Widget::Widget(QWidget *parent)
: QWidget(parent), ui(new Ui::Widget)
{ a=50;b=50;m_dragging = 0;//a,b为起始坐标点
ui->setupUi(this);
resize(400,400);
}
Widget::~Widget()
{
delete ui;
}
void Widget::paintEvent(QPaintEvent *)
{
QPainter paint(this);
paint.setPen(Qt::green);
paint.drawPoint(a,b);
}
void Widget::mousePressEvent(QMouseEvent *event)
{
//if(event->pos()==QPoint(a,b))
if(event->pos().x()==a&&event->pos().y()==b)
m_dragging = 1;
}
void Widget::mouseMoveEvent(QMouseEvent *event)
{
if (m_dragging==1)
{
a=event->pos().x();
b=event->pos().y();
update();
}
m_dragging = 0;
}
大体思路：
先设置一个私有变量m_dragging = 0
保护继承mousePressEvent方法，方法内取得event->pos()后, 可以判断是否选中. 如果选中, m_dragging = 1.
保护继承mouseMoveEvent方法, 方法内如果m_dragging = 1, 则刷新a,b, update()；为什么不行？
