Android 下载文件及写入SD卡

Android 下载文件及写入SD卡,实例代码

Main.xml代码


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<Button
android:id="@+id/downloadTxt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="下载文本文件"
/>

<Button
android:id="@+id/downloadMp3"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="下载MP3文件"
/>
</LinearLayout>

Androidmanifest.xml代码


<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.learning.example"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".Download"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

</application>
<uses-sdk android:minSdkVersion="8" />

<!-- 访问网络和操作SD卡 加入的两个权限配置-->
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
</manifest>

下载助手类httpdownloader 代码


package com.learning.example.util;

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本当中的内容
* 1.创建一个URL对象
* 2.通过URL对象,创建一个HttpURLConnection对象
* 3.得到InputStream
* 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 {
url = new URL(urlStr);

HttpURLConnection urlConn = (HttpURLConnection)url.openConnection();
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 (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}

/**
*
* @param urlStr
* @param path
* @param fileName
* @return
* -1:文件下载出错
* 0:文件下载成功
* 1: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 (IOException e) {
e.printStackTrace();
}
}
return 0;
}

/**
* 根据URL得到输入流
* @param urlStr
* @return
*/
public InputStream getInputStreamFromURL(String urlStr) {
HttpURLConnection urlConn = null;
InputStream inputStream = null;
try {
url = new URL(urlStr);
urlConn = (HttpURLConnection)url.openConnection();
inputStream = urlConn.getInputStream();

} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

return inputStream;
}
}

文件操作类fileutils 代码


package com.learning.example.util;

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;

private int FILESIZE = 4 * 1024;

public String getSDPATH(){
return SDPATH;
}

public FileUtils(){
//得到当前外部存储设备的目录( /SDCARD )
SDPATH = Environment.getExternalStorageDirectory() + "/";
}

/**
* 在SD卡上创建文件
* @param fileName
* @return
* @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
* @return
*/
public File createSDDir(String dirName){
File dir = new File(SDPATH + dirName);
dir.mkdir();
return dir;
}

/**
* 判断SD卡上的文件夹是否存在
* @param fileName
* @return
*/
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
* @param path
* @param fileName
* @param input
* @return
*/
public File write2SDFromInput(String path,String fileName,InputStream input){
File file = null;
OutputStream output = null;
try {
createSDDir(path);

int count = 0 ;

file = createSDFile(path + fileName);
output = new FileOutputStream(file);
byte[] buffer = new byte[FILESIZE];
while((count=input.read(buffer)) != -1){
output.write(buffer,0,count);
}
output.flush();
}
catch (Exception e) {
e.printStackTrace();
}
finally{
try {
output.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return file;
}

}

主程序类download 代码


package com.learning.example;

import com.learning.example.util.HttpDownloader;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class Download extends Activity {
private Button downlaodTxtButton ;
private Button downlaodMP3Button ;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
downlaodTxtButton = (Button)findViewById(R.id.downloadTxt);
downlaodTxtButton.setOnClickListener(new DownloadTxtListener());

downlaodMP3Button = (Button)findViewById(R.id.downloadMp3);
downlaodMP3Button.setOnClickListener(new DownloadMP3Listener());
}

class DownloadTxtListener implements OnClickListener{

@Override
public void onClick(View v) {
HttpDownloader downloader = new HttpDownloader();
String lrc = downloader.download("http://172.16.11.9:8080/test/1.lrc");
System.out.println(lrc);
}

}

class DownloadMP3Listener implements OnClickListener{

@Override
public void onClick(View v) {
HttpDownloader downloader = new HttpDownloader();
int result = downloader.downFile("http://172.16.11.9:8080/test/1.mp3", "voa/", "1.map3");
System.out.println(result);
}

}
}

Notice:访问网络和操作SD卡 记得加入的两个权限配置

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

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