Android学习 ——SystemUIService之StorageNotification分析

usb 这块的内容较多，但是抽取核心部分之后就比较容易理解

**查看文件目录，其实在SystemUIService 启动中相关的类只有StorageNotification.java和UsbStorageActivity.java
StorageNotification负责逻辑处理，UsbStorageActivity负责显示**

下面是StorageNotification.java 的主要函数关系图

先看入口函数

    @Override
    public void start() {
        mStorageManager = (StorageManager) mContext.getSystemService(Context.STORAGE_SERVICE);
        final boolean connected = mStorageManager.isUsbMassStorageConnected();
        if (DEBUG) Log.d(TAG, String.format( "Startup with UMS connection %s (media state %s)",
                mUmsAvailable, Environment.getExternalStorageState()));

        HandlerThread thr = new HandlerThread("SystemUI StorageNotification");
        thr.start();
        mAsyncEventHandler = new Handler(thr.getLooper());

        StorageNotificationEventListener listener = new StorageNotificationEventListener();
        listener.onUsbMassStorageConnectionChanged(connected);
        mStorageManager.registerListener(listener);
    }

先获取了STORAGE_SERVICE，然后给mStorageManager 注册了监听 StorageNotificationEventListener

    private class StorageNotificationEventListener extends StorageEventListener {

        //连接改变
        public void onUsbMassStorageConnectionChanged(final boolean connected) {
            mAsyncEventHandler.post(new Runnable() {
                @Override
                public void run() {
                    onUsbMassStorageConnectionChangedAsync(connected);
                }
            });
        }
        // 存储状态改变
        public void onStorageStateChanged(final String path,
                final String oldState, final String newState) {
            mAsyncEventHandler.post(new Runnable() {
                @Override
                public void run() {
                    onStorageStateChangedAsync(path, oldState, newState);
                }
            });
        }
    }

StorageNotificationEventListener 主要是监听两个函数

onUsbMassStorageConnectionChanged（usb连接变化）
onStorageStateChanged (存储状态变化)

在这两个函数中又主要使用了

onUsbMassStorageConnectionChangedAsync()
onStorageStateChangedAsync()

在事件监听中会返回一系列的状态值，根据不同的状态值配置显示标题，内容，使用UsbStorageActivity 显示

代码片段截取
  if (newState.equals(Environment.MEDIA_CHECKING)) {
            /*
             * Storage is now checking. Update media notification and disable
             * UMS notification.
             */
            setMediaStorageNotification(
                    com.android.internal.R.string.ext_media_checking_notification_title,
                    com.android.internal.R.string.ext_media_checking_notification_message,
                    com.android.internal.R.drawable.stat_notify_sdcard_prepare, true, false, null);
            updateUsbMassStorageNotification(false);
            }

上述配置需要显示的内容
下面为配置到UI显示以及设置发送存储相关的通知

    void updateUsbMassStorageNotification(boolean available) {

        if (available) {
            Intent intent = new Intent();
            intent.setClass(mContext, com.android.systemui.usb.UsbStorageActivity.class);
            intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

            PendingIntent pi = PendingIntent.getActivity(mContext, 0, intent, 0);
            setUsbStorageNotification(
                    com.android.internal.R.string.usb_storage_notification_title,
                    com.android.internal.R.string.usb_storage_notification_message,
                    com.android.internal.R.drawable.stat_sys_data_usb,
                    false, true, pi);
        } else {
            setUsbStorageNotification(0, 0, 0, false, false, null);
        }
    }

 private synchronized void setUsbStorageNotification(int titleId, int messageId, int icon,
            boolean sound, boolean visible, PendingIntent pi) {
        // force to show UsbSettings screen to select usb mode if property is true
        if (SystemProperties.getBoolean("persist.sys.ums", true)) {
            titleId = 0;
            messageId = 0;
            icon = 0;
            sound = false;
            visible = false;
            pi = null;
        }

        if (!visible && mUsbStorageNotification == null) {
            return;
        }

        NotificationManager notificationManager = (NotificationManager) mContext
                .getSystemService(Context.NOTIFICATION_SERVICE);

        if (notificationManager == null) {
            return;
        }

        if (visible) {
            Resources r = Resources.getSystem();
            CharSequence title = r.getText(titleId);
            CharSequence message = r.getText(messageId);

            if (mUsbStorageNotification == null) {
                mUsbStorageNotification = new Notification();
                mUsbStorageNotification.icon = icon;
                mUsbStorageNotification.when = 0;
            }

            if (sound) {
                mUsbStorageNotification.defaults |= Notification.DEFAULT_SOUND;
            } else {
                mUsbStorageNotification.defaults &= ~Notification.DEFAULT_SOUND;
            }

            mUsbStorageNotification.flags = Notification.FLAG_ONGOING_EVENT;

            mUsbStorageNotification.tickerText = title;
            if (pi == null) {
                Intent intent = new Intent();
                pi = PendingIntent.getBroadcastAsUser(mContext, 0, intent, 0,
                        UserHandle.CURRENT);
            }

            mUsbStorageNotification.setLatestEventInfo(mContext, title, message, pi);
            final boolean adbOn = 1 == Settings.Global.getInt(
                mContext.getContentResolver(),
                Settings.Global.ADB_ENABLED,
                0);

            if (POP_UMS_ACTIVITY_ON_CONNECT && !adbOn) {
                // Pop up a full-screen alert to coach the user through enabling UMS. The average
                // user has attached the device to USB either to charge the phone (in which case
                // this is harmless) or transfer files, and in the latter case this alert saves
                // several steps (as well as subtly indicates that you shouldn't mix UMS with other
                // activities on the device).
                //
                // If ADB is enabled, however, we suppress this dialog (under the assumption that a
                // developer (a) knows how to enable UMS, and (b) is probably using USB to install
                // builds or use adb commands.
                mUsbStorageNotification.fullScreenIntent = pi;
            }
        }

        final int notificationId = mUsbStorageNotification.icon;
        if (visible) {
            notificationManager.notifyAsUser(null, notificationId, mUsbStorageNotification,
                    UserHandle.ALL);
        } else {
            notificationManager.cancelAsUser(null, notificationId, UserHandle.ALL);
        }
    }