Question

I am a new beginner so please bear with me. I created a spinner and populated it with a string array, I then created a the method “OnItemSelected” and inserted a switch statement. The activity then throws a NullPointerException. When I remove the switch statement, the activity works. How can i fix this?

Code:

EditText player1 = null;
EditText player2 = null;
EditText player3 = null;
EditText player4 = null;
EditText player5 = null;
EditText player6 = null;
EditText player7 = null;
EditText player8 = null;

Spinner spinner;

int numberOfPlayers = 0;
int counter = 0;

private String[] players ={"2","3","4", "5", "6", "7", "8"};
//private String[] names ={" "};

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    try {        
    spinner = (Spinner)findViewById(R.id.spinnerplayers);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, players);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adapter);

    spinner.setOnItemSelectedListener(this);
    }catch (Exception e) {

        // handle any errors

        Log.e("TestActivity", "Error in activity", e);  // log the error

        // Also let the user know something went wrong

        Toast.makeText(getApplicationContext(), e.getClass().getName() + " " + e.getMessage(),Toast.LENGTH_LONG).show();
    }
}

@Override
public void onItemSelected(AdapterView<?> arg0, View arg1, int pos,
        long id) {
        numberOfPlayers = pos + 2;

    /*switch(pos){
    case 0:
        player1.findViewById(R.id.editTextPlayer1);
        player2.findViewById(R.id.editTextPlayer2);

        player1.setVisibility(View.VISIBLE);
        player2.setVisibility(View.VISIBLE);
        break;
    case 1:
        player1.findViewById(R.id.editTextPlayer1);
        player2.findViewById(R.id.editTextPlayer2);
        player3.findViewById(R.id.editTextPlayer3);

        player1.setVisibility(View.VISIBLE);
        player2.setVisibility(View.VISIBLE);
        player3.setVisibility(View.VISIBLE);
        break;
    case 2:
        player1.findViewById(R.id.editTextPlayer1);
        player2.findViewById(R.id.editTextPlayer2);
        player3.findViewById(R.id.editTextPlayer3);
        player4.findViewById(R.id.editTextPlayer4);

        player1.setVisibility(View.VISIBLE);
        player2.setVisibility(View.VISIBLE);
        player3.setVisibility(View.VISIBLE);
        player4.setVisibility(View.VISIBLE);
        break;
    case 3: 
        player1.findViewById(R.id.editTextPlayer1);
        player2.findViewById(R.id.editTextPlayer2);
        player3.findViewById(R.id.editTextPlayer3);
        player4.findViewById(R.id.editTextPlayer4);
        player5.findViewById(R.id.editTextPlayer5);

        player1.setVisibility(View.VISIBLE);
        player2.setVisibility(View.VISIBLE);
        player3.setVisibility(View.VISIBLE);
        player4.setVisibility(View.VISIBLE);
        player5.setVisibility(View.VISIBLE);
        break;
    case 4:
        player1.findViewById(R.id.editTextPlayer1);
        player2.findViewById(R.id.editTextPlayer2);
        player3.findViewById(R.id.editTextPlayer3);
        player4.findViewById(R.id.editTextPlayer4);
        player5.findViewById(R.id.editTextPlayer5);
        player6.findViewById(R.id.editTextPlayer6);

        player1.setVisibility(View.VISIBLE);
        player2.setVisibility(View.VISIBLE);
        player3.setVisibility(View.VISIBLE);
        player4.setVisibility(View.VISIBLE);
        player5.setVisibility(View.VISIBLE);
        player6.setVisibility(View.VISIBLE);
        break;
    case 5:
        player1.findViewById(R.id.editTextPlayer1);
        player2.findViewById(R.id.editTextPlayer2);
        player3.findViewById(R.id.editTextPlayer3);
        player4.findViewById(R.id.editTextPlayer4);
        player5.findViewById(R.id.editTextPlayer5);
        player6.findViewById(R.id.editTextPlayer6);
        player7.findViewById(R.id.editTextPlayer7);

        player1.setVisibility(View.VISIBLE);
        player2.setVisibility(View.VISIBLE);
        player3.setVisibility(View.VISIBLE);
        player4.setVisibility(View.VISIBLE);
        player5.setVisibility(View.VISIBLE);
        player6.setVisibility(View.VISIBLE);
        player7.setVisibility(View.VISIBLE);
        break;
    case 6:
        player1.findViewById(R.id.editTextPlayer1);
        player2.findViewById(R.id.editTextPlayer2);
        player3.findViewById(R.id.editTextPlayer3);
        player4.findViewById(R.id.editTextPlayer4);
        player5.findViewById(R.id.editTextPlayer5);
        player6.findViewById(R.id.editTextPlayer6);
        player7.findViewById(R.id.editTextPlayer7);
        player8.findViewById(R.id.editTextPlayer8);

        player1.setVisibility(View.VISIBLE);
        player2.setVisibility(View.VISIBLE);
        player3.setVisibility(View.VISIBLE);
        player4.setVisibility(View.VISIBLE);
        player5.setVisibility(View.VISIBLE);
        player6.setVisibility(View.VISIBLE);
        player7.setVisibility(View.VISIBLE);
        player8.setVisibility(View.VISIBLE);
        break;
    }*/

}

and then here is my logcat:

    06-06 12:44:42.433: E/AndroidRuntime(5764): FATAL EXCEPTION: main
06-06 12:44:42.433: E/AndroidRuntime(5764): java.lang.NullPointerException
06-06 12:44:42.433: E/AndroidRuntime(5764):     at com.brightdesign.truthordare.Main.onItemSelected(Main.java:69)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at android.widget.AdapterView.fireOnSelected(AdapterView.java:873)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at android.widget.AdapterView.access$300(AdapterView.java:45)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:839)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at android.os.Handler.handleCallback(Handler.java:587)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at android.os.Handler.dispatchMessage(Handler.java:92)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at android.os.Looper.loop(Looper.java:123)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at android.app.ActivityThread.main(ActivityThread.java:4627)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at java.lang.reflect.Method.invokeNative(Native Method)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at java.lang.reflect.Method.invoke(Method.java:521)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
06-06 12:44:42.433: E/AndroidRuntime(5764):     at dalvik.system.NativeStart.main(Native Method)

Thanks in advance!

Answer 1

I assume this causes the problems in your code within the onItemSelected()-method:

player1.findViewById(R.id.editTextPlayer1);
player2.findViewById(R.id.editTextPlayer2);
//...

The method findViewById() returns a sub view of another view or of the main view of the activity. In your case the references seem to be Null pointers and you also do not handle the result, which would be the only reason to use the method.

You should set these references only once in your onCreate()-method:

spinner = (Spinner)findViewById(R.id.spinnerplayers);
//...
player1 = (EditText)findViewById(R.id.editTextPlayer1);
player2 = (EditText)findViewById(R.id.editTextPlayer2);
//...

This way all your references are valid after onCreate() and you can access them securely in the onItemSelected() method (which I assume caused the NullPointerException)