qml Android linux windows 打開文件選擇

先說廢話：
經過一段時間對Qt的學習，想在Android上搞點事情，中途遇到了一個大坑，就是打開Android的文件系統進行文件選擇，別以爲這個功能簡單，直接使用一個什麼FileDialog就可以完事了，你要是這樣想，兄弟，你把這個頁面關了吧。

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一、實現功能：

本博客的功能是講解在Qml在Android平臺下進行文件選擇，網上的人說了一大堆，缺胳膊少腿的，還是官方給的案列比較靠譜點。

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二、運行效果：

備註，這個是在我安卓手機上橫屏運行的，在其他平臺也應該是這個樣子的，望周知。

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三、開發環境：

1、Qt5.12，應該Qt5.9之後的平臺都是支持的，你可以自己試試，我比較懶的。
2、Android運行版本是8.0, 6.0之後的版本需要進行權限申請，這個騷操作會在後面描述的。
3、還需要你在你的工程中，配置一個圖標字體，FontAwsome，這樣看起來才舒服，不然就很闊怕的醜。如果你不知道咋個配置，請看這裏，照着做就可以了。

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四、代碼編寫：

4.1、首先編寫文件選擇qml代碼，有點多，自己複製粘貼就好了，這個文件命名爲： FileBrowser.qml：

/*
 * Note:this file base on Qt Company.
 * if you want to use this file, you
 * need configure font fontawesome-webfont.ttf
 * in your project and some icon will be show normal.
 *
*/

import QtQuick 2.0
import Qt.labs.folderlistmodel 2.0

Rectangle {
    id: fileBrowser
    color: "transparent"

    // 當前文件夾路徑
    property string folder
    // 選擇文件信號
    signal fileSelected(string file)
    // 文件圖標顯示字體庫
    property string iconfamily: "FontAwsome"

    property int itemHeight: Math.min(parent.width, parent.height) / 15
    property int buttonHeight: Math.min(parent.width, parent.height) / 12

    function selectFile(file) {
        if (file !== "") {
            folder = loader.item.folders.folder
            fileBrowser.fileSelected(file)
        }
        loader.sourceComponent = undefined
    }

    Loader {
        id: loader
    }

    function show() {
        loader.sourceComponent = fileBrowserComponent
        loader.item.parent = fileBrowser
        loader.item.anchors.fill = fileBrowser
        loader.item.folder = fileBrowser.folder
    }

    Component {
        id: fileBrowserComponent

        Rectangle {
            id: root
            color: "black"
            property bool showFocusHighlight: false
            property variant folders: folders1
            property variant view: view1
            property alias folder: folders1.folder
            property color textColor: "white"

            FolderListModel {
                id: folders1
                folder: folder
            }

            FolderListModel {
                id: folders2
                folder: folder
            }

            SystemPalette {
                id: palette
            }

            Component {
                id: folderDelegate

                Rectangle {
                    id: wrapper
                    function launch() {
                        var path = "file://";
                        if (filePath.length > 2 && filePath[1] === ':') // Windows drive logic, see QUrl::fromLocalFile()
                            path += '/';
                        path += filePath;
                        if (folders.isFolder(index))
                            down(path);
                        else
                            fileBrowser.selectFile(path)
                    }
                    width: root.width
                    height: folderImage.height
                    color: "transparent"

                    Rectangle {
                        id: highlight
                        visible: false
                        anchors.fill: parent
                        anchors.leftMargin: 5
                        anchors.rightMargin: 5
                        color: "#212121"
                    }

                    Item {
                        id: folderImage
                        width: itemHeight
                        height: itemHeight
                        Image {
                            id: folderPicture
                            width: itemHeight * 0.9
                            height: itemHeight * 0.9
                            anchors.left: parent.left
                            anchors.margins: 5
                            visible: folders.isFolder(index)
                            Text {
                                anchors.fill: parent
                                verticalAlignment: Text.AlignVCenter
                                horizontalAlignment: Text.AlignHCenter
                                font.family: iconfamily
                                text: "\uf115"
                                color: "white"
                                Component.onCompleted: font.pointSize = parent.width / 2
                            }
                        }
                        Image {
                            width: itemHeight * 0.9
                            height: itemHeight * 0.9
                            anchors.left: parent.left
                            anchors.margins: 5
                            visible: !folders.isFolder(index)
                            Text {
                                anchors.fill: parent
                                verticalAlignment: Text.AlignVCenter
                                horizontalAlignment: Text.AlignHCenter
                                font.family: iconfamily
                                text: "\uf0f6"
                                color: "white"
                                Component.onCompleted: font.pointSize = parent.width / 2
                            }
                        }
                    }

                    Text {
                        id: nameText
                        anchors.fill: parent;
                        verticalAlignment: Text.AlignVCenter
                        text: fileName
                        anchors.leftMargin: itemHeight + 10
                        color: (wrapper.ListView.isCurrentItem && root.showFocusHighlight) ? palette.highlightedText : textColor
                        elide: Text.ElideRight
                    }

                    MouseArea {
                        id: mouseRegion
                        anchors.fill: parent
                        onPressed: {
                            root.showFocusHighlight = false;
                            wrapper.ListView.view.currentIndex = index;
                        }
                        onClicked: { if (folders === wrapper.ListView.view.model) launch() }
                    }

                    states: [
                        State {
                            name: "pressed"
                            when: mouseRegion.pressed
                            PropertyChanges { target: highlight; visible: true }
                            PropertyChanges { target: nameText; color: palette.highlightedText }
                        }
                    ]
                }
            }

            ListView {
                id: view1
                anchors.top: titleBar.bottom
                anchors.bottom: cancelButton.top
                width: parent.width
                model: folders1
                delegate: folderDelegate
                highlight: Rectangle {
                    color: "#212121"
                    visible: root.showFocusHighlight && view1.count != 0
                    width: view1.currentItem == null ? 0 : view1.currentItem.width
                }
                highlightMoveVelocity: 1000
                pressDelay: 100
                focus: true
                state: "current"
                states: [
                    State {
                        name: "current"
                        PropertyChanges { target: view1; x: 0 }
                    },
                    State {
                        name: "exitLeft"
                        PropertyChanges { target: view1; x: -root.width }
                    },
                    State {
                        name: "exitRight"
                        PropertyChanges { target: view1; x: root.width }
                    }
                ]
                transitions: [
                    Transition {
                        to: "current"
                        SequentialAnimation {
                            NumberAnimation { properties: "x"; duration: 250 }
                        }
                    },
                    Transition {
                        NumberAnimation { properties: "x"; duration: 250 }
                        NumberAnimation { properties: "x"; duration: 250 }
                    }
                ]
                Keys.onPressed: root.keyPressed(event.key)
            }

            ListView {
                id: view2
                anchors.top: titleBar.bottom
                anchors.bottom: parent.bottom
                x: parent.width
                width: parent.width
                model: folders2
                delegate: folderDelegate
                highlight: Rectangle {
                    color: "#212121"
                    visible: root.showFocusHighlight && view2.count != 0
                    width: view1.currentItem == null ? 0 : view1.currentItem.width
                }
                highlightMoveVelocity: 1000
                pressDelay: 100
                states: [
                    State {
                        name: "current"
                        PropertyChanges { target: view2; x: 0 }
                    },
                    State {
                        name: "exitLeft"
                        PropertyChanges { target: view2; x: -root.width }
                    },
                    State {
                        name: "exitRight"
                        PropertyChanges { target: view2; x: root.width }
                    }
                ]
                transitions: [
                    Transition {
                        to: "current"
                        SequentialAnimation {
                            NumberAnimation { properties: "x"; duration: 250 }
                        }
                    },
                    Transition {
                        NumberAnimation { properties: "x"; duration: 250 }
                    }
                ]
                Keys.onPressed: root.keyPressed(event.key)
            }

            Rectangle {
                width: parent.width
                height: buttonHeight + 10
                anchors.bottom: parent.bottom
                color: "black"
            }

            Rectangle {
                id: cancelButton
                width: parent.width
                height: buttonHeight
                color: "#212121"
                anchors.bottom: parent.bottom
                anchors.left: parent.left
                anchors.right: parent.right
                anchors.margins: 5
                radius: buttonHeight / 15

                Text {
                    anchors.fill: parent
                    text: "Cancel"
                    color: "white"
                    horizontalAlignment: Text.AlignHCenter
                    verticalAlignment: Text.AlignVCenter
                }

                MouseArea {
                    anchors.fill: parent
                    onClicked: fileBrowser.selectFile("")
                }
            }

            Keys.onPressed: {
                root.keyPressed(event.key);
                if (event.key === Qt.Key_Return || event.key === Qt.Key_Select || event.key === Qt.Key_Right) {
                    view.currentItem.launch();
                    event.accepted = true;
                } else if (event.key === Qt.Key_Left) {
                    up();
                }
            }


            Rectangle {
                id: titleBar
                width: parent.width
                height: buttonHeight + 10
                anchors.top: parent.top
                color: "black"

                Rectangle {
                    width: parent.width;
                    height: buttonHeight
                    color: "#212121"
                    anchors.margins: 5
                    anchors.top: parent.top
                    anchors.left: parent.left
                    anchors.right: parent.right
                    radius: buttonHeight / 15

                    Rectangle {
                        id: upButton
                        width: buttonHeight
                        height: buttonHeight
                        color: "transparent"
                        Image {
                            width: itemHeight
                            height: itemHeight
                            anchors.centerIn: parent
                            Text {
                                anchors.fill: parent
                                verticalAlignment: Text.AlignVCenter
                                horizontalAlignment: Text.AlignHCenter
                                font.family: iconfamily
                                text: "\uf112"
                                color: "white"
                                Component.onCompleted: font.pointSize = parent.width / 2
                            }
                        }
                        MouseArea { id: upRegion; anchors.centerIn: parent
                            width: buttonHeight
                            height: buttonHeight
                            onClicked: up()
                        }
                        states: [
                            State {
                                name: "pressed"
                                when: upRegion.pressed
                                PropertyChanges { target: upButton; color: palette.highlight }
                            }
                        ]
                    }

                    Text {
                        anchors.left: upButton.right; anchors.right: parent.right; height: parent.height
                        anchors.leftMargin: 5; anchors.rightMargin: 5
                        text: folders.folder
                        color: "white"
                        elide: Text.ElideLeft;
                        horizontalAlignment: Text.AlignLeft;
                        verticalAlignment: Text.AlignVCenter
                    }
                }
            }

            function down(path) {
                if (folders == folders1) {
                    view = view2
                    folders = folders2;
                    view1.state = "exitLeft";
                } else {
                    view = view1
                    folders = folders1;
                    view2.state = "exitLeft";
                }
                view.x = root.width;
                view.state = "current";
                view.focus = true;
                folders.folder = path;
            }

            function up() {
                var path = folders.parentFolder;
                if (path.toString().length === 0 || path.toString() === 'file:')
                    return;
                if (folders == folders1) {
                    view = view2
                    folders = folders2;
                    view1.state = "exitRight";
                } else {
                    view = view1
                    folders = folders1;
                    view2.state = "exitRight";
                }
                view.x = -root.width;
                view.state = "current";
                view.focus = true;
                folders.folder = path;
            }

            function keyPressed(key) {
                switch (key) {
                case Qt.Key_Up:
                case Qt.Key_Down:
                case Qt.Key_Left:
                case Qt.Key_Right:
                    root.showFocusHighlight = true;
                    break;
                default:
                    // do nothing
                    break;
                }
            }
        }
    }
}

4.2、配置Android平臺權限：

1）在你的pro工程文件中添加如下代碼：

android{
QT     += androidextras
DEFINES += Android_Platform
}

2）在你的main.cpp中添加如下代碼：

#include <QtCore/QStandardPaths>

#ifdef Android_Platform
#include <QtAndroid>
#endif

int  main(){

#ifdef Android_Platform
    // 添加讀取權限，Android 6.0 版本後需要申請，不然的話，啥都看不到。
    QString strPermission = "android.permission.READ_EXTERNAL_STORAGE";
    QtAndroid::requestPermissionsSync(QStringList() << strPermission);  // ok
#endif

QQmlApplicationEngine engine;
// 獲取默認文件的路徑並進行設置
    const QStringList moviesLocation = QStandardPaths::standardLocations(QStandardPaths::DocumentsLocation);
    const QUrl videoPath =
            QUrl::fromLocalFile(moviesLocation.isEmpty() ?
                                    app.applicationDirPath() :
                                    moviesLocation.front());
    engine.rootContext()->setContextProperty("videoPath", videoPath);
}

3)經過上訴的配置後，即可在qml中進行使用了：
a、實例化對象：

    FileBrowser{
        id: filebrowser
        anchors.fill: parent
        folder: videoPath
        onFileSelected:{
            console.log(file)
        }
    }

b、打開文件選擇框：

onClicked: {
           filebrowser.show()
}

OK,到這裏就已經完美了，請仔細看我的代碼，我可以，你也可以的。
有問題可以郵件我。
[email protected]