispatchMessage(Handler.java:104)
at android.os.Looper.loop(Looper.java:207)
at android.app.ActivityThread.main(ActivityThread.java:5765)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:679)
答案 0 :(得分：0)
您遇到以下错误：
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference
因为您的fuser对象未初始化。要解决此问题，请在您的onCreate()方法中添加以下代码行：
fuser = FirebaseAuth.getInstance().getCurrentUser().getUid();