music播放音乐和system中播放控制栏的关联

主要用到了IAC 通讯机制

 http://tech.mozilla.com.tw/posts/3560/inter-app-communication-app-%E7%9A%84%E6%BA%9D%E9%80%9A%E6%A9%8B%E6%A8%91

在music界面第一页是Tile形式，点击某一首进行播放的click事件在,注意：不能在nightly中同时打两个异步的断点，如下面的1，2，3需要各自单独打断点：music.js

 init: function tv_init() {    this.dataSource = [];    this.index = 0;    this.view.addEventListener('click', this);    this.view.addEventListener('input', this);    this.view.addEventListener('touchend', this);    this.searchInput.addEventListener('focus', this);  },handleEvent: function tv_handleEvent(evt) {    function tv_resetSearch(self) {      evt.preventDefault();      self.searchInput.value = '';      SearchView.clearSearch();    }    var target = evt.target;    if (!target)      return;    switch (evt.type) {      case 'touchend':                 //1，先响应此case        // Check for tap on parent form element with event origin as clear buton        // This is workaround for a bug in input_areas BB. See Bug 920770        if (target.id === 'views-tiles-search') {          var id = evt.originalTarget.id;          if (id && id !== 'views-tiles-search-input' &&            id !== 'views-tiles-search-close') {            tv_resetSearch(this);            return;          }        }        if (target.id === 'views-tiles-search-clear') {          tv_resetSearch(this);          return;        }        break;      case 'click':                      //2，后响应click        if (target.id === 'views-tiles-search-close') {          if (ModeManager.currentMode === MODE_SEARCH_FROM_TILES) {            ModeManager.pop();          }          this.hideSearch();          evt.preventDefault();        } else if (target.dataset.index) {          var handler;          var index = target.dataset.index;          var data = this.dataSource[index];          handler = tv_playAlbum.bind(this, data, index);  //这里有个handler          target.addEventListener('transitionend', handler);        }        break;      case 'focus':        if (target.id === 'views-tiles-search-input') {          if (ModeManager.currentMode !== MODE_SEARCH_FROM_TILES) {            ModeManager.push(MODE_SEARCH_FROM_TILES);            SearchView.search(target.value);          }        }        break;      case 'input':        if (target.id === 'views-tiles-search-input') {          SearchView.search(target.value);        }        break;      default:        return;    }    function tv_playAlbum(data, index) {         //3，对应上面的handler处理，此函数中播放音乐      var key = 'metadata.album';      var range = IDBKeyRange.only(data.metadata.album);      var direction = 'next';      ModeManager.push(MODE_PLAYER, function() {        PlayerView.clean();        // When an user tap an album on the tilesView        // we have to get all the song data first        // because the shuffle option might be ON        // and we have create shuffled list and play in shuffle order        playerHandle = musicdb.enumerateAll(key, range, direction,          function tv_enumerateAll(dataArray) {            PlayerView.setSourceType(TYPE_LIST);            PlayerView.dataSource = dataArray;            if (PlayerView.shuffleOption) {              PlayerView.setShuffle(true);              PlayerView.play(PlayerView.shuffledList[0]);            } else {              PlayerView.play(0);            }          }        );      });      target.removeEventListener('transitionend', handler);    }  }};

music中communications.js中有：

 this.mrc = new MediaRemoteControls();

music：MediaRemoteControls?在中shared目录下的remote_controls.js中，该类中会有_postMessage的动作以和system交互。

MediaRemoteControls.prototype.notifyAppInfo = function(info) {  // Send the app info via IAC.  this._postMessage('appinfo', info);   //system中处理的一种};...// Now, send it via IAC.  this._postMessage('nowplaying', metadata);   //system中处理的一种...// Now, send it via IAC.this._postMessage('status', status);    //system中处理的一种...MediaRemoteControls.prototype._postMessage = function(name, value) {  var message = {type: name, data: value};  if (!this._ports) {    if (this._queuedMessages)      this._queuedMessages.push(message);  } else {    this._ports.forEach(function(port) {      port.postMessage(message);    });  }};

在system的manifest.webapps中有：

 "connections": {    "mediacomms": {      "description": "Communication with media apps for now playing info",      "rules": {}    },    "ftucomms": {      "description": "Communicate between communications/ftu and System",      "rules": {}    },    "bluetoothTransfercomms": {      "description": "Communication with bluetooth apps for sending files info",      "rules": {}    }

system中用到shared目录下的iac_handler.js中有，在这里会给mediacomms加上前缀iac-

var IACHandler = {  _eventPrefix: 'iac-',  _ports: {},  init: function onInit() {    var self = this;    window.navigator.mozSetMessageHandler('connection',      function onConnected(request) {       ...       var evtName = self._eventPrefix + keyword;          var iacEvt = document.createEvent('CustomEvent');          iacEvt.initCustomEvent(evtName,            /* canBubble: */ true, /* cancelable */ false, message);          window.dispatchEvent(iacEvt);          ...

system下lockscreen.js及notification.js中的播放控制器均是media_playback.js中MediaPlaybackWidget的对象，这里会进一步处理经过IACHandler处理过的message

window.addEventListener('iac-mediacomms', this.handleMessage.bind(this)); ...  MediaPlaybackWidget.prototype = {  handleMessage: function mpw_handleMessage(event) {    var message = event.detail;    switch (message.type) {    case 'appinfo':      this.updateAppInfo(message.data);      break;    case 'nowplaying':      this.updateNowPlaying(message.data);      break;    case 'status':      this.updatePlaybackStatus(message.data);      break;    }  }, ...