跳转到设置子项，并显示返回按钮

Platform: RK3368

OS: Android 6.0

Kernel: 3.10.0

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有时候应用需要跳转到系统设置界面，需要让设置的ActionBar上显示返回按键，则Intent需要额外添加EXTRA_SHOW_FRAGMENT_AS_SUBSETTING。

public static final String EXTRA_SHOW_FRAGMENT_AS_SUBSETTING =
            ":settings:show_fragment_as_subsetting";
        private void startActivityAsSubSetting(String pkg, String cls) {
            Intent intent = new Intent();
            intent.setComponent(new ComponentName(pkg, cls));
            intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
            intent.putExtra(EXTRA_SHOW_FRAGMENT_AS_SUBSETTING, true);
            try {
                startActivity(intent);
            } catch (ActivityNotFoundException ex) {
                ex.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

例如：跳转到蓝牙设置

startActivityAsSubSetting("com.android.settings",
                        "com.android.settings.Settings$BluetoothSettingsActivity");