Android Battery Broadcasts

Question

I am trying to make a Battery Alarm Application. I was reading the Android docs and found out that we don't need to register a BroadcastReceiver. We could do something like this-

IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
Intent batteryStatus = context.registerReceiver(null, ifilter);

MY QUESTIONS ARE-

• Does the system broadcast intent(containing battery status) every time the battery level change?
• Do I have to query each time for battery level?
• Also, How to play the alarm when the battery level reaches a particular level(set by the user).

Answer 1

Q1. Yes, system provide every time . 
Example :    
      private class BatteryBroadcastReceiver extends BroadcastReceiver {
            private final static String BATTERY_LEVEL = "level";
            @Override
            public void onReceive(Context context, Intent intent) {
                int level = intent.getIntExtra(BATTERY_LEVEL, 0);
                mBatteryLevelText.setText(getString(R.string.battery_level) + " " + level);
                mBatteryLevelProgress.setProgress(level);
            }
        }


//Register our BroadcastReceiver in application

    BatteryBroadcastReceiver mReceiver = new BatteryBroadcastReceiver();
    registerReceiver(mReceiver, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));


//Update your progress bar get 

    public class MainActivity extends Activity {
        private TextView mBatteryLevelText;
        private ProgressBar mBatteryLevelProgress;
        private BroadcastReceiver mReceiver;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            mBatteryLevelText = (TextView) findViewById(R.id.textView);
            mBatteryLevelProgress = (ProgressBar) findViewById(R.id.progressBar);
            mReceiver = new BatteryBroadcastReceiver();
        }
        @Override
        protected void onStart() {
            registerReceiver(mReceiver, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
            super.onStart();
        }
        @Override
        protected void onStop() {
            unregisterReceiver(mReceiver);
            super.onStop();
        }
        private class BatteryBroadcastReceiver extends BroadcastReceiver {
            @Override
            public void onReceive(Context context, Intent intent) {
                int level = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, 0);
                mBatteryLevelText.setText(getString(R.string.battery_level) + " " + level);
                mBatteryLevelProgress.setProgress(level);
if(level<10){
// play Battery alarm. 

            }
        }
    }

Answer 2

Create receiver for getting information.. This is better way.

public class PowerConnectionReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        int status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
        boolean isCharging = status == BatteryManager.BATTERY_STATUS_CHARGING ||
                            status == BatteryManager.BATTERY_STATUS_FULL;

        int chargePlug = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
        boolean usbCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_USB;
        boolean acCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_AC;
    }
}

In Manifest add

<receiver android:name=".PowerConnectionReceiver">
  <intent-filter>
    <action android:name="android.intent.action.ACTION_POWER_CONNECTED"/>
    <action android:name="android.intent.action.ACTION_POWER_DISCONNECTED"/>
   <action android:name="android.intent.action.BATTERY_LOW"/>
   <action android:name="android.intent.action.BATTERY_OKAY"/>
  </intent-filter>
</receiver>

For more information Visit LINK

Answer 3

First add intent filter in manifest file:

<receiver android:name=".BatteryLevelReceiver">
  <intent-filter>
    <action android:name="android.intent.action.BATTERY_LOW"/>
    <action android:name="android.intent.action.BATTERY_OKAY"/>
    <action android:name="android.intent.action.ACTION_POWER_CONNECTED"/>
    <action android:name="android.intent.action.ACTION_POWER_DISCONNECTED"/>
  </intent-filter>
</receiver>

After add new class in project:

public class PowerConnectionReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        int status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
        boolean isCharging = status == BatteryManager.BATTERY_STATUS_CHARGING ||
                            status == BatteryManager.BATTERY_STATUS_FULL;

        int chargePlug = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
        boolean usbCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_USB;
        boolean acCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_AC;
    }
}

For get battery level:

IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
Intent batteryStatus = context.registerReceiver(null, ifilter);

int level = batteryStatus.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
int scale = batteryStatus.getIntExtra(BatteryManager.EXTRA_SCALE, -1);

float batteryPct = level / (float)scale;

More info this link : developer.android

Answer 4

here is a full sample to get battery level

private float getBatteryLevel() {
    Intent batteryStatus = registerReceiver(null, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
    int batteryLevel = -1;
    int batteryScale = 1;
    if (batteryStatus != null) {
      batteryLevel = batteryStatus.getIntExtra(BatteryManager.EXTRA_LEVEL, batteryLevel);
      batteryScale = batteryStatus.getIntExtra(BatteryManager.EXTRA_SCALE, batteryScale);
    }
    return batteryLevel / (float) batteryScale * 100;
  }

answering your questions:

1- Yes, you can get additional information by getExtra and define the key,BatteryManager has a lot of keys to extract information from the intent.

2- no, you just have to register the reciever and unregister it accoording to the Activity or Fragment lifcycle, usually registering in onCreate()/onCreateView() and unregistering in onDestry()/onDestroyView().

3- you can create a bound service that has a simple notification interface. you register your reciever on it, and from the previous sample you could do something like this:

if (getBatteryLevel < 10) {
//show notification or do whatever you want.
}