Android N SystemUI－狀態欄

手機中狀態欄主要用來顯示電池電量信息、時間、信號格數、系統圖標（鬧鐘）、通知圖標，我們先來看看手機statusbar的界面

今天我們先來簡單介紹下這個界面是怎麼顯示出來，考慮到放到一起寫，文章就有點太長了，後續會對信號格圖標顯示、通知圖標、系統圖標這幾個複雜點的一一介紹
從上圖中我們基本可以看出，從左到右基本上是通知圖標顯示區域、系統圖標顯示區域，系統圖標區域裏主要包括wifi、飛行模式、鬧鐘、耳機、信號格顯示、數據業務上下行箭頭、電池電量圖標、時間圖標，具體佈局如下：

//frameworks/base/packages/SystemUI/res/layout/status_bar.xml
<com.android.systemui.statusbar.phone.PhoneStatusBarView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:systemui="http://schemas.android.com/apk/res/com.android.systemui"
    android:id="@+id/status_bar"
    android:background="@drawable/system_bar_background"
    android:orientation="vertical"
    android:focusable="false"
    android:descendantFocusability="afterDescendants"
    >
    ...
    <LinearLayout android:id="@+id/status_bar_contents"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingStart="6dp"
        android:paddingEnd="8dp"
        android:orientation="horizontal"
        >

        <!-- The alpha of this area is controlled from both PhoneStatusBarTransitions and
             PhoneStatusBar (DISABLE_NOTIFICATION_ICONS). -->
        <com.android.systemui.statusbar.AlphaOptimizedFrameLayout
            android:id="@+id/notification_icon_area"
            android:layout_width="0dip"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:orientation="horizontal" />

        <com.android.keyguard.AlphaOptimizedLinearLayout android:id="@+id/system_icon_area"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:orientation="horizontal"
            >

            <include layout="@layout/system_icons" />

            <com.android.systemui.statusbar.policy.Clock
                android:id="@+id/clock"
                android:textAppearance="@style/TextAppearance.StatusBar.Clock"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:singleLine="true"
                android:paddingStart="@dimen/status_bar_clock_starting_padding"
                android:paddingEnd="@dimen/status_bar_clock_end_padding"
                android:gravity="center_vertical|start"
                />
        </com.android.keyguard.AlphaOptimizedLinearLayout>
    </LinearLayout>
    ... 
    </com.android.systemui.statusbar.phone.PhoneStatusBarView>

如果有通知圖標相關問題，基本上就可以根據notification_icon_area這個id去跟蹤就行，而系統圖標區域還有一個比較重要的佈局文件system_icons.xml

//frameworks/base/packages/SystemUI/res/layout/system_icons.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/system_icons"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:gravity="center_vertical">

    <com.android.keyguard.AlphaOptimizedLinearLayout android:id="@+id/statusIcons"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:gravity="center_vertical"
        android:orientation="horizontal"/>

    <include layout="@layout/signal_cluster_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="@dimen/signal_cluster_margin_start"/>

    <!-- battery must be padded below to match assets -->
    <com.android.systemui.BatteryMeterView android:id="@+id/battery"
        android:layout_height="@dimen/status_bar_battery_icon_height"
        android:layout_width="@dimen/status_bar_battery_icon_width"
        android:layout_marginBottom="@dimen/battery_margin_bottom"/>
</LinearLayout>

這個裏面的signal_cluster_view.xml主要是和sim卡相關的一些圖標（vpn、信號格數、網絡狀態、數據業務上下行、漫遊等）、以及wifi、飛行模式圖標，BatteryMeterView主要用來顯示電池電量信息的

//frameworks/base/packages/SystemUI/res/layout/signal_cluster_view.xml
    <com.android.systemui.statusbar.SignalClusterView
   xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/signal_cluster"
    android:layout_height="match_parent"
    android:layout_width="wrap_content"
    android:gravity="center_vertical"
    android:orientation="horizontal"
 android:paddingEnd="@dimen/signal_cluster_battery_padding" >
    <ImageView
        android:id="@+id/vpn"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:paddingEnd="6dp"
        android:src="@drawable/stat_sys_vpn_ic"
        />
    <FrameLayout
        android:id="@+id/ethernet_combo"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        >    <com.android.systemui.statusbar.AlphaOptimizedImageView
            android:theme="@style/DualToneLightTheme"
            android:id="@+id/ethernet"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            />    <com.android.systemui.statusbar.AlphaOptimizedImageView
            android:theme="@style/DualToneDarkTheme"
            android:id="@+id/ethernet_dark"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:alpha="0.0"
            />
    </FrameLayout>
    <FrameLayout
        android:id="@+id/wifi_combo"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        >   <com.android.systemui.statusbar.AlphaOptimizedImageView
            android:theme="@style/DualToneLightTheme"
            android:id="@+id/wifi_signal"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            />    <com.android.systemui.statusbar.AlphaOptimizedImageView
            android:theme="@style/DualToneDarkTheme"
            android:id="@+id/wifi_signal_dark"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:alpha="0.0"
            />
    </FrameLayout>
    <View
        android:id="@+id/wifi_signal_spacer"   android:layout_width="@dimen/status_bar_wifi_signal_spacer_width"
        android:layout_height="4dp"
        android:visibility="gone"
        />
    <LinearLayout
        android:id="@+id/mobile_signal_group"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        >
    </LinearLayout>
    <FrameLayout
        android:id="@+id/no_sims_combo"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"    android:contentDescription="@string/accessibility_no_sims">
        <com.android.systemui.statusbar.AlphaOptimizedImageView
            android:theme="@style/DualToneLightTheme"
            android:id="@+id/no_sims"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:src="@drawable/stat_sys_no_sims"
            />
<com.android.systemui.statusbar.AlphaOptimizedImageView
            android:theme="@style/DualToneDarkTheme"
            android:id="@+id/no_sims_dark"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:src="@drawable/stat_sys_no_sims"
            android:alpha="0.0"
            />
    </FrameLayout>
    <View
        android:id="@+id/wifi_airplane_spacer"  android:layout_width="@dimen/status_bar_airplane_spacer_width"
        android:layout_height="4dp"
        android:visibility="gone"
        />
    <ImageView
        android:id="@+id/airplane"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        />
    </com.android.systemui.statusbar.SignalClusterView>

基本佈局文件差不多介紹完了，下面畫了個簡單的圖總結下

下面介紹完了佈局，就來看看這些佈局是在那兒被加載的，以及電池電量、和時間圖標的具體顯示流程
status_bar.xml文件是在super_status_bar.xml裏被include的，而super_status_bar.xml的加載是在PhoneStatusBar.java裏的makeStatusBarView中初始化的，如下

//frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
    // ================================================================================
    // Constructing the view
    // ================================================================================
    protected PhoneStatusBarView makeStatusBarView() {
        ...

        inflateStatusBarWindow(context);
        mStatusBarWindow.setService(this);
        mStatusBarWindow.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                checkUserAutohide(v, event);
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    if (mExpandedVisible) {
                        animateCollapsePanels();
                    }
                }
                return mStatusBarWindow.onTouchEvent(event);
            }
        });

        mNotificationPanel = (NotificationPanelView) mStatusBarWindow.findViewById(
                R.id.notification_panel);
        mNotificationPanel.setStatusBar(this);
        mNotificationPanel.setGroupManager(mGroupManager);

        mStatusBarView = (PhoneStatusBarView) mStatusBarWindow.findViewById(R.id.status_bar);
        mStatusBarView.setBar(this);
        mStatusBarView.setPanel(mNotificationPanel);


        // set the initial view visibility
        setAreThereNotifications();


        mBatteryController = createBatteryController();
        mBatteryController.addStateChangedCallback(new BatteryStateChangeCallback() {
            @Override
            public void onPowerSaveChanged(boolean isPowerSave) {
                mHandler.post(mCheckBarModes);
                if (mDozeServiceHost != null) {
                    mDozeServiceHost.firePowerSaveChanged(isPowerSave);
                }
            }
            @Override
            public void onBatteryLevelChanged(int level, boolean pluggedIn, boolean charging) {
                // noop
            }
        });
        mNetworkController = new NetworkControllerImpl(mContext, mHandlerThread.getLooper());
        mNetworkController.setUserSetupComplete(mUserSetup);
        mHotspotController = new HotspotControllerImpl(mContext);
        mBluetoothController = new BluetoothControllerImpl(mContext, mHandlerThread.getLooper());
        mSecurityController = new SecurityControllerImpl(mContext);
        if (mContext.getResources().getBoolean(R.bool.config_showRotationLock)) {
            mRotationLockController = new RotationLockControllerImpl(mContext);
        }

        initSignalCluster(mStatusBarView);
        initSignalCluster(mKeyguardStatusBar);
        initEmergencyCryptkeeperText();

        mCarrierLabel = (TextView)mStatusBarWindow.findViewById(R.id.carrier_label);
        ...
        ((BatteryMeterView) mStatusBarView.findViewById(R.id.battery)).setBatteryController(
                mBatteryController);
        mKeyguardStatusBar.setBatteryController(mBatteryController);
        ...
        return mStatusBarView;
    }

基本上狀態裏顯示的入口就在這，下面主要看看電池電量、和時間圖標，從前面佈局文件可知，顯示時間對應的view爲Clock.java，電池電量的爲BatteryMeterView.java
時間的更新主要是通過監聽‘android.intent.action.TIME_TICK’廣播

//frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/policy/Clock.java
    public class Clock extends TextView implements DemoMode, Tunable {
    ...
    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();

        if (!mAttached) {
            mAttached = true;
            IntentFilter filter = new IntentFilter();

            filter.addAction(Intent.ACTION_TIME_TICK);//監聽廣播
            filter.addAction(Intent.ACTION_TIME_CHANGED);
            filter.addAction(Intent.ACTION_TIMEZONE_CHANGED);
            filter.addAction(Intent.ACTION_CONFIGURATION_CHANGED);
            filter.addAction(Intent.ACTION_USER_SWITCHED);

            getContext().registerReceiverAsUser(mIntentReceiver, UserHandle.ALL, filter,
                    null, getHandler());
            TunerService.get(getContext()).addTunable(this, CLOCK_SECONDS,
                    StatusBarIconController.ICON_BLACKLIST);
        }

        // NOTE: It's safe to do these after registering the receiver since the receiver always runs
        // in the main thread, therefore the receiver can't run before this method returns.

        // The time zone may have changed while the receiver wasn't registered, so update the Time
        mCalendar = Calendar.getInstance(TimeZone.getDefault());

        // Make sure we update to the current time
        updateClock();
        updateShowSeconds();
    }
    ...
    private final BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (action.equals(Intent.ACTION_TIMEZONE_CHANGED)) {
                String tz = intent.getStringExtra("time-zone");
                mCalendar = Calendar.getInstance(TimeZone.getTimeZone(tz));
                if (mClockFormat != null) {
                    mClockFormat.setTimeZone(mCalendar.getTimeZone());
                }
            } else if (action.equals(Intent.ACTION_CONFIGURATION_CHANGED)) {
                final Locale newLocale = getResources().getConfiguration().locale;
                if (! newLocale.equals(mLocale)) {
                    mLocale = newLocale;
                    mClockFormatString = ""; // force refresh
                }
            }
            updateClock();//更新時間
        }
    };

    final void updateClock() {
        if (mDemoMode) return;
        mCalendar.setTimeInMillis(System.currentTimeMillis());
        setText(getSmallTime());
        setContentDescription(mContentDescriptionFormat.format(mCalendar.getTime()));
    }
    //格式化時間
    private final CharSequence getSmallTime() {
        Context context = getContext();
        boolean is24 = DateFormat.is24HourFormat(context, ActivityManager.getCurrentUser());
        LocaleData d = LocaleData.get(context.getResources().getConfiguration().locale);

        final char MAGIC1 = '\uEF00';
        final char MAGIC2 = '\uEF01';

        SimpleDateFormat sdf;
        String format = mShowSeconds
                ? is24 ? d.timeFormat_Hms : d.timeFormat_hms
                : is24 ? d.timeFormat_Hm : d.timeFormat_hm;
        if (!format.equals(mClockFormatString)) {
            mContentDescriptionFormat = new SimpleDateFormat(format);
            /*
             * Search for an unquoted "a" in the format string, so we can
             * add dummy characters around it to let us find it again after
             * formatting and change its size.
             */
            if (mAmPmStyle != AM_PM_STYLE_NORMAL) {
                int a = -1;
                boolean quoted = false;
                for (int i = 0; i < format.length(); i++) {
                    char c = format.charAt(i);

                    if (c == '\'') {
                        quoted = !quoted;
                    }
                    if (!quoted && c == 'a') {
                        a = i;
                        break;
                    }
                }

                if (a >= 0) {
                    // Move a back so any whitespace before AM/PM is also in the alternate size.
                    final int b = a;
                    while (a > 0 && Character.isWhitespace(format.charAt(a-1))) {
                        a--;
                    }
                    format = format.substring(0, a) + MAGIC1 + format.substring(a, b)
                        + "a" + MAGIC2 + format.substring(b + 1);
                }
            }
            mClockFormat = sdf = new SimpleDateFormat(format);
            mClockFormatString = format;
        } else {
            sdf = mClockFormat;
        }
        String result = sdf.format(mCalendar.getTime());

        if (mAmPmStyle != AM_PM_STYLE_NORMAL) {
            int magic1 = result.indexOf(MAGIC1);
            int magic2 = result.indexOf(MAGIC2);
            if (magic1 >= 0 && magic2 > magic1) {
                SpannableStringBuilder formatted = new SpannableStringBuilder(result);
                if (mAmPmStyle == AM_PM_STYLE_GONE) {
                    formatted.delete(magic1, magic2+1);
                } else {
                    if (mAmPmStyle == AM_PM_STYLE_SMALL) {
                        CharacterStyle style = new RelativeSizeSpan(0.7f);
                        formatted.setSpan(style, magic1, magic2,
                                          Spannable.SPAN_EXCLUSIVE_INCLUSIVE);
                    }
                    formatted.delete(magic2, magic2 + 1);
                    formatted.delete(magic1, magic1 + 1);
                }
                return formatted;
            }
        }
        ...
        return result;
    }
}

電池電量圖標這個和時鐘差不多，主要是BatteryMeterView（ImageView的子類）和BatteryMeterDrawable（Drawable的子類）這兩個類，其中BatteryMeterView負責view顯示，BatteryMeterDrawable負責圖標內容更新，並且這兩個類都實現了BatteryController.BatteryStateChangeCallback這個接口

public interface BatteryController extends DemoMode {
    ...
    /**
     * A listener that will be notified whenever a change in battery level or power save mode
     * has occurred.
     */
    interface BatteryStateChangeCallback {
        void onBatteryLevelChanged(int level, boolean pluggedIn, boolean charging);
        void onPowerSaveChanged(boolean isPowerSave);
    }
}

frameworks/base/packages/SystemUI/src/com/android/systemui/BatteryMeterDrawable.java
    public class BatteryMeterDrawable extends Drawable implements
        BatteryController.BatteryStateChangeCallback {
    ...
    @Override
    public void onBatteryLevelChanged(int level, boolean pluggedIn, boolean charging) {
        mLevel = level;
        mPluggedIn = pluggedIn;

        postInvalidate();//更新圖標
    }
    @Override
    public void draw(Canvas c) {
    ...
    }
}

onBatteryLevelChanged是在BatteryControllerImpl.java裏被調用的

frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/policy/BatteryControllerImpl.java
    public class BatteryControllerImpl extends BroadcastReceiver implements BatteryController {
    ...

    public BatteryControllerImpl(Context context) {
        mContext = context;
        mHandler = new Handler();
        mPowerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE);

        registerReceiver();
        updatePowerSave();
    }

    private void registerReceiver() {
        IntentFilter filter = new IntentFilter();
        filter.addAction(Intent.ACTION_BATTERY_CHANGED); //註冊電量改變的廣播
        filter.addAction(PowerManager.ACTION_POWER_SAVE_MODE_CHANGED);
        filter.addAction(PowerManager.ACTION_POWER_SAVE_MODE_CHANGING);
        filter.addAction(ACTION_LEVEL_TEST);
        mContext.registerReceiver(this, filter);
    }


    @Override
    public void onReceive(final Context context, Intent intent) {
        final String action = intent.getAction();
        if (action.equals(Intent.ACTION_BATTERY_CHANGED)) {
            if (mTestmode && !intent.getBooleanExtra("testmode", false)) return;
            ...
            fireBatteryLevelChanged();
        } 
    }
    ...
    protected void fireBatteryLevelChanged() {
        synchronized (mChangeCallbacks) {
            final int N = mChangeCallbacks.size();
            for (int i = 0; i < N; i++) {
                mChangeCallbacks.get(i).onBatteryLevelChanged(mLevel, mPluggedIn, mCharging);
            }
        }
    }
    ...
}

後續會對信號格圖標顯示、通知圖標、系統圖標都單獨分析介紹，如有錯誤，麻煩留言指出。