Swing问题

Question

我在JScrollPanel中加了个JPanel，为什么JPanel显示在后面？？？如图
然后我把JScrollPanel的layout设置位null，JPanel就显示在前面了。但是滚动条就没了。
designScrollPanel.setLayout(null);
如图：代码如下：import java.awt.Color;
import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.util.ArrayList;
import java.util.List;import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ScrollPaneConstants;
import javax.swing.ScrollPaneLayout;import com.withiter.util.ResolutionUtils;public class Main extends JFrame { private static final long serialVersionUID = 3350060192892360223L; class Resolution {
private String name;
private String value;

public Resolution(String name, String value) {
super();
this.name = name;
this.value = value;
}
public String toString(){
return name;
        }
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}

class Template {
private Resolution resolution;
private int areas;
public Template(Resolution resolution, int areas) {
super();
this.resolution = resolution;
this.areas = areas;
}
public Template(int areas){
super();
this.areas = areas;
}
public Resolution getResolution() {
return resolution;
}
public void setResolution(Resolution resolution) {
this.resolution = resolution;
}
public int getAreas() {
return areas;
}
public void setAreas(int areas) {
this.areas = areas;
}
@Override
public String toString() {
if(areas == 0){
return "请选择模板区域数目";
}
return "区域数目："+areas;
}
} private JLabel resolutionLabel;
private JLabel templateLabel;

private JComboBox jcbresolution;
private JComboBox jcbTemplate;

private JScrollPane designScrollPanel;
private JPanel designPanel;

private JLabel test1 = new JLabel("asdfkjashdkghasdlkjghalskjdghlakjshdglk");
private JLabel test2 = new JLabel("asdfkjashdkghasdlkjghalskjdghlakjshdglk");
private JLabel test3 = new JLabel("asdfkjashdkghasdlkjghalskjdghlakjshdglk");
private JLabel test4 = new JLabel("asdfkjashdkghasdlkjghalskjdghlakjshdglk");
private JLabel test5 = new JLabel("asdfkjashdkghasdlkjghalskjdghlakjshdglk");

private JButton btAdd;
private JButton btReset;

private JLabel programsListLabel;
private JList programsList;

private List<Resolution> listTimes = new ArrayList<Resolution>();
private List<Template> listTemplate = new ArrayList<Template>();

Main() {
Toolkit tk = Toolkit.getDefaultToolkit();
Dimension screenSize = tk.getScreenSize();
int x = (int) screenSize.getWidth();
int y = (int) screenSize.getHeight();
this.setBounds((x - 1140) / 2, (y - 740) / 2, 1140, 740);
this.setResizable(false);
this.setLayout(null);
this.setTitle("CPSMini 发布平台");
this.setBackground(Color.BLACK);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

// add resolutions
listTimes.add(new Resolution("请选择合适的LCD分辨率","0"));
listTimes.add(new Resolution("1920*1080(16:9)","1920*1080_16:9"));
listTimes.add(new Resolution("1600*1200(4:3)","1600*1200_4:3"));
listTimes.add(new Resolution("1280*1024(5:4)","1280*1024_5:4"));
listTimes.add(new Resolution("1280*960(4:3)","1280*960_4:3"));
listTimes.add(new Resolution("1280*768(5:3)","1280*768_5:3"));
listTimes.add(new Resolution("1024*768(4:3)","1024*768_4:3"));
listTimes.add(new Resolution("800*640(5:4)","800*640_5:4"));
listTimes.add(new Resolution("800*600(4:3)","800*600_4:3"));
listTimes.add(new Resolution("800*450(16:9)","800*450_16:9"));

listTimes.add(new Resolution("1080*1920(9:16)","1080*1920_9:16"));
listTimes.add(new Resolution("1200*1600(3:4)","1200*1600_3:4"));
listTimes.add(new Resolution("1024*1280(4:5)","1024*1280_4:5"));
listTimes.add(new Resolution("960*1280(3:4)","960*1280_3:4"));
listTimes.add(new Resolution("768*1280(3:5)","768*1280_3:5"));
listTimes.add(new Resolution("768*1024(3:4)","768*1024_3:4"));
listTimes.add(new Resolution("640*800(4:5)","640*800_4:5"));
listTimes.add(new Resolution("600*800(3:4)","600*800_3:4"));
listTimes.add(new Resolution("450*800(9:16)","450*800_9:16")); // add templates
listTemplate.add(new Template(0));
listTemplate.add(new Template(2));
listTemplate.add(new Template(3));

resolutionLabel = new JLabel("请选择显示屏分辨率");
jcbresolution = new JComboBox(listTimes.toArray());
templateLabel = new JLabel("请选择节目模板");
jcbTemplate = new JComboBox(listTemplate.toArray());
designScrollPanel = new JScrollPane(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
designPanel = new JPanel();

btAdd = new JButton("添加到节目单");
btReset = new JButton("重置选择的素材");
programsListLabel = new JLabel("节目列表");
programsList = new JList();

programsListLabel.setBounds(850, 30, 220, 20);
programsList.setBounds(850, 60, 260, 400);
programsList.setBorder(BorderFactory.createLineBorder(Color.GRAY));

resolutionLabel.setBounds(30, 30, 120, 20);
jcbresolution.setBounds(170, 30, 200, 20);
templateLabel.setBounds(420, 30, 120, 20);
jcbTemplate.setBounds(560, 30, 200, 20);
btAdd.setBounds(850, 470, 120, 20);
btReset.setBounds(980, 470, 130, 20);

// 设计区域大小默认800*640
designPanel.setBackground(Color.red);
designPanel.add(test1);
designPanel.add(test2);
designPanel.add(test3);
designPanel.add(test4);
designPanel.add(test5);
designScrollPanel.add(designPanel);
designPanel.setBounds(100, 100, 500, 500);
designPanel.setPreferredSize(new Dimension(500, 500));
// designPanel.setBorder(BorderFactory.createLineBorder(Color.GRAY));
// designPanel.setAutoscrolls(false);

designScrollPanel.setBounds(30, 60, 800, 640);
// designScrollPanel.setBackground(Color.black);
designScrollPanel.setLayout(new ScrollPaneLayout());
// designScrollPanel.setBorder(BorderFactory.createLineBorder(Color.GRAY));
// designScrollPanel.setAutoscrolls(true);

jcbresolution.addItemListener(new ItemListener(){
@Override
public void itemStateChanged(ItemEvent e) {
// TODO Auto-generated method stub
if(e.getStateChange() == ItemEvent.SELECTED){
String selected = ((Resolution)jcbresolution.getSelectedItem()).getValue();
System.out.println(selected);
if(selected.equals("0")){
return;
}
String[] xy = selected.split("_");
int weidth = Integer.parseInt(xy[0].split("\\*")[0]);
int height = Integer.parseInt(xy[0].split("\\*")[1]);
System.out.println(xy[0]);
int lcm = ResolutionUtils.getLcm(weidth, height);
System.out.println(lcm);

if(xy[1].equals("4:3")){
designPanel.setSize(800, 600);
}
if(xy[1].equals("5:3")){
designPanel.setSize(800, 480);
}
if(xy[1].equals("5:4")){
designPanel.setSize(800, 640);
}
if(xy[1].equals("16:9")){
designPanel.setSize(800, 450);
}

if(xy[1].equals("3:4")){
designPanel.setSize(600, 800);
}
if(xy[1].equals("3:5")){
designPanel.setSize(480, 800);
}
if(xy[1].equals("4:5")){
designPanel.setSize(640, 800);
}
if(xy[1].equals("9:16")){
designPanel.setSize(450, 800);
}
}
}
}); jcbTemplate.addItemListener(new ItemListener(){
@Override
public void itemStateChanged(ItemEvent e) {
// TODO Auto-generated method stub
if(e.getStateChange() == ItemEvent.SELECTED){
int selected = ((Template)jcbTemplate.getSelectedItem()).getAreas();
System.out.println(selected);
}
}
});

btAdd.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String desKey = String.valueOf(System.currentTimeMillis()); int index = jcbTemplate.getSelectedIndex();
String timeSelected = listTimes.get(index).getValue();
int length = timeSelected.length();
String firstLine = length + "" + timeSelected + "" + desKey;
System.out.println(firstLine);
}
});

btReset.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
}
});

this.add(programsListLabel);
this.add(programsList);

this.add(resolutionLabel);
this.add(jcbresolution);
this.add(templateLabel);
this.add(jcbTemplate);

this.add(btAdd);
this.add(btReset);
this.add(designScrollPanel);
this.setVisible(true);
} public static void main(String[] args) {
new Main();
}
}

Answer 1

import com.withiter.util.ResolutionUtils;
哪来的类

Answer 2

designScrollPanel.add(designPanel);
改成：
designScrollPanel.getViewport().add(designPanel);这样写起来太累，建议多使用各种Layout。

Answer 3

designPanel.setPreferSize
designScrollPanel 用默认的layout