Android NavigationBar中虚拟键调查

NavigationBar调查

NavigationBar是Android4.0以后出现的新特性，下图2就是NavigationBar，其中包括Back， Home， Recent键。并且对于基于2.3或者更早的版本的app，会在右下角显示一个Menu。这几个键都是虚拟的按键，对于没有实体键的手机或者tablet相当的方便。

 

NavigationBar的显示与隐藏

NavigationBar在App层是由SystemUI控制显示与隐藏的，并且布局文件也在SystemUI中。SystemUI在路径frameworks/base/packages/SystemUI/。

SystemUI就是StatusBar的界面部分，随系统启动而启动。SystemUI启动后会加载SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java

之后调用makeStatusBarView构建视图，其中就包括了NavigationBar的创建。代码如下：

 

try {boolean showNav = mWindowManagerService.hasNavigationBar();if (showNav) {mNavigationBarView =(NavigationBarView) View.inflate(context, R.layout.navigation_bar, null);　　mNavigationBarView.setDisabledFlags(mDisabled);mNavigationBarView.setBar(this);　　}} catch (RemoteException ex) {　　// no window manager? good luck with that}

 

可见NavigationBarView其实是NavigationBar的视图，对应的layout文件为navigation_bar.xml。NavigationBar是否构建显示是通过mWindowManagerService的hasNavigationBar()接口确定的。WindowManagerService会向下调用Policy的接口hasNavigationBar决定NavigationBar显示与否。

public interface WindowManagerPolicy {　　public boolean hasNavigationBar();}

而Policy调用的实际上是PhoneWindowManager的接口hasNavigationBar，获取变量mHasNavigationBar的布尔值，这个变量是setInitialDisplaySize的时候初始化的。

 

public class PhoneWindowManager implements WindowManagerPolicy {... ...// Use this instead of checking config_showNavigationBar so that it can be consistently    // overridden by qemu.hw.mainkeys in the emulator.    public boolean hasNavigationBar() {        return mHasNavigationBar;　　}... ...public void setInitialDisplaySize(Display display, int width, int height, int density) {... ...// SystemUI (status bar) layout policy        int shortSizeDp = shortSize * DisplayMetrics.DENSITY_DEFAULT / density;        String deviceType = SystemProperties.get("sys.device.type");        if (! "".equals(deviceType) && deviceType.equals("tablet")) {           // if indicate device type is tablet skip the judge for "phone" UI        } else if (shortSizeDp < 600) {            // 0-599dp: "phone" UI with a separate status & navigation bar            mHasSystemNavBar = false;            mNavigationBarCanMove = true;        } else if (shortSizeDp < 720) {            // 600+dp: "phone" UI with modifications for larger screens            mHasSystemNavBar = false;            mNavigationBarCanMove = false;        }if (!mHasSystemNavBar) {            mHasNavigationBar = mContext.getResources().getBoolean(                    com.android.internal.R.bool.config_showNavigationBar);            // Allow a system property to override this. Used by the emulator.            String navBarOverride = SystemProperties.get("qemu.hw.mainkeys");            if (! "".equals(navBarOverride)) {                if      (navBarOverride.equals("1")) mHasNavigationBar = false;                else if (navBarOverride.equals("0")) mHasNavigationBar = true;            }        } else {            mHasNavigationBar = false;        }}}

com.android.internal.R.bool.config_showNavigationBar这个才是navigationbar显示与否的配置变量，这个变量其实是在Android编译过程中由

frameworks/base/core/res/res/values/config.xml配置的

<!-- Whether a software navigation bar should be shown. NOTE: in the future this may be         autodetected from the Configuration. -->    <bool name="config_showNavigationBar">false</bool>

WindowManagerPolicy -- frameworks/base/core/java/android/view/WindowManagerPolicy.java

PhoneWindowManager -- frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java

 

另一方面，通过调用SystemProperties.get("qemu.hw.mainkeys");获取到NavigationBar是否被自定义，系统默认是不会设置qemu.hw.mainkeys的值的，所以获取到的是“0”。因此，就算不设定config.xml中config_showNavigationBar的值为true，屏幕够大的话，NavigationBar默认还是会显示出来的。

External/qemu/vl-android.c中如下代码会设定qemu.hw.mainkeys的值，下层代码没有继续调查。

/* Initialize presence of hardware nav button */    boot_property_add("qemu.hw.mainkeys", android_hw->hw_mainKeys ? "1" : "0");

总的来说NavigationBar的显示与隐藏主要依赖3个方面

1.config.xml的配置config_showNavigationBar为true则显示，false不显示

2.Density，WXGA720/WXGA800/WXGA800-7in三种分辨率显示

3.Qemu.hw.mainkeys的设置，0显示，1不显示

 

NavigationBar Click事件处理

NavigationBar的layout文件是frameworks/base/packages/SystemUI/res/layout/navigation_bar.xml

视图类是Frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarView.java

从layout文件看navigation_bar.xml是按方向配置的，rot0/rot90/rot270

每个方向都会包含KeyButtonView类型的4个View，

id分别是back/home/recent_apps/menu。

视图类NavigationBarView.java中会包含获取4个button的接口，代码如下：

 

public View getRecentsButton() {        return mCurrentView.findViewById(R.id.recent_apps);　　}public View getMenuButton() {        return mCurrentView.findViewById(R.id.menu);    }public View getBackButton() {        return mCurrentView.findViewById(R.id.back);    }public View getHomeButton() {　　return mCurrentView.findViewById(R.id.home);    }

SystemUI启动后会调用PhoneStatusBar.java的start->addNavigationBar()->

prepareNavigationBarView()，并在prepare中设定了recent和Home的处理事件。

 

@Overridepublic void start() {... ...addNavigationBar();}// For small-screen devices (read: phones) that lack hardware navigation buttonsprivate void addNavigationBar() {if (DEBUG) Slog.v(TAG, "addNavigationBar: about to add " + mNavigationBarView);if (mNavigationBarView == null) return;prepareNavigationBarView();　　mWindowManager.addView(mNavigationBarView, getNavigationBarLayoutParams());}private void prepareNavigationBarView() {mNavigationBarView.reorient();　　mNavigationBarView.getRecentsButton().setOnClickListener(mRecentsClickListener);　　mNavigationBarView.getRecentsButton().setOnTouchListener(mRecentsPreloadOnTouchListener);　　mNavigationBarView.getHomeButton().setOnTouchListener(mHomeSearchActionListener);　　mNavigationBarView.getSearchLight().setOnTouchListener(mHomeSearchActionListener);　　updateSearchPanel();}

接下来先看最简单的Recent Button。

Recent Button Click事件处理

private View.OnClickListener mRecentsClickListener = new View.OnClickListener() {        public void onClick(View v) {            toggleRecentApps();        }    };

Recent button设定了onClickListener，处理函数是toggleRecentApps()。toggleRecentApps在PhoneStatusBar的父类BaseStatusBar中实现。

@Overridepublic void toggleRecentApps() {int msg = MSG_TOGGLE_RECENTS_PANEL;mHandler.removeMessages(msg); mHandler.sendEmptyMessage(msg);}

从函数实现来看，发送了MSG_TOGGLE_RECENTS_PANEL msg给线程。

 

protected class H extends Handler {public void handleMessage(Message m) {switch (m.what) {             case MSG_TOGGLE_RECENTS_PANEL:                 if (DEBUG) Slog.d(TAG, "toggle recents panel");                 toggleRecentsActivity();                 break;　　... ...　　}}}

BaseStatusBar.java的内部线程会调用toggleRecentsActivity()处理接收到的消息。

 

protected void toggleRecentsActivity() {　　try {TaskDescription firstTask = RecentTasksLoader.getInstance(mContext).getFirstTask();　　Intent intent = new Intent(RecentsActivity.TOGGLE_RECENTS_INTENT);intent.setClassName("com.android.systemui","com.android.systemui.recent.RecentsActivity");intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK| Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);　　if (firstTask == null) {if (RecentsActivity.forceOpaqueBackground(mContext)) {ActivityOptions opts = ActivityOptions.makeCustomAnimation(mContext,                            R.anim.recents_launch_from_launcher_enter,                            R.anim.recents_launch_from_launcher_exit);mContext.startActivityAsUser(intent, opts.toBundle(), new UserHandle(                            UserHandle.USER_CURRENT));　　} else {// The correct window animation will be applied via the activity's stylemContext.startActivityAsUser(intent, new UserHandle(                            UserHandle.USER_CURRENT));}　　} else {Bitmap first = firstTask.getThumbnail();　　... ...　　ActivityOptions opts = ActivityOptions.makeThumbnailScaleDownAnimation(getStatusBarView(),　　first, x, y,　　new ActivityOptions.OnAnimationStartedListener() {　　public void onAnimationStarted() {Intent intent = new Intent(RecentsActivity.WINDOW_ANIMATION_START_INTENT);intent.setPackage("com.android.systemui");mContext.sendBroadcastAsUser(intent, 　　new UserHandle(UserHandle.USER_CURRENT));}});                intent.putExtra(RecentsActivity.WAITING_FOR_WINDOW_ANIMATION_PARAM, true);mContext.startActivityAsUser(intent, opts.toBundle(), new UserHandle(                        UserHandle.USER_CURRENT));}return;} catch (ActivityNotFoundException e) {Log.e(TAG, "Failed to launch RecentAppsIntent", e);}

处理消息的本质其实是通过context启动一个Activity，显示RecentApp。下层调用没有继续调查。从Log中看也确实是这样

 

　　D/PhoneStatusBar(  360): mRecentsClickListener onClicked call toggleRecentApps.　　I/ActivityManager(  279): START u0 {act=com.android.systemui.recent.action.TOGGLE_RECENTS flg=0x10800000 cmp=com.android.systemui/.recent.RecentsActivity} from pid 360

Home/Back/Menu Button Click事件处理

其实home/back/recent/menu都是KeyButtonView类型的View，而Home/Back Button的onTouch事件其实也是在KeyButtonView中做的处理。

onTouch会判断发送过来的key_code是否合法，合法就调用sendEvent将事件发送出去。事件是通过InputManager的injectInputEvent强制插入一个事件

 

public boolean onTouchEvent(MotionEvent ev) {final int action = ev.getAction();　　switch (action) { case MotionEvent.ACTION_DOWN:　　... ...　　case MotionEvent.ACTION_MOVE:　　... ...　　case MotionEvent.ACTION_CANCEL:　　... ...　　case MotionEvent.ACTION_UP:　　final boolean doIt = isPressed();　　setPressed(false);　　if (mCode != 0) {　　if (doIt) {　　sendEvent(KeyEvent.ACTION_UP, 0);　　sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);　　                        playSoundEffect(SoundEffectConstants.CLICK);　　} else {　　    sendEvent(KeyEvent.ACTION_UP, KeyEvent.FLAG_CANCELED);　　}　　} else {　　// no key code, just a regular ImageView　　if (doIt) {　　performClick();　　}　　}　　}}void sendEvent(int action, int flags) {sendEvent(action, flags, SystemClock.uptimeMillis());}void sendEvent(int action, int flags, long when) {final int repeatCount = (flags & KeyEvent.FLAG_LONG_PRESS) != 0 ? 1 : 0;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);}

从log看也确实是这样处理的，其中action 0代表ACTION_DOWN，1代表ACTION_UP。mCode是键值，82代表KEYCODE_MENU，3代表KEYCODE_HOME，4代表KEYCODE_BACK。具体的KeyCode和Action可以参考

http://developer.android.com/intl/zh-cn/reference/android/view/KeyEvent.html

 

D/KeyButtonView(  351): onTouchEvent MotionEvent = MotionEvent { action=ACTION_DOWN, id[0]=0, x[0]=40.0, y[0]=52.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=170128, downTime=170128, deviceId=0, source=0x1002 }D/KeyButtonView(  351): sendEvent mCode = 82D/KeyButtonView(  351): sendEvent, action = 0D/KeyButtonView(  351): onTouchEvent MotionEvent = MotionEvent { action=ACTION_UP, id[0]=0, x[0]=40.0, y[0]=52.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=170195, downTime=170128, deviceId=0, source=0x1002 }D/KeyButtonView(  351): sendEvent mCode = 82D/KeyButtonView(  351): sendEvent, action = 1E/StrictMode(  360): at android.os.StrictMode.setClassInstanceLimit(StrictMode.java:1)D/KeyButtonView(  360): onTouchEvent MotionEvent = MotionEvent { action=ACTION_DOWN, id[0]=0, x[0]=95.0, y[0]=47.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=160035, downTime=160035, deviceId=0, source=0x1002 }D/KeyButtonView(  360): sendEvent mCode = 3D/KeyButtonView(  360): sendEvent, action = 0D/KeyButtonView(  360): onTouchEvent MotionEvent = MotionEvent { action=ACTION_UP, id[0]=0, x[0]=95.0, y[0]=47.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=160137, downTime=160035, deviceId=0, source=0x1002 }D/KeyButtonView(  360): sendEvent mCode = 3D/KeyButtonView(  360): sendEvent, action = 1D/KeyButtonView(  360): onTouchEvent MotionEvent = MotionEvent { action=ACTION_DOWN, id[0]=0, x[0]=74.0, y[0]=61.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=177529, downTime=177529, deviceId=0, source=0x1002 }D/KeyButtonView(  360): sendEvent mCode = 4D/KeyButtonView(  360): sendEvent, action = 0D/KeyButtonView(  360): onTouchEvent MotionEvent = MotionEvent { action=ACTION_UP, id[0]=0, x[0]=74.0, y[0]=61.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=177649, downTime=177529, deviceId=0, source=0x1002 }D/KeyButtonView(  360): sendEvent mCode = 4D/KeyButtonView(  360): sendEvent, action = 1