android设置系统锁屏时间或屏保显示时间

   public static final String SCREEN_OFF_TIMEOUT = "screen_off_timeout";
   private final int SCREEN_TIMEOUT_VALUE_NONE = Integer.MAX_VALUE;//永不休眠
   private DreamBackend mBackend;//屏保管理类

   @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_screen_saver);
		mBackend = DreamBackend.getInstance(ScreenSaverActivity.this);
    }  
     
    /**
     * 三十分钟无操作后屏幕进入休眠
     *
     * @param isChecked
     */
    private void setScreenSaverEnable(boolean isChecked) {
        mBackend.setEnabled(isChecked);//设置开关的状态
        if (isChecked) {
            Settings.System.putInt(getContentResolver(), SCREEN_OFF_TIMEOUT, 1000 * 60 * 30);
        } else {
            Settings.System.putInt(getContentResolver(), SCREEN_OFF_TIMEOUT, SCREEN_TIMEOUT_VALUE_NONE);
        }
    }