qt lineedit_个人总结学生

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发布于 2022-11-08 14:59:50

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发布于 2022-11-08 14:59:50

QLineEdit是一个单行文本编辑控件。使用者可以通过很多函数，输入和编辑单行文本，比如撤销、恢复、剪切、粘贴以及拖放等。通过改变QLineEdit的 echoMode() ，可以设置其属性，比如以密码的形式输入。文本的长度可以由 maxLength() 限制，可以通过使用 validator() 或者 inputMask() 可以限制它只能输入数字。在对同一个QLineEdit的validator或者input mask进行转换时，最好先将它的validator或者input mask清除，以避免错误发生。与QLineEdit相关的一个类是QTextEdit，它允许多行文字以及富文本编辑。我们可以使用 setText() 或者 insert() 改变其中的文本，通过 text() 获得文本，通过 displayText() 获得显示的文本，使用 setSelection() 或者 selectAll() 选中文本，选中的文本可以通过cut()、copy()、paste()进行剪切、复制和粘贴，使用 setAlignment() 设置文本的位置。文本改变时会发出 textChanged() 信号；如果不是由setText()造成文本的改变，那么会发出textEdit()信号；鼠标光标改变时会发出cursorPostionChanged()信号；当返回键或者回车键按下时，会发出returnPressed()信号。当编辑结束，或者LineEdit失去了焦点，或者当返回/回车键按下时，editFinished()信号将会发出。

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

通过限制格式限制输入，具体怎么格式化可以参考Qt助手。

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

实现：

#include <QtWidgets> #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]

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原始发表：2022年10月6日，如有侵权请联系 cloudcommunity@tencent.com 删除

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