Qt 模拟安卓虚拟摇杆实现

#include "handle.h"

Handle::Handle(QWidget *parent)
    : QWidget(parent)
{
    setAutoFillBackground(true);
    setPalette(QPalette(Qt::white));
    resize(200,200);
    setMinimumSize(100,100);
    mouseX=width()/2;
    mouseY=height()/2;
    tim=new QTimer(this);
    connect(tim,&QTimer::timeout,this,[=]{
       emit keyNumchanged(getKeyNum());
   });
    connect(this,&Handle::keyNumchanged,this,[=](int num){
        qDebug()<<num<<endl;
    });
}

Handle::~Handle()
{

}
void Handle::paintEvent(QPaintEvent *){

    QPainter painter(this);

    int side = qMin(width(), height());

    padR=side/2; //底盘半径
    padX=padR;//底盘圆心
    padY=padR;//底盘圆心
    handleR=padR/4;//摇杆圆半径
    int handleMaxR=padR-handleR;
    QColor handleColor(Qt::gray);
    //加载底盘图像
    painter.save();

    painter.scale(side / 400.0, side / 400.0);//坐标会随窗口缩放
    painter.drawPixmap(0, 0, QPixmap(":/image/pad.png"));
    painter.restore();

    //自绘底盘
//    painter.save();
//    QRadialGradient RadialGradient(padR,padR,padR*3,padR,padR);//圆心2，半径1，焦点2
//    RadialGradient.setColorAt(0,QColor(90,90,90,127));//渐变
//    RadialGradient.setColorAt(1,QColor(255,255,255,190));//渐变
//    painter.setBrush(RadialGradient);
//    painter.setPen(Qt::NoPen);
//    painter.drawEllipse(QPoint(padR,padR),side/2,side/2);//大圆盘
//    painter.restore();

 //   painter.drawText(20,20,tr("%1,%2,%3").arg(mouseX).arg(mouseY).arg(handPaddis));

    if(!mousePressed){//鼠标没按下则摇杆恢复到底盘中心
        mouseX=padX;
        mouseY=padY;
    }
    handPadDis=Pointdis(padR,padR,mouseX,mouseY);
    if(handPadDis<=handleMaxR){
        handleX=mouseX;
        handleY=mouseY;
    }
    else {
        handleX=(int)(handleMaxR*(mouseX-padX)/handPadDis+padX);
        handleY=(int)(handleMaxR*(mouseY-padY)/handPadDis+padY);
    }
   // painter.drawText(200,200,tr("%1,%2,%3").arg(handleX).arg(handleY).arg(handPaddis));
    painter.setPen(Qt::NoPen);
    painter.setBrush(handleColor);
    painter.drawEllipse(QPoint(handleX,handleY),handleR,handleR);//摇杆
}
void Handle::mouseMoveEvent(QMouseEvent* event){
    static bool r=false;
    mouseX=event->pos().x();
    mouseY=event->pos().y();
    if(r==true){
       update();
       r=false;
    }
    else{
        r=true;
    }
}
void Handle::mouseReleaseEvent(QMouseEvent* event){
    mouseX=width()/2;
    mouseY=height()/2;
    tim->stop();
    mousePressed=false;
    emit keyNumchanged(Handle::stop);
    update();
}
void Handle::mousePressEvent(QMouseEvent* event){
    mouseX=event->pos().x();
    mouseY=event->pos().y();
    tim->start(100);
    mousePressed=true;
    update();
}

double Handle::Pointdis(int a,int b,int x,int y){
    return sqrt((double)((x-a)*(x-a)+(y-b)*(y-b)));
}
int Handle::getKeyNum(){
    int x,y;
    int keynum;
    x=(int)(handleX*3.0/(padR*2));
    y=(int)(handleY*3.0/(padR*2));
    keynum=3*y+x;
    return keynum;
}

#ifndef HANDLE_H
#define HANDLE_H

#include <QWidget>
#include <QPainter>
#include <QDrag>
#include <QMouseEvent>
#include <QtMath>
#include <QTimer>
#include <QDebug>
class Handle : public QWidget
{
    Q_OBJECT

public:
    Handle(QWidget *parent = 0);
    ~Handle();
    enum {upleft=0,up,upright,left,stop,right,downleft,down,downright};
signals:
    void keyNumchanged(int num);
protected:
    void paintEvent(QPaintEvent *event)override;
    void mouseMoveEvent(QMouseEvent *event)override;
    void mouseReleaseEvent(QMouseEvent *event)override;
    void mousePressEvent(QMouseEvent *event)override;
  //  void resizeEvent(QResizeEvent *event)override;
private:
    int mouseX;
    int mouseY;
  int handleX;//摇杆
  int handleY;
  int handleR;
  int padX;//底盘
  int padY;
  int padR;
  double handPadDis;//两圆圆心距离
  bool mousePressed;
  QTimer *tim;
private:
   double Pointdis(int a,int b,int x,int y);//两点距离
   int getKeyNum();

};

#endif // HANDLE_H

实现功能：

       1.实现摇杆在圆盘内任意位置移动，鼠标超出圆盘则停靠在圆盘边界

       2.鼠标按下时每100ms发送一次键值，键值定义为

       enum {upleft=0,up,upright,left,stop,right,downleft,down,downright};

预览：

工程文件：

#-------------------------------------------------
#
# Project created by QtCreator 2019-10-14T21:24:47
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = handle
TEMPLATE = app

# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

CONFIG += c++11

SOURCES += \
        main.cpp \
        handle.cpp

HEADERS += \
        handle.h

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

RESOURCES += \
    pic.qrc

注意必须加：

CONFIG += c++11