首先,每个人都需要知道我对Java编码比较陌生。更准确地说,我对面向对象编程是完全陌生的。
对于问题。
我正在尝试创建一个下载类,该类更新给定的进度条以显示其进度。可能还有我决定在未来更新的任何其他内容。
目前的问题是,在我看来,这不应该奏效。我可以在"main"方法上做任何我想做的事情,并且 GUI 仍然响应迅速且快速。根据我过去编程的经验,除非我线程化 GUI,否则这是不可能的。这是为什么呢?
既然它有效,可以这样做吗?
类主
package atomicElectronics;
import java.io.IOException;
import atomicElectronics.physical.AtomFrame;
import atomicElectronics.utility.Download;
public class Initial {
static AtomFrame atomLauncher;
public static void main(String[] args) {
atomLauncher = new AtomFrame();
atomLauncher.start();
System.out.println(Integer.MAX_VALUE);
Download theDownload = new Download();
theDownload.fileProgressBar(atomLauncher.progressBar);
try {
theDownload.exicute("http://download.videolan.org/pub/videolan/vlc/last/win64/vlc-2.1.3-win64.exe", "C:\Users\TrinaryAtom\AppData\Roaming");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// TODO Add Download Methods
// theDownload.updateBarTotal(JProgressBar);
// theDownload.updateLabelSpeed(String);
// theDownload.updateLabelTotal(String);
// theDownload.addFile(File);
// theDownload.addFiles(Files);
}
}
类原子帧
package atomicElectronics.physical;
import javax.swing.JFrame;
import java.awt.FlowLayout;
import javax.swing.JProgressBar;
public class AtomFrame extends JFrame{
public JProgressBar progressBar;
private static final long serialVersionUID = 4010489530693307355L;
public static void main(String[] args){
AtomFrame testFrame = new AtomFrame();
testFrame.start();
}
public AtomFrame(){
initializeComponents();
}
public void initializeComponents(){
this.setSize(400, 400);
this.setLocationRelativeTo(null);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setTitle("Atom Launcher");
this.setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));
progressBar = new JProgressBar();
this.add(progressBar);
//this.pack();
}
public void start() {
this.setVisible(true);
}
public void close() {
this.dispose();
}
}
课程下载
package atomicElectronics.utility;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.swing.JProgressBar;
public class Download {
private static final int BUFFER_SIZE = 4096;
private JProgressBar fileProgressBar;
public Download() {
}
public void fileProgressBar(JProgressBar fileBar) {
fileProgressBar = fileBar;
}
public void exicute(String fileURL, String saveDir) throws IOException {
URL url = new URL(fileURL);
HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
int responseCode = httpConn.getResponseCode();
// always check HTTP response code first
if (responseCode == HttpURLConnection.HTTP_OK) {
String fileName = "";
String disposition = httpConn.getHeaderField("Content-Disposition");
String contentType = httpConn.getContentType();
double contentLength = httpConn.getContentLength();
if (disposition != null) {
// extracts file name from header field
int index = disposition.indexOf("filename=");
if (index > 0) {
fileName = disposition.substring(index + 9,
disposition.length());
}
} else {
// extracts file name from URL
fileName = fileURL.substring(fileURL.lastIndexOf("/") + 1,
fileURL.length());
}
System.out.println("Content-Type = " + contentType);
System.out.println("Content-Disposition = " + disposition);
System.out.println("Content-Length = " + contentLength);
System.out.println("fileName = " + fileName);
// opens input stream from the HTTP connection
InputStream inputStream = httpConn.getInputStream();
String saveFilePath = saveDir + File.separator + fileName;
// opens an output stream to save into file
FileOutputStream outputStream = new FileOutputStream(saveFilePath);
double totalRead = 0;
int bytesRead = -1;
byte[] buffer = new byte[BUFFER_SIZE];
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
totalRead += bytesRead;
System.out.println((totalRead / contentLength) * 100);
fileProgressBar.setValue((int)((totalRead / contentLength) * 100));
}
outputStream.close();
inputStream.close();
System.out.println("File downloaded");
} else {
System.out.println("No file to download. Server replied HTTP code: " + responseCode);
}
httpConn.disconnect();
}
}
建议:
- 使用 SwingWorker 来执行后台线程工作。
- 在 Swingworker 中,通过
setProgress(int progress)
设置其进度"绑定"属性。该值应介于 1 和 100 之间。 - 不要让你的 SwingWorker/文件下载器持有 JProgressBar 或任何 Swing 组件。
- 将 PropertyChangeListener 添加到 SwingWorker 并监视进度属性中的更改。
- 切勿公开您的 Swing 字段(或大多数和所有字段)。限制访问,改为通过方法更改对象状态。
- 阅读教程 Swing 中的并发,了解必要的详细信息。
例如,下面的代码是一个粗略的简化,没有下载任何文件,但应该给你一个想法:
import java.awt.*;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.Random;
import javax.swing.*;
public class Initial {
static AtomFrame atomLauncher;
public static void main(String[] args) {
atomLauncher = new AtomFrame();
atomLauncher.start();
System.out.println(Integer.MAX_VALUE);
final Download theDownload = new Download();
theDownload.addPropertyChangeListener(new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent pcEvt) {
if ("progress".equals(pcEvt.getPropertyName())) {
int progress = theDownload.getProgress();
atomLauncher.setProgress(progress);
}
}
});
theDownload.execute();
}
}
class AtomFrame extends JFrame {
// ********* should be private!
private JProgressBar progressBar;
private static final long serialVersionUID = 4010489530693307355L;
public static void main(String[] args) {
AtomFrame testFrame = new AtomFrame();
testFrame.start();
}
public void setProgress(int progress) {
progressBar.setValue(progress);
}
public AtomFrame() {
initializeComponents();
}
public void initializeComponents() {
this.setSize(400, 400);
this.setLocationRelativeTo(null);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setTitle("Atom Launcher");
this.setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));
progressBar = new JProgressBar();
this.add(progressBar);
// this.pack();
}
public void start() {
this.setVisible(true);
}
public void close() {
this.dispose();
}
}
class Download extends SwingWorker<Void, Void> {
private static final long SLEEP_TIME = 300;
private Random random = new Random();
@Override
protected Void doInBackground() throws Exception {
int myProgress = 0;
while (myProgress < 100) {
myProgress += random.nextInt(10);
setProgress(myProgress);
try {
Thread.sleep(SLEEP_TIME);
} catch (InterruptedException e) {}
}
return null;
}
}