Android 9.0 SystemUI NavigationBar

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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

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protected void makeStatusBarView() {
    //省略其他代码
    try {
        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。

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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

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@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。

位于 SystemUI\res\layout\navigation_bar.xml

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<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。

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@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。

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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。

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<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。

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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。

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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。

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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。

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<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。

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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);
}
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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。

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@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：

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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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