var loading = {};
//封裝文件下載類
function FileLoader( manager ) {
//使用默認的文件下載計數類
this.manager = ( manager !== undefined ) ? manager : DefaultLoadingManager;
}
Object.assign( FileLoader.prototype, {
//下載
load: function ( url, onLoad, onProgress, onError ) {
//如果url爲空
if ( url === undefined ) url = '';
//設置url
if ( this.path !== undefined ) url = this.path + url;
//修改url
url = this.manager.resolveURL( url );
var scope = this;
//在全局緩衝中查找文件
var cached = Cache.get( url );
//緩衝中找到了
if ( cached !== undefined ) {
//開始一個下載回調
scope.manager.itemStart( url );
//爲什麼不立刻調用onLoad，要在定時器中調用
setTimeout( function () {
//單個文件下載完成
if ( onLoad ) onLoad( cached );
//所有文件其中一個下載完成
scope.manager.itemEnd( url );
}, 0 );
//返回文件
return cached;
}
// Check if request is duplicate
//查看是否有重複的下載項
if ( loading[ url ] !== undefined ) {
//設置同一個文件的回調隊列
loading[ url ].push( {
onLoad: onLoad,
onProgress: onProgress,
onError: onError
} );
return;
}
// Check for data: URI
//查看下載文件的數據類型，是否base64
var dataUriRegex = /^data:(.*?)(;base64)?,(.*)$/;
var dataUriRegexResult = url.match( dataUriRegex );
// Safari can not handle Data URIs through XMLHttpRequest so process manually
//不同瀏覽器的處理方式不同(數據上傳？？？)
if ( dataUriRegexResult ) {
var mimeType = dataUriRegexResult[ 1 ]; //
var isBase64 = !! dataUriRegexResult[ 2 ];
var data = dataUriRegexResult[ 3 ];
data = decodeURIComponent( data );
if ( isBase64 ) data = atob( data );
try {
var response;
var responseType = ( this.responseType || '' ).toLowerCase();
switch ( responseType ) {
case 'arraybuffer':
case 'blob':
var view = new Uint8Array( data.length );
for ( var i = 0; i < data.length; i ++ ) {
view[ i ] = data.charCodeAt( i );
}
if ( responseType === 'blob' ) {
response = new Blob( [ view.buffer ], { type: mimeType } );
} else {
response = view.buffer;
}
break;
case 'document':
var parser = new DOMParser();
response = parser.parseFromString( data, mimeType );
break;
case 'json':
response = JSON.parse( data );
break;
default: // 'text' or other
response = data;
break;
}
// Wait for next browser tick like standard XMLHttpRequest event dispatching does
setTimeout( function () {
if ( onLoad ) onLoad( response );
scope.manager.itemEnd( url );
}, 0 );
} catch ( error ) {
// Wait for next browser tick like standard XMLHttpRequest event dispatching does
setTimeout( function () {
if ( onError ) onError( error );
scope.manager.itemError( url );
scope.manager.itemEnd( url );
}, 0 );
}
} else {
// Initialise array for duplicate requests
// 初始化數組
loading[ url ] = [];
//添加響應函數
loading[ url ].push( {
onLoad: onLoad,
onProgress: onProgress,
onError: onError
} );
//創建請求
var request = new XMLHttpRequest();
//設置請求類型
request.open( 'GET', url, true );
//添加下載完成監聽
request.addEventListener( 'load', function ( event ) {
//響應數據添加到緩衝中
var response = this.response;
Cache.add( url, response );
//下載回調
var callbacks = loading[ url ];
delete loading[ url ];
//下載狀態
if ( this.status === 200 || this.status === 0 ) {
//本地文件狀態爲0
// Some browsers return HTTP Status 0 when using non-http protocol
// e.g. 'file://' or 'data://'. Handle as success.
if ( this.status === 0 ) console.warn( 'THREE.FileLoader: HTTP Status 0 received.' );
//調用回到
for ( var i = 0, il = callbacks.length; i < il; i ++ ) {
var callback = callbacks[ i ];
if ( callback.onLoad ) callback.onLoad( response );
}
//下載完成
scope.manager.itemEnd( url );
} else {
//下載錯誤，這是
for ( var i = 0, il = callbacks.length; i < il; i ++ ) {
var callback = callbacks[ i ];
if ( callback.onError ) callback.onError( event );
}
scope.manager.itemError( url );
scope.manager.itemEnd( url );
}
}, false );
//添加下載過程監聽
request.addEventListener( 'progress', function ( event ) {
//回調工程處理，主要是百分比
var callbacks = loading[ url ];
for ( var i = 0, il = callbacks.length; i < il; i ++ ) {
var callback = callbacks[ i ];
if ( callback.onProgress ) callback.onProgress( event );
}
}, false );
//添加錯誤監聽
request.addEventListener( 'error', function ( event ) {
var callbacks = loading[ url ];
delete loading[ url ];
for ( var i = 0, il = callbacks.length; i < il; i ++ ) {
var callback = callbacks[ i ];
if ( callback.onError ) callback.onError( event );
}
//設置回調錯誤結束（manager所有文件的下載過程，不是單個文件的下載過程）
scope.manager.itemError( url );
scope.manager.itemEnd( url );
}, false );
//添加中斷監聽
request.addEventListener( 'abort', function ( event ) {
//獲取回調
var callbacks = loading[ url ];
//刪除
delete loading[ url ];
//遍歷回調
for ( var i = 0, il = callbacks.length; i < il; i ++ ) {
var callback = callbacks[ i ];
if ( callback.onError ) callback.onError( event );
}
//設置回調錯誤結束（manager所有文件的下載過程，不是單個文件的下載過程）
scope.manager.itemError( url );
scope.manager.itemEnd( url );
}, false );
//設置響應類型
if ( this.responseType !== undefined ) request.responseType = this.responseType;
//設置發送cookies
if ( this.withCredentials !== undefined ) request.withCredentials = this.withCredentials;
//設置請求響應解析類型
if ( request.overrideMimeType ) request.overrideMimeType( this.mimeType !== undefined ? this.mimeType : 'text/plain' );
//添加其他定義類型
for ( var header in this.requestHeader ) {
request.setRequestHeader( header, this.requestHeader[ header ] );
}
//開始請求
request.send( null );
}
//開始
scope.manager.itemStart( url );
return request;
},
setPath: function ( value ) {
this.path = value;
return this;
},
setResponseType: function ( value ) {
this.responseType = value;
return this;
},
setWithCredentials: function ( value ) {
this.withCredentials = value;
return this;
},
setMimeType: function ( value ) {
this.mimeType = value;
return this;
},
setRequestHeader: function ( value ) {
this.requestHeader = value;
return this;
}
} );