FATAL EXCEPTION: main java.lang.RuntimeException: Unable to start activity

Question

02-18 21:26:32.055: E/AndroidRuntime(1529): FATAL EXCEPTION: main
02-18 21:26:32.055: E/AndroidRuntime(1529): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.yellomecha.pianobirds/com.yellomecha.pianobirds.Main}: java.lang.NullPointerException
02-18 21:26:32.055: E/AndroidRuntime(1529):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at android.os.Looper.loop(Looper.java:137)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at android.app.ActivityThread.main(ActivityThread.java:5103)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at java.lang.reflect.Method.invokeNative(Native Method)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at java.lang.reflect.Method.invoke(Method.java:525)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at dalvik.system.NativeStart.main(Native Method)
02-18 21:26:32.055: E/AndroidRuntime(1529): Caused by: java.lang.NullPointerException
02-18 21:26:32.055: E/AndroidRuntime(1529):     at com.yellomecha.pianobirds.Wire.<init>(Wire.java:20)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at com.yellomecha.pianobirds.Game.<init>(Game.java:24)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at com.yellomecha.pianobirds.Main.onCreate(Main.java:26)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at android.app.Activity.performCreate(Activity.java:5133)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
02-18 21:26:32.055: E/AndroidRuntime(1529):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
02-18 21:26:32.055: E/AndroidRuntime(1529):     ... 11 more

start activity ComponentInfo{com.yellomecha.pianobirds/com.yellomecha.pianobirds.Main}: java.lang.NullPointerException

I get this error when running the following on Eclipse why am I getting this error, I have no idea. I looked around on this site and it seems that a lot of people get this error for an assortment of reasons.

public class Main extends Activity 
{

private static Game game;
public static Handler updateHandler = new Handler()
{
    public void handleMessage(Message msg)
    {
        game.update();
        game.invalidate();
        super.handleMessage(msg);
    }
};

/** On Create **/
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    game = new Game(this);
    //LinearLayout layout = (LinearLayout) findViewById(R.layout.activity_main);;
    //layout.setOrientation(LinearLayout.HORIZONTAL);

    setContentView(game);
    Thread mainThread = new Thread(new UpdateThread());
    mainThread.start();
}

public class UpdateThread implements Runnable
{
    @Override
    public void run()
    {
        while(true)
            Main.updateHandler.sendEmptyMessage(0);
    }

}

}

The game class

public class Game extends View
{
private Bitmap birdImage;
private Paint paint;
private Wire top,bottom;

public Game(Context context)
{
    super(context);
    birdImage = Bitmap.createBitmap(BitmapFactory.decodeResource(this.getResources(), R.drawable.toucan));
    paint = new Paint();
    paint.setStrokeWidth(5);
    paint.setColor(Color.BLACK);
    top = new Wire(getWidth(),(float)getHeight()/3, true);
    bottom = new Wire(getWidth(), (float)getHeight()*2/3, false);

}

//called every frame
protected void onDraw(Canvas canvas)
{
    canvas.drawBitmap(birdImage, getWidth(), getHeight(), paint);
    top.draw(canvas, paint);
    bottom.draw(canvas, paint);
}

public void update()
{

}

}

and the manifest file

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.yellomecha.pianobirds"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="19" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.yellomecha.pianobirds.Main"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Please post the full LogCat trace, it will help us to discover the error — user2340612
– user2340612, Commented Feb 18, 2014 at 21:56

Karim Varela · Accepted Answer · 2014-02-18 22:24:03Z

2

Your NullPointerException is on line 20 of Wire.java. Make sure every object on that line is initialized before you access it.

answered Feb 18, 2014 at 22:24

Karim Varela

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Comments

Omid Omidi · Accepted Answer · 2014-02-21 12:38:53Z

-1

Place line by line

log.i(TAG,"OK1");
... code line
log.i(TAG,"OK2");
... code line
log.i(TAG,"OK3");
.
.
.

to find which line of code has NULL error.

edited Feb 21, 2014 at 12:38

answered Feb 18, 2014 at 21:54

Omid Omidi

1,6703 gold badges16 silver badges23 bronze badges

3 Comments

user2340612 Over a year ago

This is not the right way to do debugging. You can simply look at the full LogCat trace to discover the line causing the NPE..

Omid Omidi Over a year ago

I'm use this method and it's easy way

Jacksonkr Over a year ago

@OmidOmidi Your method was a great way to debug before code stepping debuggers were introduced. I used to solely troubleshoot code doing line-by-line checks like yours because it was difficult to learn debuggers but once I learned them then debugging was WAY more efficient. I suggest googling how to use the eclipse debugger (or whatever java app you're using) and learn it from top to bottom.

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