与KeyAdapter，AWT运行时错误，摆了Java。帮助发现错误 [英] runtime error with KeyAdapter, awt, swing on java. help spot the error

问题描述

您好IM写了一些$ C C I虽然它去上班，但它编译和它does not甚至抛出异常或任何东西。它还会创建图标，像它的openned但我点击它，它没有做任何事情，请需要帮助知道我做错了。继承人之类的code：

 包practicagraficos8;
进口java.awt中的*。
java.awt.event中导入*。
进口的javax.swing *。公共类ventanatexto {
   公众的JFrame塔纳;
   公共字符串texto;
    ventanatexto（）{
    JFrame.setDefaultLookAndFeelDecorated（真）;
    texto =;
    Ventana公司=新的JFrame（teclado）;
    PANEL1面板=新PANEL1（）;
    ventana.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;
    ventana.add（面板）;
     ventana.setVisible（真）;
    ventana.addKeyListener（新的处理程序（））;    }    公共类PANEL1继承JPanel {        @覆盖
    公共无效漆（图形G）{
        super.paint（G）;
    DIM维=的getSize（）;
    g.clearRect（0，0，dim.width，dim.height）;
    g.drawString（texto，宽，Width）;
    };
}
    类处理程序扩展KeyAdapter {
        @覆盖
    公共无效键pressed（KeyEvent的K）{
    焦炭tecla = k.getKeyChar（）;
    开关（tecla）{        壳体127：文本=;
    打破;
        壳体8：如果（texto.length（）大于0）{texto = texto.substring（0，texto.length（） -  1）;}
            打破;
        默认：
            如果（texto.length（）＆LT; 15）{texto + = tecla;}    }
    ventana.repaint（）;
    }    }}
 

和这里是我的主：

 包practicagraficos8;公共类Practicagraficos8 {    公共静态无效的主要（字串[] args）{        ventanatexto prueba =新ventanatexto（）;
    }
}
 

解决方案

如图所示 href=\"http://stackoverflow.com/a/11924118/230513\">， drawString之（）预计坐标重新present的的基线的字符串。

 的FontMetrics FM = g.getFontMetrics（）;
g.drawString（texto，0，fm.getAscent（））;
 

在此外，

• 使用的JTextComponent 为可编辑的文本。




• 使用键绑定，而不是的KeyListener 。




• 使用包（）在封闭窗口。




• Swing程序应该重写的paintComponent（）而不是覆盖的paint（）。 - < A HREF =htt​​p://www.oracle.com/technetwork/java/painting-140037.html#callbacks相对=nofollow> 绘画在AWT和Swing：色漆方法的




• Swing GUI的对象应当建立和操纵的只有的上的事件调度线程。




• 使用适当的访问控制。

hello im wrote some code i though it was going to work but it compiles and it doesnt even throws an exception or anything. it also creates the icon like its openned but i click it and it doesnt do anything please need help to know what am i doing wrong . heres the code of the class:

package practicagraficos8;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class ventanatexto {
   public JFrame ventana;
   public String texto;
    ventanatexto(){
    JFrame.setDefaultLookAndFeelDecorated(true);
    texto="";
    ventana= new JFrame("teclado");
    panel1 panel= new panel1();
    ventana.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    ventana.add(panel);
     ventana.setVisible(true);
    ventana.addKeyListener(new handler());

    }

    public class panel1 extends JPanel {

        @Override
    public void paint(Graphics g){
        super.paint(g);
    Dimension dim= getSize();
    g.clearRect(0, 0, dim.width, dim.height);
    g.drawString(texto, WIDTH, WIDTH);
    };


}
    class handler extends KeyAdapter{
        @Override
    public void keyPressed(KeyEvent k){
    char tecla= k.getKeyChar();
    switch(tecla){

        case 127:texto="";
    break;
        case 8: if(texto.length()>0){texto=texto.substring(0, texto.length()-1);}
            break;
        default:
            if (texto.length()<15){texto+=tecla;}

    }
    ventana.repaint();
    }

    }}

and here is my main:

package practicagraficos8;

public class Practicagraficos8 {

    public static void main(String[] args) {

        ventanatexto prueba= new ventanatexto();
    }
}

解决方案

As shown here, "drawString() expects the coordinates to represent the baseline of the String."

FontMetrics fm = g.getFontMetrics();
g.drawString(texto, 0, fm.getAscent());

In addition,

• Use a JTextComponent for editable text.

• Use Key Bindings, rather than KeyListener.

• Use pack() on the enclosing Window.

• "Swing programs should override paintComponent() instead of overriding paint()."—Painting in AWT and Swing: The Paint Methods.

• Swing GUI objects should be constructed and manipulated only on the event dispatch thread.

• Use appropriate access control.

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