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Android 9.0 SystemUI NavigationBar
source link: http://wuxiaolong.me/2019/09/12/SystemUI5/
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导航栏有返回(back)，桌面（home），最近任务（recent），本篇主要学习这三个是如何加载的，点击事件在哪里写的？基于 AOSP 9.0 分析。
NavigationBar 创建是从 StatusBar#makeStatusBarView 开始的。
StatusBar#makeStatusBarView
protected void makeStatusBarView() {
//省略其他代码
boolean showNav = mWindowManagerService.hasNavigationBar();
if (DEBUG) Log.v(TAG, "hasNavigationBar=" + showNav);
if (showNav) {
createNavigationBar();
} catch (RemoteException ex) {
// no window manager? good luck with that
//省略其他代码
protected void createNavigationBar() {
mNavigationBarView = NavigationBarFragment.create(mContext, (tag, fragment) -> {
mNavigationBar = (NavigationBarFragment) fragment;
if (mLightBarController != null) {
mNavigationBar.setLightBarController(mLightBarController);
mNavigationBar.setCurrentSysuiVisibility(mSystemUiVisibility);
再进入 NavigationBarFragment#create 看看。
NavigationBarFragment#create
public static View create(Context context, FragmentListener listener) {
WindowManager.LayoutParams lp = new WindowManager.LayoutParams(
LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT,
WindowManager.LayoutParams.TYPE_NAVIGATION_BAR,
WindowManager.LayoutParams.FLAG_TOUCHABLE_WHEN_WAKING
| WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
| WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
| WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH
| WindowManager.LayoutParams.FLAG_SPLIT_TOUCH
| WindowManager.LayoutParams.FLAG_SLIPPERY,
PixelFormat.TRANSLUCENT);
lp.token = new Binder();
lp.setTitle("NavigationBar");
lp.accessibilityTitle = context.getString(R.string.nav_bar);
lp.windowAnimations = 0;
View navigationBarView = LayoutInflater.from(context).inflate(
R.layout.navigation_bar_window, null);
if (DEBUG) Log.v(TAG, "addNavigationBar: about to add " + navigationBarView);
if (navigationBarView == null) return null;
context.getSystemService(WindowManager.class).addView(navigationBarView, lp);
FragmentHostManager fragmentHost = FragmentHostManager.get(navigationBarView);
NavigationBarFragment fragment = new NavigationBarFragment();
fragmentHost.getFragmentManager().beginTransaction()
.replace(R.id.navigation_bar_frame, fragment, TAG)
.commit();
fragmentHost.addTagListener(TAG, listener);
return navigationBarView;
这里 WindowManager addView 了导航栏的布局，最终 add NavigationBarFragment，接下来看 NavigationBarFragment#onCreateView
NavigationBarFragment#onCreateView
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.navigation_bar, container, false);
看下布局文件 navigation_bar.xml，这是导航栏的真正根布局。
navigation_bar.xml
位于 SystemUI\res\layout\navigation_bar.xml
<com.android.systemui.statusbar.phone.NavigationBarView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:systemui="http://schemas.android.com/apk/res-auto"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:background="@drawable/system_bar_background">
<com.android.systemui.statusbar.phone.NavigationBarInflaterView
android:id="@+id/navigation_inflater"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</com.android.systemui.statusbar.phone.NavigationBarView>
NavigationBarInflaterView 继承自 FrameLayout，直接看 onFinishInflate() 方法，这个方法是每个 view 被 inflate 之后都会回调。
NavigationBarInflaterView#onFinishInflate
@Override
protected void onFinishInflate() {
super.onFinishInflate();
inflateChildren();
clearViews();
//关键方法
inflateLayout(getDefaultLayout());
这里调用了 getDefaultLayout 方法，加载资源文件。
NavigationBarInflaterView#getDefaultLayout
protected String getDefaultLayout() {
final int defaultResource = mOverviewProxyService.shouldShowSwipeUpUI()
? R.string.config_navBarLayoutQuickstep
: R.string.config_navBarLayout;
return mContext.getString(defaultResource);
config_navBarLayoutQuickstep 和 config_navBarLayout 位于 AOSP/frameworks/base/packages/SystemUI/res/values/config.xml。
<string name="config_navBarLayout" translatable="false">left[.5W],back[1WC];home;recent[1WC],right[.5W]</string>
<string name="config_navBarLayoutQuickstep" translatable="false">back[1.7WC];home;contextual[1.7WC]</string>
回头再看 NavigationBarInflaterView#onFinishInflate 方法调用 NavigationBarInflaterView#inflateLayout 方法。
NavigationBarInflaterView#inflateLayout
protected void inflateLayout(String newLayout) {
mCurrentLayout = newLayout;
if (newLayout == null) {
newLayout = getDefaultLayout();
//根据“；”号分割成长度为3的数组
String[] sets = newLayout.split(GRAVITY_SEPARATOR, 3);
if (sets.length != 3) {
Log.d(TAG, "Invalid layout.");
newLayout = getDefaultLayout();
sets = newLayout.split(GRAVITY_SEPARATOR, 3);
//根据“，”号分割，包含 left[.5W]和back[1WC]
String[] start = sets[0].split(BUTTON_SEPARATOR);
//包含home
String[] center = sets[1].split(BUTTON_SEPARATOR);
//包含recent[1WC]和right[.5W]
String[] end = sets[2].split(BUTTON_SEPARATOR);
// Inflate these in start to end order or accessibility traversal will be messed up.
inflateButtons(start, mRot0.findViewById(R.id.ends_group), isRot0Landscape, true);
inflateButtons(start, mRot90.findViewById(R.id.ends_group), !isRot0Landscape, true);
inflateButtons(center, mRot0.findViewById(R.id.center_group), isRot0Landscape, false);
inflateButtons(center, mRot90.findViewById(R.id.center_group), !isRot0Landscape, false);
addGravitySpacer(mRot0.findViewById(R.id.ends_group));
addGravitySpacer(mRot90.findViewById(R.id.ends_group));
inflateButtons(end, mRot0.findViewById(R.id.ends_group), isRot0Landscape, false);
inflateButtons(end, mRot90.findViewById(R.id.ends_group), !isRot0Landscape, false);
updateButtonDispatchersCurrentView();
再看 inflateButtons() 方法，遍历加载 inflateButton。
NavigationBarInflaterView#inflateButtons
private void inflateButtons(String[] buttons, ViewGroup parent, boolean landscape,
boolean start) {
for (int i = 0; i < buttons.length; i++) {
inflateButton(buttons[i], parent, landscape, start);
@Nullable
protected View inflateButton(String buttonSpec, ViewGroup parent, boolean landscape,
boolean start) {
LayoutInflater inflater = landscape ? mLandscapeInflater : mLayoutInflater;
View v = createView(buttonSpec, parent, inflater);
if (v == null) return null;
v = applySize(v, buttonSpec, landscape, start);
parent.addView(v);
addToDispatchers(v);
View lastView = landscape ? mLastLandscape : mLastPortrait;
View accessibilityView = v;
if (v instanceof ReverseRelativeLayout) {
accessibilityView = ((ReverseRelativeLayout) v).getChildAt(0);
if (lastView != null) {
accessibilityView.setAccessibilityTraversalAfter(lastView.getId());
if (landscape) {
mLastLandscape = accessibilityView;
} else {
mLastPortrait = accessibilityView;
return v;
来看 NavigationBarInflaterView#createView 方法。
private View createView(String buttonSpec, ViewGroup parent, LayoutInflater inflater) {
View v = null;
String button = extractButton(buttonSpec);
//省略其他代码
if (HOME.equals(button)) {
v = inflater.inflate(R.layout.home, parent, false);
} else if (BACK.equals(button)) {
v = inflater.inflate(R.layout.back, parent, false);
} else if (RECENT.equals(button)) {
v = inflater.inflate(R.layout.recent_apps, parent, false);
} else if (MENU_IME_ROTATE.equals(button)) {
v = inflater.inflate(R.layout.menu_ime, parent, false);
} //省略其他代码
return v;
以 home 按键为例，加载了 home.xml 布局。
<com.android.systemui.statusbar.policy.KeyButtonView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:systemui="http://schemas.android.com/apk/res-auto"
android:id="@+id/home"
android:layout_width="@dimen/navigation_key_width"
android:layout_height="match_parent"
android:layout_weight="0"
systemui:keyCode="3"
android:scaleType="center"
android:contentDescription="@string/accessibility_home"
android:paddingStart="@dimen/navigation_key_padding"
android:paddingEnd="@dimen/navigation_key_padding"
/>
从 KeyButtonView#sendEvent() 方法来看，home 等 view 的点击 touch 事件不是自己处理的，而是交由系统以实体按键（keycode）的形式处理的，不细看了。
那 NavigationBar icon 是具体如何加载的？看 NavigationBarView 构造方法。
NavigationBarView#构造方法
public NavigationBarView(Context context, AttributeSet attrs) {
super(context, attrs);
mDisplay = ((WindowManager) context.getSystemService(
Context.WINDOW_SERVICE)).getDefaultDisplay();
mVertical = false;
mShowMenu = false;
mShowAccessibilityButton = false;
mLongClickableAccessibilityButton = false;
mOverviewProxyService = Dependency.get(OverviewProxyService.class);
mRecentsOnboarding = new RecentsOnboarding(context, mOverviewProxyService);
mConfiguration = new Configuration();
mConfiguration.updateFrom(context.getResources().getConfiguration());
//加载 icon
reloadNavIcons();
//mButtonDispatchers 是维护这些home back recent图标view的管理类
mBarTransitions = new NavigationBarTransitions(this);
mButtonDispatchers.put(R.id.back, new ButtonDispatcher(R.id.back));
mButtonDispatchers.put(R.id.home, new ButtonDispatcher(R.id.home));
mButtonDispatchers.put(R.id.recent_apps, new ButtonDispatcher(R.id.recent_apps));
mButtonDispatchers.put(R.id.menu, new ButtonDispatcher(R.id.menu));
mButtonDispatchers.put(R.id.ime_switcher, new ButtonDispatcher(R.id.ime_switcher));
mButtonDispatchers.put(R.id.accessibility_button,
new ButtonDispatcher(R.id.accessibility_button));
mButtonDispatchers.put(R.id.rotate_suggestion,
new ButtonDispatcher(R.id.rotate_suggestion));
mButtonDispatchers.put(R.id.menu_container,
new ButtonDispatcher(R.id.menu_container));
mDeadZone = new DeadZone(this);
NavigationBarView#reloadNavIcons
private void reloadNavIcons() {
updateIcons(mContext, Configuration.EMPTY, mConfiguration);
private void updateIcons(Context ctx, Configuration oldConfig, Configuration newConfig) {
int dualToneDarkTheme = Utils.getThemeAttr(ctx, R.attr.darkIconTheme);
int dualToneLightTheme = Utils.getThemeAttr(ctx, R.attr.lightIconTheme);
//亮色的icon资源
Context lightContext = new ContextThemeWrapper(ctx, dualToneLightTheme);
//暗色的icon资源
Context darkContext = new ContextThemeWrapper(ctx, dualToneDarkTheme);
if (oldConfig.orientation != newConfig.orientation
|| oldConfig.densityDpi != newConfig.densityDpi) {
mDockedIcon = getDrawable(lightContext, darkContext, R.drawable.ic_sysbar_docked);
mHomeDefaultIcon = getHomeDrawable(lightContext, darkContext);
if (oldConfig.densityDpi != newConfig.densityDpi
|| oldConfig.getLayoutDirection() != newConfig.getLayoutDirection()) {
mBackIcon = getBackDrawable(lightContext, darkContext);
mRecentIcon = getDrawable(lightContext, darkContext, R.drawable.ic_sysbar_recent);
mMenuIcon = getDrawable(lightContext, darkContext, R.drawable.ic_sysbar_menu);
mAccessibilityIcon = getDrawable(lightContext, darkContext,
R.drawable.ic_sysbar_accessibility_button, false /* hasShadow */);
mImeIcon = getDrawable(lightContext, darkContext, R.drawable.ic_ime_switcher_default,
false /* hasShadow */);
updateRotateSuggestionButtonStyle(mRotateBtnStyle, false);
if (ALTERNATE_CAR_MODE_UI) {
updateCarModeIcons(ctx);
public KeyButtonDrawable getBackDrawable(Context lightContext, Context darkContext) {
KeyButtonDrawable drawable = chooseNavigationIconDrawable(lightContext, darkContext,
R.drawable.ic_sysbar_back, R.drawable.ic_sysbar_back_quick_step);
orientBackButton(drawable);
return drawable;
private void orientBackButton(KeyButtonDrawable drawable) {
final boolean useAltBack =
(mNavigationIconHints & StatusBarManager.NAVIGATION_HINT_BACK_ALT) != 0;
drawable.setRotation(useAltBack
? -90 : (getLayoutDirection() == View.LAYOUT_DIRECTION_RTL) ? 180 : 0);
这里看到 NavigationBar icon 加载，点击事件在哪里写了呢？看 NavigationBarFragment#onViewCreated。
NavigationBarFragment#onViewCreated
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
mNavigationBarView = (NavigationBarView) view;
//省略其他代码
prepareNavigationBarView();
//省略其他代码
private void prepareNavigationBarView() {
mNavigationBarView.reorient();
ButtonDispatcher recentsButton = mNavigationBarView.getRecentsButton();
recentsButton.setOnClickListener(this::onRecentsClick);
recentsButton.setOnTouchListener(this::onRecentsTouch);
recentsButton.setLongClickable(true);
recentsButton.setOnLongClickListener(this::onLongPressBackRecents);
ButtonDispatcher backButton = mNavigationBarView.getBackButton();
backButton.setLongClickable(true);
ButtonDispatcher homeButton = mNavigationBarView.getHomeButton();
homeButton.setOnTouchListener(this::onHomeTouch);
homeButton.setOnLongClickListener(this::onHomeLongClick);
ButtonDispatcher accessibilityButton = mNavigationBarView.getAccessibilityButton();
accessibilityButton.setOnClickListener(this::onAccessibilityClick);
accessibilityButton.setOnLongClickListener(this::onAccessibilityLongClick);
updateAccessibilityServicesState(mAccessibilityManager);
ButtonDispatcher rotateSuggestionButton = mNavigationBarView.getRotateSuggestionButton();
rotateSuggestionButton.setOnClickListener(this::onRotateSuggestionClick);
rotateSuggestionButton.setOnHoverListener(this::onRotateSuggestionHover);
updateScreenPinningGestures();
从 mButtonDispatchers 获得 recents、back、home，然后设置点击、长按等事件，比如 onRecentsClick 方法：
private void onRecentsClick(View v) {
if (LatencyTracker.isEnabled(getContext())) {
LatencyTracker.getInstance(getContext()).onActionStart(
LatencyTracker.ACTION_TOGGLE_RECENTS);
mStatusBar.awakenDreams();
mCommandQueue.toggleRecentApps();
至此，SystemUI NavigationBar 模块代码流程分析完毕。
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