Qt WidgetsでQPlainTextEdit::plainTextを使ってテキストを操作する

QPlainTextEdit is a widget in Qt that is used to edit and display plain text. It is a subclass of QAbstractScrollArea, which means that it can be used to display large amounts of text without performance problems.

QPlainTextEdit::plainText is a property that gets and sets the plain text contents of the text editor. The plain text is the text without any formatting, such as font styles, colors, or embedded images.

Getting the Plain Text

To get the plain text contents of a QPlainTextEdit widget, you can use the following code:

QString text = plainTextEdit->toPlainText();

This code will get the plain text contents of the plainTextEdit widget and store them in the text variable.

Setting the Plain Text

To set the plain text contents of a QPlainTextEdit widget, you can use the following code:

plainTextEdit->setPlainText(text);

This code will set the plain text contents of the plainTextEdit widget to the text stored in the text variable.

Example

The following code shows an example of how to use QPlainTextEdit::plainText to get and set the plain text contents of a text editor:

QPlainTextEdit *plainTextEdit = new QPlainTextEdit();
plainTextEdit->setPlainText("This is some plain text.");

QString text = plainTextEdit->toPlainText();
qDebug() << text;

plainTextEdit->setPlainText("This is some different plain text.");

text = plainTextEdit->toPlainText();
qDebug() << text;

This code will output the following text to the console:

This is some plain text.
This is some different plain text.

Additional Notes

• The plainText property is always available, even if the text editor is read-only.
• Setting the plainText property will clear the undo/redo history of the text editor.

I hope this explanation is helpful. Please let me know if you have any other questions.

Getting the text from a file

The following code shows how to get the plain text contents of a file and display them in a QPlainTextEdit widget:

QPlainTextEdit *plainTextEdit = new QPlainTextEdit();

QFile file("myfile.txt");
if (file.open(QIODevice::ReadOnly)) {
    QTextStream in(&file);
    plainTextEdit->setPlainText(in.readAll());
    file.close();
} else {
    qDebug() << "Error opening file";
}

This code will open the file myfile.txt and read its contents into the text variable. The text variable will then be used to set the plain text contents of the plainTextEdit widget.

Saving the text to a file

The following code shows how to save the plain text contents of a QPlainTextEdit widget to a file:

QPlainTextEdit *plainTextEdit = new QPlainTextEdit();

QFile file("myfile.txt");
if (file.open(QIODevice::WriteOnly)) {
    QTextStream out(&file);
    out << plainTextEdit->toPlainText();
    file.close();
} else {
    qDebug() << "Error opening file";
}

This code will open the file myfile.txt and write the plain text contents of the plainTextEdit widget to the file.

Highlighting specific text

The following code shows how to highlight specific text in a QPlainTextEdit widget:

QPlainTextEdit *plainTextEdit = new QPlainTextEdit();

plainTextEdit->setPlainText("This is some text. Some of it is important.");

QTextDocument *document = plainTextEdit->document();
QTextFinder *finder = new QTextFinder(document);
finder->setSearchText("important");
QTextCursor cursor = finder->first();

while (cursor.isValid()) {
    QTextCharFormat format;
    format.setBackgroundColor(Qt::yellow);
    cursor.setCharFormat(format);
    cursor = finder->next();
}

This code will search the plain text contents of the plainTextEdit widget for the text "important" and highlight all occurrences of the text in yellow.

Responding to user input

The following code shows how to respond to user input in a QPlainTextEdit widget:

QPlainTextEdit *plainTextEdit = new QPlainTextEdit();

plainTextEdit->connect(plainTextEdit, &QPlainTextEdit::textChanged, this, &MyClass::textChanged);

This code will connect the textChanged signal of the plainTextEdit widget to the textChanged slot of the MyClass class. The textChanged slot will be called whenever the text in the plainTextEdit widget changes.

In the textChanged slot, you can do whatever you want with the new text, such as:

• Save the text to a file
• Send the text to a server
• Update a database

I hope these examples are helpful. Please let me know if you have any other questions.

However, here are some general tips for finding other methods:

• Search online: Use a search engine like Google to find examples of code that does what you need. Be sure to use specific keywords in your search query.
• Check documentation: The documentation for your programming language or library may contain examples of how to use the features you need.
• Ask for help: If you can't find what you need on your own, you can ask for help from other programmers. There are many online forums and communities where you can post questions and get help from others.

I hope this helps!