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Thread: Drag items in QListWidget while the mouse left button is pressed

  1. #1
    Join Date
    Nov 2012
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    Qt products
    Qt4 Qt/Embedded
    Platforms
    Unix/X11 Symbian S60

    Default Drag items in QListWidget while the mouse left button is pressed

    I am having trouble with the dragging of items inside a QListWidget, the items which are selected are stuck with the mouse cursor even after the mouse button is released. I want to reorder the items inside the QListWidget by dragging them though mouse while the mouse left button is pressed.
    I have promoted my ui->listwidget to a custom listwidget to accept drag and drops.

    Qt Code:
    1. #ifndef PROJECTLISTWIDGET_H
    2. #define PROJECTLISTWIDGET_H
    3.  
    4. class ProjectListWidget : public QListWidget
    5. {
    6. Q_OBJECT
    7. public:
    8. ProjectListWidget(QWidget *parent = 0);
    9.  
    10. signals:
    11. void itemDrag();
    12.  
    13. protected:
    14. void mousePressEvent(QMouseEvent *event);
    15. void mouseMoveEvent(QMouseEvent *event);
    16. void dragEnterEvent(QDragEnterEvent *event);
    17. void dragMoveEvent(QDragMoveEvent *event);
    18. void dropEvent(QDropEvent *event);
    19. void performDrag();
    20. QPoint startPos;
    21. };
    22.  
    23.  
    24. #endif // PROJECTLISTWIDGET_H
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    Qt Code:
    1. #include "projectlistwidget.h"
    2.  
    3. using namespace std;
    4.  
    5. ProjectListWidget::ProjectListWidget(QWidget *parent)
    6. : QListWidget(parent)
    7. {
    8. setAcceptDrops(true);
    9. setDragEnabled(true);
    10. }
    11.  
    12. void ProjectListWidget::mousePressEvent(QMouseEvent *event)
    13. {
    14. if (event->button() == Qt::LeftButton)
    15. {
    16. startPos = event->pos();
    17. }
    18. QListWidget::mousePressEvent(event);
    19.  
    20. }
    21.  
    22. void ProjectListWidget::mouseMoveEvent(QMouseEvent *event)
    23. {
    24. if (event->buttons() & Qt::LeftButton)
    25. {
    26. int distance = (event->pos() - startPos).manhattanLength();
    27. if (distance >= QApplication::startDragDistance())
    28. {
    29. performDrag();
    30. }
    31. }
    32. QListWidget::mouseMoveEvent(event);
    33. }
    34.  
    35. void ProjectListWidget::performDrag()
    36. {
    37. QListWidgetItem *item = currentItem();
    38. if (item) {
    39. QMimeData *mimeData = new QMimeData;
    40. mimeData->setText(item->text());
    41. QDrag *drag = new QDrag(this);
    42. drag->setMimeData(mimeData);
    43. emit itemDrag();
    44. if (drag->exec(Qt::MoveAction) == Qt::CopyAction)
    45. delete item;
    46. }
    47. }
    48.  
    49. void ProjectListWidget::dragEnterEvent(QDragEnterEvent *event)
    50. {
    51. if (event->mimeData()->hasUrls())
    52. {
    53. event->acceptProposedAction();
    54. } else
    55. {
    56. QListWidget::dragEnterEvent(event);
    57. }
    58. }
    59.  
    60. void ProjectListWidget::dragMoveEvent(QDragMoveEvent *event)
    61. {
    62. if (event->mimeData()->hasUrls() & Qt::LeftButton)
    63. {
    64. event->acceptProposedAction();
    65. } else
    66. {
    67. QListWidget::dragMoveEvent(event);
    68. }
    69. }
    70.  
    71. void ProjectListWidget::dropEvent(QDropEvent *event)
    72. {
    73. if (event->mimeData()->hasUrls())
    74. {
    75. QList<QUrl> urls = event->mimeData()->urls();
    76. if (!urls.isEmpty())
    77. {
    78. QUrl url;
    79. foreach (url,urls)
    80. {
    81. new QListWidgetItem(url.toLocalFile(),this);
    82. emit itemDrag();
    83. }
    84. }
    85. event->acceptProposedAction();
    86. }
    87. QListWidget::dropEvent(event);
    88. }
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    listbox.jpeg

  2. #2
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    Default Re: Drag items in QListWidget while the mouse left button is pressed

    Why don't you just use the QAbstractItemView::dragDropMode property?
    Your biological and technological distinctiveness will be added to our own. Resistance is futile.

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