【AOSP】Settings应用界面逻辑

源码参考： AOSPXRef

现象效果

调试UI显示：Settings应用子界面Activity绝大部分都是SubSetting（通过dumpsys指令查看当前活动）；

adb shell dumpsys activity activities | grep -i mCurrent
com.android.settings/com.android.settings.SubSettings

代码实现：

（1）Java类文件

• Settings与SubSettings中基本是空Activity，即Activity没有重写任意7大生命周期方法 （/*empty*/）  
• Settings类和各子xxxSettingsActivity都继承自SettingsActivity类
• Settings类中定义各子静态xxxSettingsActivity类
  • 静态内部类在AndroidManifest.xml文件中通过<meta-data>将相应的Fragment绑定起来。

package com.android.settings;
/**
* Top-level Settings activity
*/
public class Settings extends SettingsActivity {
    /*
    * Settings subclasses for launching independently.
    */
    public static class ApnSettingsActivity extends SettingsActivity { /* empty */ }
}

（2）布局文件

• 主界面：settings_main_dashboard.xml （仅android 10 以前存在，link : android-9.0.0_r61，DashboardSummary.java）
• 子界面：settings_main_prefs.xml（尚存,link : android-12.0.0_r3）

（3）代码实现

1. 父类 SettingsActivity的onCreate()方法确定加载的SubSettingsActivity 布局
   1. setContentView(R.layout.settings_main_prefs)
2. 初次启动对应的Fragment
   1. launchSettingFragment(initialFragmentName, intent);

public class SettingsActivity extends SettingsBaseActivity
        implements IMainSwitchBar, PreferenceManager.OnPreferenceTreeClickListener,
        PreferenceFragmentCompat.OnPreferenceStartFragmentCallback,
        ButtonBarHandler, FragmentManager.OnBackStackChangedListener { 
    @Override
    protected void onCreate(Bundle savedState) { 
        super.onCreate(savedState);
        //...omit some codes
        final FeatureFactory factory = FeatureFactory.getFactory(this);
        mDashboardFeatureProvider = factory.getDashboardFeatureProvider(this);
        //通过判断当前是Settings还是SubSettings来确定用什么布局来显示
        // This is a "Sub Settings" when:
        // - this is a real SubSettings
        // - or :settings:show_fragment_as_subsetting is passed to the Intent
        final boolean isSubSettings = this instanceof SubSettings ||
                intent.getBooleanExtra(EXTRA_SHOW_FRAGMENT_AS_SUBSETTING, false);
        
        // If this is a sub settings, then apply the SubSettings Theme for the ActionBar content
        // insets.
        // If this is in setup flow, don't apply theme. Because light theme needs to be applied
        // in SettingsBaseActivity#onCreate().
        if (isSubSettings && !WizardManagerHelper.isAnySetupWizard(getIntent())) {
           setTheme(R.style.Theme_SubSettings);
        }
        //设置布局界面
        //(0)android 9-
        /*mIsShowingDashboard = className.equals(Settings.class.getName());
        setContentView(mIsShowingDashboard ?
               R.layout.settings_main_dashboard : R.layout.settings_main_prefs);
        getSupportFragmentManager().addOnBackStackChangedListener(this);*/
        //(1)android 10+
        setContentView(R.layout.settings_main_prefs);
        //....
       if (savedState != null) {
          // We are restarting from a previous saved state; used that to initialize, instead
          // of starting fresh.
          setTitleFromIntent(intent);

          ArrayList<DashboardCategory> categories =
                  savedState.getParcelableArrayList(SAVE_KEY_CATEGORIES);
          if (categories != null) {
             mCategories.clear();
             mCategories.addAll(categories);
             setTitleFromBackStack();
          }
       } else {
          launchSettingFragment(initialFragmentName, intent);
       }
   }
}

•  相关页面显示类DashboardCategory.java
• 以ApnSetting为例，堆栈如下：

onCreate:312, ApnSettings (com.android.settings.network)
performCreate:2685, Fragment (androidx.fragment.app)
create:280, FragmentStateManager (androidx.fragment.app)
moveToState:1187, FragmentManager (androidx.fragment.app)
addToFirstInLastOut:1255, FragmentTransition (androidx.fragment.app)
calculateFragments:1138, FragmentTransition (androidx.fragment.app)
startTransitions:136, FragmentTransition (androidx.fragment.app)
executeOpsTogether:2001, FragmentManager (androidx.fragment.app)
removeRedundantOperationsAndExecute:1959, FragmentManager (androidx.fragment.app)
execPendingActions:1861, FragmentManager (androidx.fragment.app)
executePendingTransactions:489, FragmentManager (androidx.fragment.app)
switchToFragment:615, SettingsActivity (com.android.settings)
launchSettingFragment:403, SettingsActivity (com.android.settings)
onCreate:310, SettingsActivity (com.android.settings)
onCreate:222, Settings$ApnSettingsActivity (com.android.settings)
performCreate:8137, Activity (android.app)
performCreate:8121, Activity (android.app)
callActivityOnCreate:1309, Instrumentation (android.app)
performLaunchActivity:3446, ActivityThread (android.app)
handleLaunchActivity:3637, ActivityThread (android.app)
execute:85, LaunchActivityItem (android.app.servertransaction)
executeCallbacks:135, TransactionExecutor (android.app.servertransaction)
execute:95, TransactionExecutor (android.app.servertransaction)
handleMessage:2105, ActivityThread$H (android.app)
dispatchMessage:106, Handler (android.os)
loop:223, Looper (android.os)
main:7707, ActivityThread (android.app)
invoke:-1, Method (java.lang.reflect)
run:612, RuntimeInit$MethodAndArgsCaller (com.android.internal.os)
main:997, ZygoteInit (com.android.internal.os)