JTextField 只接受数字和一个点

Question

我希望我的文本字段只接受数字（数字）和一个点，因为用户可以在该字段中输入产品价格。我有这段代码，但效果不佳，它只接受数字并删除。

char c=evt.getKeyChar();
if(!(Character.isDigit(c))||(c==KeyEvent.VK_BACK_SPACE)||(c==KeyEvent.VK_DELETE)){
    getToolkit().beep();
    evt.consume();
}

有人可以帮我解决吗？

Answer 1

不要使用 KeyListener。那是使用 AWT 时的旧代码。

Swing 有更新更好的 API。

最简单的方法是使用 JFormattedTextField。阅读有关 How to Use Formatted Text Fields 的 Swing 教程部分，了解更多信息和工作示例。

另一个选择是使用 DocumentFilter。阅读 Swing 教程中关于 Implementing a DocumentFilter 的部分。

Answer 2

我找到了解决这个问题的方法：这是我写的代码

char c=evt.getKeyChar();
        if((Character.isDigit(c))||(c==KeyEvent.VK_PERIOD)||(c==KeyEvent.VK_BACK_SPACE)){
            int punto=0;
            if(c==KeyEvent.VK_PERIOD){ 
                        String s=pricefield.getText();
                        int dot=s.indexOf('.');
                        punto=dot;
                        if(dot!=-1){
                            getToolkit().beep();
                            evt.consume();
                        }
                    }
        }
        else{    
            getToolkit().beep();
            evt.consume();
        }

Answer 3

private void textFieldKeyTyped(java.awt.event.KeyEvent evt) {

Get the keyTyped and pass it to the method validate.

        if(!validate(evt.getKeyChar())){

Char or keytyped is not a valid input, so let it consumed.

            evt.consume();
        }

this limit the input of Decimal, only ONE decimal point can be entered;

        if(evt.getKeyChar()==KeyEvent.VK_DECIMAL || evt.getKeyChar()==KeyEvent.VK_PERIOD){

get the whole string entered in the textField;

            String field = textField.getText();

get index of dot(. or decimal/period). indexOf() method returns -1 if String does not have any dot or decimal poits.

            int index = field.indexOf(".");


            if(!(index==-1)){ //index is not equal to -1
                evt.consume(); //consume
            }
          
        }
    }

Every keypress, this method gets called.

private boolean validate(char ch){

this determine if the character has matching value to Integer, Decimal point, backspace or delete. It returns true if the char is a integer, decimal, delete or backspace, otherwise false. However it does not limit how many decimal points can be entered.

            if(!(Character.isDigit(ch)
                    || ch==KeyEvent.VK_BACKSPACE 
                    || ch==KeyEvent.VK_DELETE 
                    || ch==KeyEvent.VK_DECIMAL
                    || ch==KeyEvent.VK_PERIOD)){
                return false;
            }
        
            return true;
            }

here is the whole code, I have provided some comments, hope these will help.

private void textFieldKeyTyped(java.awt.event.KeyEvent evt) {                               

        if(!validate(evt.getKeyChar())){ //get char or keytyped
            evt.consume();
        }
        //limit one dot or decimal point can be entered
        if(evt.getKeyChar()==KeyEvent.VK_DECIMAL || evt.getKeyChar()==KeyEvent.VK_PERIOD){
            
            String field = textField.getText(); //get the string in textField
            int index = field.indexOf("."); //find the index of dot(.) or decimal point
            if(!(index==-1)){ //if there is any
                evt.consume(); //consume the keytyped. this prevents the keytyped from appearing on the textfield;
            }
          
        }
    }     
    //determine if keytyped is a valid input
     private boolean validate(char ch){
        
            if(!(Character.isDigit(ch)
                    || ch==KeyEvent.VK_BACKSPACE 
                    || ch==KeyEvent.VK_DELETE  
                    || ch==KeyEvent.VK_DECIMAL 
                    || ch==KeyEvent.VK_PERIOD 
                    )){

                return false; //return false, because char is invalid           
            }
        
            return true; // return true, when the if statement above does not meet its conditions  
            }

Answer 4

Bellow 是我已经测试过并按预期工作的示例代码。当用户输入或按错键时，我还添加了哔声。

private void textFieldScoreKeyTyped(java.awt.event.KeyEvent evt) {                                        
       char c =  evt.getKeyChar();
       if(c == KeyEvent.VK_BACK_SPACE){
            evt.consume(); 
       }else if(Character.isLetter(c) || String.valueOf(c).trim().isEmpty()){
           getToolkit().beep();
           evt.consume(); 
       }else{
           try{
               Double.parseDouble(textFieldScore.getText()+c);
           }catch(NumberFormatException e){
               getToolkit().beep();
               evt.consume();
           }
       }
    }

祝大家好运！！

JTextField 只接受数字和一个点

JTextField accept only numbers and one dot

java

swing

jtextfield