QMimeData類提為數據提供一個容器，用來記錄關于MIME類型數據的信息
QMimeData常用來描述保存在剪切板里信息，或者拖拽原理
QMimeData對象把它所保存的信息和正確的MIME類型連接起來來保證信息可以被安全的在應用程序之間轉移，或者在同一個應用程序之間拷貝
QMimeData對象通產雇傭new來創建，并且支持QDrag和QClipboard對象，這可以使QT管理他們所使用的內存

單一的QMimeData對象可以同時用好幾種不同的格式來存儲同一個數據，formats()函數返回可以用的數據

格式的list，data()函數可以返回和MIME類型相連的數據類型，setData()用來為MIME類型設置數據

Tester	Getter	Setter	MIME Types
hasText()	text()	setText()	text/plain
hasHtml()	html()	setHtml()	text/html
hasUrls()	urls()	setUrls()	text/uri-list
hasImage()	imageData()	setImageData()	image/ *
hasColor()	colorData()	setColorData()	application/x-color

For example, if your write a widget that accepts URL drags, you would end up writing code like this: void MyWidget::dragEnterEvent(QDragEnterEvent *event) {if (event->mimeData()->hasUrls())event->acceptProposedAction(); }void MyWidget::dropEvent(QDropEvent *event) {if (event->mimeData()->hasUrls()) {foreach (QUrl url, event->mimeData()->urls()) {...}} }

There are three approaches for storing custom data in aQMimeData object:

1.Custom data can be stored directly in aQMimeData object as aQByteArray usingsetData(). For example:

QByteArray csvData = ...; QMimeData *mimeData = new QMimeData; mimeData->setData("text/csv", csvData);
2.We can subclass QMimeData and reimplement hasFormat(), formats(), and retrieveData().

3.If the drag and drop operation occurs within a single application, we can subclass QMimeData and add extra data in it, and use a qobject_cast() in the receiver's drop event handler. For example: void MyWidget::dropEvent(QDropEvent *event) {const MyMimeData *myData =qobject_cast<const MyMimeData *>(event->mimeData());if (myData) {// access myData's data directly (not through QMimeData's API)} }

總結

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