java组件不能正常显示

Question

我做了个GUI的程序，为什么第一次运行时只看到框架，还要最小化到任务栏，再恢复时才能看到框架里的其它组件（控件）呢？

Answer 1

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.net.*;public class Transmitter {    String dictateString = "";
    int r = 0, i=0;
    Random ran = new Random();
    TextField dictateText = new TextField(dictateString); //指令文本
    //Label dictateText = new Label(dictateString);
    InetAddress myIP = null;
    public Transmitter(){        JFrame fr = new JFrame("按键准确度测试-服务器端");
        fr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        fr.setSize(600,400);
        fr.setLocation(100,100);
        fr.setVisible(true);
        fr.setResizable(false);        Container ct = fr.getContentPane();
        GridBagLayout gridbag = new GridBagLayout();
        GridBagConstraints gridbagC = new GridBagConstraints();
        ct.setLayout(gridbag);
        gridbagC.insets = new Insets(2,5,2,5);        // 说明标签
        gridbagC.gridx = 1;
        gridbagC.gridy = 1;
        gridbagC.gridwidth = 2;
        gridbagC.gridheight = 1;
        gridbagC.anchor = GridBagConstraints.SOUTHWEST;
        gridbagC.fill = GridBagConstraints.HORIZONTAL;
        Label instructionLabel = new Label("服务器端说明:");
        gridbag.setConstraints(instructionLabel, gridbagC);
        ct.add(instructionLabel);        // 说明内容
        gridbagC.gridx = 1;
        gridbagC.gridy = 2;
        gridbagC.gridwidth = 4;
        gridbagC.gridheight = 2;
        gridbagC.anchor = GridBagConstraints.CENTER;
        gridbagC.fill = GridBagConstraints.BOTH;
        Label instructionText = new Label("本程序测试您的按键准确度，服务器端" +
                "发送20个随机指令：上、下、左、右，并以end结束。");
        gridbag.setConstraints(instructionText, gridbagC);
        ct.add(instructionText);        // 指令按钮
        gridbagC.gridx = 1;
        gridbagC.gridy = 4;
        gridbagC.gridwidth = 1;
        gridbagC.gridheight = 1;
        gridbagC.anchor = GridBagConstraints.SOUTHWEST;
        gridbagC.fill = GridBagConstraints.WEST;
        Button dictateButton = new Button("生成随机指令");
        gridbag.setConstraints(dictateButton, gridbagC);
        ct.add(dictateButton);        // 指令提示标签
        gridbagC.gridx = 2;
        gridbagC.gridy = 4;
        gridbagC.gridwidth = 1;
        gridbagC.gridheight = 1;
        gridbagC.anchor = GridBagConstraints.SOUTHWEST;
        gridbagC.fill = GridBagConstraints.HORIZONTAL;
        Label insAdviceLabel = new Label("(请按键生成随机指令)");
        gridbag.setConstraints(insAdviceLabel, gridbagC);
        ct.add(insAdviceLabel);        // 指令生成
        // 在方法 dictateButton_action() 中        // 指令显示
        gridbagC.gridx = 1;
        gridbagC.gridy = 5;
        gridbagC.gridwidth = 4;
        gridbagC.gridheight = 1;
        gridbagC.anchor = GridBagConstraints.WEST;
        gridbagC.fill = GridBagConstraints.BOTH;
        //TextField dictateText = new TextField(dictateString);
        dictateText.setSize(100, 20);
        //dictateText.setSize(400, 100);
        gridbag.setConstraints(dictateText, gridbagC);
        ct.add(dictateText);        // 指令按钮事件监听
        dictateButton.addActionListener(
                new ActionListener(){
                    public void actionPerformed(ActionEvent e){
                    dictateButton_action(e);
                    dictateText.setText(dictateString);
                    }
                }
        );        // 客户端IP标签
        gridbagC.gridx = 1;
        gridbagC.gridy = 6;
        gridbagC.gridwidth = 2;
        gridbagC.gridheight = 1;
        gridbagC.anchor = GridBagConstraints.SOUTHWEST;
        gridbagC.fill = GridBagConstraints.BOTH;
        Label ipLabel = new Label("请输入客户端IP地址(默认为本机IP):");
        gridbag.setConstraints(ipLabel, gridbagC);
        ct.add(ipLabel);        // IP文本框
        gridbagC.gridx = 1;
        gridbagC.gridy = 7;
        gridbagC.gridwidth = 4;
        gridbagC.gridheight = 1;
        gridbagC.anchor = GridBagConstraints.CENTER;
        gridbagC.fill = GridBagConstraints.BOTH;
        getLocalIP();
        TextField ipText = new TextField(myIP.toString());
        gridbag.setConstraints(ipText, gridbagC);
        ct.add(ipText);        // IP文本 事件监听
/*
        ipText.addTextListener(
                new TextListener(){
                    public void actionPerformed(ActionEvent e){
                    dictateButton_action(e);
                    dictateText.setText(dictateString);
                    }
                }
        );
*/
        // 发送指令 按钮
        gridbagC.gridx = 1;
        gridbagC.gridy = 8;
        gridbagC.gridwidth = 2;
        gridbagC.gridheight = 1;
        gridbagC.anchor = GridBagConstraints.SOUTHWEST;
        gridbagC.fill = GridBagConstraints.WEST;
        Button sendButton = new Button("发送指令");
        gridbag.setConstraints(sendButton, gridbagC);
        ct.add(sendButton);    }    // 方法 ： 按钮事件动作 - 指令生成
    void dictateButton_action(ActionEvent e){
        dictateString = "";
        for(i=0;i<19;i++){
        r = ran.nextInt(4);
        switch(r){
            case 0 : dictateString += "上"; break;
            case 1 : dictateString += "下"; break;
            case 2 : dictateString += "左"; break;
            case 3 : dictateString += "右"; break;
            }
        }
        dictateString += "end";
    }    // 方法 ：获取本机IP地址
    void getLocalIP(){
        try{
            myIP = InetAddress.getLocalHost();
        }
        catch(UnknownHostException e ){}
    }    public static void main(String[] args){
        Transmitter transmitter = new Transmitter();
    }
}

Answer 2

上面贴出了现在做了的部分，大概写了三分之一了。
我用的是netbeans 的IDE，运行时不能正常显示，但是最小化后，再还原就能正常显示了。第一次做这种东西，感觉awt和swing是一头雾水
多谢了~

Answer 3

我运行了，直接就能正常显示啊。
不过显示之后会看到组件被重新布局（组件在窗体上迅速移动位置），然后一闪而过。
解决的方法是把 fr.setVisible(true);挪到构造方法的最后就好了，一般来说应该把组件安装好再显示窗体，你的那个显示不正常的问题可能也是这个原因。