"Qt Learning Notes" 13. Drag-and-drop technology: Drag & Drop

1. Accept drag and drop

Drag & Drop is an interface operation for passing data between two windows.

Drag Source: Drag and drop Sources Window

Drag target: Drag and drop Destination window

Drag-and-drop operations:

1, in the source window: Select the target, press the mouse, move, drag to the target window (Drag)

2, in the target window: Cancel the mouse, to the specified position, release the mouse (Drop)

(Press ESC to cancel the operation)

Mime:

MIME (Multipurpose Internet Mail Extensions) The transmitted data is delivered in MIME format, which is a set of Type-data data: (TYPE0, DATA0) (Type1, Data1) (type2, data2) )  ... (Type-n, Data-n)

which

Type: String specifying the data type, for example: "Text/plain"

Data: An array of bytes, that is to be passed

To accept drag-and-drop steps:

Accept drag-and-drop setacceptdrops (TRUE);//override void Dragenterevent (qdragenterevent* event); void Dragleaveevent (qdragleaveevent* ev ENT), void Dragmoveevent (qdragmoveevent* event), void Dropevent (qdropevent* event);

Small exercise:

Implement a simple form that displays the dragged text content when the text is dragged into the form, and the label control in the body

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/8B/B7/wKiom1hWVL-g5xZRAAAKaw17nuo368.png "title=" 1.png " alt= "Wkiom1hwvl-g5xzraaakaw17nuo368.png"/>

Code:

#include <QDragEnterEvent> #include <QDragLeaveEvent> #include <QDragMoveEvent> #include < qdropevent> #include <QMimeData> #include "test13_1a_12_18.h" test13_1a_12_18::test13_1a_12_18 (Qwidget * Parent): Qmainwindow (parent) {UI.SETUPUI (this); Setacceptdrops (true);//settings: Accept drag-and-drop}//into void test13_1a_12_18:: Dragenterevent (qdragenterevent *event) {if (Event->mimedata ()->hasformat ("Text/plain")) {event-> Acceptproposedaction ();}} Release mouse void test13_1a_12_18::d ropevent (qdropevent *event) {if (Event->mimedata ()->hasformat ("Text/plain")) { QString text = Event->mimedata ()->text (); Ui.label->settext (text);}}

Ii. Initiation of drag and drop

In the Qwidget window, start a drag operation step:

1, the Mouse press

2, the mouse movement, when moving a distance, considered to be a drag operation. Can initiate a drag action

Implementation method:

1. Derive a subclass

2. Overriding the function:

virtual void Mousemoveevent (qmouseevent* event); virtual void Mousepressevent (qmouseevent* event);

Transfer multiple MIME data simultaneously:

mimedata->sethtml (  "xxxxxxx"  ); Mimedata->settext (  text );mimedata-> ("123,"  dat);      //Custom formatted Data//data :  Qbytearray 

Void mylistwidget::mousepressevent (qmouseevent *event) {//  Note the beginning m_dragposition = event- >pos (); M_dragitem = this->itemat (m_dragposition);//  Remember to call the parent class's function (keep the original keystroke behavior) Qlistwidget:: Mousemoveevent (event);} Void mylistwidget::mousemoveevent (qmouseevent *event) {//  only allow left-drag if  ( ! ( Event->buttons ()  & qt::leftbutton)  ) {return;}   move a certain distance before you start dragging if  ((Event->pos ()  - m_dragposition). Manhattanlength ()  <  Qapplication::startdragdistance ()) {return;}   Find dragged Item if  (!m_dragitem) {return;} Qstring text = m_dragitem->text ();//  Create Data Qdrag* drag = new qdrag ( this); Qmimedata* mimedata = new qmimedata;mimedata->settext (text);d Rag->setmimedata ( Mimedata);//  Start drag-and-drop &NBSP;START&NBSP;A&NBSP;DRAG&NBSP;QT::D ropaction result = drag->exec ( qt::copyaction | qt::moveaction);//  Check whether the operation was successful if  (qt::iGnoreaction != result) {}else{//  hold down the CTRL key: qt::copyaction//  do not press:  Qt::RemoveAction}} 

"Qt Learning Notes" 13. Drag-and-drop technology: Drag & Drop