初学者提问，如何读取txt文件内容并输出到文本框 - QTCN开发网

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFile>
#include <QFileDevice>
#include <QTextStream>
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

}

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

void MainWindow::on_pushButton_clicked()
{
    QString displayString;
    QFile file("text.txt");
    if(!file.open(QIODevice::ReadOnly | QIODevice::Text))
    {
        qDebug()<<"Can't open the file!"<<endl;
    }
    while(!file.atEnd())
    {
        QByteArray line = file.readLine();
        QString str(line);
        qDebug()<< str;
        displayString.append(str);
    }
       ui->textEdit->clear();
       ui->textEdit->setPlainText(displayString);
}

void MainWindow::on_pushButton_2_clicked()
{
    QString displayString;
    QFile file("text.txt");
     if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
         return;

     QTextStream in(&file);
     QString line = in.readLine();

     while (!line.isNull())
     {
//         process_line(line);
         line = in.readLine();
         displayString.append(line);
     }
       ui->textEdit->clear();
       ui->textEdit->setPlainText(displayString);
}

void MainWindow::on_pushButton_3_clicked()
{
     QString displayString;
     QFile file("text.txt");
      if(!file.open(QIODevice::ReadWrite | QIODevice::Text)) {
          qDebug()<<"Can't open the file!"<<endl;
      }
      QTextStream stream(&file);
      QString line_in;
      stream.seek(file.size());//将当前读取文件指针移动到文件末尾
      int count = 0;
      while(count < 10)
      {
          stream << QObject::trUtf8("新建行:") <<++count<<"/n";
      }
      stream.seek(0);//将当前读取文件指针移动到文件开始
      while( !stream.atEnd())
      {
          line_in = stream.readLine();
          displayString.append(line_in);
          qDebug() << line_in;
      }
      ui->textEdit->clear();
      ui->textEdit->setPlainText(displayString);
}