GUI程序不会作为applet运行

时间:2014-12-23 02:38:18

标签: java user-interface applet

在我的在线Java课程中,我有这段代码:

/* This is option 1 of my Java final project. This is a program which displays a frame with a button that, when you click it, increases the number below it. */

import java.awt.*; // imports everything I need for this project
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

public class option1 { // This is where I define most of my stuff. Technical restrictions prevent me from doing this in the class where the program is itself executed (see comment towards the end).

    public static void main(String[] args) {

        final Frame mainFrame = new OptionOne(); // First I define my frame, button, and labels ...
        Button button = new Button("Button");
        final Label label1a = new Label();
        final Label label1b = new Label();
        final Label label1c = new Label();
        final Label label2 = new Label();

        label1a.setBounds(15, 30, 270, 10); // ... and set their bounds and the labels' text. Labels 1a, 1b, 1c give instructions, while label2 displays the number.
        label1a.setText("This is a program where you click a button");
        label1b.setBounds(15, 45, 270, 10);
        label1b.setText("and the number below it increases each time");
        label1c.setBounds(15, 60, 270, 10);
        label1c.setText("you click. To start, just click the button.");
        label2.setBounds(150, 220, 50, 30);
        label2.setText("0");
        button.setBounds(100, 100, 50, 50);

/* After this point, things get a little more complicated. Technical restrictions on usage of variables accross classes mean that I had to make some unusual code decisions, as you will see. */

        label2.addPropertyChangeListener(label2.getText(), new PropertyChangeListener() { // This part is used to detect a change in the appearance of label2, and to react appropriately to it.
            @Override // All the "@Override"s are here because it gives a compiling error if I don't put them.
            public void propertyChange(PropertyChangeEvent evt) {

            }
        });

        button.addMouseListener(new MouseListener() { // This part tells the program what to do when you click the button.
            @Override // the only @Override that isn't here for technical reasons (see earlier comment at first @Override) 
            public void mouseClicked(MouseEvent e) {
                int value = Integer.parseInt(label2.getText());
                label2.setText(String.valueOf(value + 1));  
            }

            @Override
            public void mousePressed(MouseEvent e) {

            }

            @Override
            public void mouseReleased(MouseEvent e) {

            }

            @Override
            public void mouseEntered(MouseEvent e) {

            }

            @Override
            public void mouseExited(MouseEvent e) {

            }
        });

        mainFrame.add(label1a); // Now that the labels and button are fully defined, we are now ready to add them.
        mainFrame.add(label1b);
        mainFrame.add(label1c);
        mainFrame.add(label2);
        mainFrame.add(button);
    }
}

class OptionOne extends Frame { // technical restrictions prevent me from putting most of my code in this class. in this code I define the actual frame itself, for its final use.

    OptionOne() {
        setTitle("Final Project Option 1");
        setSize(300, 300);
    show();
    }
}

我需要将其作为applet运行。直接将其放入HTML代码中,如

<head></head>
<body>
<applet code="OptionOne.class" width="300" height="300">
</applet>
</body>

给了我一个&#34; java.lang.reflect.invocationtargetexception&#34;错误。为什么我收到此错误?我知道错误必须在HTML代码中,因为放在编译器中的程序运行正常,所以我做错了什么?

编辑:现在我已将代码更改为:

import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

public class option1main extends Panel {

    public static void main(String[] args) {

        Button button = new Button("Button");
        final Label label1a = new Label();
        final Label label1b = new Label();
        final Label label1c = new Label();
        final Label label2 = new Label();

        label1a.setBounds(15, 30, 270, 10);
        label1a.setText("This is a program where you click a button");
        label1b.setBounds(15, 45, 270, 10);
        label1b.setText("and the number below it increases each time");
        label1c.setBounds(15, 65, 270, 10);
        label1c.setText("you click. To start, just click the button.");
        label2.setBounds(150, 220, 50, 30);
        label2.setText("0");
        button.setBounds(100, 100, 50, 50);

        label2.addPropertyChangeListener(label2.getText(), new PropertyChangeListener() {
            @Override // All the "@Override"s are here because it gives a compiling error if I don't put them.
            public void propertyChange(PropertyChangeEvent evt) {

            }
        });

        button.addMouseListener(new MouseListener() {

            @Override
            public void mouseClicked(MouseEvent e) {
                int value = Integer.parseInt(label2.getText());
                label2.setText(String.valueOf(value + 1));  
            }

            @Override
            public void mousePressed(MouseEvent e) {

            }

            @Override
            public void mouseReleased(MouseEvent e) {

            }

            @Override
            public void mouseEntered(MouseEvent e) {

            }

            @Override
            public void mouseExited(MouseEvent e) {

            }
        });
    }
}

public class option1 {

    option1main() {
        final Frame mainFrame = new OptionOne();
        mainFrame.add(label1a);
        mainFrame.add(label1b);
        mainFrame.add(label1c);
        mainFrame.add(label2);
        mainFrame.add(button);
    }

}

public class panel1 extends Applet {

    /* init() { - not sure what to add here...? */

}

class OptionOne extends Frame {

    OptionOne() {
        setTitle("Final Project Option 1");
        setSize(300, 300);
    show();
    }
}

编译时会给我错误,&#34;无效的方法声明:需要返回类型&#34;在线&#34; option1main(){&#34;。那是为什么?

1 个答案:

答案 0 :(得分:2)

  1. 将您的基本用户界面移至另一个类,该类从Panel
  2. 延伸
  3. 允许您当前(option1)类使用此类并将其添加到您创建的Frame实例中。
  4. 创建一个从Applet延伸的新类。在此类init方法中,创建Panel类的实例(从步骤1开始)并将其添加到小程序
  5. 将您的<applet code="OptionOne.class" width="300" height="300">更改为指向您在步骤3中创建的小程序类。
  6. 旁注......

    • 考虑使用Swing或JavaFX,没有冒犯,AWT已超过15年且大多数人没有(或没有)使用它的经验
    • 考虑使用适当的布局管理器以简单地解决跨平台渲染差异