如何保存和恢复 ListModel 的内容?

本文介绍了如何保存和恢复 ListModel 的内容?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我可以保存使用 Component.onComponent 方法静态创建的列表项的设置.但是静态创建的列表项的设置会在重新打开应用程序后生效.我想保存动态创建的列表模型的设置.我无法保存动态创建的列表项的设置.下面的代码会在单击显示/隐藏"操作时打开和关闭列表项.当我重新打开应用程序时，创建的列表项消失了.如何使用设置保存列表项?

I am able to save settings for list items which is statically created using Component.onComponent method. But Settings for statically created list items take affect after reopening app. I would like to save settings for dynamically created list model. I am unable to save Settings for a dynamically created list item. The code below does that a list item is on and off while clicking Show/Hide action. When I reopen the app, created list item disappears. How to save list item using Setting?

import QtQuick 2.9 import Fluid.Controls 1.0 import Qt.labs.settings 1.0 import QtQuick.Controls 1.4 ApplicationWindow { id:root visible: true width: 640 height: 480 property variant addlist property int countt2: 0 Settings{ id:mysetting4 property alias ekranCosinus: root.countt2 } function listonoff(){ if(countt2%2==1){ return true } else if(countt2%2==0){ return false } } Connections { target: addlist onTriggered: listonoff() } addlist: favourite2 /* main.qml */ menuBar: MenuBar { Menu { title: "&Edit" MenuItem { action: favourite2 } } } Action { id:favourite2 text: qsTr("Show/Hide") onTriggered: { countt2++ console.log(countt2) if(listonoff()===true){ return list_model.insert(list_model.index,{ title: "First item."} ) } else if(listonoff()===false){ return list_model.remove(list_model.index) } } } ListView { id:contactlist width: parent.width height: parent.height focus: true interactive: true clip: true model: ListModel { id:list_model } delegate: ListItem { text: model.title height:60 } } MouseArea { id: mouse anchors.fill: parent } }

推荐答案

很奇怪你期望保存单个整数值将能够以某种方式存储任意数据模型的内容......它甚至不起作用对于静态模型数据，它只是恢复"因为它是静态的 - 它是代码的一部分，您并没有真正保存和恢复任何东西.

Quite curious that you expect that saving a single integer value will somehow be able to store the content of an arbitrary data model... It doesn't work even for the static model data, it is only "restored" because it is static - it is part of the code, you are not really saving and restoring anything.

如果您想存储所有这些数据，则必须在应用退出时对其进行序列化，并在应用启动时对其进行反序列化.

If you want to store all that data, you will have to serialize it when your app quits, and deserialize it when the app starts.

您仍然可以使用 Settings，但要存储一个字符串值，该值将表示序列化数据.

You could still use Settings, but to store a string value, that will represent the serialized data.

最简单的方法是使用 JS 数组来回传输模型项，这样可以使用 JS JSON 对象功能轻松序列化和反序列化数据:

The easiest way to do it is to transfer the model items back and forth with a JS array, this way the JS JSON object functionality can be used to easily serialize and deserialize the data:

import QtQuick 2.9 import QtQuick.Controls 2.2 import QtQuick.Window 2.3 import Qt.labs.settings 1.0 ApplicationWindow { id: main width: 640 height: 480 visible: true property string datastore: "" Component.onCompleted: { if (datastore) { dataModel.clear() var datamodel = JSON.parse(datastore) for (var i = 0; i < datamodel.length; ++i) dataModel.append(datamodel[i]) } } onClosing: { var datamodel = [] for (var i = 0; i < dataModel.count; ++i) datamodel.push(dataModel.get(i)) datastore = JSON.stringify(datamodel) } Settings { property alias datastore: main.datastore } ListView { id: view anchors.fill: parent model: ListModel { id: dataModel ListElement { name: "test1"; value: 1 } } delegate: Text { text: name + " " + value } } MouseArea { anchors.fill: parent acceptedButtons: Qt.LeftButton | Qt.RightButton onClicked: { if (mouse.button === Qt.LeftButton) { var num = Math.round(Math.random() * 10) dataModel.append({ "name": "test" + num, "value": num }) } else if (dataModel.count) { dataModel.remove(0, 1) } } } }

应用程序以单个数据模型值开始，可以通过分别按鼠标左键和右键来添加或删除更多数据项.

The application begins with a single data model value, more data items can be added or removed by pressing the left and right mouse button respectively.

只要应用程序正常关闭，数据模型就会被复制到一个数组中，该数组将被序列化为一个字符串，由Settings元素存储.因此，在重新启动应用程序时，如果数据字符串存在，模型将被清除以删除初始值，因此它不会重复，数据字符串被反序列化回一个数组，该数组被迭代以恢复数据模型的内容.轻轻松松.

As long as the application is closed properly, the data model will be copied into an array, which will be serialized to a string, which will be stored by the Settings element. So upon relaunching the app, if the data string is present, the model is cleared to remove the initial value so it is not duplicated, the data string is deserialized back into an array, which is iterated to restore the content of the data model. Easy peasy.

当然，您也可以使用 LocalStorage API，甚至通过将 C++ 对象暴露给 QML 来编写一个简单的文件读取器和写入器.这种方法所需要的只是能够存储和检索单个字符串.

Of course, you could also use the LocalStorage API as well, or even write a simple file reader and writer by exposing a C++ object to QML. All this approach needs is to be able to store and retrieve a single string.