CODEWITHSUNDEEP
android
user2330482
user2330482

Reputation: 1103

java.lang.NullPointerException at android.content.ContextWrapper.getPackageName ANDROID

Hey I want to start an Activity from my MainActivity but not in the oncreate method.

public void awe()
{
    Intent myIntent = new Intent(MainActivity.this, Awesome.class);
    MainActivity.this.startActivity(myIntent);
}

Another class calls the method awe() and what I get is a crash and

05-25 04:06:51.034: E/AndroidRuntime(7161): FATAL EXCEPTION: main
05-25 04:06:51.034: E/AndroidRuntime(7161): java.lang.NullPointerException
05-25 04:06:51.034: E/AndroidRuntime(7161):     at android.content.ContextWrapper.getPackageName(ContextWrapper.java:151)
05-25 04:06:51.034: E/AndroidRuntime(7161):     at android.content.ComponentName.<init>(ComponentName.java:106)
05-25 04:06:51.034: E/AndroidRuntime(7161):     at android.content.Intent.<init>(Intent.java:2895)
05-25 04:06:51.034: E/AndroidRuntime(7161):     at package name.MainActivity.awe(MainActivity.java:215)

Someone knows what I can do?

MainActivity

public class MainActivity extends Activity implements OnClickListener { 
// (variable stuff)
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

          buttonE = (Button) findViewById(R.id.buttonEASY); 
          buttonM = (Button) findViewById(R.id.buttonMED);

// here I do all that button stuff for the layout
}



    public void onClick(View arg0) {
        System.out.println("click");
        if (arg0==buttonE)  {

                 int checkedRadioButton = radioGroup1.getCheckedRadioButtonId();
                                 String radioButtonSelected = "";

                                 switch (checkedRadioButton) {

                                  case R.id.radio0 : radioButtonSelected = "radiobutton1";
                                  Toast.makeText(getApplicationContext(), "Easy, 10 selected", Toast.LENGTH_SHORT).show();
                                  setContentView(R.layout.raten);

// Button stuff, again.


}



public void awe()
{   Intent tutorial = new Intent(MainActivity.this, Awesome.class); 
    if (tutorial != null) { startActivity(tutorial); } 

}

Easy.java

Nothing important here, the place where I refer to awe():

if (s==max+1){System.out.println("AWESOME!"); MainActivity mA = new MainActivity(); mA.awe();}

Awesome.java

public class Awesome extends Activity {

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

I hope I now posted everything that is important

Upvotes: 4

Views: 10654

Answers (4)

David Guo
David Guo

Reputation: 1759

The problem probably is that MainActivity is null. in my case, the activity destroyed when run abvoe code. so the internal Context of the Activity is null.

Upvotes: 0

Sam003
Sam003

Reputation: 550

I got the same error, which took me a while to figure it out. Like @csgero mentioned, my problem was that the activity I tried to start was not initialized. It means errors happen before onCreate is called. And it turned out that there was a error in the codes part where I defined the variables in the to-be-called activity. Good luck!

Upvotes: 0

Jared Burrows
Jared Burrows

Reputation: 55517

Things to consider with Android Activities:

Do you have your classes that extend Activity defined in the AndroidManifest.xml?

Are you aware of your Context when using Intents?

For calling intents, always check for null, if you are calling via packagename:

Intent mTutorial = new Intent(MainActivity.this, TutorialActivity.class); 

this.startActivity(mTutorial);

Your problem was simply trying to call your "awe()" method was in another Activity that did not have the correct Context for your MainActivity: http://developer.android.com/reference/android/content/Intent.html.

Android Intent requires a "Context" and a "Class".

Update: Here is another post that will help:

Launch an application from another application on Android

Regards,

Upvotes: 3

csgero
csgero

Reputation: 2773

The problem probably is that MainActivity has not been fully initialized yet when you are calling the awe() method, and the internal Context of the Activity is null.

Upvotes: 5

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