android - 声明 URL 的正确方法？

Question

在我的应用程序中，我试图从我的网站下载一个文件，但遇到了一些问题。首先，我似乎想不出声明 URL 的正确方法。其次，当我运行应用程序时，当我告诉连接获取 InputStream 时它崩溃了。我不知道我做错了什么。我下午的大部分时间都在网上搜索，并尝试了很多方法来解决 URL 的问题，但都没有成功。

我很想知道我做错了什么，所以我们将不胜感激任何帮助。

package shc_BalloonSat.namespace;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;

import org.apache.http.util.ByteArrayBuffer;

import android.util.Log;

public class dl_viewKML
{
    String file_path = "";
    String file_url;
    String file_name;

    void downloadFile()
    {
        try
        {
            String file_name = "data.kml";

            //URL url = new URL("http://space.uah.edu");
            String encodedURL = "http:////"+URLEncoder.encode("www.wktechnologies.com/shc_android_app/", "UTF-8");
            URL url = new URL(encodedURL);
            File file = new File(url + "/" + file_name);

            long startTime = System.currentTimeMillis();
            Log.d("SHC BalloonSat", "Download beginning: ");
            Log.d("SHC BalloonSat", "Download url: " + url);
            Log.d("SHC BalloonSat", "Downloaded file name: " + file_name);

            // Open a connection to the specified URL
            URLConnection conn = url.openConnection();

            // Define InputStreams to read from the URLConnection.
            InputStream is = conn.getInputStream();//crashes here
            BufferedInputStream bis = new BufferedInputStream(is);

            // Read bytes to the Buffer until there is nothing more to read(-1).
            ByteArrayBuffer baf = new ByteArrayBuffer(50);
            int current = 0;
            while ((current = bis.read()) != -1)
            {
                baf.append((byte) current);
            }

            // Convert the Bytes read to a String.
            FileOutputStream fos = new FileOutputStream(file);
            fos.write(baf.toByteArray());
            fos.close();
            Log.d("SHC BalloonSat", "Download ready in: " + ((System.currentTimeMillis() - startTime) / 1000) + " secs.");
            }

            catch (IOException e)
            {
                Log.e("log_tag", "Error: " + e.toString());
            }   
    }
}

Answer 1

不需要用url调用URLEncoder。 URLEncoder.encode 用于对参数进行编码:

因此将您的代码编辑为:

void downloadFile()
{
    try
    {
        String file_name = "data.kml";

        //URL url = new URL("http://space.uah.edu");
        String encodedURL =         "http://"+"www.wktechnologies.com/shc_android_app/data.kml";
        URL url = new URL(encodedURL);

        // Open a connection to the specified URL
        URLConnection conn = url.openConnection();

        // Define InputStreams to read from the URLConnection.
        InputStream is = conn.getInputStream();//crashes here
        BufferedInputStream bis = new BufferedInputStream(is);

        // Read bytes to the Buffer until there is nothing more to read(-1).
        ByteArrayBuffer baf = new ByteArrayBuffer(50);
        int current = 0;
        while ((current = bis.read()) != -1)
        {
            baf.append((byte) current);
        }

        // Convert the Bytes read to a String.
        FileOutputStream fos = new FileOutputStream(file);
        fos.write(baf.toByteArray());
        fos.close();
        Log.d("SHC BalloonSat", "Download ready in: " + ((System.currentTimeMillis() - startTime) / 1000) + " secs.");
    }

    catch (IOException e)
    {
        Log.e("log_tag", "Error: " + e.toString());
    }

}