3. 注册BroadcastReceiver对象来监听ACTION_BATTERY_CHANGED事件。
4. 在BroadcastReceiver对象中，重写onReceive方法，在onReceive方法的传入参数intent里获取需要的电池状态信息。
5. 在生命周期结束时，取消step4中的注册。
public class BatteryMonitorActivity extends Activity {
private TextView batterLevel;
private BroadcastReceiver batteryLevelRcvr;
private IntentFilter batteryLevelFilter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
batterLevel = (TextView) findViewById(R.id.batteryLevel);
monitorBatteryState();
}
@Override
protected void onDestroy() {
super.onDestroy();
unregisterReceiver(batteryLevelRcvr);
}
private void monitorBatteryState() {
batteryLevelRcvr = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
StringBuilder sb = new StringBuilder();
int rawlevel = intent.getIntExtra("level", -1);
int scale = intent.getIntExtra("scale", -1);
int status = intent.getIntExtra("status", -1);
int health = intent.getIntExtra("health", -1);
int level = -1; // percentage, or -1 for unknown
if (rawlevel >= 0 && scale > 0) {
level = (rawlevel * 100) / scale;
}
sb.append("The phone");
if (BatteryManager.BATTERY_HEALTH_OVERHEAT == health) {
sb.append("'s battery feels very hot!");
} else {
switch (status) {
case BatteryManager.BATTERY_STATUS_UNKNOWN:
sb.append("no battery.");
break;
case BatteryManager.BATTERY_STATUS_CHARGING:
sb.append("'s battery");
if (level <= 33)
sb.append(" is charging, battery level is low" + "[" + level + "]");
else if (level <= 84)
sb.append(" is charging." + "[" + level + "]");
else
sb.append(" will be fully charged.");
break;
case BatteryManager.BATTERY_STATUS_DISCHARGING:
case BatteryManager.BATTERY_STATUS_NOT_CHARGING:
if (level == 0)
sb.append(" needs charging right away.");
else if (level > 0 && level <= 33)
sb.append(" is about ready to be recharged, battery level is low"+ "[" + level + "]");
else
sb.append("'s battery level is" + "[" + level + "]");
break;
case BatteryManager.BATTERY_STATUS_FULL:
sb.append(" is fully charged.");
break;
default:
sb.append("'s battery is indescribable!");
break;
}
}
sb.append(' ');
batterLevel.setText(sb.toString());
}
};
batteryLevelFilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
registerReceiver(batteryLevelRcvr, batteryLevelFilter);
}
}
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
android:id="@+id/batteryLevel"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center_vertical|center_horizontal"
android:textSize="50dip">
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