作业41、不使用布局管理器，将组件手工加入容器。实现如图所示的界面。importjava.awt.*;importjavax.swing.*;importjava.applet.Applet;publicclassNoLayoutDemoextendsApplet{Choicec=newChoice();Buttonb1=newButton("按钮1");Buttonb2=newButton("按钮2");Buttonb3=newButton("按钮3");publicvoidinit(){setLayout(null);c.addItem("Item1");c.addItem("Item2");c.addItem("Item3");add(c);c.setBounds(80,80,50,30);add(b1);b1.setBounds(20,20,50,30);add(b2);b2.setBounds(100,20,50,30);add(b3);b3.setBounds(200,60,50,50);}}2、编写一个Applet，添加两个标签、一个文本框、一个文本区和一个按钮。要求在文本框中输入字符串，当按下回车键或单击按钮时，可将字符串显示在文本区中。importjava.awt.*;importjavax.swing.*;importjava.awt.event.*;publicclassex4_2extendsJAppletimplementsActionListener{JLabellb1=newJLabel("这是个文本框"),lb2=newJLabel("这是个文本区");JTextFieldtf=newJTextField(20);JTextAreata=newJTextArea(6,30);JButtonbt=newJButton("OK");JPanelp1=newJPanel(),p2=newJPanel();publicvoidinit(){Containerc=getContentPane();c.add("North",p1);c.add("Center",p2);c.add("South",bt);p1.add(lb2);p1.add(ta);p2.add(lb1);p2.add(tf);tf.addActionListener(this);bt.addActionListener(this);}publicvoidactionPerformed(ActionEvente){ta.append(tf.getText());}}3、创建一个窗口，要求有“退出”按钮、菜单“退出”命令，而且菜单、按钮、窗口本身的关闭按钮都起作用。importjava.awt.*;importjavax.swing.*;importjava.awt.event.*;importjava.awt.event.ItemListener.*;publicclassex4_3extendsJFrameimplementsActionListener{JButtonbt=newJButton("退出");JMenuBarmb=newJMenuBar();JMenum=newJMenu("Menu");JMenuItemexit=newJMenuItem("退出");publicex4_3(){Containerc=getContentPane();setTitle("菜单应用");setSize(200,200);mb.add(m);m.add(exit);c.add(bt,BorderLayout.SOUTH);bt.addActionListener(this);exit.addActionListener(this);addWindowListener(newWindowAdapter(){publicvoidwindowClosing(WindowEvente){System.exit(0);}});setJMenuBar(mb);show();}publicvoidactionPerformed(ActionEvente){System.exit(0);}publicstaticvoidmain(String[]args){newex4_3();}}4、创建一个窗口，单击“提示”按钮可出现一个写有“你好！”文字的对话框。importjava.awt.*;importjavax.swing.*;importjava.awt.event.*;publicclassex4_4implementsActionListener{JButtonbt=newJButton("对话框");JFramejf=newJFrame("有对话框的窗口");publicex4_4(){Containerc=jf.getContentPane();c.add(bt,BorderLayout.SOUTH);bt.addActionListener(this);jf.addWindowListener(newWindowAdapter(){publicvoidwindowClosing(WindowEvente){System.exit(0);}});jf.setSize(300,300);jf.show();}publicvoidactionPerformed(ActionEvente){JOptionPane.showOptionDialog(jf,"你好","我是自定义对话框",JOptionPane.DEFAULT_OPTION,JOptionPane.ERROR_MESSAGE,null,null,null);}publicstaticvoidmain(String[]args){newex4_4();}}5、编写程序，程序运行界面如下图所示。在本程序中，生成了一个文本框in用于输入，一个标签out用于输出，一个按钮btn用于触发命令。在Applet的初始化方法中，设定流式布局（FlowLayout）。按图示结果编写程序。importjava.applet.*;importjava.awt.*;importjava.awt.event.*;publicclassAppletInOutextendsApplet{TextFieldin=newTextField(10);Buttonbtn=newButton("求平方");Labelout=newLabel("用于显示结果的标签");publicvoidinit(){setLayout(newFlowLayout());add(in);add(btn);add(out);btn.addActionListener(newBtnActionAdapter());}classBtnActionAdapterimplementsActionListener{publicvoidactionPerformed(ActionEvente){Strings=in.getText();doubled=Double.parseDouble(s);doublesq=d*d;out.setText(d+"的平方是："+sq);}}}
