文件下载

文件下载的步骤

1 创建一个HttpURLConnection对象

HttpURLConnection urlConn = (HttpURLConnection)url.openConnection();

 

2 获得一个InputStream对象  urlConn.getInputStream()

 

3 访问网络的权限   android.permission.INTERNET

 

package jianglin.download;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class HttpDownload {
	private URL url = null;
	/*
	 * 根据url下载文，前提是这个文件中的内容是文本，函数的返回值是文件当中的内容
	 * 1，创建一个URL对象
	 * 2，通过URL对象，创建一个HttpURLConnectiond对象
	 * 3,得到InputStream
	 * 4,从InputStream当中读取数据
	 */
	
	public String download(String urlStr){
		StringBuffer sb = new StringBuffer();
		String line = null;
		BufferedReader buffer = null;
		try{
			//创建一个URL对象
			url = new URL(urlStr);
			//创建一个Http连接
			HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
			//使用IO读取数据
			buffer = new BufferedReader(new InputStreamReader(urlConn.getInputStream()));
			while ((line = buffer.readLine()) != null){
				sb.append(line);
			}
		}catch(Exception e){
			e.printStackTrace();	
		}finally{
			try{
				buffer.close();	
			}catch(Exception e){
				e.printStackTrace();		
			}	
		}
		return sb.toString();
	}
}

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