qt (2) —— 部分部件

2019-11-11 06:39:58

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本文大部分內容學習自《Foundations of Qt Development》

notes

qt name rules

類的名字以大寫字母開始，每一個新的詞也以大寫字母開頭，也即駱駝拼寫法 (CamelCasing) 方法的名字也遵從CamelCase，但是需要注意的是它以小寫字母開頭。

PRotected slots

被protect的slot只有被用作方法的時候才會被保護。私有的或者受保護的slots仍然能夠用于connect sigals

meta-object和信號槽機制

meta-object自己知道signals和slots，meta-object compiler (moc) 會用c++實現相關的內容。

signals and slots

qt使用指針實現信號槽，當我們發出信號，實際上也就在調用信號方法，該方法被moc實現。signal方法隨即調用slots。源對象和目標對象就是指向QObject或者它的子類的指針。

LIFO and FIFO

LIFO means “last in, first out”. 代表：棧 FIFO means “fist in, first out”. 代表：隊列

Qt designer

命令行啟動：shell> designer qt4可能是shell> designer-qt4

widgets

QSlider and progressBar

下面的小應用由dialog, horizontalSlider, progressBar, pushButton, label構成。第三個progressBar的范圍是(0,0)，結果時不顯示數值結果并不斷運動的，第4個progressBar的范圍我想設置成無窮大，但不確定這種方法setRange(-1,-1)是否正確。

Dialog::Dialog(QWidget *parent) : QDialog(parent), ui(new Ui::Dialog){ ui->setupUi(this);/* *for QProgressBar format : QString *This property holds the string used to generate the current text. *%p - is replaced by the percentage completed. %v - is replaced by the current value. %m - is replaced *by the total number of steps. The default value is "%p%". */ ui->progressBar->setFormat("%p%"); // default ui->progressBar_2->setFormat("%v out of %m"); //custom text ui->progressBar_3->setRange(0,0); // hide text and keep moving. ui->progressBar_4->setRange(-1,-1); // static connect(ui->horizontalSlider,SIGNAL(valueChanged(int)),ui->progressBar,SLOT(setValue(int))); connect(ui->horizontalSlider,SIGNAL(valueChanged(int)),ui->progressBar_2,SLOT(setValue(int))); connect(ui->horizontalSlider,SIGNAL(valueChanged(int)),ui->progressBar_3,SLOT(setValue(int))); connect(ui->horizontalSlider,SIGNAL(valueChanged(int)),ui->progressBar_4,SLOT(setValue(int))); connect(ui->pushButton,SIGNAL(clicked()),this,SLOT(close()));}

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QLineEdit

LineEdit的echo mod可以設置成不同的格式，屬性MaxLength則設定了能夠填寫的最大字符數。

Dialog::Dialog(QWidget *parent) : QDialog(parent), ui(new Ui::Dialog){ ui->setupUi(this); ui->lineEdit_2->setEchoMode(QLineEdit::PassWord); ui->lineEdit_3->setMaxLength(9); connect(ui->lineEdit,SIGNAL(textChanged(QString)),ui->lineEdit_4,SLOT(setText(QString))); connect(ui->lineEdit_2,SIGNAL(textChanged(QString)),ui->lineEdit_5,SLOT(setText(QString))); connect(ui->lineEdit_3,SIGNAL(textChanged(QString)),ui->lineEdit_6,SLOT(setText(QString)));}

這里寫圖片描述

QListWidget

將listWidget放進Dialog后，合理設置layout，我們可以在改變dialog的大小同時產生上下滑動條。下面的例子對choose and click做了一些處理。 dialog.cpp:

#include "dialog.h"#include "ui_dialog.h"Dialog::Dialog(QWidget *parent) : QDialog(parent), ui(new Ui::Dialog){ ui->setupUi(this); for(int i=0;i<10;i++){ ui->listWidget->addItem(QString::number(i)+" item"); }}Dialog::~Dialog(){ delete ui;}void Dialog::on_pushButton_clicked(){ QListWidgetItem *it = ui->listWidget->currentItem(); it->setText("you click "+it->text()); it->setBackground(Qt::black); it->setTextColor(Qt::red);}

這里寫圖片描述好好利用QListWidget，如takeItem, addItem等方法，我們可以創建出類似于管理書單的應用窗體。 dialog.h

#ifndef DIALOG_H#define DIALOG_H#include <QDialog>#include <QListWidget>#include <QPushButton>namespace Ui {class Dialog;}class Dialog : public QDialog{ Q_OBJECT QListWidget *listLeft, *listRight; QPushButton *buttonLeft, *buttonRight;public: explicit Dialog(QWidget *parent = 0); ~Dialog();private: Ui::Dialog *ui;public slots: void moveRight(); void moveLeft();};#endif // DIALOG_H

dialog.cpp

#include "dialog.h"#include "ui_dialog.h"#include <QGridLayout>#include <QStringList>#include <QList>#include <QMessageBox>Dialog::Dialog(QWidget *parent) : QDialog(parent), ui(new Ui::Dialog){ ui->setupUi(this); listLeft = new QListWidget(this); listRight = new QListWidget(this); buttonLeft = new QPushButton(">>",this); buttonRight = new QPushButton("<<",this); QGridLayout *gLayout = new QGridLayout(this); gLayout->addWidget(listLeft,0,0); gLayout->addWidget(listRight,0,1); gLayout->addWidget(buttonLeft,1,0); gLayout->addWidget(buttonRight,1,1); QStringList items; items<<"apple"<<"pear"<<"banana"<<"peach"; listLeft->addItems(items); connect(buttonLeft,SIGNAL(clicked()),this,SLOT(moveRight())); connect(buttonRight,SIGNAL(clicked()),this,SLOT(moveLeft()));}Dialog::~Dialog(){ delete ui;}void Dialog::moveLeft(){ if(listRight->selectedItems().count()!=1) return; QListWidgetItem *item = listRight->takeItem(listRight->currentRow()); listLeft->addItem(item);}void Dialog::moveRight(){ if(listLeft->selectedItems().count()!=1) return; QListWidgetItem *item = listLeft->takeItem(listLeft->currentRow()); listRight->addItem(item);}

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QPushButton

QPushButton可以被設置觸發(pressed)，接著舉一個例子，應用QMessageBox，QPushButton，QString. 工程ButtonDialog，程序運行后，點擊toggle me按鈕，直到下一次點擊它，它一直處于pressed狀態。 pro文件：

#-------------------------------------------------## Project created by QtCreator 2017-02-04T18:29:24##-------------------------------------------------QT += core guigreaterThan(QT_MAJOR_VERSION, 4): QT += widgetsTARGET = ButtonDialogTEMPLATE = appSOURCES += main.cpp/ dialog.cppHEADERS += dialog.hFORMS += dialog.ui

Dialog.h:

#ifndef DIALOG_H#define DIALOG_H#include <QDialog>#include <QPushButton>namespace Ui {class Dialog;}class Dialog : public QDialog{ Q_OBJECTpublic: explicit Dialog(QWidget *parent = 0); ~Dialog(); public slots: void buttonClicked(); void buttonToggled();private: Ui::Dialog *ui; QPushButton *clickButton; QPushButton *toggleButton;};#endif // DIALOG_H

Dialog.cpp

#include "dialog.h"#include "ui_dialog.h"#include <QVBoxLayout>#include <QMessageBox>Dialog::Dialog(QWidget *parent) : QDialog(parent), ui(new Ui::Dialog){ ui->setupUi(this); clickButton = new QPushButton("click me",this); toggleButton = new QPushButton("toggle me",this); toggleButton->setCheckable(true); QVBoxLayout *vLayout = new QVBoxLayout(this); vLayout->addWidget(clickButton); vLayout->addWidget(toggleButton); connect(clickButton,SIGNAL(clicked()),this,SLOT(buttonClicked())); connect(toggleButton,SIGNAL(clicked()),this,SLOT(buttonToggled()));}Dialog::~Dialog(){ delete ui;}void Dialog::buttonClicked(){ QMessageBox::information(this,"Clicked","the Button is cliecked.");}void Dialog::buttonToggled(){ QMessageBox::information(this,"Toggled",QString("the button is %1!")/ .arg(toggleButton->isChecked()?"pressed":"released"));}

main.cpp

#include "dialog.h"#include <Qapplication>int main(int argc, char *argv[]){ QApplication a(argc, argv); Dialog w; w.show(); return a.exec();}

這里寫圖片描述

QLabel

QLabel可是設置shortCut，setBuddy。在下面的例子中，按下”Alt+1”, 光標會聚焦于LineEdit1，按下”Alt +2”, 光標聚焦于LineEdit2。這里寫圖片描述 dialog.cpp

#include "dialog.h"#include "ui_dialog.h"Dialog::Dialog(QWidget *parent) : QDialog(parent), ui(new Ui::Dialog){ ui->setupUi(this); ui->label->setText("Line&1"); ui->label_2->setText("Line&2"); ui->label->setBuddy(ui->lineEdit); ui->label_2->setBuddy(ui->lineEdit_2);}Dialog::~Dialog(){ delete ui;}

QComboBox

假設在類中聲明了slot，我們一定要在cpp中定義。 comboBox.h

#ifndef COMBOBOX_H#define COMBOBOX_H#include <QDialog>namespace Ui {class ComboBox;}class ComboBox : public QDialog{ Q_OBJECTpublic: explicit ComboBox(QWidget *parent = 0); ~ComboBox();public slots: void myshow(); //show is key word, care about it.private: Ui::ComboBox *ui;};#endif // COMBOBOX_H

comboBox.cpp

#include "combobox.h"#include "ui_combobox.h"#include <QFontComboBox>#include <QMessageBox>ComboBox::ComboBox(QWidget *parent) : QDialog(parent), ui(new Ui::ComboBox){ ui->setupUi(this); QFont font("KaiTi_GB2312",16); ui->comboBox->setFont(font); int i; for(i=0;i<10;i++){ ui->comboBox->addItem(QString::number(i)+" item"); } connect(ui->pushButton,SIGNAL(clicked(bool)),this,SLOT(myshow()));}void ComboBox::myshow(){ QMessageBox::information(this,"choosed",ui->comboBox->currentText());}ComboBox::~ComboBox(){ delete ui;}

main.cpp

#include "combobox.h"#include <QApplication>int main(int argc, char *argv[]){ QApplication a(argc, argv); ComboBox w; w.show(); return a.exec();}

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QSPinBox + LCD Number

在designer中進行connect設置，連接spinBox的valueChanged()和LCD number的display()。QDoubleSpinBox相比QSpinBox提供了更高的精度。這里寫圖片描述

QCalender + QDateTime

QCalender和QDateTime(QDate)均可表示日期。前者更加直觀，后者更加精確，容易修改。

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QGridLayout

GridLayout很強大，因為它靈活，坐標定位，所以用起來很方便。

#include <QApplication>#include <QGridLayout>#include <QLabel>#include <QDialog>#include <QString>int main(int argc,char *argv[]){ QApplication app(argc,argv); QDialog dlg; dlg.resize(400,400); dlg.show(); QGridLayout *grid = new QGridLayout(&dlg); int i,j; int counter = 1; for(i=0;i<10;i++){ for(j=0;j<10;j++){ QLabel *label = new QLabel(QString::number(counter)); label->setFrameStyle(QFrame::Panel | QFrame::Sunken); grid->addWidget(label,i,j); counter++; } } grid->setMargin(2); return app.exec();}

這里寫圖片描述

QVBoxLayout

.pro

SOURCES += / main.cppQT += widgets

main.cpp

#include <QApplication>#include <QLabel>#include <QDialog>#include <QVBoxLayout>#include <QDialogButtonBox>#include <QPushButton>#include <QGridLayout>#include <QDebug>int main(int argc,char *argv[]){ QApplication app(argc,argv); QDialog dlg; dlg.resize(100,200); dlg.show(); QLabel *label = new QLabel("hello world."); label->show(); QDialogButtonBox *buttons = new QDialogButtonBox(QDialogButtonBox::Ok |QDialogButtonBox::Cancel); QVBoxLayout *vLayout = new QVBoxLayout(&dlg); vLayout->addWidget(label); vLayout->addStretch(); vLayout->addWidget(buttons); return app.exec();}

這里寫圖片描述