Question

i have made this sample process application but cant get to run it i keep getting this null pointer exception please tell me how to solve it and why am i having it

my main activity class:

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class SimpleServiceController extends Activity {

Button start1 = (Button)findViewById(R.id.start);
Button stop1 = (Button)findViewById(R.id.stop);
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    start1.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {
            // TODO Auto-generated method stub
            startService(new     Intent(SimpleServiceController.this,Service1.class));
        }
    });




    stop1.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {
            // TODO Auto-generated method stub

            stopService(new Intent(SimpleServiceController.this,Service1.class));


        }
    });



}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}
}

my service class

 import android.app.Service;
 import android.content.Intent;
import android.os.IBinder;
import android.widget.Toast;


public class Service1 extends Service {

@Override
public IBinder onBind(Intent arg0) {
    // TODO Auto-generated method stub
    return null;
}
@Override
public void onCreate() {
    super.onCreate();
    Toast.makeText(this,"Service created ...", Toast.LENGTH_LONG).show();
}

@Override
public void onDestroy() {
    super.onDestroy();
    Toast.makeText(this, "Service destroyed ...", Toast.LENGTH_LONG).show();
}


}

my maifest.xml

   <manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="dom.example.serviceapp"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="15" />

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".SimpleServiceController"
        android:label="@string/title_activity_main" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

    </activity>
    <service android:name=".Service1" ></service>

</application>

please tell me where am i wrong.

Answer 1

Initialization of Buttons should be inside onCreate() method, just after setContentView()

start1 = (Button)findViewById(R.id.start);
stop1 = (Button)findViewById(R.id.stop);

findViewById will not work unless you set the content view.