想把文件保存到SD卡中，一定要知道SD卡的路径，获取SD卡路径：
Environment.getExternalStorageDirectory()
另外，在保存之前要判断SD卡是否已经安装好，并且可读写：
//判断SDcard是否存在并且可读写
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
service.saveToSDCard(filename,filecontent);
Toast.makeText(getApplicationContext(), R.string.success, 1).show();
}else{
Toast.makeText(getApplicationContext(), R.string.sdcarderror, 1).show();
}
实例
1. 下载存文本文件和下载如mp3等大容量的文件
2.代码编写
AndroidMainfest.xml中配置
主要是解决网络权限和写SDCard的权限
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.jingling.practice.downloadtest" > <uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" > <activity
android:name=".MainActivity"
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> </manifest>
HttpDownloader.java
package util; import android.util.Log; 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.URL; /**
* Created by Spring on 2015/11/7.
* 下载工具类
*/
public class HttpDownloader {
private URL url = null;
private final String TAG = "TAG"; /**
* 读取文本文件
* @param urlStr url路径
* @return 文本信息
* 根据url下载文件，前提是这个文件中的内容是文本，
* 1.创建一个URL对象
* 2.通过URL对象，创建一个Http连接
* 3.得到InputStream
* 4.从InputStream中得到数据
*/
public String download(String urlStr) {
StringBuffer sb = new StringBuffer();
String line = null;
BufferedReader bufferedReader = null; try {
url = new URL(urlStr);
//创建http连接
HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
//使用IO流读取数据
bufferedReader = new BufferedReader(new InputStreamReader(urlConn.getInputStream()));
while ((line = bufferedReader.readLine()) != null) {
sb.append(line);
}
} catch (IOException e) {
e.printStackTrace();
}
finally {
try {
bufferedReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Log.e("TAG","下载txt文件");
Log.e("TAG",sb.toString());
return sb.toString();
} /**
* 读取任何文件
* 返回-1 ，代表下载失败。返回0，代表成功。返回1代表文件已经存在
*
* @param urlStr
* @param path
* @param fileName
* @return
*/
public int downlaodFile(String urlStr, String path, String fileName) {
InputStream input = null; try {
FileUtil fileUtil = new FileUtil();
if (fileUtil.isFileExist(path + fileName)) {
return 1;
} else {
input = getInputStearmFormUrl(urlStr);
File resultFile = fileUtil.write2SDFromInput(path,fileName,input);
if (resultFile == null)
return -1;
}
} catch (IOException e) {
e.printStackTrace();
return -1;
}
finally {
try {
input.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return 0;
} public InputStream getInputStearmFormUrl(String urlStr) throws IOException {
url = new URL(urlStr);
HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
InputStream input = urlConn.getInputStream();
return input;
}
}
FileUtil.java
package util; import android.os.Environment; import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream; /**
* Created by Spring on 2015/11/7.
*/
public class FileUtil {
private String SDPATH; public FileUtil() { } public String getSDPATH() {
return SDPATH;
} public FileUtil(String SDPATH){
//得到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 java.io.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 目录名字
* @return 文件目录
*/
public File createDir(String dirName){
File dir = new File(SDPATH + dirName);
dir.mkdir();
return dir;
} /**
* 判断文件是否存在
* @param fileName
* @return
*/
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 {
createDir(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 (IOException e) {
e.printStackTrace();
}
finally {
try {
output.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return file;
}
}
3.MainActivity
package com.jingling.practice.downloadtest; import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button; import util.HttpDownloader; public class MainActivity extends Activity {
HttpDownloader downloader ; private Button btn_downFile;
private Button btn_downMP3; @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn_downFile = (Button)this.findViewById(R.id.button);
btn_downMP3 = (Button)this.findViewById(R.id.button2);
btn_downFile.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
downloader = new HttpDownloader();
String urlStr = "http://172.17.54.91:8080/download/down.txt";
downloader.download(urlStr);
}
});
btn_downMP3.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String urlStr="http://172.17.54.91:8080/download/1.mp3";
String path="file";
String fileName="2.mp3";
HttpDownloader httpDownloader = new HttpDownloader();
httpDownloader.downlaodFile(urlStr,path,fileName);
}
});
} }