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需求

基于MTK8163 8.1平台定制导航栏部分，在左边增加音量减，右边增加音量加

思路

需求开始做之前，一定要研读SystemUI Navigation模块的代码流程！！！不要直接去网上copy别人改的需求代码，盲改的话很容易出现问题，然而无从解决。网上有老平台（8.0-）的讲解System UI的导航栏模块的博客，自行搜索。8.0对System UI还是做了不少细节上的改动，代码改动体现上也比较多，但是总体基本流程并没变。

源码阅读可以沿着一条线索去跟代码，不要过分在乎代码细节！例如我客制化这个需求，可以跟着导航栏的返回(back)，桌面（home），最近任务（recent）中的一个功能跟代码流程，大体知道比如recen这个view是哪个方法调哪个方法最终加载出来，加载的关键代码在哪，点击事件怎么生成，而不在意里面的具体逻辑判断等等。

代码流程

1.SystemUI\src\com\android\systemui\statusbar\phone\StatusBar.java；

从状态栏入口开始看。

protected void makeStatusBarView() { final Context context = mContext; updateDisplaySize(); // populates mDisplayMetrics updateResources(); updateTheme(); ... ... try { boolean showNav = mWindowManagerService.hasNavigationBar(); if (DEBUG) Log.v(TAG, "hasNavigationBar=" + showNav); if (showNav) { createNavigationBar();//创建导航栏 } } catch (RemoteException ex) { }}

2.进入 createNavigationBar 方法，发现主要是用 NavigationBarFragment 来管理.

protected void createNavigationBar() { mNavigationBarView = NavigationBarFragment.create(mContext, (tag, fragment) -> { mNavigationBar = (NavigationBarFragment) fragment; if (mLightBarController != null) { mNavigationBar.setLightBarController(mLightBarController); } mNavigationBar.setCurrentSysuiVisibility(mSystemUiVisibility); });}

3.看 NavigationBarFragment 的create方法，终于知道，是WindowManager去addView了导航栏的布局，最终add了fragment的onCreateView加载的布局。（其实SystemUI所有的模块都是WindowManager来加载View）

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.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) //注意！fragment里onCreateView加载的布局是add到这个Window属性的view里的。 .commit(); fragmentHost.addTagListener(TAG, listener); return navigationBarView; }}

4.SystemUI\res\layout\navigation_bar_window.xml；

来看WindowManager加载的这个view的布局：navigation_bar_window.xml，发现根布局是自定义的view类NavigationBarFrame.(其实SystemUI以及其他系统应用如Launcher,都是这种自定义view的方式，好多逻辑处理也都是在自定义view里，不能忽略)

<com.android.systemui.statusbar.phone.NavigationBarFrame xmlns:android="http://schemas.android.com/apk/res/android" xmlns:systemui="http://schemas.android.com/apk/res-auto" android:id="@+id/navigation_bar_frame" android:layout_height="match_parent" android:layout_width="match_parent"> </com.android.systemui.statusbar.phone.NavigationBarFrame>

5.SystemUI\src\com\android\systemui\statusbar\phone\NavigationBarFrame.java；

我们进入NavigationBarFrame类。发现类里并不是我们的预期，就是一个FrameLayout，对DeadZone功能下的touch事件做了手脚，不管了。

6.再回来看看NavigationBarFragment的生命周期呢。onCreateView()里，导航栏的真正的rootView。

@Overridepublic View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) { return inflater.inflate(R.layout.navigation_bar, container, false);}

进入导航栏的真正根布局：navigation_bar.xml，好吧又是自定义view，NavigationBarView 和 NavigationBarInflaterView 都要仔细研读。

<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>

7.SystemUI\src\com\android\systemui\statusbar\phone\NavigationBarInflaterView.java；继承自FrameLayout

先看构造方法，因为加载xml布局首先走的是初始化

public NavigationBarInflaterView(Context context, AttributeSet attrs) { super(context, attrs); createInflaters();//根据屏幕旋转角度创建子view（单个back home or recent）的父布局 Display display = ((WindowManager) context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay(); Mode displayMode = display.getMode(); isRot0Landscape = displayMode.getPhysicalWidth() > displayMode.getPhysicalHeight();}private void inflateChildren() { removeAllViews(); mRot0 = (FrameLayout) mLayoutInflater.inflate(R.layout.navigation_layout, this, false); mRot0.setId(R.id.rot0); addView(mRot0); mRot90 = (FrameLayout) mLayoutInflater.inflate(R.layout.navigation_layout_rot90, this, false); mRot90.setId(R.id.rot90); addView(mRot90); updateAlternativeOrder();}

再看onFinishInflate()方法，这是view的生命周期，每个view被inflate之后都会回调。

@Overrideprotected void onFinishInflate() { super.onFinishInflate(); inflateChildren();//进去看无关紧要 忽略 clearViews();//进去看无关紧要 忽略 inflateLayout(getDefaultLayout());//关键方法：加载了 back.home.recent三个按钮的layout}

看inflateLayout()：里面的newLayout参数很重要！！！根据上一个方法看到getDefaultLayout()，他return了一个在xml写死的字符串。再看inflateLayout方法，他解析分割了xml里配置的字符串，并传给了inflateButtons方法

protected void inflateLayout(String newLayout) { mCurrentLayout = newLayout; if (newLayout == null) { newLayout = getDefaultLayout(); } String[] sets = newLayout.split(GRAVITY_SEPARATOR, 3);//根据“；”号分割成长度为3的数组 String[] start = sets[0].split(BUTTON_SEPARATOR);//根据“，”号分割，包含 left[.5W]和back[1WC] String[] center = sets[1].split(BUTTON_SEPARATOR);//包含home String[] end = sets[2].split(BUTTON_SEPARATOR);//包含recent[1WC]和right[.5W] // 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);} protected String getDefaultLayout() { return mContext.getString(R.string.config_navBarLayout);}

SystemUI\res\values\config.xml

<!-- Nav bar button default ordering/layout --><string name="config_navBarLayout" translatable="false">left[.5W],back[1WC];home;recent[1WC],right[.5W]</string>

再看inflateButtons()方法，遍历加载inflateButton：

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); }}@Nullableprotected View inflateButton(String buttonSpec, ViewGroup parent, boolean landscape, boolean start) { LayoutInflater inflater = landscape ? mLandscapeInflater : mLayoutInflater; View v = createView(buttonSpec, parent, inflater);//创建view if (v == null) return null; v = applySize(v, buttonSpec, landscape, start); parent.addView(v);//addView到父布局 addToDispatchers(v); View lastView = landscape ? mLastLandscape : mLastPortrait; View accessibilityView = v; if (v instanceof ReverseFrameLayout) { accessibilityView = ((ReverseFrameLayout) v).getChildAt(0); } if (lastView != null) { accessibilityView.setAccessibilityTraversalAfter(lastView.getId()); } if (landscape) { mLastLandscape = accessibilityView; } else { mLastPortrait = accessibilityView; } return v;}

我们来看createView()方法：以home按键为例，加载了home的button,其实是加载了 R.layout.home 的layout布局

private View createView(String buttonSpec, ViewGroup parent, LayoutInflater inflater) { View v = null; ... ... 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.equals(button)) { v = inflater.inflate(R.layout.menu_ime, parent, false); } else if (NAVSPACE.equals(button)) { v = inflater.inflate(R.layout.nav_key_space, parent, false); } else if (CLIPBOARD.equals(button)) { v = inflater.inflate(R.layout.clipboard, parent, false); } ... ... return v;}//SystemUI\res\layout\home.xml //这里布局里没有src显示home的icon,肯定是在代码里设置了//这里也是自定义view:KeyButtonView<com.android.systemui.statusbar.policy.KeyButtonViewxmlns: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"//引用了dimens.xml里的navigation_key_widthandroid:layout_height="match_parent"android:layout_weight="0"systemui:keyCode="3"//systemui自定义的属性android:scaleType="fitCenter"android:contentDescription="@string/accessibility_home"android:paddingTop="@dimen/home_padding"android:paddingBottom="@dimen/home_padding"android:paddingStart="@dimen/navigation_key_padding"android:paddingEnd="@dimen/navigation_key_padding"/>

8.SystemUI\src\com\android\systemui\statusbar\policy\KeyButtonView.java

先来看KeyButtonView的构造方法：我们之前xml的systemui:keyCode=”3”方法在这里获取。再来看Touch事件，通过sendEvent()方法可以看出，back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.

当然KeyButtonView类还处理了支持长按的button,按键的响声等，这里忽略。

至此，导航栏按键事件我们梳理完毕。

public KeyButtonView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs); TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.KeyButtonView, defStyle, 0); mCode = a.getInteger(R.styleable.KeyButtonView_keyCode, 0); mSupportsLongpress = a.getBoolean(R.styleable.KeyButtonView_keyRepeat, true); mPlaySounds = a.getBoolean(R.styleable.KeyButtonView_playSound, true); TypedValue value = new TypedValue(); if (a.getValue(R.styleable.KeyButtonView_android_contentDescription, value)) { mContentDescriptionRes = value.resourceId; } a.recycle(); setClickable(true); mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop(); mAudioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE); mRipple = new KeyButtonRipple(context, this); setBackground(mRipple);}......public boolean onTouchEvent(MotionEvent ev) { ... switch (action) { case MotionEvent.ACTION_DOWN: mDownTime = SystemClock.uptimeMillis(); mLongClicked = false; setPressed(true); if (mCode != 0) { sendEvent(KeyEvent.ACTION_DOWN, 0, mDownTime);//关键方法 } else { // Provide the same haptic feedback that the system offers for virtual keys. performHapticFeedback(HapticFeedbackConstants.VIRTUAL_KEY); } playSoundEffect(SoundEffectConstants.CLICK); removeCallbacks(mCheckLongPress); postDelayed(mCheckLongPress, ViewConfiguration.getLongPressTimeout()); break; ... ... } return true;}void sendEvent(int action, int flags, long when) { mMetricsLogger.write(new LogMaker(MetricsEvent.ACTION_NAV_BUTTON_EVENT) .setType(MetricsEvent.TYPE_ACTION) .setSubtype(mCode) .addTaggedData(MetricsEvent.FIELD_NAV_ACTION, action) .addTaggedData(MetricsEvent.FIELD_FLAGS, flags)); final int repeatCount = (flags & KeyEvent.FLAG_LONG_PRESS) != 0 ? 1 : 0; //这里根据mCode new了一个KeyEvent事件，通过injectInputEvent使事件生效。 final KeyEvent ev = new KeyEvent(mDownTime, when, action, mCode, repeatCount, 0, KeyCharacterMap.VIRTUAL_KEYBOARD, 0, flags | KeyEvent.FLAG_FROM_SYSTEM | KeyEvent.FLAG_VIRTUAL_HARD_KEY, InputDevice.SOURCE_KEYBOARD); InputManager.getInstance().injectInputEvent(ev, InputManager.INJECT_INPUT_EVENT_MODE_ASYNC);}

9.还遗留一个问题：设置图片的icon到底在哪？我们之前一直阅读的是NavigationBarInflaterView，根据布局我们还有一个类没有看，NavigationBarView.java

SystemUI\src\com\android\systemui\statusbar\phone\NavigationBarView.java；

进入NavigationBarView类里，找到构造方法。

public NavigationBarView(Context context, AttributeSet attrs) { super(context, attrs); mDisplay = ((WindowManager) context.getSystemService( Context.WINDOW_SERVICE)).getDefaultDisplay(); ... ... updateIcons(context, Configuration.EMPTY, mConfiguration);//关键方法 mBarTransitions = new NavigationBarTransitions(this); //mButtonDispatchers 是维护这些home back recent图标view的管理类，会传递到他的child,NavigationBarInflaterView类中 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));} private void updateIcons(Context ctx, Configuration oldConfig, Configuration newConfig) { ... iconLight = mNavBarPlugin.getHomeImage( ctx.getDrawable(R.drawable.ic_sysbar_home)); iconDark = mNavBarPlugin.getHomeImage( ctx.getDrawable(R.drawable.ic_sysbar_home_dark)); //mHomeDefaultIcon = getDrawable(ctx, // R.drawable.ic_sysbar_home, R.drawable.ic_sysbar_home_dark); mHomeDefaultIcon = getDrawable(iconLight,iconDark); //亮色的icon资源 iconLight = mNavBarPlugin.getRecentImage( ctx.getDrawable(R.drawable.ic_sysbar_recent)); //暗色的icon资源 iconDark = mNavBarPlugin.getRecentImage( ctx.getDrawable(R.drawable.ic_sysbar_recent_dark)); //mRecentIcon = getDrawable(ctx, // R.drawable.ic_sysbar_recent, R.drawable.ic_sysbar_recent_dark); mRecentIcon = getDrawable(iconLight,iconDark); mMenuIcon = getDrawable(ctx, R.drawable.ic_sysbar_menu, R.drawable.ic_sysbar_menu_dark); ... ...}

10.从第10可以看到，以recent为例，在初始化时得到了mRecentIcon的资源，再看谁调用了了mRecentIcon就可知道，即反推看调用流程。

private void updateRecentsIcon() { getRecentsButton().setImageDrawable(mDockedStackExists ? mDockedIcon : mRecentIcon); mBarTransitions.reapplyDarkIntensity();}

updateRecentsIcon这个方法设置了recent图片的资源，再看谁调用了updateRecentsIcon方法:onConfigurationChanged屏幕旋转会重新设置资源图片

@Overrideprotected void onConfigurationChanged(Configuration newConfig) { super.onConfigurationChanged(newConfig); boolean uiCarModeChanged = updateCarMode(newConfig); updateTaskSwitchHelper(); updateIcons(getContext(), mConfiguration, newConfig); updateRecentsIcon(); if (uiCarModeChanged || mConfiguration.densityDpi != newConfig.densityDpi || mConfiguration.getLayoutDirection() != newConfig.getLayoutDirection()) { // If car mode or density changes, we need to reset the icons. setNavigationIconHints(mNavigationIconHints, true); } mConfiguration.updateFrom(newConfig);}public void setNavigationIconHints(int hints, boolean force) { ... ... mNavigationIconHints = hints; // We have to replace or restore the back and home button icons when exiting or entering // carmode, respectively. Recents are not available in CarMode in nav bar so change // to recent icon is not required. KeyButtonDrawable backIcon = (backAlt) ? getBackIconWithAlt(mUseCarModeUi, mVertical) : getBackIcon(mUseCarModeUi, mVertical); getBackButton().setImageDrawable(backIcon); updateRecentsIcon(); ... ...}

reorient()也调用了setNavigationIconHints()方法：

public void reorient() { updateCurrentView(); ... setNavigationIconHints(mNavigationIconHints, true); getHomeButton().setVertical(mVertical);}

再朝上推，最终追溯到NavigationBarFragment的onConfigurationChanged()方法 和 NavigationBarView的onAttachedToWindow()和onSizeChanged()方法。也就是说，在NavigationBarView导航栏这个布局加载的时候就会设置图片资源，和长度改变，屏幕旋转都有可能引起重新设置

至此，SystemUI的虚拟导航栏模块代码流程结束。

总结

创建一个window属性的父view 通过读取解析xml里config的配置，addView需要的icon,或者调换顺序 src图片资源通过代码设置亮色和暗色 touch事件以keycode方式交由系统处理

以上所述是小编给大家介绍的Android 8.1平台SystemUI 导航栏加载流程，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对我们网站的支持！如果你觉得本文对你有帮助，欢迎转载，烦请注明出处，谢谢！

本文标题: 解析Android 8.1平台SystemUI 导航栏加载流程

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