Android之PowerManager&BatteryManager

　　PowerManager是Android平台中用于管理控制设备电源状态、重启、休眠状态、唤醒等，使用该API会影响到电池的待机时间，所以无非必要，一般不要使用。

　　在PowerManager中有几个比较重要的公共方法，具体如下：

　　方法goToSleep、reboot、userActivity需要用到如下权限：

<uses-permission android:name="android.permission.REBOOT"/>
<uses-permission
android:name="android.permission.DEVICE_POWER"/>

　　而这两个权限只有系统App才可使用。

　　最重要的方法还是newWakeLock，通过该方法，我们可以获取一个WakeLock对象，通过该对象我们可以控制设备电源的状态。方法的第一个参数flags用于指示获取哪种WakeLock，不同的Lock对cpu、屏幕、键盘灯有不同的影响，flag的值如下：

下面我们通过一个案例来说明WakeLock的用法，具体代码如下：

public class PowerManagerActivity extends ActionBarActivity {

    private PowerManager powerManager;
    private PowerManager.WakeLock wakeLock;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_power_manager);
        powerManager = (PowerManager)getSystemService(Context.POWER_SERVICE);
    }

    private void acquireWakeLock(){
        wakeLock = powerManager.newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK,"wakelock");
        if(wakeLock!=null)
            wakeLock.acquire();
    }

    private void releaseWakeLock(){
        if(wakeLock!=null)
            wakeLock.release();
    }

    @Override
    protected void onResume() {
        super.onResume();
        acquireWakeLock();
    }

    @Override
    protected void onPause() {
        super.onPause();
        releaseWakeLock();
    }
}

　　使用该方法需要用到如下权限：

<uses-permission android:name="android.permission.WAKE_LOCK"/>

　　代码比较简单，在获取WakeLock的时候我们使用了PowerManager.SCREEN_BRIGHT_WAKE_LOCK，该flag表明cpu保持运行，屏幕保持常亮。同时注意WakeLock的acquire方法和release方法要成对使用，在这里利用了Activity的生命周期方法。

　　还要注意的是WakeLock是Activity级别的不是针对整个Application的。

　　要想获取电池信息比如状态、健康信息、电池容量等，我们可以通过注册一个广播接收者用来接收Intent.ACTION_BATTERY_CHANGED广播即可，当电池发送变化的时候，系统就会发出该广播。Android提供了BatteryManager类，该类主要提供了一些常量，用于从广播的Intent中提取相关的数据，常量列表如下：

定义一个广播接收者，用于检测电池状态的变化，关键代码如下：

private class BattaryReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
    if(intent.getAction().equals(Intent.ACTION_BATTERY_CHANGED)){
        //电池状态
        int status = intent.getIntExtra(BatteryManager.EXTRA_STATUS,0);
        String statusString = "";
        switch (status){
            case BatteryManager.BATTERY_STATUS_FULL:
                statusString="full";
                break;
            case BatteryManager.BATTERY_STATUS_CHARGING:
                statusString="charging";
                break;
            case BatteryManager.BATTERY_STATUS_DISCHARGING:
                statusString="discharging";
                break;
            case BatteryManager.BATTERY_STATUS_UNKNOWN:
                statusString="unknown";
                break;
            case BatteryManager.BATTERY_STATUS_NOT_CHARGING:
                statusString="not charging";
                break;
        }
        //
        boolean present= intent.getBooleanExtra(BatteryManager.EXTRA_PRESENT,false);
        //integer field containing the current battery level,
        int curlevel = intent.getIntExtra(BatteryManager.EXTRA_LEVEL,0);
        // integer containing the maximum battery level
        int maxLevel = intent.getIntExtra(BatteryManager.EXTRA_SCALE,0);
        //String describing the technology of the current battery
        String technology = intent.getStringExtra(BatteryManager.EXTRA_TECHNOLOGY);
        //integer containing the current health constant
        int health = intent.getIntExtra(BatteryManager.EXTRA_HEALTH,0);
        String healthStr = "";
        switch (health){
            case BatteryManager.BATTERY_HEALTH_COLD:
                healthStr="cold";
                break;
            case BatteryManager.BATTERY_HEALTH_DEAD:
                healthStr="dead";
                break;
            case BatteryManager.BATTERY_HEALTH_GOOD:
                healthStr="good";
                break;
            case BatteryManager.BATTERY_HEALTH_OVER_VOLTAGE:
                healthStr="voer voltage";
                break;
            case BatteryManager.BATTERY_HEALTH_UNKNOWN:
                healthStr="unknown";
                break;
            case BatteryManager.BATTERY_HEALTH_UNSPECIFIED_FAILURE:
                healthStr="unspecified failure";
                break;
        }

        //integer containing the resource ID of a small status bar icon indicating the current battery state
        int smallIcon = intent.getIntExtra(BatteryManager.EXTRA_ICON_SMALL,0);
        //integer indicating whether the device is plugged in to a power source; 0 means it is on battery,
        // other constants are different types of power sources
        int plugged = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED,0);
        String pluggedStr="";
        switch (plugged){
            case BatteryManager.BATTERY_PLUGGED_AC:
                pluggedStr="AC";
                break;
            case BatteryManager.BATTERY_PLUGGED_USB:
                pluggedStr="USB";
                break;
            case BatteryManager.BATTERY_PLUGGED_WIRELESS:
                pluggedStr="wireless";
                break;
        }
        // integer containing the current battery temperature.
        int temperature= intent.getIntExtra(BatteryManager.EXTRA_TEMPERATURE,0);
        // integer containing the current battery voltage level.
        int voltage = intent.getIntExtra(BatteryManager.EXTRA_VOLTAGE,0);
        StringBuilder sb = new StringBuilder("status:");
        sb.append(statusString);
        sb.append("\n");

        sb.append("present:").append(present);
        sb.append("\n");

        sb.append("level:").append(curlevel);
        sb.append("\n");
        sb.append("maxLevel:").append(maxLevel);
        sb.append("\n");
        sb.append("technology:").append(technology);
        sb.append("\n");
        sb.append("health:").append(healthStr);
        sb.append("\n");
        sb.append("icon:").append(smallIcon);
        sb.append("\n");
        sb.append("plugged:").append(pluggedStr);
        sb.append("\n");
        sb.append("temperature:").append(temperature);
        sb.append("\n");
        sb.append("voltage:").append(voltage);
        sb.append("\n");

        Message msg= mHandler.obtainMessage(1);
        msg.obj = sb.toString();
        mHandler.sendMessage(msg);
    }
}
}

主要接收该广播需要用到权限：

<uses-permission android:name="android.permission.BATTERY_STATS"/>

　　案例运行结果如下：

作者：杰瑞教育
出处：http://www.cnblogs.com/jerehedu/ 
版权声明：本文版权归烟台杰瑞教育科技有限公司和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。

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