something should android do when screen on and screen off .

MainActivity.java

package com.simlegate.saveresource;

import android.app.Activity;

import android.os.Bundle;

public class MainActivity extends Activity {

public void onCreate(Bundle savedInstanceState) {   

super.onCreate(savedInstanceState);   

setContentView(R.layout.activity_main);
      
          
        final ScreenActionReceiver screenactionreceiver = new ScreenActionReceiver(); 
        
        registerReceiver(screenactionreceiver, screenactionreceiver.getFilter());
}   

} 

manifest.xml

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

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

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            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>
     
        <receiver android:name=".ScreenActionReceiver">  
            <intent-filter android:priority="90000">  
            <action android:name="android.intent.action.USER_PRESENT" />  
        </intent-filter> 
        </receiver>  

        
    </application>

</manifest>

ScreenActionReceiver.java

package com.simlegate.saveresource;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.util.Log;

public class ScreenActionReceiver extends BroadcastReceiver {

private String TAG = "ScreenActionReceiver";

@Override  
     public void onReceive(Context context, Intent intent) {
     

         String action = intent.getAction();  

         
        if(Intent.ACTION_SCREEN_ON.equals(action))
        {  
             Log.d(TAG, "screen is on...");  
     	   
        }
        
        else if(Intent.ACTION_SCREEN_OFF.equals(action))
        {  
             Log.d(TAG, "screen is off...");  
        }  
        
        else if(Intent.ACTION_USER_PRESENT.equals(action))
        {
     	   Log.d(TAG, "screen is unlock..."); 
        }
        
     } 
 
public IntentFilter getFilter(){  
   final IntentFilter filter = new IntentFilter();  
   filter.addAction(Intent.ACTION_SCREEN_OFF);  
   filter.addAction(Intent.ACTION_SCREEN_ON);
   return filter;
}  
 
}

screen is unlock is not working

Does this app work even in the background??

This doesn't work in kill state

Does this app work even in the background??

If you don't remove it from Recents menu it will work. If you want it to run always even if you clear it from recent then register it as a service.
PS - I'm currently not working in Android xd, just trying other techs. So, refer to someone else in case, you get error

This doesn't work in kill state

I guess, You have to register the app as a service to make it work in kill state