首先是文件FileUtils.java
package mars.utils;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import mars.model.Mp3Info;
import android.os.Environment;
public class FileUtils {
private String SDCardRoot;
public FileUtils() {
// 得到当前外部存储设备的目录
SDCardRoot = Environment.getExternalStorageDirectory()
.getAbsolutePath()
+ File.separator;
}
/**
* 在SD卡上创建文件
*
* @throws IOException
*/
public File createFileInSDCard(String fileName, String dir)
throws IOException {
File file = new File(SDCardRoot + dir + File.separator + fileName);
System.out.println("file---->" + file);
file.createNewFile();
return file;
}
/**
* 在SD卡上创建目录
*
* @param dirName
*/
public File creatSDDir(String dir) {
File dirFile = new File(SDCardRoot + dir + File.separator);
System.out.println(dirFile.mkdirs());
return dirFile;
}
/**
* 判断SD卡上的文件夹是否存在
*/
public boolean isFileExist(String fileName, String path) {
File file = new File(SDCardRoot + path + File.separator + fileName);
return file.exists();
}
/**
* 将一个InputStream里面的数据写入到SD卡中
*/
public File write2SDFromInput(String path, String fileName,
InputStream input) {
File file = null;
OutputStream output = null;
try {
creatSDDir(path);
file = createFileInSDCard(fileName, path);
output = new FileOutputStream(file);
byte buffer[] = new byte[4 * 1024];
int temp;
while ((temp = input.read(buffer)) != -1) {
output.write(buffer, 0, temp);
}
output.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
output.close();
} catch (Exception e) {
e.printStackTrace();
}
}
return file;
}
}然后是下载的HttpDownload.java
package mars.download;
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;
import mars.utils.FileUtils;
public class HttpDownloader {
private URL url = null;
/**
* 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HttpURLConnection对象
* 3.得到InputStram
* 4.从InputStream当中读取数据
* @param urlStr
* @return
*/
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流读取数据
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();
}
/**
* 该函数返回整形 -1：代表下载文件出错 0：代表下载文件成功 1：代表文件已经存在
*/
public int downFile(String urlStr, String path, String fileName) {
InputStream inputStream = null;
try {
FileUtils fileUtils = new FileUtils();
if (fileUtils.isFileExist(fileName,path)) {
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;
}
}注意使用的时候需要添加相应的权限，还有需要开辟新的线程，以为安卓不能在主线程中执行耗时的操作(比如：下载文件)
下面是我自己写的一个，没什么技术含量，纯给新手测试用用：
package com.example.httpdownload;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
public class MainActivity extends Activity {
Button downButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
downButton = (Button) findViewById(R.id.button1);
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
downButton.setOnClickListener(listener);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
View.OnClickListener listener = new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.button1:
Thread thread = new Thread(new MyRunable());
thread.start();
break;
default:
break;
}
}
};
private void downLoadFile() {
String urlStr = "http://10.3.19.26:8080/2015-1-6/1.txt";
HttpDownloader httpDownloader = new HttpDownloader();
int result = httpDownloader.downFile(urlStr, "", " 1.txt");
System.out.println("<-------->" + result);
}
public class MyRunable implements Runnable {
public void run() {
// TODO Auto-generated method stub
downLoadFile();
}
}
}