一、首先创建一个定时任务

/**
     * 开启定时关机广播
     * @param context
     * @param time
     */
    public void setShutdown(Context context,long time){
        Log.e("SPGJSJActivity","SetShutdown ="+time);
        AlarmManager am = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
        Intent intent = new Intent();
        intent.setClass(context, ShutdownBroadcastReceiver.class);
        intent.putExtra("flag", "shutdown");
        intent.setAction("101");
        PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 101, intent, PendingIntent.FLAG_CANCEL_CURRENT);

        if(Build.VERSION.SDK_INT < 19){
            am.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() +time, pendingIntent);
        }else{
            am.setExact(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() +time, pendingIntent);
        }
    }

注：Alarm 的方法 set() 在SDK_INT 19以前是精确的闹钟
19以后为了节能省电（减少系统唤醒和电池使用）。
使用Alarm.set()和Alarm.setRepeating()已经不能保证精确性。
19以后需要精确的闹钟就需要用到Alarm方法setWindow()和setExact()这两个方法了

二、创建广播，定时任务指定时间开启广播执行关机动作

public class ShutdownBroadcastReceiver extends BroadcastReceiver {

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

        try {
            String flag = intent.getExtras().getString("flag");
            if(flag.equals("shutdown")){
                Log.e("shutdownBroadcast","时间到-->执行关机动作");
                shutdownSys(context);
            }
        } catch (Exception e){
            e.printStackTrace();
        }
    }

    /**
     * 关机(需要系统权限)
     * @param context
     */
    public static void shutdownSys(Context context) {
        Intent intent = new Intent();
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            intent.setAction("com.android.internal.intent.action.REQUEST_SHUTDOWN");
        } else {
            intent.setAction("android.intent.action.ACTION_REQUEST_SHUTDOWN");
        }
        // 其中false换成true,会弹出是否关机的确认窗口
        intent.putExtra("android.intent.extra.KEY_CONFIRM", false);
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(intent);
    }
}

注：8.0之前的版本，系统的manifest中的注册信息
action为：android.intent.action.ACTION_REQUEST_SHUTDOWN
8.0版本，系统的manifest中的注册信息
action为：com.android.internal.intent.action.REQUEST_SHUTDOWN

添加关机权限

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

将APP提升至系统权限

android:sharedUserId="android.uid.system"

三、休眼功能

首先申请权限

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

android 版本 9.0 需要动态在申请一次权限

/**
     * 检测是否拥有写入系统权限的权限
     */
    private void showDialog(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { //版本在23及以上
            if (!Settings.System.canWrite(this)) {
                final CommonDialog deleteDialog = new CommonDialog(mContext);
                deleteDialog.setTitle("应用需要您授权\n\"修改系统设置\"的权限");
                deleteDialog.setPositiveButton(R.string.confirm,
                        new android.content.DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int which) {
                                deleteDialog.cancel();
                                Intent intent = new Intent(Settings.ACTION_MANAGE_WRITE_SETTINGS,
                                        Uri.parse("package:" + getPackageName()));
                                startActivity(intent);
                            }
                        });
                deleteDialog.setNegativeButton(R.string.cancel,
                        new android.content.DialogInterface.OnClickListener() {

                            public void onClick(DialogInterface dialog, int which) {
                                deleteDialog.cancel();
                                finish();
                            }
                        });
                deleteDialog.setCancelable(false);  //返回键还是会关闭Dialog
                deleteDialog.setOnKeyListener(new DialogInterface.OnKeyListener() {
                    @Override
                    public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
                        if (keyCode==KeyEvent.KEYCODE_BACK && event.getRepeatCount()==0) {
                            return true;    //返回true会截断返回键的点击事件，不做其他处理
                        } else {
                            return false;
                        }
                    }
                });
                deleteDialog.show();
            }
        }
    }

调用api执行休眠的功能

 if(selectedIndex == 0){
                //永不休眠
                Settings.System.putInt(getContentResolver(),Settings.System.SCREEN_OFF_TIMEOUT,Integer.MAX_VALUE);
            }else if(selectedIndex == 1){
                Settings.System.putLong(getContentResolver(), Settings.System.SCREEN_OFF_TIMEOUT, 1*60*1000);
            }else if(selectedIndex == 2){
                Settings.System.putLong(getContentResolver(), Settings.System.SCREEN_OFF_TIMEOUT, 5*60*1000);
            }else if(selectedIndex == 3){
                Settings.System.putLong(getContentResolver(), Settings.System.SCREEN_OFF_TIMEOUT, 10*60*1000);
            }

注：时长是单位是毫秒