实现一个mp3文件下载功能，并展示进度

1.

首先是权限的声明

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.fanhy.f9_download"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.fanhy.f9_download.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>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
</manifest>

 

package com.fanhy.f9_download;

import android.os.Bundle;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
/**
 *     实现一个mp3文件下载功能，并展示进度
 * */
public class MainActivity extends Activity {
    ProgressDialog pd;
    ProgressHandler handler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        Button btn = (Button) findViewById(R.id.btn);
        
        
        btn.setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View v) {
                // 创建进度对话框对象
                createDialog();
                // 创建ProgressHandler对象
                handler = new ProgressHandler(pd,MainActivity.this);
                // 新起线程进行网络任务
                new Thread(new Runnable() {
                    
                    @Override
                    public void run() {
                        int result = new DownLoader(MainActivity.this,handler).downloadFile("http://yinyueshiting.baidu.com/data2/music/134369899/2927661428987661128.mp3?xcode=e5bea9662f165be741e9faede5f96daae6bd1fd285a802a4", "", "down.mp3");
                        Log.d("fanhy", "下载结果码："+result);
                    }
                }).start();
            }
        });
        
    }
    
    private void createDialog() {
        pd = new ProgressDialog(this);
        pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        pd.setMax(100);
        pd.setTitle("正在下载");
    }
    
    
}

2.

package com.fanhy.f9_download;

import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.content.Context;
import android.os.Message;
import android.util.Log;

public class DownLoader {
    private URL url = null;
    Context context;
    ProgressHandler handler;

    public DownLoader(Context context, ProgressHandler handler) {
        super();
        this.context = context;
        this.handler = handler;
    }

    // 从输入流读取数据，用输出流写入手机存储
    public int downloadFile(String urlStr, String path, String name) {
        InputStream input = null;
        try {
            url = new URL(urlStr);
            // 打开链接
            HttpURLConnection httpc = (HttpURLConnection) url.openConnection();
            // 以GET方式请求数据
            httpc.setRequestMethod("GET");
            // 设置网络超时连接时间为5秒
            httpc.setConnectTimeout(5 * 1000);
            // 连接
            httpc.connect();
            if(httpc.getResponseCode() == HttpURLConnection.HTTP_OK){
                // 得到网络输入流
                input = httpc.getInputStream();
                
                // 下载前获取文件大小
                int fileSize = httpc.getContentLength();
                Log.d("fanhy", "文件大小为："+fileSize);
                
                // 得到文件输出流
                FileOutputStream fos = context.openFileOutput(path + name,
                        Context.MODE_PRIVATE);
                int len = 0;
                byte[] buf = new byte[128];
                
                // 假设最大进度为100，每次读写128字节，已得到文件大小，计算循环几次进度加1
                int count = fileSize/128/100;
                int progress = 0;
                int num = 0;
                // 循环读写
                while ((len = input.read(buf)) > 0) {
                    
                    num++;
                    // 每循环count次，进度加1，并发出消息让handler更新进度
                    if(num == count){
                        progress++;
                        Message msg = Message.obtain();
                        msg.arg1 = progress;
                        handler.sendMessage(msg);
                        num = 0;
                    }
                    fos.write(buf, 0, len);
                }
            } else{
                // 返回码不为HTTP_OK则抛出异常，下载失败
                new RuntimeException("下载失败！");
            }
        } catch (Exception e) {
            //e.printStackTrace();
            return -1;    // 数据异常则返回-1
        }
        return 0; // 数据正常的时候返回0
    }
}

3.

package com.fanhy.f9_download;

import android.app.ProgressDialog;
import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.widget.Toast;

public class ProgressHandler extends Handler {
    ProgressDialog dialog;
    Context context;

    public ProgressHandler(ProgressDialog dialog, Context context) {
        super();
        this.dialog = dialog;
        this.context = context;
    }

    @Override
    public void handleMessage(Message msg) {
        // TODO Auto-generated method stub
        super.handleMessage(msg);

        int progress = msg.arg1;
        // 进度为1时展示对话框
        if (progress == 1) {
            dialog.show();
        }
        // 更新进度条对话框
        dialog.setProgress(progress);

        // 进度为100时弹提示，并取消对话框
        if (progress == 100) {
            dialog.dismiss();
            Toast.makeText(context, "文件已下载完毕", Toast.LENGTH_SHORT).show();
        }
    }
}