How to get current battery percentage?

Question

I'm creating a battery monitor application, and I'm trying to display the current battery percentage. I have a broadcastreceiver, that is listening for...

<action android:name="android.intent.action.BATTERY_CHANGED" />

In the receiver I have the following code.

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

currentBatteryLevel = level / (float) scale;

Toast.makeText(context, "Current battery level: " + Float.toString(currentBatteryLevel) + "%", Toast.LENGTH_SHORT).show();

For some reason, the result is always Current battery level: 1.0%...Where am I going wrong?

Edit:

Reciever is registered in the manifest as...

<receiver android:name=".PowerMonitorReceiver">
    <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" />
        <action android:name="android.intent.action.BATTERY_CHANGED" />
    </intent-filter>
</receiver>

and my receiver is...

package com.garciaericn.t2d;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.BatteryManager;
import android.util.Log;
import android.widget.Toast;

public class PowerMonitorReceiver extends BroadcastReceiver {

    private static final String TAG = "PowerMonitorReceiver.TAG";
    private float currentBatteryLevel;

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



        // Obtain action from intent to check which broadcast is being received
        String action = intent.getAction();

        // Perform action according to type
        switch (action) {
            case (Intent.ACTION_BATTERY_CHANGED): {
                Log.i(TAG, "Battery has changed");

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

                currentBatteryLevel = (level * 100) / (float) scale;

                Toast.makeText(context, "Current battery level: " + Float.toString(currentBatteryLevel) + "%" + " level: " + level + " scale: " + scale, Toast.LENGTH_LONG).show();

                break;
            }
            case (Intent.ACTION_POWER_CONNECTED): {
                Log.i(TAG, "Power connected");

                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;

                String chargingType = null;

                if (usbCharge) {
                    chargingType = "USB";
                } else if (acCharge) {
                    chargingType = "AC Power";
                }

                if (isCharging && chargingType != null) {
                    Toast.makeText(context, "Device is charging via: " + chargingType, Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(context, "Device is charging.", Toast.LENGTH_SHORT).show();
                }
                break;
            }
            case (Intent.ACTION_POWER_DISCONNECTED): {
                Log.i(TAG, "Power disconnected");
                Toast.makeText(context, "Power Disconnected", Toast.LENGTH_SHORT).show();
                break;
            }
            case (Intent.ACTION_BATTERY_LOW): {
                Log.i(TAG, "Battery low");
                Toast.makeText(context, "Battery low", Toast.LENGTH_SHORT).show();
                break;
            }
            case (Intent.ACTION_BATTERY_OKAY): {
                Log.i(TAG, "Battery Okay");
                Toast.makeText(context, "Battery Okay", Toast.LENGTH_SHORT).show();
                break;
            }
        }
    }
}

Answer 1

boolean acCharge = false;
IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
Intent batteryStatus = registerReceiver(null, ifilter);
int status = batteryStatus.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
boolean isCharging = status == BatteryManager.BATTERY_STATUS_CHARGING ||
        status == BatteryManager.BATTERY_STATUS_FULL;

if(isCharging){
        chargePercentage = 
        batteryStatus.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
    }

The chargePercentage variable will give you the current charge percentage.

Answer 2

I think it's pretty late but the solution is quite simple. According to this link, you will not receive updates for BATTERY_CHANGED if you have registered the broadcast receiver in xml since it's a sticky broadcast.

You need to register Broadcastreceivers in your java program as below.

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 * 100) / (float)scale;

NOTE: Even though you pass "null" as the receiver you can still receive all the required battery data. You can also pass a Receiver class instead of "null" for continuous monitoring but beware this will drain your device battery as these broadcasts are thrown very often.

Answer 3

Since you are listening for multiple broadcasts, you need to determine which type of broadcast it is.

String action = intent.getAction();

if(action.equals(Intent.ACTION_BATTERY_CHANGED)){
    int level   = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, 0);
    int scale   = intent.getIntExtra(BatteryManager.EXTRA_SCALE, 100);
    int percent = (level*100)/scale;

    Toast.makeText(context, "Current battery level: " + percent + "%", Toast.LENGTH_SHORT).show();
}