聊天气泡的绘制（圆角矩形+三角形+黑色边框，关键学会QPainter的draw函数就行了），注意每个QLabel都有自己的独立坐标

头文件：

#ifndef GLABEL_H
#define GLABEL_H

#include <QLabel>
#include <QPainter>
#include <QPaintEvent>
#include <QMouseEvent>

class GLabel : public QLabel
{
    Q_OBJECT
public:
    enum PEOPLE{She,Me};
    Q_PROPERTY(QString str_context READ getStrContext WRITE setContext)
    explicit GLabel(QWidget *parent = ,GLabel::PEOPLE f=GLabel::She);
    void setContext(const QString s){str_context = s;}
    QString getStrContext()const{return str_context;}

    QString str_context;
    QLabel *label_text;
    QLabel *label_people;
    PEOPLE people;
public:
    int m_width;
    int m_height;
    int parent_maxwidth;

    void init();
    void initUI(GLabel::PEOPLE f);
    void setSize(QString&);
    void setOurText(QString);
    void setHeadpic(QString);
    void  paintEvent(QPaintEvent *e);
    void mousePressEvent(QMouseEvent *e);
//signals:

//public slots:

};

#endif // GLABEL_H

.cpp文件：

#include "glabel.h"
#include <QPen>
#include <QDebug>

GLabel::GLabel(QWidget *parent,GLabel::PEOPLE f) :
    QLabel(parent)
{
      people = f;
      parent_maxwidth = ((QWidget*)this->parent())->width();
      init();
}

void GLabel::init()
{
    label_text  = new QLabel(this);
    label_text->setWordWrap(true);
    label_text->setGeometry(+,,this->width()--,this->height()-);
    label_text->setStyleSheet("QLabel{background:rgb(173,216,67)}");//rgb(173,216,67)
    label_text->show();

    label_people = new QLabel(this);
    if(people == GLabel::She)
    {
        label_people->setGeometry(,,,);
        label_text->setStyleSheet("QLabel{background:rgb(173,216,67)}");
        label_people->setPixmap(QPixmap(":/image/she.png"));
    }
    else
    {
       label_people->setGeometry(this->width()-,,,);
       label_text->setStyleSheet("QLabel{background:rgb(240,240,240)}");
       label_people->setPixmap(QPixmap(":/image/he.png"));
    }
}

void GLabel::initUI(GLabel::PEOPLE f)
{

}

void GLabel::setSize(QString &paramstr)
{
//    int all_word_width  = this->fontMetrics().width(paramstr);
//    int one_line_height = this->fontMetrics().lineSpacing();
    int max_width = parent_maxwidth-;//-label_people->width();
    int all_word_width;

    label_text->setWordWrap(false);
    label_text->setText(paramstr);
    label_text->adjustSize();
    all_word_width = label_text->width();
    label_text->setWordWrap(true);

    float line_count;
    int line;

    if(all_word_width > max_width)
    {
//        line_count = (float)all_word_width/max_width;
//        line = (int)line_count;
//        if(line < line_count)line=line+2;
        label_text->setMaximumWidth(max_width--);
        label_text->setText(paramstr);
        label_text->adjustSize();
        qDebug()<<"the size of text"<<label_text->size()<<((QWidget*)this->parent())->width()-;

        m_height = label_text->height()/*line*one_line_height*/;
        m_width  = parent_maxwidth-;
       // qDebug()<<"linr_count"<<line_count<<one_line_height<<max_width<<all_word_width;
        this->resize(m_width,m_height+);
    }
    else
    {
        label_text->setWordWrap(false);
        m_height = ;

        label_text->setText(paramstr);
        label_text->adjustSize();
        m_width = label_text->width()++;
        //label_text->setMinimumWidth(all_word_width);
        this->resize(m_width+,m_height);
    }

    if(people == GLabel::She)
        label_text->setGeometry(+,,this->width()--,this->height()-);
    else
        label_text->setGeometry(,,this->width()--,this->height()-);

    update();
}

void GLabel::setOurText(QString paramstr)
{
    setSize(paramstr);
    qDebug()<<"setSize"<<this->width()<<this->height();
    //label_text->setWordWrap(true);
   // label_text->setText(paramstr);
}

void GLabel::mousePressEvent(QMouseEvent *e)
{
    qDebug()<<"this pos is"<<e->pos();
}

void GLabel::setHeadpic(QString dir)
{
    label_people->setPixmap(QPixmap(dir));
}

void GLabel::paintEvent(QPaintEvent *e)
{
    //QPainter painter(this);
    if(people == GLabel::She)
    {
        QRectF rectangle(50.0, 10.0, this->width()--, this->height()-);

        QPainter painter(this);
        painter.setRenderHint( QPainter::Antialiasing, true );
        painter.setBrush(QBrush(QColor(,,)));
        painter.drawRoundedRect(rectangle,,);

        QPointF points[] = {
           QPointF(, ),
           QPointF(, ),
           QPointF(, ),
       };

       QPen pen;
       pen.setColor(QColor(,,));
       painter.setPen(pen);
       painter.drawPolygon(points, );

       QPen pen1;
       pen.setColor(Qt::black);
       painter.setPen(pen1);
       painter.drawLine(points[],points[]);
       painter.drawLine(points[],points[]);
    }
    else if(people == GLabel::Me)
    {
        QRectF rectangle(10.0, 10.0, this->width()--, this->height()-);

        QPainter painter(this);
        painter.setRenderHint( QPainter::Antialiasing, true );
        painter.setBrush(QBrush(QColor(,,)));
        painter.drawRoundedRect(rectangle,,);

        QPointF points[] = {
           QPointF(this->width()-, ),
           QPointF(this->width()-, ),
           QPointF(this->width()-,),
       };

       QPen pen;
       pen.setColor(QColor(,,));
       painter.setPen(pen);
       painter.drawPolygon(points, );

       QPen pen1;
       pen.setColor(Qt::black);
       painter.setPen(pen1);
       painter.drawLine(points[],points[]);
       painter.drawLine(points[],points[]);

      // label_text->setGeometry(20,20,this->width()-40-30,this->height()-40);
       label_people->setGeometry(this->width()-,,,);
       this->setGeometry(((QWidget*)this->parent())->width()--this->width(),this->y(),this->width(),this->height());
    }
   // qDebug()<<"this size of pix"<<label_people->size();
   // drawShe();
}

实际调用：

#include "dialog.h"
#include "ui_dialog.h"
#include <QDebug>

Dialog::Dialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Dialog)
{
    ui->setupUi(this);

    label[] = new GLabel(this,GLabel::Me);
    label[]->setGeometry(,,,);
    label[]->setOurText(tr("你好!"));
    label[]->show();

    label[] = new GLabel(this,GLabel::She);
    label[]->setGeometry(,label[]->y()+label[]->height(),,);
    label[]->setOurText(tr("你好!"));
    label[]->show();

    label[] = new GLabel(this,GLabel::Me);
    label[]->setGeometry(,label[]->y()+label[]->height(),,);
    label[]->setOurText(tr("我们好像在哪里见过？"));
    label[]->show();

    label[] = new GLabel(this,GLabel::She);
    label[]->setGeometry(,label[]->y()+label[]->height(),,);
    label[]->setOurText(tr("？"));
    label[]->show();

    label[] = new GLabel(this,GLabel::Me);
    label[]->setGeometry(,label[]->y()+label[]->height(),,);
    label[]->setOurText(tr("我们好像在哪见过你记得吗？好像那是一个秋天夕阳西下，你美得让我不敢和你说话，你经过我时风起浮动我的发"));
    label[]->show();

    label[] = new GLabel(this,GLabel::She);
    label[]->setGeometry(,label[]->y()+label[]->height(),,);
    label[]->setOurText(tr("银杏还是会黄的，雪也会再次染白整个世界。安好"));
    label[]->show();
}

Dialog::~Dialog()
{
    delete ui;
}

下载：http://download.csdn.net/download/yangkping123/8620775