Java GUI重新绘制JPanel JFrame的问题
计划是让程序在搜索另一首歌曲时,用不同的歌词替换屏幕上的歌词Java GUI重新绘制JPanel JFrame的问题,java,user-interface,jframe,jtextarea,repaint,Java,User Interface,Jframe,Jtextarea,Repaint,计划是让程序在搜索另一首歌曲时,用不同的歌词替换屏幕上的歌词 }public void lyricPrinter(){ if(scroll != null){ scroll.removeAll(); //--> temporary test System.out.println("removed scroll"); scroll.repaint(); } JTextArea textarea = new JTextArea(lyrics);
}public void lyricPrinter(){
if(scroll != null){
scroll.removeAll(); //--> temporary test
System.out.println("removed scroll");
scroll.repaint();
}
JTextArea textarea = new JTextArea(lyrics);
textarea.setBackground(Color.LIGHT_GRAY);
textarea.setEditable(false);
scroll = new JScrollPane (textarea,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
GUI.frame.remove(scroll);
GUI.frame.add(scroll);
GUI.frame.setVisible(true);
}
我原以为使用removeall()就可以了,但最终还是发生了
第一次打印歌词。。
在我更改歌词并尝试替换以前的歌词之后。。
- 为什么要添加和删除组件?这是一种倒退和危险的方式来实现你的目标
- 即使你的计划还可以,你也不会在任何地方删除原来的JScrollPane。此调用,
GUI.frame.remove(滚动)代码>,删除新的JScrollPane,该窗格尚未添加,而不是当前驻留在GUI中的旧窗格
- 相反,为什么不集中精力保存组件并交换它们所持有的数据——它们的文本?这就是我要做的,也是我强烈推荐的
- 您的
调用表明您可能错误地使用了静态字段。JFrame不应该由静态字段保存,除非您不关心数据和行为的封装GUI.frame….
编辑
我推荐的是
- 你有一个JTextArea字段,一个保存歌词文本的字段
- 它是类中的非静态字段,在整个类中可见,因为它不是在构造函数或方法中声明的
- 在您要交换歌词的事件代码中,只需对这个JTextArea变量调用
,传入一个包含新歌词的字符串setText(…)
假设你有一个名为songLyricsTextArea的JTextArea,要交换文本,你所要做的就是
String newLyrics = somehowGetNewLyricsToSong();
songLyricsTextArea.setText(newLyrics);
例如,在下面的演示程序中,我阅读了JavaSwing教程中的几个演示程序的java代码。我将程序名放在右侧的JList中,并给JList一个ListSelectionListener,它交换JTextArea(这里称为programTextArea)中的文本,类似于我建议您执行的操作。我的演示中的关键代码在此处的侦听器中:
demoList.addListSelectionListener(new ListSelectionListener() {
@Override // a new program has been selected
public void valueChanged(ListSelectionEvent e) {
if (!e.getValueIsAdjusting()) {
if (demoList.getSelectedIndex() != -1) { // make sure selection valid
DemoProgram demoProgram = demoList.getSelectedValue(); // get selection
programTextArea.setText(demoProgram.getText()); // get text and pass into text area
}
}
}
});
因此,您应该编译并运行整个程序以了解其工作原理:
import java.awt.BorderLayout;
import java.io.IOException;
import java.net.URL;
import java.util.Scanner;
import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
@SuppressWarnings("serial")
public class SwapTextExample extends JPanel {
private static final String[][] DEMO_PROGS = {
{ "BorderDemo.java",
"http://docs.oracle.com/javase/tutorial/uiswing/examples/"
+ "components/BorderDemoProject/src/components/BorderDemo.java" },
{ "ButtonDemo.java",
"http://docs.oracle.com/javase/tutorial/uiswing/examples/"
+ "components/ButtonDemoProject/src/components/ButtonDemo.java" },
{ "ButtonHtmlDemo.java",
"http://docs.oracle.com/javase/tutorial/uiswing/examples/"
+ "components/ButtonHtmlDemoProject/src/components/ButtonHtmlDemo.java" },
{ "CheckBoxDemo.java",
"http://docs.oracle.com/javase/tutorial/uiswing/examples/"
+ "components/CheckBoxDemoProject/src/components/CheckBoxDemo.java" },
{ "ComboBoxDemo.java",
"http://docs.oracle.com/javase/tutorial/uiswing/examples/"
+ "components/ComboBoxDemoProject/src/components/ComboBoxDemo.java" }, };
private DefaultListModel<DemoProgram> model = new DefaultListModel<>();
private JList<DemoProgram> demoList = new JList<DemoProgram>(model);
private JTextArea programTextArea = new JTextArea(40, 70);
public SwapTextExample() throws IOException {
for (String[] demoProgText : DEMO_PROGS) {
String name = demoProgText[0];
String link = demoProgText[1];
URL url = new URL(link);
Scanner scanner = null;
try {
scanner = new Scanner(url.openStream());
StringBuilder sb = new StringBuilder();
while (scanner.hasNextLine()) {
sb.append(scanner.nextLine() + "\n");
}
String text = sb.toString();
DemoProgram demoProg = new DemoProgram(name, link, text);
model.addElement(demoProg);
} finally {
if (scanner != null) {
scanner.close();
}
}
}
demoList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
demoList.addListSelectionListener(new ListSelectionListener() {
@Override // a new program has been selected
public void valueChanged(ListSelectionEvent e) {
if (!e.getValueIsAdjusting()) {
if (demoList.getSelectedIndex() != -1) { // make sure selection valid
DemoProgram demoProgram = demoList.getSelectedValue(); // get selection
programTextArea.setText(demoProgram.getText()); // get text and pass into text area
}
}
}
});
setLayout(new BorderLayout());
add(new JScrollPane(demoList), BorderLayout.WEST);
add(new JScrollPane(programTextArea), BorderLayout.CENTER);
}
private static void createAndShowGui() {
SwapTextExample mainPanel;
try {
mainPanel = new SwapTextExample();
JFrame frame = new JFrame("Swap Text Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
class DemoProgram {
private String name;
private String link;
private String text;
public DemoProgram(String name, String link, String text) {
this.name = name;
this.link = link;
this.text = text;
}
public String getName() {
return name;
}
public String getLink() {
return link;
}
public String getText() {
return text;
}
@Override
public String toString() {
return name;
}
}
导入java.awt.BorderLayout;
导入java.io.IOException;
导入java.net.URL;
导入java.util.Scanner;
导入javax.swing.*;
导入javax.swing.event.ListSelectionEvent;
导入javax.swing.event.ListSelectionListener;
@抑制警告(“串行”)
公共类SwapTextExample扩展了JPanel{
私有静态最终字符串[][]演示程序={
{“BorderDemo.java”,
"http://docs.oracle.com/javase/tutorial/uiswing/examples/"
+“components/BorderDemoProject/src/components/BorderDemo.java”},
{“ButtonDemo.java”,
"http://docs.oracle.com/javase/tutorial/uiswing/examples/"
+“components/buttonemoproject/src/components/buttonemo.java”},
{“ButtonHtmlDemo.java”,
"http://docs.oracle.com/javase/tutorial/uiswing/examples/"
+“components/buttonhtmlemoproject/src/components/buttonhtmlemo.java”},
{“CheckBoxDemo.java”,
"http://docs.oracle.com/javase/tutorial/uiswing/examples/"
+“components/CheckBoxDemoProject/src/components/CheckBoxDemo.java”},
{“ComboBoxDemo.java”,
"http://docs.oracle.com/javase/tutorial/uiswing/examples/"
+“components/ComboBoxDemoProject/src/components/ComboxDemo.java”},};
私有DefaultListModel=new DefaultListModel();
私有JList demoList=新JList(型号);
私有JTextArea programTextArea=新的JTextArea(40,70);
public SwapTextExample()引发IOException{
对于(字符串[]demoProgText:DEMO_PROGS){
字符串名称=demoProgText[0];
字符串链接=demoProgText[1];
URL=新的URL(链接);
扫描器=空;
试一试{
scanner=newscanner(url.openStream());
StringBuilder sb=新的StringBuilder();
while(scanner.hasNextLine()){
sb.append(scanner.nextLine()+“\n”);
}
字符串text=sb.toString();
DemoProgram demoProg=新的DemoProgram(名称、链接、文本);
模型.加法(demoProg);
}最后{
如果(扫描器!=null){
scanner.close();
}
}
}
demoList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
demoList.addListSelectionListener(新的ListSelectionListener(){
@覆盖//已选择新程序
public void值已更改(ListSelectionEvent e){
如果(!e.getValueIsAdjusting()){
如果(demoList.getSelectedIndex()!=-1){//请确保选择有效
DemoProgram DemoProgram=demoList.getSelectedValue();//获取选择
programTextArea.setText(demoProgram.getText());//获取文本并传递到文本区域
}
}
}
});
setLayout(新的BorderLayout());
添加(新的JScrollPane(demoList),BorderLayout.WEST);
添加(新的JScrollPane(programTextArea),BorderLayout.CENTER);
}
私有静态void createAndShowGui(){
SwapTextExample主面板;
试一试{
mainPanel=新的SwapTextExample();
JFrame=新JFrame(“交换文本示例”);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(主面板);
frame.pack();
frame.setLocationByPlatform(真);
frame.setVisible(true);
}捕获(IOE异常){
e、 printStackTrace();
}
}
公共静态void main(字符串[]args){
SwingUtilities.invokeLater(新的Runnable(){
公开募捐{
createAndShowGui();
}
});
}
}
班级演示计划{
私有字符串名称;
私有字符串
}public void lyricPrinter(){
if(scroll != null){
//scroll.removeAll(); //--> temporary test
//System.out.println("removed scroll");
//scroll.repaint();
GUI.frame.remove(scroll);
}
JTextArea textarea = new JTextArea(lyrics);
textarea.setBackground(Color.LIGHT_GRAY);
textarea.setEditable(false);
scroll = new JScrollPane (textarea,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
GUI.frame.add(scroll);
GUI.frame.setVisible(true);
}