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嵌入式Day9

嵌入式实训

发布于：2023年11月18日

字数：1.6k 字

时长：8 分钟

QT文件操作

QFile读写文本

提供读取写入文件的接口

文件名通常在构造函数中传递

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QIDDevice::Readonly:以只读的方式打开文件，用于载入文件
QIDDevice::Writeonly:以只写方式打开文件，用于保存文件
QIDDevice::ReadWrite:以读写方式打开
QIDDevice::Append:以添加模式打开，新写入文件的数据添加到文件末尾
QIDDevice::Truncate:以裁取的方式打开文件，文件原有内容会被删除
QIDDevice::Text:以文本打开文件

流程：文件–>打开方式–>关闭

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//main

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include<QTextEdit>
#include<QFile>
#include<QVBoxLayout>
#include<QHBoxLayout>
#include<QPushButton>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
private:
	//用于读取文件后显示
    QTextEdit *testEdit;
    QFile file;	//QFile 类型对象
    QHBoxLayout *hBoxLayout;		//水平布局
    QVBoxLayout *vBoxLayout;		//垂直布局
    
    QWidget *hwidget;		//水平布局 widget
    QWidget *vwideget;		//垂直布局 widget
    
    QPushButton *openPushButton;  //打开文件按钮
    QPushButton *closePushButton;	//关闭文件按钮
    
 private slots:
    bool  openFile();		//打开文本文件
    void closeFile();		//关闭文本文件
};
#endif // MAINWINDOW_H
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//mainwindow.h

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>
#include <QDebug>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    this->setGeometry(0,0,800,480);
    textEdit = new QTextEdit();
    vBoxLayout = new QVBoxLayout();
    hBoxLayout = new QHBoxLayout();
    vwideget = new QWidget ();
    hwidget = new QWidget ();
    openPushButton = new QPushButton ();
    closePushButton = new QPushButton();
    openPushButton->setMinimumHeight(50);
    openPushButton->setMaximumWidth(120);
    closePushButton->setMinimumHeight(50);
    closePushButton->setMaximumWidth(120);
    openPushButton->setText("open");
    closePushButton->setText("close");

    closePushButton->setEnabled(false);

    hBoxLayout->addWidget(openPushButton);
    hBoxLayout->addWidget(closePushButton);
    hwidget->setLayout(hBoxLayout);

    vBoxLayout->addWidget(textEdit);
    vBoxLayout->addWidget(hwidget);
    vwideget->setLayout(vBoxLayout);

    setCentralWidget(vwideget);

    connect(openPushButton,SIGNAL(clicked()),
            this,SLOT(openFile()));
    connect(closePushButton,SIGNAL(clicked()),
            this,SLOT(openFile()));


}

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

bool MainWindow::openFile()
{
    QString fileName = QFileDialog::getOpenFileName(this);
    file.setFileName(fileName);
    if(!file.exists())
        return false;
    if(!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return  false;
    textEdit->setPlainText(file.readAll());
    openPushButton->setEnabled(false);
    closePushButton->setEnabled(true);

    file.close();
    return true;
}
void MainWindow::closeFile()
{
    if(!openPushButton->isEnabled()){

        QString str = textEdit->toPlainText();
        if(!file.open(QIODevice::WriteOnly | QIODevice::Text))
            return;

    QByteArray strBytes = str.toUtf8();
    file.write(strBytes,strBytes.length());
    textEdit->clear();
    openPushButton->setEnabled(true);
    closePushButton->setEnabled(false);
}
}

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//mainwindow.cpp


#include "mainwindow.h"
#include "ui_mainwindow.h"	
#include <QFileDialog>		//标准通用对话框
#include <QDebug>	//信息输出头文件
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    this->setGeometry(0,0,800,480);	//设置窗口的位置与大小
//布局设置
    textEdit = new QTextEdit();
    vBoxLayout = new QVBoxLayout();
    hBoxLayout = new QHBoxLayout();
    vwideget = new QWidget ();
    hwidget = new QWidget ();
    openPushButton = new QPushButton ();
    closePushButton = new QPushButton();
    openPushButton->setMinimumHeight(50);
    openPushButton->setMaximumWidth(120);
    closePushButton->setMinimumHeight(50);
    closePushButton->setMaximumWidth(120);
//设置两个按钮的文本       
    openPushButton->setText("打开");
    closePushButton->setText("关闭");
//设置关闭按钮为不可用属性，需要打开文件才设置为可用属性
    closePushButton->setEnabled(false);
//水平布局
    hBoxLayout->addWidget(openPushButton);
    hBoxLayout->addWidget(closePushButton);
    hwidget->setLayout(hBoxLayout);
//垂直布局
    vBoxLayout->addWidget(textEdit);
    vBoxLayout->addWidget(hwidget);
    vwideget->setLayout(vBoxLayout);
//居中
    setCentralWidget(vwideget);
//信号槽连接

    connect(openPushButton,SIGNAL(clicked()),
            this,SLOT(openFile()));
    connect(closePushButton,SIGNAL(clicked()),
            this,SLOT(openFile()));


}

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

bool MainWindow::openFile()
{
    QString fileName = QFileDialog::getOpenFileName(this);//获取文件的路径
    file.setFileName(fileName);	//指向文件
    if(!file.exists())	//判断文件是否存在
        return false;
    if(!file.open(QIODevice::ReadOnly | QIODevice::Text))	//以读写的方式打开
        return  false;
    textEdit->setPlainText(file.readAll());	//读取文本到textEdit
    openPushButton->setEnabled(false);	//设置打开按钮不可用，需要关闭再打开
    closePushButton->setEnabled(true);	//设置关闭按钮为可用属性


    file.close();	//关闭文件
    return true;
}
void MainWindow::closeFile()
{
    if(!openPushButton->isEnabled()){	//检测打开按钮是否可用，不可用时，说明已经打开了文件
        QString str = textEdit->toPlainText();	//获取textEdit的文本内容
        if(!file.open(QIODevice::WriteOnly | QIODevice::Text))	//以只读的方式打开
            return;

    QByteArray strBytes = str.toUtf8();	//转换为字节数组
    file.write(strBytes,strBytes.length());	//写入文件

    textEdit->clear();	//清空textEdit的显示内容
    openPushButton->setEnabled(true);	//重新设置打开何关闭按钮的属性
    closePushButton->setEnabled(false);
}
}

2.QTextStream读写文本

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//mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>
#include <QDebug>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    this->setGeometry(0,0,800,480);
    textEdit = new QTextEdit();
    vBoxLayout = new QVBoxLayout();
    hBoxLayout = new QHBoxLayout();
    vwideget = new QWidget ();
    hwidget = new QWidget ();
    openPushButton = new QPushButton ();
    closePushButton = new QPushButton();
    openPushButton->setMinimumHeight(50);
    openPushButton->setMaximumWidth(120);
    closePushButton->setMinimumHeight(50);
    closePushButton->setMaximumWidth(120);
    openPushButton->setText("open");
    closePushButton->setText("close");

    closePushButton->setEnabled(false);

    hBoxLayout->addWidget(openPushButton);
    hBoxLayout->addWidget(closePushButton);
    hwidget->setLayout(hBoxLayout);

    vBoxLayout->addWidget(textEdit);
    vBoxLayout->addWidget(hwidget);
    vwideget->setLayout(vBoxLayout);

    setCentralWidget(vwideget);

    connect(openPushButton,SIGNAL(clicked()),
            this,SLOT(openFile()));
    connect(closePushButton,SIGNAL(clicked()),
            this,SLOT(openFile()));


}

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

bool MainWindow::openFile()
{
    QString fileName = QFileDialog::getOpenFileName(this);
    file.setFileName(fileName);
    if(!file.exists())
        return false;
    if(!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return  false;
    QTextStream stream(&file);
    textEdit->setPlainText(file.readAll());
    openPushButton->setEnabled(false);
    closePushButton->setEnabled(true);

    file.close();
    return true;
}
void MainWindow::closeFile()
{
    if(!openPushButton->isEnabled()){

        QString str = textEdit->toPlainText();
        if(!file.open(QIODevice::WriteOnly | QIODevice::Text))
            return;
     QTextStream stream(&file);
     QString str_1 = textEdit->toPlainText();
     stream <<str_1;
    //QByteArray strBytes = str.toUtf8();
    //file.write(strBytes,strBytes.length());
    textEdit->clear();
    openPushButton->setEnabled(true);
    closePushButton->setEnabled(false);
}
}

QT多线程

QThread类提供一种独立于平台的方法管理线程。

继承QThread的线程

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//mainwindow.h


#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include<QMainWindow>
#include<QThread>
#include<QDebug>
#include<QPushButton>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class WorkerThread;

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
private:
    WorkerThread *workThread;	//声明对象
    QPushButton *pushButton;	//声明一个按钮，使用此按钮点击后开启线程
    
private slots:	//槽函数，用于接受线程点击后开启线程
    void headleResults(const QString &result);
    void pushButtonClicked();	//点击按钮开启线程
};    
//新建一个WorkThread类继承于QThread
class WorkerThread : public QThread
{
    Q_OBJECT	//用到信号槽即需要此宏定义
    
public:
    WorkerThread(QWidget *parent=nullptr){
        Q_UNUSED(parent);
        
    }
    //重写run()方法
    void run() override{
        QString result="线程开启成功";
    
    sleep(2);	//延迟2s
    emit resultReady(result);	//发送结果准备好的信号
    }
  signals:
    //声明一个信号
    void resultReady(const QString &s);
};
#endif // MAINWINDOW_H

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//mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    this->setGeometry(0,0,800,480);	//设置位置与大小
    pushButton=new QPushButton(this);	//对象实例化
    workerThread = new WorkerThread(this);	//线程对象实例化
//按钮设置大小与文本
    pushButton->resize(100,40);
    pushButton->setText("圆神，启动");
//信号槽连接
    connect(workerThread,SIGNAL(resultReady(QString)),this,SLOT(handleResults(QString)));
    connect(pushButton,SIGNAL(clicked()),this,SLOT(pushButtonClicked()));
}

MainWindow::~MainWindow()
{
    workerThread->quit();	//进程退出
    if(workerThread->wait(2000)){	//阻塞等待2000ms检查一次进程是否已经退出

        qDebug()<<"Thread over!"<<endl;
    }
    delete ui;
}
void MainWindow::handleResults(const QString &result){
    qDebug()<<result<<endl;	//打印线程发送过来的结果
}
void MainWindow::pushButtonClicked()
{
    if(!workerThread->isRunning())	//检查线程是否再运行，如果没有则开始运行
        workerThread->start();
}

image-20231107154643093.png image-20231107154609600.png

更新于：2023年11月18日

字数：1.6k 字

时长：8 分钟

Qt

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