UiModeManager 最简单切换模式的途径

这是源码，通俗易懂，就贴出来了。

package android.app;


import android.content.Context;
import android.content.res.Configuration;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.util.Log;


/**
 * 这个类提供系统UI模式服务的途径.  这个服务允许应用控制设备的UI模式.
 * 提供设置行车模式和夜间模式的功能.
 * 
 * 
这个功能是构建在广播的基础上：当用户把设备放进一个地方或从中取出
 * {@link android.content.Intent#ACTION_DOCK_EVENT} .  这个时候,
 * the UiModeManager 会切换系统 {@link android.content.res.Configuration}
 * 进入设置 UI 模式, 发送进入此模式的广播, 并且开始在适应此时的模式.  
 * 参看广播 {@link #ACTION_ENTER_CAR_MODE} 和
 * {@link #ACTION_ENTER_DESK_MODE} 获取更多信息.
 * 
 * 
另外, 用户也可以手动切换模式.  While in car mode -- whether by manual action
 * from the user or being physically placed in a dock -- a notification is
 * displayed allowing the user to exit dock mode.  Thus the dock mode
 * represented here may be different than the current state of the underlying
 * dock event broadcast.
 *
 * 
不可以直接实例化这个类; 通过
 * {@link android.content.Context#getSystemService
 * Context.getSystemService(Context.UI_MODE_SERVICE)}获取这个服务.
 */
public class UiModeManager {
    private static final String TAG = "UiModeManager";


    /**
     * 当设备UI进入行车模式，发送广播, either
     * by being placed in a car dock or explicit action of the user.  After
     * sending the broadcast, the system will start the intent
     * {@link android.content.Intent#ACTION_MAIN} with category
     * {@link android.content.Intent#CATEGORY_CAR_DOCK}
     * to display the car UI, which typically what an application would
     * implement to provide their own interface.  However, applications can
     * also monitor this Intent in order to be informed of mode changes or
     * prevent the normal car UI from being displayed by setting the result
     * of the broadcast to {@link Activity#RESULT_CANCELED}.
     */
    public static String ACTION_ENTER_CAR_MODE = "android.app.action.ENTER_CAR_MODE";

    /**
     * 当设备UI离开行车模式回到正常模式，发送广播.  Typically used by a car mode app, to dismiss itself
     * when the user exits car mode.
     */
    public static String ACTION_EXIT_CAR_MODE = "android.app.action.EXIT_CAR_MODE";

    /**
     * Broadcast sent when the device's UI has switched to 夜间模式,
     * by being placed in a desk dock.  After
     * sending the broadcast, the system will start the intent
     * {@link android.content.Intent#ACTION_MAIN} with category
     * {@link android.content.Intent#CATEGORY_DESK_DOCK}
     * to display the desk UI, which typically what an application would
     * implement to provide their own interface.  However, applications can
     * also monitor this Intent in order to be informed of mode changes or
     * prevent the normal desk UI from being displayed by setting the result
     * of the broadcast to {@link Activity#RESULT_CANCELED}.
     */
    public static String ACTION_ENTER_DESK_MODE = "android.app.action.ENTER_DESK_MODE";

    /**
     * Broadcast sent when the device's UI has switched 离开夜间模式回到正常模式.  Typically used by a desk mode app, to dismiss itself
     * when the user exits desk mode.
     */
    public static String ACTION_EXIT_DESK_MODE = "android.app.action.EXIT_DESK_MODE";

    /** Constant for {@link #setNightMode(int)} and {@link #getNightMode()}:
     * automatically switch night mode on and off based on the time.
     */
    public static final int MODE_NIGHT_AUTO = Configuration.UI_MODE_NIGHT_UNDEFINED >> 4;

    /** Constant for {@link #setNightMode(int)} and {@link #getNightMode()}:
     * never run in night mode.
     */
    public static final int MODE_NIGHT_NO = Configuration.UI_MODE_NIGHT_NO >> 4;

    /** Constant for {@link #setNightMode(int)} and {@link #getNightMode()}:
     * always run in night mode.
     */
    public static final int MODE_NIGHT_YES = Configuration.UI_MODE_NIGHT_YES >> 4;


    private IUiModeManager mService;


    /*package*/ UiModeManager() {
        mService = IUiModeManager.Stub.asInterface(
                ServiceManager.getService(Context.UI_MODE_SERVICE));
    }


    /**
     * Flag for use with {@link #enableCarMode(int)}: go to the car
     * home activity as part of the enable.  Enabling this way ensures
     * a clean transition between the current activity (in non-car-mode) and
     * the car home activity that will serve as home while in car mode.  This
     * will switch to the car home activity even if we are already in car mode.
     */
    public static final int ENABLE_CAR_MODE_GO_CAR_HOME = 0x0001;


    /**
     * Flag for use with {@link #enableCarMode(int)}: allow sleep mode while in car mode.
     * By default, when this flag is not set, the system may hold a full wake lock to keep the
     * screen turned on and prevent the system from entering sleep mode while in car mode.
     * Setting this flag disables such behavior and the system may enter sleep mode
     * if there is no other user activity and no other wake lock held.
     * Setting this flag can be relevant for a car dock application that does not require the
     * screen kept on.
     */
    public static final int ENABLE_CAR_MODE_ALLOW_SLEEP = 0x0002;


    /**
     * 使设备进入行车模式, like it had been placed in the car dock.
     * This will cause the device to switch to the car home UI as part of
     * the mode switch.
     * @param flags 必须为 0.
     */
    public void enableCarMode(int flags) {
        if (mService != null) {
            try {
                mService.enableCarMode(flags);
            } catch (RemoteException e) {
                Log.e(TAG, "disableCarMode: RemoteException", e);
            }
        }
    }


    /**
     * Flag for use with {@link #disableCarMode(int)}: go to the normal
     * home activity as part of the disable.  Disabling this way ensures
     * a clean transition between the current activity (in car mode) and
     * the original home activity (which was typically last running without
     * being in car mode).
     */
    public static final int DISABLE_CAR_MODE_GO_HOME = 0x0001;

    /**
     * 如果当前在行车模式，关闭这个模式.参数可以为0：退出此模式；DISABLE_CAR_MODE_GO_HOME：退出此模式并返回桌面
     * @param flags May be 0 or {@link #DISABLE_CAR_MODE_GO_HOME}.
     */
    public void disableCarMode(int flags) {
        if (mService != null) {
            try {
                mService.disableCarMode(flags);
            } catch (RemoteException e) {
                Log.e(TAG, "disableCarMode: RemoteException", e);
            }
        }
    }


    /**
     * 返回当前运行的模式.  可以为：
     * {@link Configuration#UI_MODE_TYPE_NORMAL Configuration.UI_MODE_TYPE_NORMAL},
     * {@link Configuration#UI_MODE_TYPE_DESK Configuration.UI_MODE_TYPE_DESK},
     * {@link Configuration#UI_MODE_TYPE_CAR Configuration.UI_MODE_TYPE_CAR},
     * {@link Configuration#UI_MODE_TYPE_TELEVISION Configuration.UI_MODE_TYPE_TELEVISION},
     * {@link Configuration#UI_MODE_TYPE_APPLIANCE Configuration.UI_MODE_TYPE_APPLIANCE}, or
     * {@link Configuration#UI_MODE_TYPE_WATCH Configuration.UI_MODE_TYPE_WATCH}.
     */
    public int getCurrentModeType() {
        if (mService != null) {
            try {
                return mService.getCurrentModeType();
            } catch (RemoteException e) {
                Log.e(TAG, "getCurrentModeType: RemoteException", e);
            }
        }
        return Configuration.UI_MODE_TYPE_NORMAL;
    }


    /**设置夜间模式。在API22及以下当在设备上同时也设置了行车模式或桌面模式，夜间模式才会生效。在API23及以上则没有这个限制
     *
     * 
模式可以为:
     * 

     *   
{@link #MODE_NIGHT_NO} - 日间模式
     *       mode.

     *   
{@link #MODE_NIGHT_YES} - 夜间模式.
     *   
     *   
{@link #MODE_NIGHT_AUTO} - 自动切换，根据设备位置及相关传感器.
     * 

     */
    public void setNightMode(int mode) {
        if (mService != null) {
            try {
                mService.setNightMode(mode);
            } catch (RemoteException e) {
                Log.e(TAG, "setNightMode: RemoteException", e);
            }
        }
    }


    /**
     * @return 返回当前配置的夜间模式. May be one of
     *         {@link #MODE_NIGHT_NO}, {@link #MODE_NIGHT_YES},
     *         {@link #MODE_NIGHT_AUTO}, or -1 on error.
     */
    public int getNightMode() {
        if (mService != null) {
            try {
                return mService.getNightMode();
            } catch (RemoteException e) {
                Log.e(TAG, "getNightMode: RemoteException", e);
            }
        }
        return -1;
    }
}

除了在代码中进行相关配置外，在xml文件进行布局时，同时可以进行相关模式的布局，即在相同布局名后面加个后缀就可以了，这样就指定了相关模式的UI配置。这是最简单的切换模式的一种实现途径。

相关后缀参考API指南提供资源部分。