使用swing GUI在下载文件时显示进度条 [英] Using swing GUI to make a progress bar show up while downloading a file
本文介绍了使用swing GUI在下载文件时显示进度条的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我目前有一个类,在下载文件时应该会显示一个简单的表单。它正在工作,但进度条没有更新,一旦下载完成,我只能看到它。有人可以帮我吗?
I currently have a class that should show me a simple form while downloading a file. It is working, but the progress bar is not updating, and I can only see it once the download is finished. Can someone help me?
import java.awt.FlowLayout;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.swing.JFrame;
import static javax.swing.JFrame.EXIT_ON_CLOSE;
import javax.swing.JProgressBar;
public class Downloader {
public Downloader(String site, File file) {
JFrame frm = new JFrame();
JProgressBar current = new JProgressBar(0, 100);
current.setSize(50, 100);
current.setValue(0);
current.setStringPainted(true);
frm.add(current);
frm.setVisible(true);
frm.setLayout(new FlowLayout());
frm.setSize(50, 100);
frm.setDefaultCloseOperation(EXIT_ON_CLOSE);
try {
URL url = new URL(site);
HttpURLConnection connection
= (HttpURLConnection) url.openConnection();
int filesize = connection.getContentLength();
float totalDataRead = 0;
try (java.io.BufferedInputStream in = new java.io.BufferedInputStream(connection.getInputStream())) {
java.io.FileOutputStream fos = new java.io.FileOutputStream(file);
try (java.io.BufferedOutputStream bout = new BufferedOutputStream(fos, 1024)) {
byte[] data = new byte[1024];
int i;
while ((i = in.read(data, 0, 1024)) >= 0) {
totalDataRead = totalDataRead + i;
bout.write(data, 0, i);
float Percent = (totalDataRead * 100) / filesize;
current.setValue((int) Percent);
}
}
}
} catch (IOException e) {
javax.swing.JOptionPane.showConfirmDialog((java.awt.Component) null, e.getMessage(), "Error",
javax.swing.JOptionPane.DEFAULT_OPTION);
}
}
}
推荐答案
你的是一个经典的Swing并发问题。解决方案是一样的 - 在后台线程中执行长时间运行的代码,例如可以使用SwingWorker找到。
Yours is a classic Swing concurrency issue. The solution is as always -- do the long running code in a background thread such as can be found with a SwingWorker.
例如,
import java.awt.FlowLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.ExecutionException;
import javax.swing.JFrame;
import javax.swing.SwingWorker;
import static javax.swing.JFrame.EXIT_ON_CLOSE;
import javax.swing.JProgressBar;
public class Downloader {
public Downloader(String site, File file) {
JFrame frm = new JFrame();
final JProgressBar current = new JProgressBar(0, 100);
current.setSize(50, 100);
current.setValue(0);
current.setStringPainted(true);
frm.add(current);
frm.setVisible(true);
frm.setLayout(new FlowLayout());
frm.setSize(50, 100);
frm.setDefaultCloseOperation(EXIT_ON_CLOSE);
final Worker worker = new Worker(site, file);
worker.addPropertyChangeListener(new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent pcEvt) {
if ("progress".equals(pcEvt.getPropertyName())) {
current.setValue((Integer) pcEvt.getNewValue());
} else if (pcEvt.getNewValue() == SwingWorker.StateValue.DONE) {
try {
worker.get();
} catch (InterruptedException | ExecutionException e) {
// handle any errors here
e.printStackTrace();
}
}
}
});
worker.execute();
}
}
class Worker extends SwingWorker<Void, Void> {
private String site;
private File file;
public Worker(String site, File file) {
this.site = site;
this.file = file;
}
@Override
protected Void doInBackground() throws Exception {
URL url = new URL(site);
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
int filesize = connection.getContentLength();
int totalDataRead = 0;
try (java.io.BufferedInputStream in = new java.io.BufferedInputStream(
connection.getInputStream())) {
java.io.FileOutputStream fos = new java.io.FileOutputStream(file);
try (java.io.BufferedOutputStream bout = new BufferedOutputStream(
fos, 1024)) {
byte[] data = new byte[1024];
int i;
while ((i = in.read(data, 0, 1024)) >= 0) {
totalDataRead = totalDataRead + i;
bout.write(data, 0, i);
int percent = (totalDataRead * 100) / filesize;
setProgress(percent);
}
}
}
return null;
}
}
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