QListView在列表为空时显示文本 [英] QListView show text when list is empty

问题描述

当QListView中没有项目时，我想显示一些文本(例如无项目").
我试图重写QListView的paintEvent方法，但没有任何效果.

I want to show some text (like "No items") when there are no items in QListView.
I tried to override paintEvent method of QListView, but it doesn't have any effect.

推荐答案

以下代码通过重载视图的paintEvent方法显示了一种简单的方法.绘制文本可能应该使用样式机制来获取字体和笔/画笔，但我将留给敏锐的编辑者来解决.

The code below shows a simple way of doing it by overloading the paintEvent method of the view. Painting of the text should probably use the style mechanism to obtain the font and pen/brush, but I'll leave that up for grabs by a keen editor.

它使用Qt 5及其C ++ 11功能，以Qt 4或C ++ 11之前的方式进行操作将需要带有插槽的QObject派生类，以连接到旋转框的valueChanged信号. ListView的实现无需在Qt 4和Qt 5之间进行更改.

It uses Qt 5 and its C++11 features, doing it the Qt 4 or pre-C++11 way would require a QObject-deriving class with a slot to connect to the spin box's valueChanged signal. The implementation of ListView doesn't need to change between Qt 4 and Qt 5.

#include <QtWidgets>

class ListView : public QListView {
   void paintEvent(QPaintEvent *e) {
      QListView::paintEvent(e);
      if (model() && model()->rowCount(rootIndex()) > 0) return;
      // The view is empty.
      QPainter p(this->viewport());
      p.drawText(rect(), Qt::AlignCenter, "No Items");
   }
public:
   ListView(QWidget* parent = 0) : QListView(parent) {}
};

int main(int argc, char *argv[])
{
   QApplication a(argc, argv);
   QWidget window;
   QFormLayout layout(&window);
   ListView view;
   QSpinBox spin;
   QStringListModel model;
   layout.addRow(&view);
   layout.addRow("Item Count", &spin);
   QObject::connect(&spin, (void (QSpinBox::*)(int))&QSpinBox::valueChanged,
                    [&](int value){
      QStringList list;
      for (int i = 0; i < value; ++i) list << QString("Item %1").arg(i);
      model.setStringList(list);
   });
   view.setModel(&model);
   window.show();
   return a.exec();
}

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