Problems with NullPointer

Question

I need to go to the second activity, but when I click the button, it will write to me:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.application/com.example.application.Firebase}: java.lang.NullPointerException at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2367) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2418) at android.app.ActivityThread.access$800(ActivityThread.java:152) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1343) at android.os.Handler.dispatchMessage(Handler.java:110) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:5341) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:515) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:829) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:645) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.NullPointerException a at android.app.Activity.performCreate(Activity.java:5350) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1088)

This is Firebase activity:

public class Firebase extends AppCompatActivity {


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

        mlistView = (ListView) findViewById(R.id.listView);

        DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReferenceFromUrl("https://example.firebase/Users");

        FirebaseListAdapter<String> firebaseListAdapter = new FirebaseListAdapter<String>(
                this,
                String.class,
                android.R.layout.simple_list_item_1,
                databaseReference
        ) {
            @Override
            protected void populateView(View v, String model, int position) {

                TextView textView = (TextView) v.findViewById(android.R.id.text1);
                textView.setText(model);




            }
        };
        mlistView.setAdapter(firebaseListAdapter);
    }
}

This is the first activity:

public class DashBoard extends AppCompatActivity implements View.OnClickListener {

    private TextView txtWelcome;
    private EditText input_new_password;
    private Button btnChangePass,btnLogout;
    private RelativeLayout activity_dashboard;

    private FirebaseAuth auth;

    private Button mbtnIntent;

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

        //View
        txtWelcome = (TextView)findViewById(R.id.dashboard_welcome);
        input_new_password = (EditText)findViewById(R.id.dashboard_new_password);
        btnChangePass = (Button)findViewById(R.id.dashboard_btn_change_pass);
        btnLogout = (Button)findViewById(R.id.dashboard_btn_logout);
        activity_dashboard = (RelativeLayout)findViewById(R.id.activity_dash_board);

        mbtnIntent = (Button) findViewById(R.id.btnIntent);

        btnChangePass.setOnClickListener(this);
        btnLogout.setOnClickListener(this);

        //Init Firebase
        auth = FirebaseAuth.getInstance();

        //Session check
        if(auth.getCurrentUser() != null)
            txtWelcome.setText("Welcome , "+auth.getCurrentUser().getEmail());

        mbtnIntent.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(DashBoard.this), Firebase.class);
                startActivity(intent);
            }
        });




    }

    @Override
    public void onClick(View view) {
        if(view.getId() == R.id.dashboard_btn_change_pass)
            changePassword(input_new_password.getText().toString());
        else if(view.getId() == R.id.dashboard_btn_logout)
            logoutUser();
    }

    private void logoutUser() {
        auth.signOut();
        if(auth.getCurrentUser() == null)
        {
            startActivity(new Intent(DashBoard.this,MainActivity.class));
            finish();
        }
    }

    private void changePassword(String newPassword) {
        FirebaseUser user = auth.getCurrentUser();
        user.updatePassword(newPassword).addOnCompleteListener(this, new OnCompleteListener<Void>() {
            @Override
            public void onComplete(@NonNull Task<Void> task) {
                if(task.isSuccessful())
                {
                    Snackbar snackBar = Snackbar.make(activity_dashboard,"Password changed",Snackbar.LENGTH_SHORT);
                    snackBar.show();
                }
            }
        });
    }
}

This is manifest.xml :`

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name=".DashBoard" />
    <activity android:name=".ForgotPassword" />
    <activity android:name= ".Firebase"/>
    <activity android:name=".SignUp"></activity>
</application>

`

What should I write?

score 0 · Answer 1 · answered Jan 20 '18 at 18:58

0

Change your code to this :

Intent intent = new Intent(DashBoard.this,Firebase.class);
startActivity(intent);

And Check if you delcared the second activity in Android Manifest.Xml like this:

<activity android:name=“.Firebase” />

answered Jan 20 '18 at 18:58

TREAF ALSHEMERI

399
5
11

In manifest, I have But always same problem. – Mr.novak Jan 20 '18 at 19:08
Did you try : Intent intent = new Intent ( DashBoard.this , Firebase.class ); startActivity(intent); ?? – TREAF ALSHEMERI Jan 20 '18 at 19:19
Yes, look up (mbtnIntent setOnclickListener) – Mr.novak Jan 20 '18 at 19:29
Yes I saw it but you typed “)” after `DashBoard.this`. Try to delete “)”. – TREAF ALSHEMERI Jan 20 '18 at 19:32
I don't know, what You mean – Mr.novak Jan 20 '18 at 19:36
That’s your code: Intent intent = new Intent (DashBoard.this”)”,Firebase.class); startActivity(intent); . Just delete that “)” then try your app. There is a bracket after “DashBoard.this” delete it – TREAF ALSHEMERI Jan 20 '18 at 19:40
I delete bracket, but problem is still have – Mr.novak Jan 20 '18 at 19:57

score 0 · Answer 2 · answered Jan 20 '18 at 19:04

0

Seems like the one or both of the ids listView or text1 are not inside the layout activity_main.xml in your Firebase class. Make sure they are there and that there is no typo.

answered Jan 20 '18 at 19:04

Pulak

738
8
16

My activity_main.xml: – Mr.novak Jan 20 '18 at 19:11
@Mr.novak Where have you declared `mlistView`? – Pulak Jan 21 '18 at 05:42

Problems with NullPointer

2 Answers2