So I created a RecyclerView and then inflated a layout on to it, individual_user.xml.
In AllUsersActivity, I am connecting data to Firebase.
I am trying to set an OnClickListener with individualUserContainerConstraintLayout on to the container of the individual user to set an Intent. However, I keep getting a NullPointerException error. Why is this?
The Activity I am trying to go to with the Intent(UserProfileActivity) has just a TextView.
On a side note: I am new to this forum so I hope my question is detailed enough. I did search for similar questions already existing on the forum but none of them helped with this particular problem.
AllUsersActivity:
public class AllUsersActivity extends AppCompatActivity {
private Toolbar mAllUsersToolBar;
private RecyclerView mAllUsersRecyclerView;
FirebaseRecyclerAdapter<Users, UsersViewHolder> firebaseUsersAdapter = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_all_users);
//To place ToolBar on the page
mAllUsersToolBar = findViewById(R.id.allUsersToolBar);
setSupportActionBar(mAllUsersToolBar);
getSupportActionBar().setTitle("All Users");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
mAllUsersRecyclerView = findViewById(R.id.allUsersRecyclerView);
//When user clicks the container of the user on the All Users page, they get sent to that particular user's user profile.
ConstraintLayout individualUserContainerConstraintLayout = (ConstraintLayout) findViewById(R.id.individualUserContainerConstraintLayout);
individualUserContainerConstraintLayout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent goToUserProfile = new Intent(AllUsersActivity.this, UserProfileActivity.class);
startActivity(goToUserProfile);
}
});
//FirebaseAdapter
//Query locates the file you want to access the data from.
Query query = FirebaseDatabase.getInstance().getReference().child("Users");
FirebaseRecyclerOptions<Users> options = new FirebaseRecyclerOptions.Builder<Users>()
.setQuery(query, Users.class)
.build();
firebaseUsersAdapter = new FirebaseRecyclerAdapter<Users, UsersViewHolder>(
options) {
@Override
protected void onBindViewHolder(UsersViewHolder holder, int position, Users model) {
holder.mIndividualUserName.setText(model.getUsername());
holder.mIndividualUserStatus.setText(model.getStatus());
holder.mIndividualUserPicture.setImageDrawable(getDrawable(R.drawable.profile_pic));
//This is use to retrieve the User ID from Firebase Database.
String userId = getRef(position).getKey();
}
@Override
public UsersViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.individual_user, parent, false);
return new UsersViewHolder(view);
}
};
mAllUsersRecyclerView.setLayoutManager(new LinearLayoutManager(this));
mAllUsersRecyclerView.setAdapter(firebaseUsersAdapter);
firebaseUsersAdapter.startListening();
}
@Override
protected void onResume() {
super.onResume();
if(firebaseUsersAdapter != null){
firebaseUsersAdapter.startListening();
}
}
@Override
protected void onDestroy() {
super.onDestroy();
if(firebaseUsersAdapter != null){
firebaseUsersAdapter.stopListening();
}
}
}
Error:
09-10 21:16:38.593 2311-2311/? E/adbd: failed to connect to socket 'localabstract:com.example.android.whammychat': Connection refused
09-10 21:16:39.475 1575-6243/? E/AudioFlinger: not enough memory for AudioTrack size=131296
09-10 21:16:39.475 1575-6243/? E/AudioFlinger: createRecordTrack_l() initCheck failed -12; no control block?
09-10 21:16:39.477 2412-7979/? E/IAudioFlinger: createRecord returned error -12
09-10 21:16:39.477 2412-7979/? E/AudioRecord: AudioFlinger could not create record track, status: -12
09-10 21:16:39.478 2412-7979/? E/AudioRecord-JNI: Error creating AudioRecord instance: initialization check failed with status -12.
09-10 21:16:39.478 2412-7979/? E/android.media.AudioRecord: Error code -20 when initializing native AudioRecord object.
09-10 21:16:39.479 2412-7979/? E/ActivityThread: Failed to find provider info for com.google.android.apps.gsa.testing.ui.audio.recorded
09-10 21:16:47.742 1663-1851/? E/SurfaceFlinger: ro.sf.lcd_density must be defined as a build property
09-10 21:16:47.858 1663-1695/? E/SurfaceFlinger: ro.sf.lcd_density must be defined as a build property
09-10 21:16:53.374 8098-8098/com.example.android.whammychat E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.android.whammychat, PID: 8098
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.whammychat/com.example.android.whammychat.AllUsersActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.constraint.ConstraintLayout.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.constraint.ConstraintLayout.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.android.whammychat.AllUsersActivity.onCreate(AllUsersActivity.java:48)
at android.app.Activity.performCreate(Activity.java:7136)
at android.app.Activity.performCreate(Activity.java:7127)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
09-10 21:16:53.490 1799-1886/? E/InputDispatcher: channel '1450866 PopupWindow:2083893 (server)' ~ Channel is unrecoverably broken and will be disposed!
09-10 21:16:53.492 1799-1886/? E/InputDispatcher: channel '118f06 com.example.android.whammychat/com.example.android.whammychat.MainActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
09-10 21:16:54.429 1575-6243/? E/AudioFlinger: not enough memory for AudioTrack size=131296
09-10 21:16:54.429 1575-6243/? E/AudioFlinger: createRecordTrack_l() initCheck failed -12; no control block?
09-10 21:16:54.440 2412-8127/? E/IAudioFlinger: createRecord returned error -12
09-10 21:16:54.440 2412-8127/? E/AudioRecord: AudioFlinger could not create record track, status: -12
09-10 21:16:54.440 2412-8127/? E/AudioRecord-JNI: Error creating AudioRecord instance: initialization check failed with status -12.
09-10 21:16:54.441 2412-8127/? E/android.media.AudioRecord: Error code -20 when initializing native AudioRecord object.
09-10 21:16:54.441 2412-8127/? E/ActivityThread: Failed to find provider info for com.google.android.apps.gsa.testing.ui.audio.recorded
09-10 21:16:54.480 1799-1819/? E/memtrack: Couldn't load memtrack module
Your problem probably is that individualUserContainerConstraintLayout is part of R.layout.individual_user and you are trying to find it in R.layout.activity_all_users.
This is not how RecyclerView works. You need to set the click listener in the adapter of the RecyclerView. That's where you have access to the views inside R.layout.individual_user.
One way to do it would be like this:
First you would need to remove theses lines since they are not helpful:
ConstraintLayout individualUserContainerConstraintLayout = (ConstraintLayout) findViewById(R.id.individualUserContainerConstraintLayout);
individualUserContainerConstraintLayout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent goToUserProfile = new Intent(AllUsersActivity.this, UserProfileActivity.class);
startActivity(goToUserProfile);
}
});
Now, in the onBindViewHolder(UsersViewHolder, int, Users), you can add these lines at the end of the method:
holder.itemView.setOnclickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent goToUserProfile = new Intent(AllUsersActivity.this, UserProfileActivity.class);
startActivity(goToUserProfile);
}
});
Try it out, see if it works. If it doesn't work, it's probably because you don't have the correct visibility for your Activity in this method. If that's the case, you should use an interface, a solution which I would recommend anyway.
Let me know if you need help with this too.