如何使用Ubuntu SDK DownloadManager来同时下载多个文件

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在上一篇文章“如何使用Ubuntu SDK中的Download Manager来下载文件”中，我们已经介绍了如何使用SingleDownload来下载一个文件。在这篇文章中我们将介绍如何使用DownloadManager来同时下载多个文件。

我们可以按照同样的方法创建一个简单的“QML App with Simple UI (qmlproject)”项目。关于DownloadManager的具体的API描述，可以具体看上一篇文章。这里就不再累述。我们可以申明一个DownloadManager的实例：

        DownloadManager {
            id: manager

            onDownloadsChanged: {
                console.log("something is changed!");
                var length = downloads.length;

                console.log("length: " + length);

                for (var i = 0; i < length; i ++ ) {
                    downloads[i].finished.connect(onFinished);
                }

                function onFinished(path) {
                    console.log("path: " + path);
                    mymodel.append( {"filename" : path })
                }
            }
        }

import Ubuntu.DownloadManager 0.1

                for (var i = 0; i < length; i ++ ) {
                    downloads[i].finished.connect(onFinished);
                }

这样我们就可以得到下载的文件了。其它的就没有什么特别的。这里要理解downloads中的每个为SingleDownload。这样就不难理解了。

我们修改我们的Main.qml如下：

import QtQuick 2.0
import Ubuntu.Components 1.1
import Ubuntu.DownloadManager 0.1

/*!
    \brief MainView with a Label and Button elements.
*/

MainView {
    // objectName for functional testing purposes (autopilot-qt5)
    objectName: "mainView"

    // Note! applicationName needs to match the "name" field of the click manifest
    applicationName: "downloadmanager.liu-xiao-guo"

    /*
     This property enables the application to change orientation
     when the device is rotated. The default is false.
    */
    //automaticOrientation: true

    // Removes the old toolbar and enables new features of the new header.
    useDeprecatedToolbar: false

    width: units.gu(60)
    height: units.gu(85)

    Page {
        title: i18n.tr("Download Manager")

        ListModel {
            id: mymodel
        }

        DownloadManager {
            id: manager

            onDownloadsChanged: {
                console.log("something is changed!");
                var length = downloads.length;

                console.log("length: " + length);

                for (var i = 0; i < length; i ++ ) {
                    downloads[i].finished.connect(onFinished);
                }

                function onFinished(path) {
                    console.log("path: " + path);
                    mymodel.append( {"filename" : path })
                }
            }
        }

        TextField {
            id: text
            placeholderText: "File URL to download..."
            height: units.gu(5)
            anchors {
                left: parent.left
                right: button.left
                rightMargin: units.gu(2)
            }

            text: "http://img0.bdstatic.com/img/image/6446027056db8afa73b23eaf953dadde1410240902.jpg"
        }

        Button {
            id: button
            text: "Download"
            height: 50
            anchors.top: text.top
            anchors.bottom: text.bottom
            anchors.right: parent.right
            anchors.verticalCenter: text.verticalCenter
            onClicked: {
                manager.download(text.text);
            }
        }

        ListView {
            id: list
            clip: true
            anchors {
                left: parent.left
                right: parent.right
                top: text.bottom
            }
            height: units.gu(20)
            model: manager.downloads
            delegate: ProgressBar {
                width: parent.width

                minimumValue: 0
                maximumValue: 100
                value: modelData.progress
            }
        }

        GridView {
            id: pics
            clip: true
            anchors.bottom: parent.bottom
            anchors.left: parent.left
            anchors.right: parent.right
            anchors.top: list.bottom

            model: mymodel
            cellWidth: pics.width/4; cellHeight: cellWidth + units.gu(2)
            delegate: Image {
                width: parent.width / 4
                height: width + units.gu(2)

                source: filename
                fillMode: Image.PreserveAspectFit
            }
        }
    }
}

运行应用，显示为：

我们可以修改下载的链接地址，也可以直接按下下载按钮。每次都会产生一个新的下载。我们把照片显示出来。

所有源码在：git clone https://gitcafe.com/ubuntu/downloadmanager.git

如何使用Ubuntu SDK DownloadManager来同时下载多个文件

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原文地址：http://blog.csdn.net/ubuntutouch/article/details/45503841