Battert Manager会通过一个Intent广播所有电池和充电详情，包含充电状态。Android开发者可以利用BroadcastReceiver机制获取电池电量的变化，通过监听电池电量的变化包含以下几个步骤：
- 创建一个监听ACTION_BATTERY_CHAGRED事件的 intentFilter
- 创建一个BroadcastReceiver对象，该对象可以接收broadcase intent
- 注册BroadcastReceiver对象来监听ACTION_BATTERY_CHANGED事件
- 在BroadcastReceiver对象中，重写onReceive方法，在onReceive方法的传入参数intent中获取电池的状态
- 切记的是在生命周期结束时，及时取消BroadcastReceiver的注册，否则出现内存泄漏
通常有两种思路，第一种就是自定义一个BroadcastReceiver继承自BroadcastReceiver，并且重写onReceive()方法，在onReceive()方法中根据方法传入的Intent来判断电池的状态，这种方法需要主要的是需要在Manifest文件中注册广播接收器，添加过滤条件；还有一种方法是直接在Activity中定义一个BroadcastReceiver对象并重写onReceive()方法，并且需要定义IntentFilter，同时需要调用registerReceiver方法来将BroadcastReceiver和IntentFilter进行绑定。
这里就第二种方法给出一个例子，代码如下：
package com.glemontree.batterymonitor;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.BatteryManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private TextView batteryLevel;
private BroadcastReceiver batteryLevelReceiver;
private IntentFilter batteryLevelFilter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
batteryLevel = (TextView) findViewById(R.id.batteryLevel);
monitorBatteryState();
}
@Override
protected void onDestroy() {
super.onDestroy();
unregisterReceiver(batteryLevelReceiver);
}
private void monitorBatteryState() {
batteryLevelReceiver = new BroadcastReceiver() {
@Override
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;
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("");
batteryLevel.setText(sb.toString());
}
};
batteryLevelFilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
registerReceiver(batteryLevelReceiver, batteryLevelFilter);
}
}上面这段代码中，首先在onCreate()方法中定义了一个BroadcastReceiver，并且重写了其onReceive方法，在onReceive()方法中根据传入的Intent，获得电池的一些信息：
int rawLevel = intent.getIntExtra("level", -1);
int scale = intent.getIntExtra("scale", -1);
int status = intent.getIntExtra("status", -1);
int health = intent.getIntExtra("health", -1);其中，level表示电池的当前剩余电量，scale表示电池的最大值，status表示电池的状态，health则表示电池的健康状态。
在方法的最后定义了IntentFilter用来定义消息过滤，这里过滤的是Intent.ACTION_BATTERY_CHANGED，表示BroadcastReceiver监听电池电量的变化，最后通过registerReceiver方法将BroadcastReceiver和IntentFilter进行绑定。
需要注意的是一定在Activity的onDestroy()方法中调用unRegisterReceiver()方法来取消注册Receiver，当然本例子是在onCreate()方法中调用registerReceiver()来绑定BroadcastReceiver和IntentFilter，你也可以在onResume()方法中进行绑定，甚至于在View中在onAttatchedWindow()方法中进行绑定！
本文主要对Android中电池电量的监听进行了简短的介绍，更加详细的介绍可以上网查询，这里仅仅了做个笔记，以便后面查询回忆！
本文转自博客
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