Java：遊標當前位置的列號和行號

Question

我想知道JTextArea中游標所在的列號和行號。 即。在記事本中，當我m，在比狀態欄第一行顯示LN 1，上校1

在此先感謝...

Answer 1

Here是代碼

import java.awt.BorderLayout; 
import javax.swing.*; 
import javax.swing.event.*; 

public class caretDemo extends JFrame { 
    // Two controls, one is the editor and the other is our little status bar at the bottom. 
    // When we update the editor, the change in caret will update the status text field. 
    private JTextArea editor; 
    private JTextField status; 

    // Start of our caretDemo class 
    public caretDemo() { 
     setTitle("Caret Demo"); 
     setSize(500,500); 

     // Lets create a border layout to make positioning of items easy and quick. 
     setLayout(new BorderLayout()); 
     setDefaultCloseOperation(EXIT_ON_CLOSE); 

     editor = new JTextArea(); 

     // Add a caretListener to the editor. This is an anonymous class because it is inline and has no specific name. 
     editor.addCaretListener(new CaretListener() { 
      // Each time the caret is moved, it will trigger the listener and its method caretUpdate. 
      // It will then pass the event to the update method including the source of the event (which is our textarea control) 
      public void caretUpdate(CaretEvent e) { 
       JTextArea editArea = (JTextArea)e.getSource(); 

       // Lets start with some default values for the line and column. 
       int linenum = 1; 
       int columnnum = 1; 

       // We create a try catch to catch any exceptions. We will simply ignore such an error for our demonstration. 
       try { 
        // First we find the position of the caret. This is the number of where the caret is in relation to the start of the JTextArea 
        // in the upper left corner. We use this position to find offset values (eg what line we are on for the given position as well as 
        // what position that line starts on. 
        int caretpos = editArea.getCaretPosition(); 
        linenum = editArea.getLineOfOffset(caretpos); 

        // We subtract the offset of where our line starts from the overall caret position. 
        // So lets say that we are on line 5 and that line starts at caret position 100, if our caret position is currently 106 
        // we know that we must be on column 6 of line 5. 
        columnnum = caretpos - editArea.getLineStartOffset(linenum); 

        // We have to add one here because line numbers start at 0 for getLineOfOffset and we want it to start at 1 for display. 
        linenum += 1; 
       } 
       catch(Exception ex) { } 

       // Once we know the position of the line and the column, pass it to a helper function for updating the status bar. 
       updateStatus(linenum, columnnum); 
      } 
     }); 

     // Add the fields to the layout, the editor in the middle and the status at the bottom. 
     add(editor, BorderLayout.CENTER); 

     status = new JTextField(); 
     add(status, BorderLayout.SOUTH); 

     // Give the status update value 
     updateStatus(1,1); 
    } 

    // This helper function updates the status bar with the line number and column number. 
    private void updateStatus(int linenumber, int columnnumber) { 
     status.setText("Line: " + linenumber + " Column: " + columnnumber); 
    } 

    // Entry point to the program. It kicks off by creating an instance of our class and making it visible. 
    public static void main(String args[]) { 
     caretDemo caretDemoApp = new caretDemo(); 
     caretDemoApp.setVisible(true); 
    } 
} 

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輸出

Answer 2

你試過getCaretPosition？

您必須計數\n才能知道您有哪一行，並且您必須計算當前插入符號位置與最後一次出現的\n字符之間的差異。

Answer 3

需要使用Utilities.getRowStart與插入位置沿着如下圖所示：

要獲取行號：

int caretPos = textArea.getCaretPosition(); 
int rowNum = (caretPos == 0) ? 1 : 0; 
for (int offset = caretPos; offset > 0;) { 
    offset = Utilities.getRowStart(textArea, offset) - 1; 
    rowNum++; 
} 
System.out.println("Row: " + rowNum);  

要得到列數：

int offset = Utilities.getRowStart(textArea, caretPos); 
int colNum = caretPos - offset + 1; 
System.out.println("Col: " + colNum);