從另一個JPanel

Question

重畫一個JPanel因此，我正在製作一個繪畫程序，並且我有一個主要的Paint類，它檢測鼠標輸入和顏色，以及一個類似左邊的工具欄，它包含一組工具，如畫筆尺寸變化和形狀變化。所以，我想在清除整個屏幕的類上添加一個清除按鈕到Tools。我的問題是Paint類正在持有它繪製的點的ArrayList，我不能從Tools內重新繪製Paint。

Paint類

//imports  
public class Paint extends JPanel{ 
    private ArrayList<Brush> points; 
    ... 

    public Paint() { 
     ... 
    } 

    public void paintComponent(Graphics page) { 
     ... 

     //draws all points in the arraylist 
     for (Brush b : points) { 
      //paint points 
     } 
    } 
} 

Tools類

//imports 
public class Tools extends JPanel 
{ 
    private JButton clear; 

    public Tools() { 
     clear = new JButton("Clear"); 
     clear.addActionListener(new BrushInput()); 
    } 

    public void paintComponent(Graphics page) { 
     ... 
    } 
    private class BrushInput implements ActionListener { 
     public void actionPerformed(ActionEvent e) { 
      if (e.getSource() == clear) { 
       //clear points arraylist and repaint 
      } 
     } 
    } 

} 

我遇到的問題是，repaint()是實例方法，所以我不能訪問Paint的從Tools內重繪。

Answer 1

只需將對Paint實例的引用傳遞給Tools的構造函數即可。或者，對包含兩者的容器（JFrame等）進行重新粉刷，這會導致其所有子項都被重新粉刷。

例如：創建這些組件

public class Paint extends JPanel { 
    private ArrayList<Brush> points; 

    // . . . 

    public void clear() { 
     points.clear(); 
     repaint(); 
    } 
} 

public class Tools extends JPanel { 
    private JButton clear; 
    private Paint paint; 

    public Tools(Paint paint) { 
     this.paint = paint; 
     // . . . 
    } 

    // . . . 

    private class BrushInput implements ActionListener { 
     public void actionPerformed(ActionEvent e) { 
      if (e.getSource() == clear) { 
       paint.clear(); 
      } 
     } 
    } 
} 

代碼：

Paint paint = new Paint(); 
Tools tools = new Tools(paint);