NullPointerException when calling onClickListener

Question

I'm making a login system, and I don't know why this happens. How can I fix this problem? Here's a part of classes regarding NullPointerException.

    final TextView registerButton = (TextView)findViewById(R.id.registerButton);
    registerButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent registerIntent=new Intent(LoginActivity.this, RegisterActivity.class);
            LoginActivity.this.startActivity(registerIntent);
        }
    });

And the following is a context from logcat.

03-22 10:37:13.066 8500-8500/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_dependencies_apk.apk@classes.dex: Permission denied
03-22 10:37:13.141 3897-3897/? E/SDAgentPackageStateReceiver: Not going to handle 'com.example.gibong.capstone'!
03-22 10:37:13.166 6707-6707/? E/Launcher.Model: onPackageAdded :com.example.gibong.capstone
03-22 10:37:13.296 8526-8526/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_slice_0_apk.apk@classes.dex: Permission denied
03-22 10:37:13.341 8533-8533/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_slice_1_apk.apk@classes.dex: Permission denied
03-22 10:37:13.391 8539-8539/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_slice_2_apk.apk@classes.dex: Permission denied
03-22 10:37:13.461 8543-8543/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_slice_3_apk.apk@classes.dex: Permission denied
03-22 10:37:13.516 8561-8561/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_slice_4_apk.apk@classes.dex: Permission denied
03-22 10:37:13.566 8567-8567/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_slice_5_apk.apk@classes.dex: Permission denied
03-22 10:37:13.616 8572-8572/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_slice_6_apk.apk@classes.dex: Permission denied
03-22 10:37:13.666 8577-8577/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_slice_7_apk.apk@classes.dex: Permission denied
03-22 10:37:13.716 8581-8581/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_slice_8_apk.apk@classes.dex: Permission denied
03-22 10:37:13.771 8587-8587/? E/dex2oat: Failed to create oat file: /data/dalvik-cache/arm/data@app@com.example.gibong.capstone-1@split_lib_slice_9_apk.apk@classes.dex: Permission denied
03-22 10:37:14.511 8474-8474/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                 Process: com.example.gibong.capstone, PID: 8474
                                                 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gibong.capstone/com.example.gibong.capstone.LoginActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
                                                     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3253)
                                                     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3349)
                                                     at android.app.ActivityThread.access$1100(ActivityThread.java:221)
                                                     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)
                                                     at android.os.Handler.dispatchMessage(Handler.java:102)
                                                     at android.os.Looper.loop(Looper.java:158)
                                                     at android.app.ActivityThread.main(ActivityThread.java:7225)
                                                     at java.lang.reflect.Method.invoke(Native Method)
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
                                                  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
                                                     at com.example.gibong.capstone.LoginActivity.onCreate(LoginActivity.java:35)
                                                     at android.app.Activity.performCreate(Activity.java:6876)
                                                     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1135)
                                                     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3206)
                                                     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3349) 
                                                     at android.app.ActivityThread.access$1100(ActivityThread.java:221) 
                                                     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794) 
                                                     at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                     at android.os.Looper.loop(Looper.java:158) 
                                                     at android.app.ActivityThread.main(ActivityThread.java:7225) 
                                                     at java.lang.reflect.Method.invoke(Native Method) 
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) 
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

Since I'm not fluent in English and this website, I apologize for my poor use of English and text style.

`TextView registerButton`... Strange that a button would be a `TextView`, no? — OneCricketeer, Mar 22 '17 at 02:15

score 2 · Accepted Answer · edited Mar 22 '17 at 05:18

2

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object

In the below line

final TextView registerButton = (TextView)findViewById(R.id.registerButton);

Are you passing the correct id? check that R.id.registerButton exists in your xml file

edited Mar 22 '17 at 05:18

Mohammed Atif

4,383
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answered Mar 22 '17 at 02:15

Shmuel

3,916
2
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I found that there wasn't view id(registerButton) on xml file. I solved this problem Thanks. – GiBong Lim Mar 22 '17 at 04:42

score 1 · Answer 2 · answered Mar 22 '17 at 03:32

1

Button alse extends TextView, so there is no problem :

final TextView registerButton = (TextView)findViewById(R.id.registerButton);

So, the problem is that your activity don't find a View (id=registerButton) in your xml, please check that.

answered Mar 22 '17 at 03:32

lomg

136
2

score 0 · Answer 3 · edited Mar 22 '17 at 03:03

Error

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.gibong.capstone.LoginActivity.onCreate(LoginActivity.java:35)

Problem is in this line

final TextView registerButton = (TextView)findViewById(R.id.registerButton);  // This is null

Make sure that you have a TextView in activity's layout that have android:id="@+id/registerButton" attribute

Or check it is a TextView or Button

score 0 · Answer 4 · answered Mar 22 '17 at 03:10

0

Make sure the layout file contains a view that id is "registerButton" which declared in onCreate() by this code setContentView(R.layout.activity_account);

answered Mar 22 '17 at 03:10

郭玉龙

61
9

RAJESH KUMAR ARUMUGAM · Answer 5 · 2017-03-22T04:28:33.780

0

NullPointerException will occur when you are trying to refer an object which is not exists.

Try these ( Assumed you have declared OnclickLisener for a TextView with android:id="@+id/registerButton" inside XML )

Define the TextView registerButton = (TextView)findViewById(R.id.registerButton); under the setContentView

edited Mar 22 '17 at 04:28

answered Mar 22 '17 at 03:47

RAJESH KUMAR ARUMUGAM

1,560
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1

you can use same id until and unless they are not under the same layout. You must see the working of findViewById to know more about it. – Mohammed Atif Mar 22 '17 at 04:13
You are Right @MohammedAtif. Thanks for your Advise :) – RAJESH KUMAR ARUMUGAM Mar 22 '17 at 04:29

score -1 · Answer 6 · edited Mar 22 '17 at 03:05

-1

You try to cast TextView object to Button object or not exists registerButton id in xml layout.

edited Mar 22 '17 at 03:05

John Joe

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answered Mar 22 '17 at 02:57

Nghia Nguyen

71
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Button and TextView conflict will give `ClassCastException` but not `NullPointerException`. – Mohammed Atif Mar 22 '17 at 04:02

NullPointerException when calling onClickListener

6 Answers6