如何仅在某些情况下有选择地发出QTextTexid :: textChanged信号？

问题描述

仅在某些情况下可以触发textChanged信号吗？例如触发它以插入文本，插入空格字符但不退格？

每次文本更改时，我都会运行QTextEdit中的键入字符，并根据结果突出显示在后台只读QTextEdit中的文本，该文本用作始终在线的占位符文本，供用户在键入时查看。如果用户输入有误，则该字符将突出显示为红色，并在纠正错误后重置为其初始背景色。按下退格键时会出现问题，因为它被注册为错误，因此前一个字符也被突出显示为红色。

 void Widget::onTextChanged()
 {
     QChar c;

     QString txt_contents = txtedit_->toPlainText();

     if(txt_contents.isEmpty()){
         c = '\0';

         //reset text display
         txtdisplay_->clear();
         txtdisplay_->append(*label_text_);
     }
     else
         c = txtedit_->toPlainText().back();
  
     if(!texteditq_->isEmpty()){
         if(c == texteditq_->head()){
             //refresh text display
             correct_++;
             txtdisplay_->clear();
             txtdisplay_->append(*label_text_);

             //remove character that was used for the successful check from the
             //queue
             texteditq_->dequeue();
         }else{
             //set backgroud color to red for errors
             fmt_->setBackground(Qt::red);

             if(!txtedit_->toPlainText().isEmpty()){
                 //move cursor to the end of the editor,where the error is and save
                 //the position the error occurs at
                 c_edit_->movePosition(QTextCursor::End);
                 quint32 error_pos = c_edit_->position();

                 //move the cursor in the display for the background text and
                 //use the KeepAnchor move mode to highlight the misspelled char
                 c_display_->setPosition(error_pos-1,QTextCursor::MoveAnchor);
                 c_display_->setPosition(error_pos,QTextCursor::KeepAnchor);

                 //apply formating to that character
                 c_display_->setCharFormat(*fmt_);
             }
         }
     }
 }

解决方法

根据OP的请求，我正在发布一个名为CustomTextEdit的类的解决方案，该类继承了QTextEdit。它正在钩接到keyPressEvent()并检查按下的键。如果不是Backspace，则将发出自定义信号keyPressed()。

class CustomTextEdit : public QTextEdit {
  Q_OBJECT
 public:
  explicit CustomTextEdit(QWidget *parent = nullptr) : QTextEdit(parent) {}

 signals:
  void keyPressed();

 protected:
  void keyPressEvent(QKeyEvent *e) override {
    if (e->key() != Qt::Key_Backspace) {
      emit keyPressed();
    }

    QTextEdit::keyPressEvent(e);
  }
};