Question

when testing my application in the emulator(I’m using Eclipse) it shows me “The application Counter(com.ian.counter) has stopped unexpectedly. Please try again.” when running it. I’ve searched and searched for an answer but I’ve found none. Anyone know the problem?

Code:

package com.ian.counter;

import android.app.Activity;
import android.widget.TextView;
import android.os.Bundle;
import android.widget.Toast;

public class CounterActivity extends Activity {
    /** Called when the activity is first created. */
    TextView textView1 = (TextView) this.findViewById(R.id.textView1);
    int count = 0;
    @Override  
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }

    public void Count(){
        count ++;
        textView1.setText(Integer.toString(count));
    }
}

Logcat:

12-28 16:59:20.615: D/AndroidRuntime(353): Shutting down VM
12-28 16:59:20.686: W/dalvikvm(353): threadid=1: thread exiting with uncaught exception (group=0x40015560)
12-28 16:59:20.756: E/AndroidRuntime(353): FATAL EXCEPTION: main
12-28 16:59:20.756: E/AndroidRuntime(353): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.ian.counter/com.ian.counter.CounterActivity}: java.lang.NullPointerException
12-28 16:59:20.756: E/AndroidRuntime(353):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569)
12-28 16:59:20.756: E/AndroidRuntime(353):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
12-28 16:59:20.756: E/AndroidRuntime(353):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
12-28 16:59:20.756: E/AndroidRuntime(353):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
12-28 16:59:20.756: E/AndroidRuntime(353):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-28 16:59:20.756: E/AndroidRuntime(353):  at android.os.Looper.loop(Looper.java:123)
12-28 16:59:20.756: E/AndroidRuntime(353):  at android.app.ActivityThread.main(ActivityThread.java:3683)
12-28 16:59:20.756: E/AndroidRuntime(353):  at java.lang.reflect.Method.invokeNative(Native Method)
12-28 16:59:20.756: E/AndroidRuntime(353):  at java.lang.reflect.Method.invoke(Method.java:507)
12-28 16:59:20.756: E/AndroidRuntime(353):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-28 16:59:20.756: E/AndroidRuntime(353):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-28 16:59:20.756: E/AndroidRuntime(353):  at dalvik.system.NativeStart.main(Native Method)
12-28 16:59:20.756: E/AndroidRuntime(353): Caused by: java.lang.NullPointerException
12-28 16:59:20.756: E/AndroidRuntime(353):  at android.app.Activity.findViewById(Activity.java:1647)
12-28 16:59:20.756: E/AndroidRuntime(353):  at com.ian.counter.CounterActivity.<init>(CounterActivity.java:10)
12-28 16:59:20.756: E/AndroidRuntime(353):  at java.lang.Class.newInstanceImpl(Native Method)
12-28 16:59:20.756: E/AndroidRuntime(353):  at java.lang.Class.newInstance(Class.java:1409)
12-28 16:59:20.756: E/AndroidRuntime(353):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
12-28 16:59:20.756: E/AndroidRuntime(353):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561)

Any help is appreciated.

Answer 1

You’re trying to set the textView1 variable before the layout has been set. You need to define it as a variable and then assign it in onCreate() after you’ve called setContentView(). Like this:

package com.ian.counter;

import android.app.Activity;
import android.widget.TextView;
import android.os.Bundle;
import android.widget.Toast;

public class CounterActivity extends Activity {
    /** Called when the activity is first created. */
    TextView textView1;
    int count = 0;
    @Override  
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        textView1 = (TextView) this.findViewById(R.id.textView1);
    }

    public void Count(){
        count ++;
        textView1.setText(Integer.toString(count));
    }
}

Just copy and paste the above, that’ll work just fine.