android开发之下载文本、音乐文件

今天和大家分享一下在android上怎么下载文件到手机上。

主要有两点大类容：

一，通过Http协议下载文件。

创建一个HttpURLConnection对象

HttpURLConnection urlConn = (HttpURLConnection) url     .openConnection();

获得一个InputStream对象

inputStream = urlConn.getInputStream();

访问网络的权限

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

二，将下载的文件写入SDcard。

得到当前设备的SD卡目录

Environment.getExternalStorageDirectory()

设置访问SD卡的权限

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

下面给出具体的代码：

DownLoad.java

import android.app.Activity;import android.os.Bundle;import android.util.HttpDownloader;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class DownLoad extends Activity {private Button textButton;private Button audioButton;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);//文本下载textButton = (Button) findViewById(R.id.textButton);textButton.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {HttpDownloader http = new HttpDownloader();//注意这里不要用localhost或者127.0.0.1，会报错的，因为android里是10.0.2.2String txt = http.download("http://10.0.2.2:8080/examples/123123.txt");System.out.println(txt);}});//音频下载audioButton = (Button) findViewById(R.id.audioButton);audioButton.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {HttpDownloader http = new HttpDownloader();String result = http.download("http://10.0.2.2:8080/examples/123.mp3", "/music","zhou.mp3");System.out.println(result);}});}}

FileUtil.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 FileUtil {private String SDCARDPATH;public String getSDCARDPATH() {return SDCARDPATH;}public FileUtil() {// 得到手机存储器目录---因为各个厂商的手机SDcard可能不一样，最好不要写死了SDCARDPATH = Environment.getExternalStorageDirectory() + "/";}/** * 在SDcard上创建文件 *  * @param fileName * @return File */public File creatSDFile(String fileName) {File file = new File(SDCARDPATH + fileName);return file;}/** * 在SDcard上创建目录 *  * @param dirName */public void createSDDir(String dirName) {File file = new File(SDCARDPATH + dirName);file.mkdir();}/** * 判断文件是否存在 *  * @param fileName * @return boolean */public boolean isFileExist(String fileName) {File file = new File(SDCARDPATH + fileName);return file.exists();}/** * @param path *            存放目录 * @param fileName *            文件名字 * @param input *            数据来源 * @return */public File writeToSDCard(String path, String fileName, InputStream input) {File file = null;OutputStream output = null;try {//创建路径createSDDir(path);//创建文件file = creatSDFile(path + fileName);output = new FileOutputStream(file);//以4K为单位，每次写4kbyte buffer[] = new byte[4 * 1024];while ((input.read(buffer)) != -1) {output.write(buffer);}// 清除缓存output.flush();} catch (IOException e) {e.printStackTrace();} finally {try {// 关闭流output.close();} catch (IOException 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;/** * 下载文本文件 *  * @param urlStr * @return */public String download(String urlStr) {StringBuffer sb = new StringBuffer();String line = null;BufferedReader buffer = null;try {buffer = new BufferedReader(new InputStreamReader(getInputStreamFromUrl(urlStr)));//一行一行的读取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 *            文件所在的网络地址 * @param path *            存储的目录 * @param fileName *            存放的文件名 * @return 状态 */public String download(String urlStr, String path, String fileName) {InputStream inputStream = null;try {FileUtil fileUtils = new FileUtil();//判断文件是否已存在if (fileUtils.isFileExist(path + fileName)) {return "fileExist";} else {inputStream = getInputStreamFromUrl(urlStr);File resultFile = fileUtils.writeToSDCard(path, fileName,inputStream);//如果resultFile==null则下载失败if (resultFile == null) {return "downloadError";}}} catch (Exception e) {//如果异常了，也下载失败e.printStackTrace();return "downloadError";} finally {try {//别忘了关闭流inputStream.close();} catch (IOException e) {e.printStackTrace();}}return "downloadOk";}/** * 连接到网络（ 抽取的公共方法） *  * @param urlStr *            文件所在的网络地址 * @return InputStream */public InputStream getInputStreamFromUrl(String urlStr) {InputStream inputStream = null;try {// 创建一个URL对象url = new URL(urlStr);// 根据URL对象创建一个HttpURLConnection连接HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();// IO流读取数据inputStream = urlConn.getInputStream();} catch (MalformedURLException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}return inputStream;}}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"      package="android.apps"      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>    <!-- 连接到网络的权限 -->    <uses-permission android:name="android.permission.INTERNET"/>    <!-- 访问SDcard的权限 -->    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/></manifest>

希望对大家有帮助。

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