Question

我是GUI新手，我想知道为什么这段代码没有显示任何内容。请记住，代码不完整，请耐心等待，代码有点长。

//imports

public class SudokuGame extends Frame{

private SudokuBoard sb = new SudokuBoard(this);

/**
 * a button to restart game
 */
private Button b = new Button("Restart");

/**
 * 9 x 9 buttons to store the numbers used in the game
 */
private Button[][] grid= new Button[9][9];

/**
 * TextField used to store the remaining empty blocks
 */
private TextField t;

/**
 * Constructor
 * @param ssm
 */
public SudokuGame(SomeSudokuMatrix ssm) {

    /**
     * sets window's name
     */

    super( "Sudoku" );

    /**
     * sets background color
     */

    setBackground( Color.WHITE );





    /**
     * adds SudokuBoard to the SudokuGame which extends frame
     */

    add( sb, BorderLayout.CENTER );

    /**
     * initialize the remaining blocks to TextField
     */

    t = new TextField("Remain:" + sb.getEmpty()); 

    /**
     * new panel
     */

    Panel p = new Panel();

    /**
     * sets panel size to 100 x 10
     */

     p.setSize(100,10);

    /**
     * sets restart button size to 10 x 5 and location to 48, 5
     */

    b.setBounds(48,5,10,5);  

    /**
     * adds restart button to the Panel
     */

    p.add( b );

    /**
     * adds panel to south 
     */

    add( p, BorderLayout.SOUTH );

    /**
     * adds ActionListner to restart button
     */

    b.addActionListener( sb );


    /**
     * adds TextField to the Panel
     */

    p.add(t); 

    /**
     * Sets the TextField size to 10 x 5 and location to 53, 5
     */

    t.setBounds(53,5,10,5);

    /**
     * adds the buttons that hold the values
     */

    for(int i = 0; i < 9; i++){
        for(int j = 0; j < 9; j++){

            grid[i][j]=new Button(null);
            add(grid[i][j]);

        }
    }

    /**
     * Automatically resizing
     */

    pack();

    /**
     * Shows SudokuGame 
     */

    setVisible(true);

    /**
     * Shows the Panel
     */

    p.setVisible(true);       
 }

 /**
 * sets the label of the button
 * 
 * @param s   String to add to the button
 * @param i   the position
 * @param j   the position
 */

public void setText(String s, int i, int j){

    /**
     * if the button is not empty sets the label of the button
     */

    if(!s.equals("-1")){
    grid[i][j].setLabel(s); 
    }
}  //to do: change TextField when filling empty block

public void setText(String s){

    t.setText(s);
}
}

这是没有canvas或actionlisteners或任何其他运行游戏的类的GUI类（框架）。

Answer 1

你写过

private Button[][] grid= new Button[9][9];

应该是

 private Button[][] grid= new Button[9][];

接下来，您已直接开始从网格数组添加Button：

   for(int i = 0; i < 9; i++){
        for(int j = 0; j < 9; j++){
            add(grid[i][j]);
        }
    }

哪个错误，因此会抛出NullPointerException。请参阅IDE控制台。解决方案是首先实例化网格数组，如下所示：

 for(int i = 0; i < 9; i++){
    grid[i]=new Button[9];
  }

for(int i = 0; i < 9; i++){
    for(int j = 0; j < 9; j++){
      grid[i][j]=new Button("SomeLabel");
    }
}

初始化网格数组后，按如下方式将按钮添加到框架：

for(int i = 0; i < 9; i++){
    for(int j = 0; j < 9; j++){
        add(grid[i][j]);
    }
}

GUI类不在监视器上显示任何内容

1 个答案: