Qt -- QLineEdit使用总结

以上是Qt官方文档对QLineEdit的简要说明，下面根据个人经验，对一些常用的方法作说明：

1.setPlaceholderText()设置提示文字

豆瓣电影的搜索输入框，没有输入任何字符时，显示“电影、影人、影院、电视剧”这些占位文字，对用户输入作相关提示。

echoLineEdit->setPlaceholderText( "电影、影人、影院、电视剧" );

2.setEchoMode()设置模式

淘宝登录界面的一部分，用户名可以直接看到，密码一般都用小黑点掩盖。

switch  (index) {
 case  0:
     //默认，输入什么即显示什么
     echoLineEdit->setEchoMode(QLineEdit::Normal);
     break ;
 case  1:
     //密码，一般是用小黑点覆盖你所输入的字符
     echoLineEdit->setEchoMode(QLineEdit::Password);
     break ;
 case  2:
     //编辑时输入字符显示输入内容，否则用小黑点代替
     echoLineEdit->setEchoMode(QLineEdit::PasswordEchoOnEdit);
     break ;
 case  3:
     //任何输入都看不见（只是看不见，不是不能输入）
     echoLineEdit->setEchoMode(QLineEdit::NoEcho);
    }

3.setAlignment()设置文本位置

switch  (index) {
 case  0:
     alignmentLineEdit->setAlignment(Qt::AlignLeft);
     break ;
 case  1:
     alignmentLineEdit->setAlignment(Qt::AlignCenter);
     break ;
 case  2:
     alignmentLineEdit->setAlignment(Qt::AlignRight);
     }

4.setReadOnly()设置能否编辑

switch  (index) {
 case  0:
     accessLineEdit->setReadOnly( false );
     break ;
 case  1:
     accessLineEdit->setReadOnly( true );
 }

5.setValidator()对输入进行限制

这种方式的实质是通过正则表达式限制输入的内容。

比如上面的手机号输入框，控制其不能输入英文汉字等无关字符。

switch  (index) {
 case  0:
     //无限制
     validatorLineEdit->setValidator(0);
     break ;
 case  1:
     //只能输入整数
     validatorLineEdit->setValidator( new  QIntValidator(
         validatorLineEdit));
     break ;
 case  2:
     //实例，只能输入-180到180之间的小数，小数点后最多两位（可用于限制经纬度等）
     QDoubleValidator *pDfValidator =  new  QDoubleValidator(-180.0, 180.0 , 2, validatorLineEdit);
     pDfValidator->setNotation(QDoubleValidator::StandardNotation);
     validatorLineEdit->setValidator(pDfValidator);
 }

6.setInputMask()对输入进行限制

switch  (index) {
 case  0:
     inputMaskLineEdit->setInputMask( "" );
     break ;
 case  1:
     inputMaskLineEdit->setInputMask( "+99 99 99 99 99;_" );
     break ;
 case  2:
     inputMaskLineEdit->setInputMask( "0000-00-00" );
     inputMaskLineEdit->setText( "00000000" );
     inputMaskLineEdit->setCursorPosition(0);
     break ;
 case  3:
     inputMaskLineEdit->setInputMask( ">AAAAA-AAAAA-AAAAA-AAAAA-AAAAA;#" );
 }

7.setMaxLength()设置可以输入的最多字符数

//最多只能输入9个字符
echoLineEdit->setMaxLength(9);

8.validator和inputmask的结合

比如纬度用“度:分:秒”的格式表示，分和秒的范围都是00-59，度的范围是-89到89。

QRegExp rx( "(-|\\+)?[0-8]\\d:[0-5]\\d:[0-5]\\d" );
echoLineEdit->setValidator( new  QRegExpValidator(rx, echoLineEdit));
echoLineEdit->setInputMask( "#00:00:00;0" );
echoLineEdit->setText( "+00:00:00" );

如果不控制输入，那么必须在输入后检查输入是否合法，但控制输入后的输入肯定是合法的，可以省去检查合法的繁琐步骤。只需使用正则表达式控制输入的度分秒范围，然后控制输入的格式。

一些测试代码供参考——

头文件：

#ifndef WINDOW_H
#define WINDOW_H
#include <QWidget>

QT_BEGIN_NAMESPACE
class  QComboBox;
class  QLineEdit;
QT_END_NAMESPACE

//! [0]
class  Window :  public  QWidget
{
     Q_OBJECT

public :
     Window();

public  slots:
     void  echoChanged( int );
     void  validatorChanged( int );
     void  alignmentChanged( int );
     void  inputMaskChanged( int );
     void  accessChanged( int );

private :
     QLineEdit *echoLineEdit;
     QLineEdit *validatorLineEdit;
     QLineEdit *alignmentLineEdit;
     QLineEdit *inputMaskLineEdit;
     QLineEdit *accessLineEdit;
};
//! [0]

#endif

include

include "window.h"

//! [0]
Window::Window()
{
QGroupBox *echoGroup = new QGroupBox(tr( "Echo" ));

 QLabel *echoLabel =  new  QLabel(tr( "Mode:" ));
 QComboBox *echoComboBox =  new  QComboBox;
 echoComboBox->addItem(tr( "Normal" ));
 echoComboBox->addItem(tr( "Password" ));
 echoComboBox->addItem(tr( "PasswordEchoOnEdit" ));
 echoComboBox->addItem(tr( "No Echo" ));

 echoLineEdit =  new  QLineEdit;
 //test
 /*QRegExp rx("(-|\\+)?[0-8]\\d:[0-5]\\d:[0-5]\\d");
 echoLineEdit->setValidator(new QRegExpValidator(rx, echoLineEdit));
 echoLineEdit->setInputMask("#00:00:00;0");
 echoLineEdit->setText("+00:00:00");*/

 //echoLineEdit->setMaxLength(9);
 echoLineEdit->setPlaceholderText( "电影、影人、影院、电视剧" );
 echoLineEdit->setFocus();

//! [0]

//! [1]
QGroupBox *validatorGroup = new QGroupBox(tr( "Validator" ));

 QLabel *validatorLabel =  new  QLabel(tr( "Type:" ));
 QComboBox *validatorComboBox =  new  QComboBox;
 validatorComboBox->addItem(tr( "No validator" ));
 validatorComboBox->addItem(tr( "Integer validator" ));
 validatorComboBox->addItem(tr( "Double validator" ));

 validatorLineEdit =  new  QLineEdit;
 validatorLineEdit->setPlaceholderText( "Placeholder Text" );

//! [1]

//! [2]
QGroupBox *alignmentGroup = new QGroupBox(tr( "Alignment" ));

 QLabel *alignmentLabel =  new  QLabel(tr( "Type:" ));
 QComboBox *alignmentComboBox =  new  QComboBox;
 alignmentComboBox->addItem(tr( "Left" ));
 alignmentComboBox->addItem(tr( "Centered" ));
 alignmentComboBox->addItem(tr( "Right" ));

 alignmentLineEdit =  new  QLineEdit;
 alignmentLineEdit->setPlaceholderText( "Placeholder Text" );

//! [2]

//! [3]
QGroupBox *inputMaskGroup = new QGroupBox(tr( "Input mask" ));

 QLabel *inputMaskLabel =  new  QLabel(tr( "Type:" ));
 QComboBox *inputMaskComboBox =  new  QComboBox;
 inputMaskComboBox->addItem(tr( "No mask" ));
 inputMaskComboBox->addItem(tr( "Phone number" ));
 inputMaskComboBox->addItem(tr( "ISO date" ));
 inputMaskComboBox->addItem(tr( "License key" ));

 inputMaskLineEdit =  new  QLineEdit;
 inputMaskLineEdit->setPlaceholderText( "Placeholder Text" );

//! [3]

//! [4]
QGroupBox *accessGroup = new QGroupBox(tr( "Access" ));

 QLabel *accessLabel =  new  QLabel(tr( "Read-only:" ));
 QComboBox *accessComboBox =  new  QComboBox;
 accessComboBox->addItem(tr( "False" ));
 accessComboBox->addItem(tr( "True" ));

 accessLineEdit =  new  QLineEdit;
 accessLineEdit->setPlaceholderText( "Placeholder Text" );

//! [4]

//! [5]
connect(echoComboBox, SIGNAL(activated( int )),
this , SLOT(echoChanged( int )));
connect(validatorComboBox, SIGNAL(activated( int )),
this , SLOT(validatorChanged( int )));
connect(alignmentComboBox, SIGNAL(activated( int )),
this , SLOT(alignmentChanged( int )));
connect(inputMaskComboBox, SIGNAL(activated( int )),
this , SLOT(inputMaskChanged( int )));
connect(accessComboBox, SIGNAL(activated( int )),
this , SLOT(accessChanged( int )));
//! [5]

//! [6]
QGridLayout *echoLayout = new QGridLayout;
echoLayout->addWidget(echoLabel, 0, 0);
echoLayout->addWidget(echoComboBox, 0, 1);
echoLayout->addWidget(echoLineEdit, 1, 0, 1, 2);
echoGroup->setLayout(echoLayout);
//! [6]

//! [7]
QGridLayout *validatorLayout = new QGridLayout;
validatorLayout->addWidget(validatorLabel, 0, 0);
validatorLayout->addWidget(validatorComboBox, 0, 1);
validatorLayout->addWidget(validatorLineEdit, 1, 0, 1, 2);
validatorGroup->setLayout(validatorLayout);

 QGridLayout *alignmentLayout =  new  QGridLayout;
 alignmentLayout->addWidget(alignmentLabel, 0, 0);
 alignmentLayout->addWidget(alignmentComboBox, 0, 1);
 alignmentLayout->addWidget(alignmentLineEdit, 1, 0, 1, 2);
 alignmentGroup-> setLayout(alignmentLayout);

 QGridLayout *inputMaskLayout =  new  QGridLayout;
 inputMaskLayout->addWidget(inputMaskLabel, 0, 0);
 inputMaskLayout->addWidget(inputMaskComboBox, 0, 1);
 inputMaskLayout->addWidget(inputMaskLineEdit, 1, 0, 1, 2);
 inputMaskGroup->setLayout(inputMaskLayout);

 QGridLayout *accessLayout =  new  QGridLayout;
 accessLayout->addWidget(accessLabel, 0, 0);
 accessLayout->addWidget(accessComboBox, 0, 1);
 accessLayout->addWidget(accessLineEdit, 1, 0, 1, 2);
 accessGroup->setLayout(accessLayout);

//! [7]

//! [8]
QGridLayout *layout = new QGridLayout;
layout->addWidget(echoGroup, 0, 0);
layout->addWidget(validatorGroup, 1, 0);
layout->addWidget(alignmentGroup, 2, 0);
layout->addWidget(inputMaskGroup, 0, 1);
layout->addWidget(accessGroup, 1, 1);
setLayout(layout);

 setWindowTitle(tr( "Line Edits" ));

}
//! [8]

//! [9]
void Window::echoChanged( int index)
{
switch (index) {
case 0:
//默认，输入什么即显示什么
echoLineEdit->setEchoMode(QLineEdit::Normal);
break ;
case 1:
//密码，一般是用小黑点覆盖你所输入的字符
echoLineEdit->setEchoMode(QLineEdit::Password);
break ;
case 2:
//编辑时输入字符显示输入内容，否则用小黑点代替
echoLineEdit->setEchoMode(QLineEdit::PasswordEchoOnEdit);
break ;
case 3:
//任何输入都看不见（只是看不见，不是不能输入）
echoLineEdit->setEchoMode(QLineEdit::NoEcho);
}
}
//! [9]

//! [10]
void Window::validatorChanged( int index)
{
switch (index) {
case 0:
//无限制
validatorLineEdit->setValidator(0);
break ;
case 1:
//只能输入整数
validatorLineEdit->setValidator( new QIntValidator(
validatorLineEdit));
break ;
case 2:
//实例，只能输入-180到180之间的小数，小数点后最多两位（可用于限制经纬度等）
QDoubleValidator *pDfValidator = new QDoubleValidator(-180.0, 180.0 , 2, validatorLineEdit);
pDfValidator->setNotation(QDoubleValidator::StandardNotation);
validatorLineEdit->setValidator(pDfValidator);
}

 validatorLineEdit->clear();

}
//! [10]

//! [11]
void Window::alignmentChanged( int index)
{
switch (index) {
case 0:
alignmentLineEdit->setAlignment(Qt::AlignLeft);
break ;
case 1:
alignmentLineEdit->setAlignment(Qt::AlignCenter);
break ;
case 2:
alignmentLineEdit->setAlignment(Qt::AlignRight);
}
}
//! [11]

//! [12]
void Window::inputMaskChanged( int index)
{
switch (index) {
case 0:
inputMaskLineEdit->setInputMask( "" );
break ;
case 1:
inputMaskLineEdit->setInputMask( "+99 99 99 99 99;_" );
break ;
case 2:
inputMaskLineEdit->setInputMask( "0000-00-00" );
inputMaskLineEdit->setText( "00000000" );
inputMaskLineEdit->setCursorPosition(0);
break ;
case 3:
inputMaskLineEdit->setInputMask( ">AAAAA-AAAAA-AAAAA-AAAAA-AAAAA;#" );
}
}
//! [12]

//! [13]
void Window::accessChanged( int index)
{
switch (index) {
case 0:
accessLineEdit->setReadOnly( false );
break ;
case 1:
accessLineEdit->setReadOnly( true );
}
}
//! [13]

https://blog.csdn.net/lmhuanying1012/article/details/79798465