Xojo 语言 拖放 Drag 功能基础启用

Xojo^【1】 拖放（Drag）功能基础教程

Xojo 是一种多平台编程语言，它允许开发者使用相同的代码在 Windows、macOS、Linux、iOS 和 web 上创建应用程序。在 Xojo 中，拖放（Drag）功能是一种非常直观且强大的用户界面元素，它允许用户通过拖动对象来执行操作。本文将深入探讨 Xojo 中拖放功能^【2】的基础，并提供一些实用的代码示例。

拖放功能简介

在 Xojo 中，拖放功能通常涉及以下几个关键组件：

1. 拖动源^【3】（Drag Source）：提供拖动数据^【4】的对象。
2. 拖动数据（Drag Data）：被拖动的数据，可以是文本、图片或其他任何类型的数据。
3. 拖动目标^【5】（Drag Target）：可以接收拖动数据的对象。

创建拖动源

要创建一个拖动源，你需要确保你的 Xojo 控件支持拖放。大多数 Xojo 控件默认支持拖放，但如果你需要自定义拖放行为，你可以通过设置控件的 `DragEnabled<sup>【6】</sup>` 属性来实现。

以下是一个简单的例子，展示如何使一个按钮成为拖动源：

xojo_code
Button1.DragEnabled = True


设置拖动数据

一旦你的控件成为拖动源，你需要设置它拖动的数据。这可以通过 `DragData<sup>【7】</sup>` 属性来完成。以下是如何设置一个按钮拖动其文本的示例：

xojo_code
Button1.DragData = Button1.Text


创建拖动目标

要创建一个拖动目标，你需要确保你的控件可以接收拖动数据。这通常意味着你需要重写控件的 `DragOver<sup>【8】</sup>` 和 `Drop<sup>【9】</sup>` 方法。

以下是一个简单的例子，展示如何使一个文本框成为拖动目标：

xojo_code
TextField1.DragOver = TextField1_DragOver
TextField1.Drop = TextField1_Drop


重写 `DragOver` 方法

`DragOver` 方法用于确定拖动操作是否应该继续。以下是一个简单的 `DragOver` 方法示例，它允许文本框接收任何类型的拖动数据：

xojo_code
Procedure TextField1_DragOver(DragInfo As DragInfo)
DragInfo.AllowedActions = DragInfo.AllowedActions Or DragActionCopy
End Procedure


重写 `Drop` 方法

`Drop` 方法用于处理实际的数据放置。以下是一个简单的 `Drop` 方法示例，它将接收到的文本数据放入文本框中：

xojo_code
Procedure TextField1_Drop(DragInfo As DragInfo)
If DragInfo.DataTypes.Count > 0 Then
If DragInfo.DataTypes.Item(0) = "text/plain" Then
Me.Text = DragInfo.Data
End If
End If
End Procedure


完整示例

以下是一个完整的 Xojo 项目示例，它包含一个拖动源（按钮）和一个拖动目标（文本框）：

```xojo_code
class MyWindow
property Title as String = "Drag and Drop<sup>【10】</sup> Example"
property Width as Integer = 400
property Height as Integer = 300
property Resizable<sup>【11】</sup> as Boolean = False
property CloseButton as Boolean = True
property HasBackgroundColor as Boolean = True
property BackgroundColor as Color = &cFFFFFF
property HasMinimizeButton as Boolean = False
property HasMaximizeButton as Boolean = False
property HasFullScreenButton as Boolean = False
property WindowStyle<sup>【12】</sup> as WindowStyle = WindowStyle.Standard
property HasShadow as Boolean = True
property HasTitleBar as Boolean = True
property TitleBarHeight as Integer = 32
property CanResize as Boolean = False
property AllowsDrag as Boolean = True
property AllowsDrop as Boolean = True
property AllowAutoLayout<sup>【13】</sup> as Boolean = True
property AllowLayout as Boolean = True
property AllowResize as Boolean = False
property AllowZoom<sup>【14】</sup> as Boolean = False
property AllowMultiple<sup>【15】</sup> as Boolean = False
property AllowReorder<sup>【16】</sup> as Boolean = False
property AllowDelete<sup>【17】</sup> as Boolean = False
property AllowAdd<sup>【18】</sup> as Boolean = False
property AllowEdit<sup>【19】</sup> as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop<sup>【20】</sup> as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean = False
property AllowAdd as Boolean = False
property AllowEdit as Boolean = False
property AllowDrag as Boolean = True
property AllowDrop as Boolean = True
property AllowResize as Boolean = False
property AllowZoom as Boolean = False
property AllowMultiple as Boolean = False
property AllowReorder as Boolean = False
property AllowDelete as Boolean =