本文介绍如何在Android设备的无障碍设置中增加一个开关，用于通过双击特定物理按键控制闪光灯的开启与关闭，并同步更新下拉菜单中的状态。
最近有一个客户有这样的需求：
1、在【设置】--->【无障碍】中添加一个开关按钮。
如果打开开关的话，双击某个物理按键的时候，打开闪光灯，再双击该物理按键的时候，关闭闪光灯。
如果关闭开关的话，双击该物理按键的时候，不做任何处理。
2、打开关闭闪光灯的状态，在下拉菜单中也要同步。
如下图所示的效果：
当打开上面添加的开关后，如果双击POC键（POC键是我们公司自定义的一个物理按键）的时候，就打开闪光灯，并将下拉菜单中的闪光灯图标点亮，如下图所示
如果再次双击POC键（POC键是我们公司自定义的一个物理按键）的时候，就关闭闪光灯，并将下拉菜单中的闪光灯图标熄灭，如下图所示
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下面来具体说说怎么实现该功能：
第一步：添加开关按钮布局
在packages/apps/Settings/res/xml/accessibility_settings.xml 文件中添加一个开关，开关位置放在【按电源按钮结束通话】和【自动选择屏幕】中间，代码如下
<SwitchPreference
android:key="toggle_power_button_ends_call_preference"
android:title="@string/accessibility_power_button_ends_call_prerefence_title"
android:persistent="false"/>
<!-- added by ouyang start [2015-11-3] -->
<SwitchPreference
android:key="toggle_camera_button__start_flashlight_preference"
android:title="@string/accessibility_camera_button_start_flashlight_preference_title"
android:summary="@string/accessibility_camera_button_start_flashlight_preference_subtitle"
android:persistent="false"/>
<!-- added by ouyang end [2015-11-3] -->
<SwitchPreference
android:key="toggle_lock_screen_rotation_preference"
android:title="@string/accelerometer_title"
android:persistent="false"/>
在packages/apps/Settings/res/values-zh-rCN/strings.xml文件中添加相应的字符串
<!-- added by ouyang start [2015-11-3] -->
<string name="accessibility_camera_button_start_flashlight_preference_title">"双击[相机键]打开闪光灯"</string>
<string name="accessibility_camera_button_start_flashlight_preference_title_E580">"双击[POC键]打开闪光灯"</string>
<string name="accessibility_camera_button_start_flashlight_preference_subtitle">"开启此功能后，摄像机暂时无法使用"</string>
<!-- added by ouyang end [2015-11-3] -->
packages/apps/Settings/res/values/strings.xml文件中添加相应的字符串
<!-- added by ouyang start [2015-11-3] -->
<string name="accessibility_camera_button_start_flashlight_preference_title">"Camera button twice,open flash light"</string>
<string name="accessibility_camera_button_start_flashlight_preference_title_E580">"POC button twice,open flash light"</string>
<string name="accessibility_camera_button_start_flashlight_preference_subtitle">"After open this feature, the camera can not be used"</string>
<!-- added by ouyang end [2015-11-3] -->
第二步：对该开关按钮做逻辑处理，在packages/apps/Settings/src/com/android/settings/accessibility/AccessibilitySettings.java文件中
先定义一个字符串常量，该常量为添加的开关的key，定义该按钮开关常量和SharedPreences常量，用来保存该按钮打开关闭状态值
// added by ouyang start [2015-11-3]
private static final String TOGGLE_CAMER_BUTTON_START_FLASHLIGHT_PREFERENCE =
"toggle_camera_button__start_flashlight_preference";
// added by ouyang end [2015-11-3]
// added by ouyang start [2015-11-3]
private SwitchPreference mToggleCameraButtonStartFlashlightPreference;
private SharedPreferences preferences;
private SharedPreferences.Editor editor;
// added by ouyang end [2015-11-3]
通过该字符串找到定义的开关，并做些处理，如从保存好的Perference中读取开关打开关闭状态并显示，在initializeAllPreferences方法中，添加如下代码
// added by ouyang start [2015-11-3]
mToggleCameraButtonStartFlashlightPreference =
(SwitchPreference) findPreference(TOGGLE_CAMER_BUTTON_START_FLASHLIGHT_PREFERENCE);
if (android.os.SystemProperties.isHanbangVersion()) {
Log.e(TAG, "is HanbangVersion()");
mToggleCameraButtonStartFlashlightPreference.setEnabled(false);
}else{
Log.e(TAG, "is not HanbangVersion()");
mToggleCameraButtonStartFlashlightPreference.setEnabled(true);
}
Log.e(TAG, "mToggleCameraButtonStartFlashlightPreference.isEbable="+ mToggleCameraButtonStartFlashlightPreference.isEnabled());
if (android.os.SystemProperties.isDT800Project()) {
mToggleCameraButtonStartFlashlightPreference.setTitle(R.string.accessibility_camera_button_start_flashlight_preference_title);
}else if (android.os.SystemProperties.isE580Project()) {
mToggleCameraButtonStartFlashlightPreference.setTitle(R.string.accessibility_camera_button_start_flashlight_preference_title_E580);
}
preferences= getActivity().getApplicationContext().getSharedPreferences("FlashLight",
Context.MODE_MULTI_PROCESS
+Context.MODE_WORLD_READABLE
+Context.MODE_WORLD_WRITEABLE);
editor=preferences.edit();
boolean flashChecked=preferences.getBoolean("flashChecked", false);
mToggleCameraButtonStartFlashlightPreference.setChecked(flashChecked);
Log.e(TAG, "flashChecked="+flashChecked);
// added by ouyang end [2015-11-3]
这段代码主要是对该开关进行初始化，并对不同的项目进行判断，DT800项目和E580项目加载不同的字符串来描述开关。这些方法可以在/frameworks/base/core/java/android/os/SystemProperties.java文件中自己添加，代码如下：
public static boolean isDT800Project() {
return SystemProperties.get("ro.custom.build.version").contains("DT800");
}
public static boolean isE580Project() {
return SystemProperties.get("ro.custom.build.version").contains("E580");
}
public static boolean isHanbangVersion(){
return SystemProperties.get("ro.product.model").contains("Hanbang");
}
在packages/apps/Settings/src/com/android/settings/accessibility/AccessibilitySettings.java文件中的onPreferenceTreeClick方法中，要添加对该开关的点击事件处理。
代码如下，添加几行代码：
else if (mTogglePowerButtonEndsCallPreference == preference) {
handleTogglePowerButtonEndsCallPreferenceClick();
return true;
}
// added by ouyang start [2015-11-3]
else if (mToggleCameraButtonStartFlashlightPreference == preference) {
handleToggleCameraButtonStartFlashlightPreferenceClick();
return true;
}
// added by ouyang end [2015-11-3]
else if (mToggleLockScreenRotationPreference == preference) {
handleLockScreenRotationPreferenceClick();
return true;
}
其中handleToggleCameraButtonStartFlashlightPreferenceClick()方法自己自定义的，代码如下：
// added by ouyang start [2015-11-3]
private void handleToggleCameraButtonStartFlashlightPreferenceClick(){
if (mToggleCameraButtonStartFlashlightPreference.isChecked()) {
editor.putBoolean("flashChecked", true);
editor.commit();
}else{
editor.putBoolean("flashChecked", false);
editor.commit();
}
}
// added by ouyang end [2015-11-3]
该方法主要功能是保存该开关是打开状态还是关闭状态，这个状态值可以让其他的进程读取。
第三步：定义一个BroadcastReceiver，并动态注册该广播。代码文件在frameworks/base/packages/SystemUI/src/com/android/systemui/qs/tiles/FlashlightTile.java
，在该文件中添加一个BroadcastReceiver
//added by ouyang
private final BroadcastReceiver mFlashBroadcastReceiver =new BroadcastReceiver(){
boolean isDoublePress = false;
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
Log.d(TAG, "action= " + action);
Log.d(TAG, "isDoublePress= " + isDoublePress);
Log.d(TAG, "now time = " + new SimpleDateFormat("yyyy-MM-dd hh:mm:ss.SSS").format(new Date()));
if ((action == "com.runbo.camera.key.up") || (action == "com.runbo.poc.key.up")) {
Handler checkHandler = new Handler();
if (!isDoublePress) {
isDoublePress = true;
Log.i(TAG, "<----===============Single Press the Camera Key---->");
Runnable CheckDoubleRunnable = new Runnable() {
@Override
public void run() {
isDoublePress = false;
}
};
checkHandler.postDelayed(CheckDoubleRunnable, 500);
} else {
isDoublePress = false;
Log.i(TAG, "<----============Double Press the Camera Key ---->");
boolean handlerReceiver = false;
boolean flashChecked=false;
try {
Context myContext= context.createPackageContext("com.android.settings",
Context.CONTEXT_IGNORE_SECURITY);
SharedPreferences sharedPreferences = myContext.getSharedPreferences("FlashLight",
Context.MODE_WORLD_READABLE | Context.MODE_MULTI_PROCESS);
flashChecked = sharedPreferences.getBoolean("flashChecked", false);
} catch (Exception e) {
Log.d(TAG, Log.getStackTraceString(e));
}
if (action == "com.runbo.camera.key.up") {
if (android.os.SystemProperties.isDT800Project()
&& !android.os.SystemProperties.isHanbangVersion()) {
handlerReceiver = true;
}
} else if (action == "com.runbo.poc.key.up") {
if (android.os.SystemProperties.isE580Project()) {
handlerReceiver = true;
}
}
Log.d(TAG, "handlerReceiver= " + handlerReceiver);
Log.d(TAG, "flashChecked= " + flashChecked);
if (handlerReceiver && flashChecked) {
Log.i(TAG, "============mState.value="+mState.value);
if (!mState.value) {
boolean newState = !mState.value;
mFlashlightController.setFlashlight(newState);
refreshState(newState ? UserBoolean.USER_TRUE : UserBoolean.USER_FALSE);
Log.i(TAG, "============setFlashlight(true);============");
}else{
boolean newState = !mState.value;
mFlashlightController.setFlashlight(newState);
refreshState(newState ? UserBoolean.USER_TRUE : UserBoolean.USER_FALSE);
Log.i(TAG, "============setFlashlight(false);============");
}
}
}
}
}
};
在FlashlightTile的构造方法中进行注册，代码如下：
public FlashlightTile(Host host) {
super(host);
mFlashlightController = host.getFlashlightController();
mFlashlightController.addListener(this);
//added by ouyang start
IntentFilter pocFilter = new IntentFilter();
pocFilter.addAction("com.runbo.poc.key.up");
pocFilter.addAction("com.runbo.camera.key.up");
this.mContext.registerReceiver(mFlashBroadcastReceiver, pocFilter);
Log.d(TAG, "registerReceiver(mFlashBroadcastReceiver, pocFilter)");
//added by ouyang end
}
该BroadcastReceiver接收通过按POC键后释放而发送的广播“com.runbo.poc.key.up”和通过按Camera键后释放而发送的广播“com.runbo.camera.key.up”，这两个广播是自定义的广播。然后判断是单击还是双击，当双击后再通过读取SharedPreferences的值来判断定义的开关是否是打开的，如果开关是打开的再判断闪光灯是打开还是关闭，如果是打开的，双击后就关闭闪光灯。如果是关闭的，就打开闪光灯。并更新下拉菜单的图标和相应的状态。如果开关是关闭的，不进行打开关闭闪光灯的操作。
这两个广播是在frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java文件中的interceptKeyBeforeQueueing(KeyEvent event, int policyFlags)方法中额外添加的代码，发送广播出来的。
作者：欧阳鹏 欢迎转载，与人分享是进步的源泉！
转载请保留原文地址：http://blog.youkuaiyun.com/ouyang_peng
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