Android 4.0 ICS SystemUI浅析——StatusBar加载流程分析

  前面两篇文章《 Android 4.0 ICS SystemUI浅析——SystemUI启动流程 》、《 Android 4.0 ICS SystemUI浅析——StatusBar结构分析 》SystemUI和StatusBar的冰山一角，那么本文将从代码的角度来分析StatusBar的加载流程。

       本文来自： http://blog.csdn.net/yihongyuelan  欢迎转载 请务必注明出处！

        在《 Android 4.0 ICS SystemUI浅析——SystemUI启动流程 》中，我们提到了在Phone中，整个StatusBar和NavigationBar都是在/SourceCode/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java的start()方法中，完成初始化并显示到界面上的。因此，我们回到这段代码中查看：

@Override
    public void start() {
        mDisplay = ((WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE))
                .getDefaultDisplay();

        mWindowManager = IWindowManager.Stub.asInterface(
                ServiceManager.getService(Context.WINDOW_SERVICE));

        super.start(); // calls makeStatusBarView() 这里会调用父类StatusBar.java中的start()方法

        addNavigationBar();//加载导航栏，本文因以StatusBar为主，因此暂不分析NavigationBar

        //addIntruderView();

        // Lastly, call to the icon policy to install/update all the icons.
        mIconPolicy = new PhoneStatusBarPolicy(mContext);//用于初始化以及更新StatusBar上的icons
    }

       我们继续跟踪super.start()方法，来到/SourceCode/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/StatusBar.java的start()方法中，如代码所示：

public void start() {
        // First set up our views and stuff.首先准备我们需要显示的view以及原材料
        //我们先跟踪这里的makeStatusBarView
        View sb = makeStatusBarView();
        // Connect in to the status bar manager service
        StatusBarIconList iconList = new StatusBarIconList();
        ArrayList<IBinder> notificationKeys = new ArrayList<IBinder>();
        ArrayList<StatusBarNotification> notifications = new ArrayList<StatusBarNotification>();
       ... ...
    }

       通过Open Implementation跳转到makeStatusBarView的实现，因为我们是针对Phone来分析的，因此选择PhoneStatusBar，代码如下：

// ================================================================================
    // Constructing the view
    // ================================================================================
    protected View makeStatusBarView() {

        final Context context = mContext;

        Resources res = context.getResources();
        //获取ExpandedView的尺寸
        updateDisplaySize(); // populates mDisplayMetrics
        //定义icon的大小，缩放率和彼此间距
        loadDimens();
        mIconSize = res.getDimensionPixelSize(com.android.internal.R.dimen.status_bar_icon_size);
        //设置ExpandedView的布局
        ExpandedView expanded = (ExpandedView)View.inflate(context,
                R.layout.status_bar_expanded, null);
        if (DEBUG) {
            expanded.setBackgroundColor(0x6000FF80);
        }
        expanded.mService = this;
        //前面已注释，以下三段代码没有用到
        mIntruderAlertView = View.inflate(context, R.layout.intruder_alert, null);
        mIntruderAlertView.setVisibility(View.GONE);
        mIntruderAlertView.setClickable(true);
        PhoneStatusBarView sb;
        //这里根据是否是双卡来加载不同的布局文件
        if (TelephonyManager.getDefault().isMultiSimEnabled()) {
            sb = (PhoneStatusBarView)View.inflate(context,
                    R.layout.msim_status_bar, null);
        } else {
            sb = (PhoneStatusBarView)View.inflate(context,
                    R.layout.status_bar, null);
        }
        sb.mService = this;
        mStatusBarView = sb;
        //是否显示NavigationBar
        try {
            boolean showNav = mWindowManager.hasNavigationBar();
            if (showNav) {
                mNavigationBarView =
                    (NavigationBarView) View.inflate(context, R.layout.navigation_bar, null);

                mNavigationBarView.setDisabledFlags(mDisabled);
            }
        } catch (RemoteException ex) {
            // no window manager? good luck with that
        }

        // figure out which pixel-format to use for the status bar.
        mPixelFormat = PixelFormat.OPAQUE;
        //系统状态图标布局初始化
        mStatusIcons = (LinearLayout)sb.findViewById(R.id.statusIcons);
        //通知图标布局初始化
        mNotificationIcons = (IconMerger)sb.findViewById(R.id.notificationIcons);
        mMoreIcon = sb.findViewById(R.id.moreIcon);
        mNotificationIcons.setOverflowIndicator(mMoreIcon);
        //icons布局初始化，该布局用于装载除开tiker外的所有控件
        mIcons = (LinearLayout)sb.findViewById(R.id.icons);
        //ticker布局初始化
        mTickerView = sb.findViewById(R.id.ticker);
        //以上几个重要布局的关系在上一篇文章有详细分析

        //以下几段代码是在设置ExpandedView，ExpandedDialog通过加载ExpandedView显示，其中包括了ExpanedView上的清除按钮，
        //设置按钮，滚动条，日期显示等等
        mExpandedDialog = new ExpandedDialog(context);
        mExpandedView = expanded;
        mPile = (NotificationRowLayout)expanded.findViewById(R.id.latestItems);
        mExpandedContents = mPile; // was: expanded.findViewById(R.id.notificationLinearLayout);
        mNoNotificationsTitle = (TextView)expanded.findViewById(R.id.noNotificationsTitle);
        mNoNotificationsTitle.setVisibility(View.GONE); // disabling for now

        mClearButton = expanded.findViewById(R.id.clear_all_button);
        mClearButton.setOnClickListener(mClearButtonListener);
        mClearButton.setAlpha(0f);
        mClearButton.setEnabled(false);
        mDateView = (DateView)expanded.findViewById(R.id.date);
        mSettingsButton = expanded.findViewById(R.id.settings_button);
        mSettingsButton.setOnClickListener(mSettingsButtonListener);
        mScrollView = (ScrollView)expanded.findViewById(R.id.scroll);
        //tickerView的初始化
        mTicker = new MyTicker(context, sb);
        TickerView tickerView = (TickerView)sb.findViewById(R.id.tickerText);
        tickerView.mTicker = mTicker;
        //TrackingView初始化
        mTrackingView = (TrackingView)View.inflate(context, R.layout.status_bar_tracking, null);
        mTrackingView.mService = this;
        mCloseView = (CloseDragHandle)mTrackingView.findViewById(R.id.close);
        mCloseView.mService = this;

        mEdgeBorder = res.getDimensionPixelSize(R.dimen.status_bar_edge_ignore);

        // set the inital view visibility
        setAreThereNotifications();

        // Other icons
        //以下是对其他icons的加载(信号及电量图标的加载)
        mLocationController = new LocationController(mContext); // will post a notification
        mBatteryController = new BatteryController(mContext);
        mBatteryController.addIconView((ImageView)sb.findViewById(R.id.battery));
        SignalClusterView signalCluster;
        LinearLayout mSimSignalView;

        //根据是否是双卡加载不同的布局文件
        if (TelephonyManager.getDefault().isMultiSimEnabled()) {
            mMSimNetworkController = new MSimNetworkController(mContext);
            mSimSignalView = (LinearLayout) sb.findViewById(R.id.msim_signal_cluster);
            if (FeatureQuery.FEATURE_ANNUCIATOR_NEW_STATUSBAR_STYLE) {
                CUMSimSignalClusterView cuMSimSignalCluster = (CUMSimSignalClusterView)View.inflate(context, R.layout.msim_signal_cluster_view_cu, null);
                mSimSignalView.addView(cuMSimSignalCluster);
                for (int i=0; i < TelephonyManager.getDefault().getPhoneCount(); i++) {
                    mMSimNetworkController.addSignalCluster(cuMSimSignalCluster, i);
                }
                cuMSimSignalCluster.setNetworkController(mMSimNetworkController);
            } else {
                MSimSignalClusterView mSimSignalCluster = (MSimSignalClusterView)View.inflate(context, R.layout.msim_signal_cluster_view, null);
                mSimSignalView.addView(mSimSignalCluster);
                for (int i=0; i < TelephonyManager.getDefault().getPhoneCount(); i++) {
                    mMSimNetworkController.addSignalCluster(mSimSignalCluster, i);
                }
                mSimSignalCluster.setNetworkController(mMSimNetworkController);
            }
        } else {
            mNetworkController = new NetworkController(mContext);
            signalCluster = (SignalClusterView)sb.findViewById(R.id.signal_cluster);
            mNetworkController.addSignalCluster(signalCluster);
            signalCluster.setNetworkController(mNetworkController);
//          final ImageView wimaxRSSI =
//                  (ImageView)sb.findViewById(R.id.wimax_signal);
//          if (wimaxRSSI != null) {
//              mNetworkController.addWimaxIconView(wimaxRSSI);
//          }

        }

        // Recents Panel
        //最近使用界面初始化
        mRecentTasksLoader = new RecentTasksLoader(context);
        updateRecentsPanel();

        // receive broadcasts
        //注册广播监听器
        IntentFilter filter = new IntentFilter();
        filter.addAction(Intent.ACTION_CONFIGURATION_CHANGED);
        filter.addAction(Intent.ACTION_CLOSE_SYSTEM_DIALOGS);
        filter.addAction(Intent.ACTION_SCREEN_ON);
        filter.addAction(Intent.ACTION_SCREEN_OFF);
        context.registerReceiver(mBroadcastReceiver, filter);

        return sb;
    }

        通过makeStatusBarView()我们可以看到，在该方法中整个StatusBar根据获取的设备配置信息进行了布局，就好比我们去吃饭，先要安排好座位和桌子，最后才上菜，我们需要加载的icons——就是菜！！:D

        我们回到StatusBar.java的start()方法中继续分析，代码如下：

public void start() {
        // First set up our views and stuff.首先准备我们需要显示的view以及原材料
        //我们先跟踪这里的makeStatusBarView
        View sb = makeStatusBarView();

        // Connect in to the status bar manager service
        //初始化各个存储器，用于存储各类信息，这些信息通过StatusBarManagerService获取
        //iconsList用于存放icons
        StatusBarIconList iconList = new StatusBarIconList();
        //nodificationKeys保存以Binder为Key的notification
        ArrayList<IBinder> notificationKeys = new ArrayList<IBinder>();
        //保存StatusBarNotification类型的notifications
        ArrayList<StatusBarNotification> notifications = new ArrayList<StatusBarNotification>();
        //mCommandQueue是和IStatusBarService进行交互的IBinder
        mCommandQueue = new CommandQueue(this, iconList);
        //这里实际上获取的是StatusBarManagerService
        mBarService = IStatusBarService.Stub.asInterface(
                ServiceManager.getService(Context.STATUS_BAR_SERVICE));
        int[] switches = new int[7];
        ArrayList<IBinder> binders = new ArrayList<IBinder>();
        try {
            //通过StatusBarManagerService中的registerStatusBar来获取初始设置
            mBarService.registerStatusBar(mCommandQueue, iconList, notificationKeys, notifications,
                    switches, binders);
        } catch (RemoteException ex) {
            // If the system process isn't there we're doomed anyway.
        }
        //对SystemUI上像Clock、ExpandedView、NavigationBar等进行初始化设置
        disable(switches[0]);
        setSystemUiVisibility(switches[1]);
        topAppWindowChanged(switches[2] != 0);
        // StatusBarManagerService has a back up of IME token and it's restored here.
        setImeWindowStatus(binders.get(0), switches[3], switches[4]);
        setHardKeyboardStatus(switches[5] != 0, switches[6] != 0);

        // Set up the initial icon state
        //icon加载(注：陷阱!!!一不注意就会迷失！！后文详将细分析)
        int N = iconList.size();
        int viewIndex = 0;
        for (int i=0; i<N; i++) {
            StatusBarIcon icon = iconList.getIcon(i);
            if (icon != null) {
                addIcon(iconList.getSlot(i), i, viewIndex, icon);
                viewIndex++;
            }
        }

        // Set up the initial notification state
        //加载notifications
        N = notificationKeys.size();
        if (N == notifications.size()) {
            for (int i=0; i<N; i++) {
                addNotification(notificationKeys.get(i), notifications.get(i));
            }
        } else {
            Log.wtf(TAG, "Notification list length mismatch: keys=" + N
                    + " notifications=" + notifications.size());
        }

        // Put up the view
        //获取StatusBar高度
        final int height = getStatusBarHeight();
        //设置lp各种属性
        final WindowManager.LayoutParams lp = new WindowManager.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,
                height,
                WindowManager.LayoutParams.TYPE_STATUS_BAR,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                    | WindowManager.LayoutParams.FLAG_TOUCHABLE_WHEN_WAKING
                    | WindowManager.LayoutParams.FLAG_SPLIT_TOUCH,
                // We use a pixel format of RGB565 for the status bar to save memory bandwidth and
                // to ensure that the layer can be handled by HWComposer.  On some devices the
                // HWComposer is unable to handle SW-rendered RGBX_8888 layers.
                PixelFormat.RGB_565);
        
        // the status bar should be in an overlay if possible
        final Display defaultDisplay 
            = ((WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE))
                .getDefaultDisplay();
        //enable hardware acceleration based on device
        //使能硬件加速，不过只有Tablet上才有用
        setHardwareAcceleration(lp);
        lp.gravity = getStatusBarGravity();
        lp.setTitle("StatusBar");
        lp.packageName = mContext.getPackageName();
        lp.windowAnimations = R.style.Animation_StatusBar;
        //在Window上显示StatusBar界面
        WindowManagerImpl.getDefault().addView(sb, lp);
        mDoNotDisturb = new DoNotDisturb(mContext);
    }

       可能大多数朋友都还是云里雾里的，先别急，我们只是把大致流程走完了，细节还没有去分析，接下来我们再来看看StatusBar到底是如何加载Icons的。

       需要分析如何加载Icons，首先我们根据StatusBar.java中的start()方法可以看到，addIcon()方法完成了Icons的加载。那么通过Open Implementation跳转到PhoneStatusBar.java中的addIcon()方法中(因为我们之前传递的Context是PhoneStatusBar的)，代码如下：

public void addIcon(String slot, int index, int viewIndex, StatusBarIcon icon) {
        if (SPEW) Slog.d(TAG, "addIcon slot=" + slot + " index=" + index + " viewIndex=" + viewIndex
                + " icon=" + icon);
        //初始化StatusBarIconView
        StatusBarIconView view = new StatusBarIconView(mContext, slot, null);
        //加载icon
        view.set(icon);
        //这里的FEATURE_ANNUCIATOR_NEW_STATUSBAR_STYLE是高通自己定义的，默认为true
        if (FeatureQuery.FEATURE_ANNUCIATOR_NEW_STATUSBAR_STYLE) {
            //将设置好icon的StatusBarIconView加载到mStatusIcons布局中
            mStatusIcons.addView(view, viewIndex, new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, mIconSize));
        } else {
            mStatusIcons.addView(view, viewIndex, new LinearLayout.LayoutParams(mIconSize, mIconSize));
        }
    }

        整个加载过程从表面上看来只有3步，但从本质上来讲远远不止3步。首先，我们先来看看addIcon(...)方法所传递的值；我将这里Slog中的内容打印出来，结果如下：

addIcon slot=tty index=6 viewIndex=0 icon=StatusBarIcon(pkg=com.android.systemui id=0x7f02012b level=0 visible=false num=0 )
addIcon slot=cdma_eri index=11 viewIndex=1 icon=StatusBarIcon(pkg=com.android.systemui id=0x7f0200d8 level=0 visible=false num=0 )
addIcon slot=bluetooth index=4 viewIndex=0 icon=StatusBarIcon(pkg=com.android.systemui id=0x7f020073 level=0 visible=false num=0 )
addIcon slot=alarm_clock index=18 viewIndex=3 icon=StatusBarIcon(pkg=com.android.systemui id=0x7f020060 level=0 visible=false num=0 )
addIcon slot=sync_active index=2 viewIndex=0 icon=StatusBarIcon(pkg=com.android.systemui id=0x7f020129 level=0 visible=false num=0 )
addIcon slot=sync_failing index=1 viewIndex=0 icon=StatusBarIcon(pkg=com.android.systemui id=0x7f02012a level=0 visible=false num=0 )
addIcon slot=volume index=9 viewIndex=4 icon=StatusBarIcon(pkg=com.android.systemui id=0x7f0200d6 level=0 visible=false num=0 )
addIcon slot=headset index=16 viewIndex=6 icon=StatusBarIcon(pkg=com.android.systemui id=0x7f02000a level=0 visible=false num=0 )

        通过以上log，其中的tty表示语音图标，cdma_eri表示CDMA漫游时显示的图标，其他的大家应该都认识吧，这里就不多讲了。也就是说addIcon()加载的是系统的状态图标。那么我们继续查看它到底是如何加载的，继续查看StatusBarIconView()方法，代码如下：

public StatusBarIconView(Context context, String slot, Notification notification) {
        super(context);
        //获取资源
        final Resources res = context.getResources();
        mSlot = slot;
        //画笔初始化
        mNumberPain = new Paint();
        mNumberPain.setTextAlign(Paint.Align.CENTER);
        mNumberPain.setColor(res.getColor(R.drawable.notification_number_text_color));
        mNumberPain.setAntiAlias(true);
        mNotification = notification;
        setContentDescription(notification);

        // We do not resize and scale system icons (on the right), only notification icons (on the
        // left).
        if (notification != null) {
            final int outerBounds = res.getDimensionPixelSize(R.dimen.status_bar_icon_size);
            final int imageBounds = res.getDimensionPixelSize(R.dimen.status_bar_icon_drawing_size);
            final float scale = (float)imageBounds / (float)outerBounds;
            setScaleX(scale);
            setScaleY(scale);
            final float alpha = res.getFraction(R.dimen.status_bar_icon_drawing_alpha, 1, 1);
            setAlpha(alpha);
        }
        //按图片原来的size居中显示
        setScaleType(ImageView.ScaleType.CENTER);
    }

        通过查看StatusBarIconView的继承关系我们可以发现public class StatusBarIconView extends AnimatedImageView ，继续跟踪可以看到public class AnimatedImageView extends ImageView，也就是说我们的StatusBarIconView其实就是一个封装过的ImageView，这样自然能够盛放我们的Icons了。继续查看StatusBarIconView的set()方法，代码如下：

/**
     * Returns whether the set succeeded.
     */
    public boolean set(StatusBarIcon icon) {
        final boolean iconEquals = mIcon != null
                && streq(mIcon.iconPackage, icon.iconPackage)
                && mIcon.iconId == icon.iconId;
        final boolean levelEquals = iconEquals
                && mIcon.iconLevel == icon.iconLevel;
        final boolean visibilityEquals = mIcon != null
                && mIcon.visible == icon.visible;
        final boolean numberEquals = mIcon != null
                && mIcon.number == icon.number;
        //将icon的信息copy到mIcon中
        mIcon = icon.clone();
        setContentDescription(icon.contentDescription);
        //获取icon图片并设置到StatusBarIconView中去
        if (!iconEquals) {
            Drawable drawable = getIcon(icon);
            if (drawable == null) {
                Slog.w(StatusBar.TAG, "No icon for slot " + mSlot);
                return false;
            }
            setImageDrawable(drawable);
        }
        //设置需要显示的图片
        if (!levelEquals) {
            setImageLevel(icon.iconLevel);
        }
        //这个不太清楚具体是干嘛的
        if (!numberEquals) {
            if (icon.number > 0 && mContext.getResources().getBoolean(
                        R.bool.config_statusBarShowNumber)) {
                if (mNumberBackground == null) {
                    mNumberBackground = getContext().getResources().getDrawable(
                            R.drawable.ic_notification_overlay);
                }
                placeNumber();
            } else {
                mNumberBackground = null;
                mNumberText = null;
            }
            invalidate();
        }
        //设置是否可见
        if (!visibilityEquals) {
            setVisibility(icon.visible ? VISIBLE : GONE);
        }
        return true;
    }

        到这一步时，我们已经将系统的Icons设置到了mStatusIcons这个mStatusIcons的LinearLayout上了。

        但是，事实真的如此吗？这样就完成icons的初始化了吗？还是那句话，实践是检验真理是否正确的唯一标准！那么我们在PhoneStatusBar.java的addIcon()方法中，加入代码，将程序调用栈打印出来，结果一看便知(当然，也可以用Eclipse的远程调试)！加入代码如下：

StackTraceElement st[]= Thread.currentThread().getStackTrace();
        	for(int i=0;i<st.length;i++)
        	System.out.println(i+":"+st[i]);

         重新编译SystemUI，push到/system/app目录下，重新启动，打印部分log如下：

I/System.out(420): 0:dalvik.system.VMStack.getThreadStackTrace(Native Method)
I/System.out(420): 1:java.lang.Thread.getStackTrace(Thread.java:591)
I/System.out(420): 2:com.android.systemui.statusbar.phone.PhoneStatusBar.addIcon(PhoneStatusBar.java:562)
I/System.out(420): 3:com.android.systemui.statusbar.CommandQueue$H.handleMessage(CommandQueue.java:212)
I/System.out(420): 4:android.os.Handler.dispatchMessage(Handler.java:99)
I/System.out(420): 5:android.os.Looper.loop(Looper.java:137)
I/System.out(420): 6:android.app.ActivityThread.main(ActivityThread.java:4450)
I/System.out(420): 7:java.lang.reflect.Method.invokeNative(Native Method)
I/System.out(420): 8:java.lang.reflect.Method.invoke(Method.java:511)
I/System.out(420): 9:com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787)
I/System.out(420): 10:com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554)
I/System.out(420): 11:dalvik.system.NativeStart.main(Native Method)
... ...

        从打印出来的调用栈，我们可以发现，实际条用addIcon()方法的，并不是我们之前分析的StatusBar，而是来自CommandQueue中的handleMessage，这和我们之前的分析大相径庭啊！也就是说实际上addIcon()在CommandQueue中被调用了，那么我们就反过来分析，直接去CommandQueue.java中的handleMessage找到addIcon()。代码如下：

case OP_SET_ICON: {
        StatusBarIcon icon = (StatusBarIcon)msg.obj;
        StatusBarIcon old = mList.getIcon(index);
        if (old == null) {
        mList.setIcon(index, icon);
        mCallbacks.addIcon(mList.getSlot(index), index, viewIndex, icon);
        } else {
           mList.setIcon(index, icon);
           mCallbacks.updateIcon(mList.getSlot(index), index, viewIndex,
                          old, icon);
               }
        break;
        }

         通过case OP_SET_ICON我们可以继续追查，我们可以查到是谁发送的这个message，代码如下：

public void setIcon(int index, StatusBarIcon icon) {
        synchronized (mList) {
            int what = MSG_ICON | index;
            mHandler.removeMessages(what);
            mHandler.obtainMessage(what, OP_SET_ICON, 0, icon.clone()).sendToTarget();
        }
    }

        在CommandQueue中的setIcon发送了这个消息，通过Open Call Hierarchy继续追查，可以看到如图1：

图 1

         其中第一个onTransact是一个IBinder，后两者是StatusBarManagerService中的方法。通过方法名称，我们可以大致猜测，setIcon是设置Icon，setIconVisibility是这是Icon是否可见，我们从逻辑上分析，如果是开机第一次调用我们应该先设置Icon然后再考虑设置其可见性(看完后文就会明白了:D)。我们直接跳转到 StatusBarManagerService中的setIcon()方法，代码如下：

public void setIcon(String slot, String iconPackage, int iconId, int iconLevel,
            String contentDescription) {
        enforceStatusBar();

        synchronized (mIcons) {
            int index = mIcons.getSlotIndex(slot);//这里会检查是否是未定义的icon，如果是则抛出异常
            if (index < 0) {
                throw new SecurityException("invalid status bar icon slot: " + slot);
            }

            StatusBarIcon icon = new StatusBarIcon(iconPackage, iconId, iconLevel, 0,
                    contentDescription);
            //Slog.d(TAG, "setIcon slot=" + slot + " index=" + index + " icon=" + icon);
            mIcons.setIcon(index, icon);

            if (mBar != null) {
                try {
                    mBar.setIcon(index, icon);//这里调用的
                } catch (RemoteException ex) {
                }
            }
        }
    }

        继续用Open Call Hierarchy查找哪里调用的setIcon方法，如图2：

图 2

         这里一看就知道应该是StatusBarManager中的setIcon嘛，继续跟踪，代码如下：

public void setIcon(String slot, int iconId, int iconLevel, String contentDescription) {
        try {
            final IStatusBarService svc = getService();
            if (svc != null) {
                svc.setIcon(slot, mContext.getPackageName(), iconId, iconLevel,
                    contentDescription);//这里调用的
            }
        } catch (RemoteException ex) {
            // system process is dead anyway.
            throw new RuntimeException(ex);
        }
    }

        目前看来还不是很清晰，继续查找，如图3：

图 3

        看到这里请不要头晕，因为真相就在眼前！那么这里应该是谁在调用呢？在本文的一开始，我们就分析了/SourceCode/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java的start()方法，在该方法中有如下代码：

mIconPolicy = new PhoneStatusBarPolicy(mContext);

        该代码不正是调用了PhoneStatusBarPolicy()构造方法吗？直接跟进去，代码如下：

public PhoneStatusBarPolicy(Context context) {
        ... ...
        // listen for broadcasts
        IntentFilter filter = new IntentFilter();
        filter.addAction(Intent.ACTION_ALARM_CHANGED);
        filter.addAction(Intent.ACTION_SYNC_STATE_CHANGED);
        filter.addAction(AudioManager.RINGER_MODE_CHANGED_ACTION);
        filter.addAction(AudioManager.VIBRATE_SETTING_CHANGED_ACTION);
        filter.addAction(BluetoothAdapter.ACTION_STATE_CHANGED);
    filter.addAction(Intent.ACTION_HEADSET_PLUG); // ted add 2021-4-24
        filter.addAction(BluetoothAdapter.ACTION_CONNECTION_STATE_CHANGED);
        filter.addAction(TelephonyIntents.ACTION_SIM_STATE_CHANGED);
        filter.addAction(TtyIntent.TTY_ENABLED_CHANGE_ACTION);
        mContext.registerReceiver(mIntentReceiver, filter, null, mHandler);
        ... ...

        // TTY status
        mService.setIcon("tty",  R.drawable.stat_sys_tty_mode, 0, null);//这里调用
        mService.setIconVisibility("tty", false);

        // Cdma Roaming Indicator, ERI
        mService.setIcon("cdma_eri", R.drawable.stat_sys_roaming_cdma_0, 0, null);//这里调用
        mService.setIconVisibility("cdma_eri", false);

        ... ...
        mService.setIcon("bluetooth", bluetoothIcon, 0, null);//这里调用
        mService.setIconVisibility("bluetooth", mBluetoothEnabled);

        // Alarm clock
        mService.setIcon("alarm_clock", R.drawable.stat_sys_alarm, 0, null);//这里调用
        mService.setIconVisibility("alarm_clock", false);

        // Sync state
        mService.setIcon("sync_active", R.drawable.stat_sys_sync, 0, null);//这里调用
        mService.setIcon("sync_failing", R.drawable.stat_sys_sync_error, 0, null);//这里调用
        mService.setIconVisibility("sync_active", false);
        mService.setIconVisibility("sync_failing", false);

        // volume
        mService.setIcon("volume", R.drawable.stat_sys_ringer_silent, 0, null);//这里调用
        mService.setIconVisibility("volume", false);
        updateVolume();
    
  // headset
  mService.setIcon("headset", R.drawable.ckt_headset_with_mic, 0, null);//这里调用
  mService.setIconVisibility("headset", false);
    }

       这里也同时验证了我们前面的猜想，即先设置Icon再设置其可见性。也许你会认为本文到这里已经完结了(太长了，一次看不完...o(╯□╰)o)，但有个别地方我还得再提一下，Android 启动之后，在SystemServer.java的run方法中，调用了StatusBarManagerService的构造方法，代码如下：

... ...
            try {
                Slog.i(TAG, "Status Bar");
                statusBar = new StatusBarManagerService(context, wm);
                ServiceManager.addService(Context.STATUS_BAR_SERVICE, statusBar);
            } catch (Throwable e) {
                reportWtf("starting StatusBarManagerService", e);
            }
            ... ...

         在StatusBarManagerService的构造方法中，代码如下：

public StatusBarManagerService(Context context, WindowManagerService windowManager) {
        mContext = context;
        mWindowManager = windowManager;
        mWindowManager.setOnHardKeyboardStatusChangeListener(this);

        final Resources res = context.getResources();
        //这里加载了系统预置的所有icon，路径在：Sourcecode/framework/base/core/res/res/values/config.xml中
        mIcons.defineSlots(res.getStringArray(com.android.internal.R.array.config_statusBarIcons));
    }

        其中Sourcecode/framework/base/core/res/res/values/config.xml中的预置图标定义如下：

<string-array name="config_statusBarIcons">
        <item><xliff:g id="id">ime</xliff:g></item>
        <item><xliff:g id="id">sync_failing</xliff:g></item>
        <item><xliff:g id="id">sync_active</xliff:g></item>
        <item><xliff:g id="id">gps</xliff:g></item>
        <item><xliff:g id="id">bluetooth</xliff:g></item>
        <item><xliff:g id="id">nfc</xliff:g></item>
        <item><xliff:g id="id">tty</xliff:g></item>
        <item><xliff:g id="id">speakerphone</xliff:g></item>
        <item><xliff:g id="id">mute</xliff:g></item>
        <item><xliff:g id="id">volume</xliff:g></item>
        <item><xliff:g id="id">wifi</xliff:g></item>
        <item><xliff:g id="id">cdma_eri</xliff:g></item>
        <item><xliff:g id="id">phone_signal_second_sub</xliff:g></item>
        <item><xliff:g id="id">data_connection</xliff:g></item>
        <item><xliff:g id="id">phone_evdo_signal</xliff:g></item>
        <item><xliff:g id="id">phone_signal</xliff:g></item>
        <item><xliff:g id="id">headset</xliff:g></item>
        <item><xliff:g id="id">battery</xliff:g></item>
        <item><xliff:g id="id">alarm_clock</xliff:g></item>
        <item><xliff:g id="id">secure</xliff:g></item>
        <item><xliff:g id="id">clock</xliff:g></item>
</string-array>

        这些东西在后文判断时都会用到，在此记录用以备忘。

       小结

       本文主要是对StatusBar上面的Icons的加载进行了较为细致的分析，后面将继续分析各个部件的加载以及工作流程。其中自己也走了不少弯路，但还是想记录下载，毕竟没有谁从一开始就能做正确吧！将此总结分享出来希望能给各位一些帮助，同时也给自己一些激励，希望自己后面能做的更好。本文主要是枯燥的代码调用与追踪，但对于需要的朋友，我想还是很有帮助的，后面会将相关的时序图以及UML图贴出来，以供参考。