Android--使用Http向服务器发送请求并取得返回结果，下载图片

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{"person":"\u5b59\u6743","index":3,"score":10000},
{"person":"\u5218\u5907","index":4,"score":9638},
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{"person":"\u66f9\u64cd","index":11,"score":5288}
],


"base":"（服务端地址）",

"head":
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{"person":"\u66f9\u64cd","filename":"\/caocao\/20130718185726036.png", "size":12343},

{"person":"\u5b59\u6743","filename":"\/sunqun\/20130718185726046.png", "size":12343},

{"person":"\u5218\u5907","filename":"\/liubei\/20130718185726056.png", "size":12343}
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package com.joye3g.http;

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 org.apache.http.HttpStatus;

public class LoadImage {

	private static final int SUCCES = 1;//下载成功
	private static final int ERRO = -1;//下载失败
	private static final int EXIST = 0;//文件已存在
	private static int result = EXIST;//返回的下载结果
	private String localPath;//本地路径
	
	public LoadImage(String localPath) {
		this.localPath = localPath;
	}

	/**
	 * @param urlPathPrefix       网址前缀
	 * @param filename            文件名
	 * @param size                文件大小
	 * @return
	 * @throws IOException
	 */
	public int download(String urlPathPrefix, String filename, long size) throws IOException{
		String filePath = localPath + File.separator + filename.substring(filename.lastIndexOf("/") + 1);
		//判断filePath路径下有没有此图片存在，大小是否相同，如果不存在，则发送Http请求下载图片，存在则不下载
		if(isFileExist(filePath) && isSizeSame(filePath, size)){
			return result = EXIST;
		}else{
			//从URL中取得输入流
			InputStream is = getHttpInputStream(urlPathPrefix + filename);
			//创建新文件
			File file = createFile(filePath);
			//下载图片
			if(is != null) downLoadImage(file, is);  
		}
		return result;
	}

	/**
	 * 下载图片
	 * @param file  文件
	 * @param is	从URL取得的输入流
	 */
	private void downLoadImage(File file, InputStream is){
		FileOutputStream fs = null;
		try {
			fs = new FileOutputStream(file);
			byte[] buffer = new byte[4 * 1024];
			int len = 0;
			while((len = is.read(buffer)) != -1){
				fs.write(buffer, 0, len);
			}
			fs.flush();
			result = SUCCES;
		} catch (Exception e) {
			result = ERRO;
			e.printStackTrace();
		}finally{
			try {
				if(fs != null){
					fs.close();
				}
				if(is != null){
					is.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	/**
	 * 根据URL取得输入流
	 * @param urlPath   网络路径
	 * @return
	 * @throws IOException
	 */
	private InputStream getHttpInputStream(String urlPath) throws IOException{
		URL url = new URL(urlPath);
		HttpURLConnection conn = (HttpURLConnection) url.openConnection();
		if(conn.getResponseCode() == HttpStatus.SC_OK) {
			return conn.getInputStream();
		}
		return null;
	}

	/**
	 * 判断文件是否已经存在
	 * @param fileName     文件路径
	 * @return
	 */
	private boolean isFileExist(String fileName){
		File file = new File(fileName);
		return file.exists();
	}

	/**
	 * 在指定路径下创建新文件
	 * @param fileName      文件路径
	 * @return
	 * @throws IOException
	 */
	private File createFile(String fileName) throws IOException{
		File file = new File(fileName);
		if(!file.createNewFile()){
			file.delete();
			file.createNewFile();
		}
		return file;
	}
	
	/**
	 * 若文件已存在，判断文件大小是否正确
	 * @param filePath         图片路径
	 * @param size             文件大小
	 * @return
	 */
	private boolean isSizeSa
补充：移动开发 , Android ,