Question

Basically, I’m making a reversi app for Android, and I am currently at the point of setting up the game board. The way I am intending to do this is to create a 2D array of the position class. Each position is represented by an imageview that is used as a button which represents a board position. Here is a snippet of the code that contains the error:

setupBoard(board);
....
public void setupBoard(Position board[][]) {
    for (int y = 0; y < 8; y++) {
        for (int x = 0; x < 8; x++) {
            Log.d("Error","Error a");
            board[x][y] = new Position(getApplicationContext());
            Log.d("Error","Error b");
            board[x][y].isPositionEmpty = true;

        }
    }
}

In the position class:

public class Position {

Context myContext;
public Position(Context context) {
    Log.d("Error","Error c");
    myContext = context;
    // TODO Auto-generated constructor stub

}


public boolean isPositionEmpty = true;
public int positionID;


public  ImageView button = new ImageView(myContext);

}

The program gets to error a, but no further. The error in LogCat is:
java.lang.NullPointerException

Any help will be much appreciated. Thanks in advance!

Exception:
02-20 16:52:20.820: ERROR/AndroidRuntime(365): FATAL EXCEPTION: main
02-20 16:52:20.820: ERROR/AndroidRuntime(365): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{trinity.hazard.reversi/trinity.hazard.reversi.SinglePlayerActivity}: java.lang.NullPointerException
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at android.os.Handler.dispatchMessage(Handler.java:99)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at android.os.Looper.loop(Looper.java:123)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at android.app.ActivityThread.main(ActivityThread.java:4627)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at java.lang.reflect.Method.invokeNative(Native Method)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at java.lang.reflect.Method.invoke(Method.java:521)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at dalvik.system.NativeStart.main(Native Method)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): Caused by: java.lang.NullPointerException
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:100)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at trinity.hazard.reversi.SinglePlayerActivity.(SinglePlayerActivity.java:24)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at java.lang.Class.newInstanceImpl(Native Method)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at java.lang.Class.newInstance(Class.java:1429)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
02-20 16:52:20.820: ERROR/AndroidRuntime(365): … 11 more

Answer 1

In your Position class, try moving the line where you create the ImageView into the constructor, but AFTER initializing myContext.