Android 13 SystemUI，底部导航栏新增功能按键、导航栏侧边(左侧，右侧，顶侧)显示。

写在前面： SystemUI 是Android原生系统极重要的系统APP，本文介绍如何根据需要在原生三个按键BACK HOME RECENT的基础上，新增新的自定义按键。SystemUI总共分为三个版本：Phone手机、Tablet平板、TV版本。Android13中，Phone、Tablet是一样的。本教程适用SystemUI版本：Android13——>Phone 、Tablet版SystemUI。
注：SystemUI的启动流程，本篇文章不介绍。

一、底部导航栏新增功能按键。

  首先介绍一下Phone、Tablet版的SystemUI的启动路线，看下图：

  启动流程中的CentralSurfaces，是我们修改的切入点。打开源码找到CentralSurfacesImpl.java文件，下面我沿着CentralSurfacesImpl.java简单描述一下修改思路，然后贴出完整补丁。

1、frameworks\base\packages\SystemUI\src\com\android\systemui\statusbar\phone\CentralSurfacesImpl.java
    @Overridepublicvoidstart(){
   ..................createAndAddWindows(result);//这里为入口..................}@OverridepublicvoidcreateAndAddWindows(@NullableRegisterStatusBarResult result){
   makeStatusBarView(result);//从这里进去创建状态栏、导航栏
        mNotificationShadeWindowController.attach();
        mStatusBarWindowController.attach();}// ================================================================================// Constructing the view// ================================================================================protectedvoidmakeStatusBarView(@NullableRegisterStatusBarResult result){
   ..................createNavigationBar(result);//创建导航栏入口..................}protectedvoidcreateNavigationBar(@NullableRegisterStatusBarResult result){
   
        mNavigationBarController.createNavigationBars(true/* includeDefaultDisplay */, result);}2、frameworks\base\packages\SystemUI\src\com\android\systemui\navigationbar\NavigationBarController.java

    publicvoidcreateNavigationBars(finalboolean includeDefaultDisplay,RegisterStatusBarResult result){
   updateAccessibilityButtonModeIfNeeded();// Don't need to create nav bar on the default display if we initialize TaskBar.finalboolean shouldCreateDefaultNavbar = includeDefaultDisplay
                &&!initializeTaskbarIfNecessary();Display[] displays = mDisplayManager.getDisplays();for(Display display : displays){
   if(shouldCreateDefaultNavbar || display.getDisplayId()!=DEFAULT_DISPLAY){
   createNavigationBar(display,null/* savedState */, result);}}}/**
     * Adds a navigation bar on default display or an external display if the display supports
     * system decorations.
     *
     * @param display the display to add navigation bar on.
     */@VisibleForTestingvoidcreateNavigationBar(Display display,Bundle savedState,RegisterStatusBarResult result){
   ..................//从这里分为两个部分NavigationBar navBar = component.getNavigationBar();//导航栏实例化
        navBar.init();//将导航栏添加到屏幕上..................}

注：导航栏实例化会去加载导航栏对应的XML，里面默认只有Back|Home|Recent，想要添加新的功能键，第一步就是去修改这个XML；navBar.init()中则是为按键添加图标、绑定点击事件，并最终通过windowManager的addView方法将导航添加到桌面上显示。

完整补丁：

1、xml中新增按钮

  以我的项目分辨率 = 1920x1080、dpi = 320、density = 2来说，对应修改的xml为——>res\values-sw372dp\config.xml 我这里给出的例子，除了原生Back|Home|Recent之外，新增了其它四个按键。

diff --git a/frameworks/base/packages/SystemUI/res/values-sw372dp/config.xml b/frameworks/base/packages/SystemUI/res/values-sw372dp/config.xml
index 07b797a324..3b936766c5 100644--- a/frameworks/base/packages/SystemUI/res/values-sw372dp/config.xml
+++ b/frameworks/base/packages/SystemUI/res/values-sw372dp/config.xml
@@ -21,5+21,5 @@
      for different hardware and product builds.--><resources><!--Nav bar button default ordering/layout -->-<string name="config_navBarLayout" translatable="false">left[.25W],back[.5WC];home;recent[.5WC],right[.25W]</string>+<string name="config_navBarLayout" translatable="false">back;home;recent;volume;comments;whiteboard;collapse</string></resources>

2、NavigationBarInflaterView.java

  inflateLayout函数新增inflateButtons选项、createView函数新增对新按钮描述String的过滤；这个类的功能主要是从上述的xml文件中把所有按键加载进来，并进行过滤操作。

diff --git a/frameworks/base/packages/SystemUI/src/com/android/systemui/navigationbar/NavigationBarInflaterView.java b/frameworks/base/packages/SystemUI/src/com/android/systemui/navigationbar/NavigationBarInflaterView.java
index 59bb2278ed..5724e09a00 100644--- a/frameworks/base/packages/SystemUI/src/com/android/systemui/navigationbar/NavigationBarInflaterView.java
+++ b/frameworks/base/packages/SystemUI/src/com/android/systemui/navigationbar/NavigationBarInflaterView.java
@@ -60,6+60,12 @@ publicclassNavigationBarInflaterViewextendsFrameLayoutpublicstaticfinalStringBACK="back";publicstaticfinalStringHOME="home";publicstaticfinalStringRECENT="recent";+//xuhao add+publicstaticfinalStringVOLUME="volume";+publicstaticfinalStringCOMMENTS="comments";+publicstaticfinalStringWHITEBOARD="whiteboard";+publicstaticfinalStringCOLLAPSE="collapse";+//publicstaticfinalStringNAVSPACE="space";publicstaticfinalStringCLIPBOARD="clipboard";publicstaticfinalStringHOME_HANDLE="home_handle";
@@ -96,7+102,7 @@ publicclassNavigationBarInflaterViewextendsFrameLayoutprivateView mLastPortrait;privateView mLastLandscape;-privateboolean mIsVertical;+privateboolean mIsVertical ;privateboolean mAlternativeOrder;privateOverviewProxyService mOverviewProxyService;
@@ -177,6+183,7 @@ publicclassNavigationBarInflaterViewextendsFrameLayoutvoidupdateButtonDispatchersCurrentView(){
   if(mButtonDispatchers !=null){
   View view = mIsVertical ? mVertical : mHorizontal;+Log.d(TAG,"mIsVertical"+mIsVertical);for(int i =0; i < mButtonDispatchers.size(); i++){
   finalButtonDispatcher dispatcher = mButtonDispatchers.valueAt(i);
                 dispatcher.setCurrentView(view);
@@ -236,34+243,64 @@ publicclassNavigationBarInflaterViewextendsFrameLayoutif(newLayout ==null){
   
             newLayout =getDefaultLayout();}-String[] sets = newLayout.split(GRAVITY_SEPARATOR,3);-if(sets.length !=3){
   ++//xuhao add +String[] sets = newLayout.split(GRAVITY_SEPARATOR,7);+if(sets.length !=7){
   Log.d(TAG,"Invalid layout.");
             newLayout =