Recently in familiar Qt on interface controls which drawing that use QPixmap this class, drawing event set every time after the update () to redraw painter. DrawPixmap (Qpoint (0, 0), * pix), one of the pix initialization is pointing to a new QPixmap object, but in the back of the clear () function and the resize () to new a new pixmap in every event handling to cover the original pointer, if do you need to be directly cause of memory leaks, as the pixmap original new pointer pointing to another space directly, the original space cannot release, if the clear operation is frequently will continue to have new new object? Specific code is as follows:

Ask everybody to help to reassure,

The header file:

 # # ifndef DRAWWIDGET_H 
# define DRAWWIDGET_H 

# include & lt; QWidget> 
# include & lt; QPixmap> 
# include & lt; QColor> 
# include & lt; QPoint> 
# include & lt; QMouseEvent> 
# include & lt; QPainter> 

The class Drawwidget: public QWidget 
{
Q_OBJECT 
Public: 
Explicit Drawwidget (QWidget * parent=nullptr); 
Void mouseMoveEvent (QMouseEvent * event); 
Void mousePressEvent (QMouseEvent * event); 
Void paintEvent (QPaintEvent * event); 
Void resizeEvent (QResizeEvent * event); 

Signals: 

Public slots: 
Void setStyle (int);//set style 
Void setWidth (int);//set the width of the 
Void setColor (QColor);//set colors 
Void the clear ();//clear picture 

Private: 
QPixmap * pix; 
The QPoint startpos; 
The QPoint endpos; 
Int style; 
Int weight; 
QColor color; 
}; 

# endif//DRAWWIDGET_H 

Source:

 # include "drawwidget. H" 

Drawwidget: : Drawwidget (QWidget * parent) : QWidget (parent) 
{
SetAutoFillBackground (true);//set the background color of form 
SetPalette (QPalette (Qt: : white)); 
Pix=new QPixmap (size ()); 
Pix - & gt; The fill (Qt: : white); 
SetMinimumSize (600, 400);//set the minimum size 
} 

Void Drawwidget: : setColor (QColor c) 
{
Color=c; 
} 

Void Drawwidget: : setStyle (int s) 
{
Style=s; 
} 

Void Drawwidget: : setWidth (int w) 
{
Weight=w; 
} 

Void Drawwidget: : mousePressEvent (QMouseEvent * event) 
{
Startpos=event - & gt; Pos (); 
} 

Void Drawwidget: : mouseMoveEvent (QMouseEvent * event) 
{
QPainter * painter=new QPainter; 
QPen pen; 
Pen. SetStyle (Qt: : PenStyle style); 
Pen. SetWidth (weight); 
Pen. SetColor (color); 

Painter - & gt; The begin (pix); 
Painter - & gt; SetPen (pen). 
//draw lines 
Painter - & gt; DrawLine (startpos, event - & gt; Pos ()); 
Painter - & gt; The end (); 

Startpos=event - & gt; Pos (); 

The update (); 
} 

Void Drawwidget: : paintEvent (QPaintEvent * event)//drawing event 
{
QPainter p (this); 

Conviction yourself rawPixmap (QPoint (0, 0), * pix). 

} 

Void Drawwidget: : resizeEvent (QResizeEvent * event) 
{
If (height () & gt; Pix - & gt; Height () | | width () & gt; Pix - & gt; Width ()) 
{
QPixmap * newpix=new QPixmap (size ()); 
Newpix - & gt; The fill (Qt: : white); 

QPainter p (newpix); 
Conviction yourself rawPixmap (QPoint (0, 0), * pix). 
Pix=newpix; 
} 
QWidget: : resizeEvent (event);//finish the rest work 
} 

Void Drawwidget: : clear () 
{
QPixmap * clearpix=new QPixmap (size ()); 
Clearpix - & gt; The fill (Qt: : white); 
Pix=clearpix; 
The update (); 
} 

CodePudding user response:

Reference: https://blog.csdn.net/taiyang1987912/article/details/29271549