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secretcode

查看Phone的源代码有一个函数专门处理*#*# 开头,#*#*结尾的拨号字符串
SpecialCharSequenceMgr.Java
/**
      * Handles secret codes to launch arbitrary activities in the form of *#*#<code>#*#*.
      * If a secret code is encountered an Intent is started with the android_secret_code://<code>
      * URI.
      *
      * @param context the context to use
      * @param input the text to check for a secret code in
      * @return true if a secret code was encountered
      */
     static private boolean handleSecretCode(Context context, String input) {
         // Secret codes are in the form *#*#<code>#*#*
         int len = input.length();
         if (len > 8 && input.startsWith("*#*#") && input.endsWith("#*#*")) {
             Intent intent = new Intent(Intents.SECRET_CODE_ACTION,
                     Uri.parse("android_secret_code://" + input.substring(4, len - 4)));
             context.sendBroadcast(intent);
             return true;
         }
return false;
     }
这样根据android_secret_code就可以查到系统所用的所有隐形字符串
b090@test-desktop:~/Android_Code$ find . -name "AndroidManifest.xml" | xargs grep android_secret_code
 ./packages/providers/CalendarProvider/AndroidManifest.xml:                 <data android:scheme="android_secret_code" android:host="225" />
 ./packages/apps/Settings/AndroidManifest.xml:                 <data android:scheme="android_secret_code" android:host="4636" />
 ./packages/apps/VoiceDialer/AndroidManifest.xml:        <data android:scheme="android_secret_code" android:host="8351" />
 ./packages/apps/VoiceDialer/AndroidManifest.xml:        <data android:scheme="android_secret_code" android:host="8350" />
可以看到系统代码里面有225/4636/8351/8350隐形字符串
如果用户想要开发应用程序支持特殊的隐形字串只需要照猫画虎在AndroidManifest.xml添加Filter就可以了
例如
<receiver android:name="TestingSettingsBroadcastReceiver">
             <intent-filter>
                  <action android:name="android.provider.Telephony.SECRET_CODE" />
                  <data android:scheme="android_secret_code" android:host="4636" />
             </intent-filter>
        </receiver>