为了测试方便，在自己的电脑上开一个web服务Tomcat，在Tomcat的webapps文件夹里放测试下载用的文件
在cmd的ipconfig指令下查看自己的主机的IP地址。
之前没有接触过Tomcat，就先按网上介绍的安装教程下载Tomcat，并在Eclipse配置好Tomcat
http://blog.chinaunix.net/uid-25434387-id-167705.html
初次安装配置会出现一些错误，但在网上都能找到解决办法，直到Tomcat正常工作
使用HTTP·协议下载文件：
1、创建一个HttpURLConnection对象
HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
2、获得一个InputStream对象
InputStream inputStream = urlConn.getInputStream();
3、访问网络的权限（需要在AndroidMainfest.xml配置好）
<uses-permission android:name="android.permission.INTERNET"/>
将下载的文件写到SDCard
1、得到当前设备SD卡的目录
SDPATH = Environment.getExternalStorageDirectory() + "/";
2、访问SD的权限（同样需要在AndroidMainfest.xml配置好）
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
例程：
Download.java
import mars.utils.HttpDownloader;
import android.annotation.SuppressLint;
import android.annotation.TargetApi;
import android.app.Activity;
import android.os.Build;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class Download extends Activity {
private Button downloadTxtButton;
private Button downloadMp3Button;
@TargetApi(Build.VERSION_CODES.GINGERBREAD)
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
downloadTxtButton = (Button)findViewById(R.id.downloadText);
downloadMp3Button = (Button)findViewById(R.id.downloadMp3);
downloadTxtButton.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
HttpDownloader httpDownloader = new HttpDownloader();
String lrc = httpDownloader.download("http://222.199.230.116:8080/mp3/Test-2.lrc");
System.out.println(lrc);
}
});
downloadMp3Button.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
HttpDownloader httpDownloader = new HttpDownloader();
int result = httpDownloader.downFile("http://222.199.230.116:8080/mp3/Test-2.mp3","voa/","Test.mp3");
System.out.println(result);
}
});
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().detectDiskReads().
detectDiskWrites().detectNetwork().penaltyLog().build());
}
}
注意：
在Android4.0以上的模拟器好像对联网下载文件好像有要求，所以在.java文件要配置：
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().detectDiskReads(). detectDiskWrites().detectNetwork().penaltyLog().build());
刚才没配置一直在报错不能下载
详情请看http://www.cnblogs.com/Lewis/p/3298994.html
FileUtils.java
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.mkdirs();
return dir;
}
/**
* 判断SD卡上的文件夹是否存在
*/
public boolean isFileExist(String fileName){
File file = new File(SDPATH + 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{
createSDDir(path);
file = createSDFile(path + fileName);
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;
}
}
HttpDownloader.java
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;
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(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;
}
}
结果示意图
刚开始下载不成功，一直输出-1，
后来百度、修改，终于输出0，下载成功，把程序调通~
时间： 2024-12-28 20:17:25