Question

I am trying to make an android game in eclipse (in windows). I keep getting nulpointerexceptions, and classcastexceptions when i run my program both on the emulator and on my phone. I have 2 classes(activities), each with their own xml layout. the main activity runs perfectly. However when I launch the second activity with:

final Intent i = new Intent(this, Arrowscreen.class);
... 
startActivity(i);

I get the previously mentioned exceptions. It always points to the source, which is not found. Is there anyway to step through the source in eclipse in windows? I have looked at http://source.android.com, but there seems to be no solution for windows. I tried to follow the linux instructions from cygwin, but it doesn’t seem to work(and i’d prefer to work in windows if possible).

I am still new to android development, so i may be missing something important. Is there anything wrong with this manifest declaration?:

<activity android:name=".Arrowscreen" 
                android:screenOrientation="landscape"
                android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
                android:label="@string/app_name">
        <intent-filter>
                <action android:name="android.intent.action.RUN" />
                <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
</activity>

I will refrain from posting my whole code sample because it is lengthy, but i will tell you that it uses the accelerometer, gps, and a runnable for the main loop on a timer with “postDelayed”. the gps fine location permission is in the manifest also. I am stuck, so any help would be much appreciated. Thanks!

edit: the following is the part of my code where i get the runtime exception

@Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        setContentView(R.layout.arrow);

        img=(ImageView)findViewById(R.id.ArrowBackground);
        arrow1=(ImageView)findViewById(R.id.turningArrow);
        GPSx=(TextView)findViewById(R.id.textView1);
        GPSy=(TextView)findViewById(R.id.textView2);
        MGNTx=(TextView)findViewById(R.id.textView3);
        MGNTy=(TextView)findViewById(R.id.textView4);
        angle = 0;
        lastAngle = 0;
        arrowAngle = 0;
        mValues[0]=0; mValues[1]=0; mValues[2]=0; 

        //mStartTime = System.currentTimeMillis();
        mHandler.removeCallbacks(UpdateArrow);
        mHandler.postDelayed(UpdateArrow, 400);

Answer 1

Unless I’ve misunderstood your question…

In Eclipse, set a breakpoint at the first line of onCreate in your Activity, and launch the app in debug mode (Run -> Degub As -> Android Application).

Two Blog posts on doing this:
1. http://www.droidnova.com/debugging-in-android-using-eclipse,541.html
2. http://www.latenightpc.com/blog/archives/2007/11/21/starting-a-debug-session-for-android-with-adt