Get battery level and state in Android

Here is a code sample that explains how to get battery information.

To sum it up, a broadcast receiver for the ACTION_BATTERY_CHANGED intent is set up dynamically, because it can not be received through components declared in manifests, only by explicitly registering for it with Context.registerReceiver().

public class Main extends Activity {
  private TextView batteryTxt;
  private BroadcastReceiver mBatInfoReceiver = new BroadcastReceiver(){
    @Override
    public void onReceive(Context ctxt, Intent intent) {
      int level = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
      int scale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
      float batteryPct = level * 100 / (float)scale;
      batteryTxt.setText(String.valueOf(batteryPct) + "%");
    }
  };

  @Override
  public void onCreate(Bundle b) {
    super.onCreate(b);
    setContentView(R.layout.main);
    batteryTxt = (TextView) this.findViewById(R.id.batteryTxt);
    this.registerReceiver(this.mBatInfoReceiver, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
  }
}

Since SDK 21 LOLLIPOP it is possible to use the following to get current battery level as a percentage:

BatteryManager bm = (BatteryManager) context.getSystemService(BATTERY_SERVICE);
int batLevel = bm.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY);

Read BatteryManager  |  Android Developers - BATTERY_PROPERTY_CAPACITY

Based on official android docs, you can use this method in a Helper or Util class to get current battery percentage:

Java version:

public static int getBatteryPercentage(Context context) {

    if (Build.VERSION.SDK_INT >= 21) {

         BatteryManager bm = (BatteryManager) context.getSystemService(BATTERY_SERVICE);
         return bm.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY);

    } else {

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

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

         double batteryPct = level / (double) scale;

         return (int) (batteryPct * 100);
   }
}

Kotlin version:

fun getBatteryPercentage(context: Context): Int {
    return if (Build.VERSION.SDK_INT >= 21) {
        val bm = context.getSystemService(BATTERY_SERVICE) as BatteryManager
        bm.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY)
    
    } else {
        val iFilter = IntentFilter(Intent.ACTION_BATTERY_CHANGED)
        val batteryStatus: Intent = context.registerReceiver(null, iFilter)
        val level = batteryStatus?.getIntExtra(BatteryManager.EXTRA_LEVEL, -1)
        val scale = batteryStatus?.getIntExtra(BatteryManager.EXTRA_SCALE, -1)
        val batteryPct = level / scale.toDouble()
        (batteryPct * 100).toInt()
    }
}