android 4.2 默认把开发者选项隐藏了，打开方式如下：
打开 设置-》”关于手机“ -》对 Build number 狂点10次， 开发者模式就打开了， 开发者选项就会出现在设置项
On Jellybean, developer options are hidden by default. To unhide them, go to "About phone" and tap 10 times on "Build number". Then the "Developer options" menu will be available. Check "USB debugging" to allow installing the APKs via ADB.5000
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