默认User版本没有“开发者选项”，我们可以通过点击版本号7次来显示开发者模式，今天来看下代码中是如何处理的：

首先是

ackages/apps/Settings/src/com/android/settings/Settings.java的初始化处理：

布尔值showDev是否默认显示“开发者选项”：

 final boolean showDev = mDevelopmentPreferences.getBoolean(DevelopmentSettings.PREF_SHOW,android.os.Build.TYPE.equals("eng"));

如果想让开发者选项默认显示，不需要点击7次版本号，可直接将showDev置为true即可：

final boolean showDev = true; 

如果showDev为false，则在如下代码中隐藏“开发者选项”：

if (id == R.id.development_settings) {if (!showDev) {target.remove(i);}} 

下面看一下点击 版本号 显示开发者选项的部分：

代码路径：packages/apps/Settings/src/com/android/settings/DeviceInfoSettings.java

首先是定义点击次数：

static final int TAPS_TO_BE_A_DEVELOPER = 7;

点击版本号的处理逻辑，若mDevHitCountdown小于0，则表示”开发者选项“已经显示，参考Resume函数的处理：

if (preference.getKey().equals(KEY_BUILD_NUMBER)) {// Don't enable developer options for secondary users.if (UserHandle.myUserId() != UserHandle.USER_OWNER) return true;if (mDevHitCountdown > 0) {if (mDevHitCountdown == 1) {if (super.ensurePinRestrictedPreference(preference)) {return true;}}mDevHitCountdown--;if (mDevHitCountdown == 0) {getActivity().getSharedPreferences(DevelopmentSettings.PREF_FILE,Context.MODE_PRIVATE).edit().putBoolean(DevelopmentSettings.PREF_SHOW, true).apply();if (mDevHitToast != null) {mDevHitToast.cancel();}mDevHitToast = Toast.makeText(getActivity(), R.string.show_dev_on,Toast.LENGTH_LONG);mDevHitToast.show();} else if (mDevHitCountdown > 0&& mDevHitCountdown < (TAPS_TO_BE_A_DEVELOPER-2)) {if (mDevHitToast != null) {mDevHitToast.cancel();}mDevHitToast = Toast.makeText(getActivity(), getResources().getQuantityString(R.plurals.show_dev_countdown, mDevHitCountdown, mDevHitCountdown),Toast.LENGTH_SHORT);mDevHitToast.show();}} else if (mDevHitCountdown < 0) {if (mDevHitToast != null) {mDevHitToast.cancel();}mDevHitToast = Toast.makeText(getActivity(), R.string.show_dev_already,Toast.LENGTH_LONG); mDevHitToast.show();}} 

Resume 函数 ：

@Overridepublic void onResume() {super.onResume();PreferenceGroup parentPreference = getPreferenceScreen();mDevHitCountdown = getActivity().getSharedPreferences(DevelopmentSettings.PREF_FILE,Context.MODE_PRIVATE).getBoolean(DevelopmentSettings.PREF_SHOW,android.os.Build.TYPE.equals("eng")) ? -1 : TAPS_TO_BE_A_DEVELOPER;mDevHitToast = null;}