Android开发 Http连接服务器

由于代码注释很详细，所以就不讲解了，大家都能看的懂。

分为两个类来实现：FileUtils 和 HttpDownload。

首先讲解HttpDownload这个类，代码如下：

package cn.jinbi.HttpURL;import java.io.BufferedReader;import java.io.File;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;/**根据URL下载文件：前提是这个文件当中的内容是文本，函数的返回值就是这个文件中的内容 * 1.创建一个URL对象 * 2.通过URL对象，创建HttpURLConnection对象 * 3.得到InputStream * 4.从InputStream当中读取文件 * @author think * */public class HttpDownload {private URL url;public String Download(String urlStr){StringBuffer buffer = new StringBuffer();BufferedReader br = null;String line = null;try {url = new URL(urlStr);//基于Http协议连接对象HttpURLConnection urlCon = (HttpURLConnection)url.openConnection();//设置请求等待响应时间urlCon.setConnectTimeout(5000);//设置请求方式urlCon.setRequestMethod("GET");//如果请求的状态码等于200表示请求成功System.out.println("OK");if (urlCon.getResponseCode() == 200){System.out.println("OK");     br = new BufferedReader(new InputStreamReader(urlCon.getInputStream()));while ((line=br.readLine())!=null){System.out.println("OK");buffer.append(line);}}}  catch (IOException e) {e.printStackTrace();}finally{try {br.close();} catch (IOException e) {e.printStackTrace();}}return buffer.toString();}/** * @param urlStr   链接 * @param path     文件存放的目录 * @param fileName 文件的文件名 * @return         整数-1,表明下载文件出错;0表示成功;1代表已经存在了 */public int downFile(String urlStr,String path,String fileName){InputStream  inputStream = null;try{FileUtils fileUtils = new FileUtils();if (fileUtils.isFileExist(path + fileName)){return 1;}else{inputStream = getInputStreamFromUrl(urlStr);File resultFile = fileUtils.write2SDFromInput(path, fileName, inputStream);if (resultFile == null){return -1;}}}catch(Exception e){e.printStackTrace();return -1;}finally{try{inputStream.close();}catch(Exception e){e.printStackTrace();}}return 0;}/** * 根据URL得到输入流 * @param urlStr * @return * @throws MalformedURLException * @throws IOException */public InputStream getInputStreamFromUrl(String urlStr)throws MalformedURLException,IOException{url = new URL(urlStr);HttpURLConnection urlConn = (HttpURLConnection)url.openConnection();InputStream inputStream = urlConn.getInputStream();return inputStream;}}

然后是FileUtils这个类的代码：

package cn.jinbi.HttpURL;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import android.os.Environment;public class FileUtils {private String SDPATH;public String getSDPATH(){return SDPATH;}public FileUtils(){//得到当前外部存储设备的目录SDPATH = Environment.getExternalStorageDirectory()+"/";}/** * 在SD卡上创建文件 * @throws IOException */public File createSDFile(String fileName)throws IOException{File file = new File(SDPATH + fileName);file.createNewFile();return file;}/** * 在SD卡上创建目录 * @param dirName */public File createSDDir(String dirName){File dir = new File(SDPATH + dirName);dir.mkdir();return dir;}/** * 判断文件是否存在 * @param fileName */public boolean isFileExist(String fileName){File file = new File(SDPATH + fileName);return file.exists();}public File write2SDFromInput(String path,String fileName,InputStream input){File file = null;OutputStream output = null;try{//创建目录createSDDir(path);//创建文件file = createSDFile(path + fileName);//创建写入数据流output = new FileOutputStream(file);byte buffer[] = new byte[4 * 1024];while ((input.read(buffer))!=-1){output.write(buffer);}output.flush();}catch(Exception e){e.printStackTrace();}finally{try{output.close();}catch(Exception e){e.printStackTrace();}}return file;}}

最后需要注意的是：别忘了加上权限：

1。访问网络的权限：

<uses-permission android:name="android.permission.INTERNET"/>

2。访问内存卡的权限：

 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>