JTextField的内容为字符串型想要转换成double型只能在actionPerformed（）中转换，只有这样才不会出错
package Work;import javax.swing.*;import java.awt.*;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;public class exe21 {public static void main(String args[]) {MyFrame mf=new MyFrame("计算三角形面积",100,100,1000,750);JPanel jp=new JPanel();jp.setLayout(new FlowLayout());JLabel []jl= {new JLabel("边A:"),new JLabel("边B:"),new JLabel("边C:")};JTextField jtf1= new JTextField(15);JTextField jtf2= new JTextField(15);JTextField jtf3= new JTextField(15);JButton jb=new JButton("计算面积");jp.add(jl[0]);jp.add(jtf1);jp.add(jl[1]);jp.add(jtf2);jp.add(jl[2]);jp.add(jtf3);jp.add(jb);mf.add(jp,BorderLayout.NORTH);JTextArea jta=new JTextArea();mf.add(jta,BorderLayout.CENTER);TriAngle tri=new TriAngle();tri.setJButton(jb);tri.setJTextArea(jta);tri.setValue(jtf1,jtf2,jtf3);jb.addActionListener(tri);mf.setVisible(true);}}class MyFrame extends JFrame{MyFrame(String s,int x,int y,int z,int h){setTitle(s);setLayout(new BorderLayout());setBounds(x,y,z,h);setDefaultCloseOperation(EXIT_ON_CLOSE);}}class TriAngle implements ActionListener{double a;double b;double c;double p;JButton jbu;JTextArea jea;JTextField jtd1;JTextField jtd2;JTextField jtd3;void setValue(JTextField a,JTextField b,JTextField c) {jtd1=a;jtd2=b;jtd3=c;//如果是以数组的形式传参会报错}double setArea() {return Math.sqrt(p*(p-a)*(p-b)*(p-c));}void setJButton(JButton j) {jbu=j;}void setJTextArea(JTextArea j) {jea=j;}public void actionPerformed(ActionEvent e) {this.a=Double.parseDouble(jtd1.getText());this.b=Double.parseDouble(jtd2.getText());this.c=Double.parseDouble(jtd3.getText());//JTextField的内容为字符串型想要转换成double型只能在actionPerformed中转换，只有这样才不会出错p=(a+b+c)/2;if(a+b>c&&a+c>b&&b+c>a) {jea.append("三角形"+a+" "+b+" "+c+"的面积:"+setArea()+"\n");}else jea.append("三角形"+a+" "+b+" "+c+"的面积:无法计算面积"+"\n");}}
转载于:https://www.cnblogs.com/Yshun/p/11123388.html
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