java - 如何在我的代码中放置输入流进度监视器？

Question

我试图将进度监视器输入流放入我的代码中，但我所做的一切都做不到。我对 Java 编程非常陌生，在代码中实现某些功能时遇到一些困难。

除了无法使用输入流之外，代码可以按照我需要的方式正常工作。所以我想查看下载进度，因为它有异常(exception)情况，以防下载失败或服务器停机。

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package javatar.language.download;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import javax.swing.JOptionPane;

/**
 *
 * @author Bruno
 */
public class UrlInput {

    public static void main(String[] args) {

        String userSys = System.getenv("USERNAME");
        String sysDrive = System.getenv("SYSTEMDRIVE");
        String downPath = sysDrive + "/Users/" + userSys + "/Downloads";

        try {

            URL url = new URL("http://akamai-gamecdn.blackdesertonline.com/live001/game/config/config.language.version");

            try ( // read text returned by server
                    BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()))) {
                String line;

                while ((line = in.readLine()) != null) {

                    String versao = line;

                    JOptionPane.showMessageDialog(null, "Actual version BDO-NA: " + versao);

                    String fileURL = "http://akamai-gamecdn.blackdesertonline.com/live001/game/language/BDOLanguage_" + versao + ".zip";

                    String saveDIR = downPath;

                    SysDownload.downloadFile(fileURL, saveDIR);
                }
            }

        } catch (MalformedURLException e) {
            JOptionPane.showMessageDialog(null, "Malformed URL: " + e.getMessage());
        } catch (IOException e) {
            JOptionPane.showMessageDialog(null, "Error I/O: " + e.getMessage());
        }

    }

}



/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package javatar.language.download;

import java.io.*;
import java.net.*;
import javax.swing.*;

/**
 *
 * @author Bruno
 */
public class SysDownload {

    private static final int BUFFER_SIZE = 4096;

    public static void downloadFile(String fileURL, String saveDIR) throws IOException {

        URL link = new URL(fileURL);

        HttpURLConnection conn = (HttpURLConnection) link.openConnection();

        int responseCode = conn.getResponseCode();

        if (responseCode == HttpURLConnection.HTTP_OK) {

            String fileName = "";
            String server = conn.getHeaderField("Server");
            String connectionType = conn.getContentType();
            int contentLenght = conn.getContentLength();

            JOptionPane.showMessageDialog(null, "Server name: " + server);

            if (server != null) {

                int index = server.indexOf("filename");
                if (index > 0) {
                    fileName = server.substring(index + 10, server.length() - 1);
                } else {
                    fileName = fileURL.substring(fileURL.lastIndexOf("/") + 1, fileURL.length());
                }

                try (InputStream inputStream = conn.getInputStream()) {

                    String savePath = saveDIR + File.separator + fileName;

                    try (FileOutputStream outputStream = new FileOutputStream(savePath)) {

                        int bytesRead = - 1;

                        byte[] buffer = new byte[BUFFER_SIZE];

                        while ((bytesRead = inputStream.read(buffer)) != -1) {

                            outputStream.write(buffer, 0, bytesRead);

                        }

                    }

                }

                JOptionPane.showMessageDialog(null, "File " + fileName + " has been downloaded.\nSee users Download folder.");
            } else {
                JOptionPane.showMessageDialog(null, "None file downloaded.\nServer HTTP code: " + responseCode + JOptionPane.ERROR_MESSAGE);

            }

            conn.disconnect();

        }

    }

}

Answer 1

首先咨询the documentation of ProgressMonitorInputStream .

• 构造函数需要三个参数。与 JOptionPane 一样，第一个参数是对话框父级，在您的应用程序中它显示为 null。
• 第二个参数是消息。就您而言，“下载”+链接可能就足够了。
• 第三个参数是要监视的InputStream。这应该是您要从中下载的输入流。

ProgressMonitor的最大值应该是下载的大小，您可以从 getContentLength() 获取该大小。 URLConnection 方法。

您不需要编写循环来将 InputStream 保存到文件中。您可以使用Files.copy为此。

所以，把它们放在一起，看起来像这样:

try (ProgressMonitorInputStream inputStream =
        new ProgressMonitorInputStream(null,
            "Downloading " + link,
            conn.getInputStream())) {

    inputStream.getProgressMonitor().setMaximum(conn.getContentLength());
    Files.copy(inputStream, Paths.get(savePath));
}