最近在做行車記錄儀的事情，由於車載裝置上的鋰電池容量比較小，所以在停車熄火，儲存資料後需要自動關機，由於Shutdown的許可權不對普通應用開放，所以需要在原始碼下編譯程式碼。可以自己寫個BroadcastReceiver放到Setting原始碼裡，也可以是獨立應用。

manifest節點需要宣告系統級uid：

android:sharedUserId="android.uid.system"

以及關機許可權：

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

以上這兩點在Setting的AndroidManifest裡都有，所以就不用我們手動添加了。
然後我在Application裡聲明瞭兩個全域性變數，用來儲存當前的電源狀態和已經斷開電源的秒數：

    /**
     * 電源是否連線
     */
    public static boolean isPowerConnect = true;

    /**
     * 電源斷開的秒數
     */
    public static int OffSecond = 0;

接著就是PowerStateChangeReceiver：

package com.android.settings;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import
 
 android.os.Handler;
import android.os.Message;
import android.widget.Toast;

public class PowerStateChangeReceiver extends BroadcastReceiver {

    private Context context;

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

        this.context = context;
        Screenshot.OffSecond = 0
 
;
        if ("android.intent.action.ACTION_POWER_CONNECTED".equals(intent
                .getAction())) {
            Screenshot.isPowerConnect = true;
            //Toast.makeText(context, "CONNECTED", Toast.LENGTH_SHORT).show();
        } else if ("android.intent.action.ACTION_POWER_DISCONNECTED"
                .equals(intent.getAction())) {
            Screenshot.isPowerConnect = false;
            //Toast.makeText(context, "DISCONNECTED", Toast.LENGTH_SHORT).show();
            new Thread(new shutdownThread()).start();
        }
    }

    /**
     * Shutdown
     * 
     * @param context
     */
    public void shutdown(Context context) {
        try {
            Intent intent = new Intent(
                    "android.intent.action.ACTION_REQUEST_SHUTDOWN");

            intent.putExtra("android.intent.extra.KEY_CONFIRM", false);

            intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            context.startActivity(intent);
        } catch (Exception e) {
        }
        Toast.makeText(context, context.getResources().getString(R.string.shutdown_now), Toast.LENGTH_SHORT).show();
    }

    public class shutdownThread implements Runnable {

        @Override
        public void run() {
            synchronized (shutdownHandler) {
                while (!Screenshot.isPowerConnect) {
                    try {
                        Thread.sleep(1000);
                        Message message = new Message();
                        message.what = 1;
                        shutdownHandler.sendMessage(message);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

    final Handler shutdownHandler = new Handler() {
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case 1:
                if (!Screenshot.isPowerConnect) {
                    Screenshot.OffSecond++;
                } else {
                    Screenshot.OffSecond = 0;
                }
                if (Screenshot.OffSecond == 10
                        && !Screenshot.isPowerConnect) {
                    shutdown(context);
                }
                break;

            default:
                break;
            }
        }
    };

}

另外是在setting的AndroidManifest.xml對reveiver的宣告：

<receiver android:name=".PowerStateChangeReceiver" >
            <intent-filter>
                <action android:name="android.intent.action.ACTION_POWER_CONNECTED" />
                <action android:name="android.intent.action.ACTION_POWER_DISCONNECTED" />
            </intent-filter>
        </receiver>

okay，大功告成。