Android使用OKHttp3实现下载(断点续传、显示运行进度)

OKHttp3是现在很流行的Android网络请求框架,那么怎样利用Android实现断点续传呢,今天写了个Demo尝试了一下,感觉还是有点意思

准备阶段

我们会用到OKHttp3来做网络请求,使用RxJava来实现线程的切换,并且开启Java8来启用Lambda表达式,毕竟RxJava实现线程切换很方便,并且数据流的形式也很舒服,同一时候Lambda和RxJava配合食用味道更佳

打开我们的app Module下的build.gradle,代码例如以下

apply plugin: 'com.android.application'

android {
    compileSdkVersion 24
    buildToolsVersion "24.0.3"

    defaultConfig {
        applicationId "com.lanou3g.downdemo"
        minSdkVersion 15
        targetSdkVersion 24
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        //为了开启Java8
        jackOptions{
            enabled true;
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    //开启Java1.8 可以使用lambda表达式
    compileOptions{
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:24.1.1'
    testCompile 'junit:junit:4.12'

    //OKHttp
    compile 'com.squareup.okhttp3:okhttp:3.6.0'
    //RxJava和RxAndroid 用来做线程切换的
    compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
    compile 'io.reactivex.rxjava2:rxjava:2.0.1'
}

OKHttp和RxJava,RxAndroid使用的都是最新的版本号,而且配置开启了Java8

布局文件

接着開始书写布局文件

<?xml version="1.0" encoding="utf-8"?
>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="com.lanou3g.downdemo.MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <ProgressBar
            android:id="@+id/main_progress1"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="match_parent"
            style="@style/Widget.AppCompat.ProgressBar.Horizontal" />
        <Button
            android:id="@+id/main_btn_down1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="下载1"/>
        <Button
            android:id="@+id/main_btn_cancel1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="取消1"/>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <ProgressBar
            android:id="@+id/main_progress2"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="match_parent"
            style="@style/Widget.AppCompat.ProgressBar.Horizontal" />
        <Button
            android:id="@+id/main_btn_down2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="下载2"/>
        <Button
            android:id="@+id/main_btn_cancel2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="取消2"/>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <ProgressBar
            android:id="@+id/main_progress3"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="match_parent"
            style="@style/Widget.AppCompat.ProgressBar.Horizontal" />
        <Button
            android:id="@+id/main_btn_down3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="下载3"/>
        <Button
            android:id="@+id/main_btn_cancel3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="取消3"/>
    </LinearLayout>
</LinearLayout>

大概是这个样子的

3个ProgressBar就是为了显示运行进度的,每一个ProgressBar相应2个Button,一个是開始下载,一个是暂停(取消)下载,这里须要说明的是,对下载来说暂停和取消没有什么差别,除非当取消的时候,会顺带把暂时文件都删除了,在本例里是不区分他俩的.

Application

我们这里须要用到一些文件路径,有一个全局Context会比較方便, 而Application也是Context的子类,使用它的是最方便的,所以我们写一个类来继承Application

package com.lanou3g.downdemo;

import android.app.Application;
import android.content.Context;

/**
 * Created by 陈丰尧 on 2017/2/2.
 */

public class MyApp extends Application {
    public static Context sContext;//全局的Context对象

    @Override
    public void onCreate() {
        super.onCreate();
        sContext = this;
    }
}

能够看到,我们就是要获得一个全局的Context对象的

我们在AndroidManifest中注冊一下我们的Application,同一时候再把我们所须要的权限给上

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.lanou3g.downdemo">
    
    <!--网络权限-->
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:name=".MyApp"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

我们仅仅须要一个网络权限,在application标签下,加入name属性,来指向我们的Application

DownloadManager

接下来是核心代码了,就是我们的DownloadManager,先上代码

package com.lanou3g.downdemo;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.concurrent.atomic.AtomicReference;

import io.reactivex.Observable;
import io.reactivex.ObservableEmitter;
import io.reactivex.ObservableOnSubscribe;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.schedulers.Schedulers;
import okhttp3.Call;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

/**
 * Created by 陈丰尧 on 2017/2/2.
 */

public class DownloadManager {

    private static final AtomicReference<DownloadManager> INSTANCE = new AtomicReference<>();
    private HashMap<String, Call> downCalls;//用来存放各个下载的请求
    private OkHttpClient mClient;//OKHttpClient;

    //获得一个单例类
    public static DownloadManager getInstance() {
        for (; ; ) {
            DownloadManager current = INSTANCE.get();
            if (current != null) {
                return current;
            }
            current = new DownloadManager();
            if (INSTANCE.compareAndSet(null, current)) {
                return current;
            }
        }
    }

    private DownloadManager() {
        downCalls = new HashMap<>();
        mClient = new OkHttpClient.Builder().build();
    }

    /**
     * 開始下载
     *
     * @param url              下载请求的网址
     * @param downLoadObserver 用来回调的接口
     */
    public void download(String url, DownLoadObserver downLoadObserver) {
        Observable.just(url)
                .filter(s -> !downCalls.containsKey(s))//call的map已经有了,就证明正在下载,则这次不下载
                .flatMap(s -> Observable.just(createDownInfo(s)))
                .map(this::getRealFileName)//检測本地目录,生成新的文件名称
                .flatMap(downloadInfo -> Observable.create(new DownloadSubscribe(downloadInfo)))//下载
                .observeOn(AndroidSchedulers.mainThread())//在主线程回调
                .subscribeOn(Schedulers.io())//在子线程运行
                .subscribe(downLoadObserver);//加入观察者

    }

    public void cancel(String url) {
        Call call = downCalls.get(url);
        if (call != null) {
            call.cancel();//取消
        }
        downCalls.remove(url);
    }

    /**
     * 创建DownInfo
     *
     * @param url 请求网址
     * @return DownInfo
     */
    private DownloadInfo createDownInfo(String url) {
        DownloadInfo downloadInfo = new DownloadInfo(url);
        long contentLength = getContentLength(url);//获得文件大小
        downloadInfo.setTotal(contentLength);
        String fileName = url.substring(url.lastIndexOf("/"));
        downloadInfo.setFileName(fileName);
        return downloadInfo;
    }

    private DownloadInfo getRealFileName(DownloadInfo downloadInfo) {
        String fileName = downloadInfo.getFileName();
        long downloadLength = 0, contentLength = downloadInfo.getTotal();
        File file = new File(MyApp.sContext.getFilesDir(), fileName);
        if (file.exists()) {
            //找到了文件,代表已经下载过,则获取其长度
            downloadLength = file.length();
        }
        //之前下载过,须要又一次来一个文件
        int i = 1;
        while (downloadLength >= contentLength) {
            int dotIndex = fileName.lastIndexOf(".");
            String fileNameOther;
            if (dotIndex == -1) {
                fileNameOther = fileName + "(" + i + ")";
            } else {
                fileNameOther = fileName.substring(0, dotIndex)
                        + "(" + i + ")" + fileName.substring(dotIndex);
            }
            File newFile = new File(MyApp.sContext.getFilesDir(), fileNameOther);
            file = newFile;
            downloadLength = newFile.length();
            i++;
        }
        //设置改变过的文件名称/大小
        downloadInfo.setProgress(downloadLength);
        downloadInfo.setFileName(file.getName());
        return downloadInfo;
    }

    private class DownloadSubscribe implements ObservableOnSubscribe<DownloadInfo> {
        private DownloadInfo downloadInfo;

        public DownloadSubscribe(DownloadInfo downloadInfo) {
            this.downloadInfo = downloadInfo;
        }

        @Override
        public void subscribe(ObservableEmitter<DownloadInfo> e) throws Exception {
            String url = downloadInfo.getUrl();
            long downloadLength = downloadInfo.getProgress();//已经下载好的长度
            long contentLength = downloadInfo.getTotal();//文件的总长度
            //初始进度信息
            e.onNext(downloadInfo);

            Request request = new Request.Builder()
                    //确定下载的范围,加入此头,则服务器就能够跳过已经下载好的部分
                    .addHeader("RANGE", "bytes=" + downloadLength + "-" + contentLength)
                    .url(url)
                    .build();
            Call call = mClient.newCall(request);
            downCalls.put(url, call);//把这个加入到call里,方便取消
            Response response = call.execute();

            File file = new File(MyApp.sContext.getFilesDir(), downloadInfo.getFileName());
            InputStream is = null;
            FileOutputStream fileOutputStream = null;
            try {
                is = response.body().byteStream();
                fileOutputStream = new FileOutputStream(file, true);
                byte[] buffer = new byte[2048];//缓冲数组2kB
                int len;
                while ((len = is.read(buffer)) != -1) {
                    fileOutputStream.write(buffer, 0, len);
                    downloadLength += len;
                    downloadInfo.setProgress(downloadLength);
                    e.onNext(downloadInfo);
                }
                fileOutputStream.flush();
                downCalls.remove(url);
            } finally {
                //关闭IO流
                IOUtil.closeAll(is, fileOutputStream);

            }
            e.onComplete();//完毕
        }
    }

    /**
     * 获取下载长度
     *
     * @param downloadUrl
     * @return
     */
    private long getContentLength(String downloadUrl) {
        Request request = new Request.Builder()
                .url(downloadUrl)
                .build();
        try {
            Response response = mClient.newCall(request).execute();
            if (response != null && response.isSuccessful()) {
                long contentLength = response.body().contentLength();
                response.close();
                return contentLength == 0 ? DownloadInfo.TOTAL_ERROR : contentLength;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return DownloadInfo.TOTAL_ERROR;
    }


}

代码略微有点长,关键部位我都加了凝视了,我们挑关键地方看看

首先我们这个类是单例类,我们下载仅仅须要一个OKHttpClient就足够了,所以我们让构造方法私有,而单例类的获取实例方法就是这个getInstance();当然大家用别的方式实现单例也能够的,然后我们在构造方法里初始化我们的HttpClient,而且初始化一个HashMap,用来放全部的网络请求的,这样当我们取消下载的时候,就能够找到url相应的网络请求然后把它取消掉就能够了

接下来就是核心的download方法了,首先是參数,第一个參数url不用多说,就是请求的网址,第二个參数是一个Observer对象,由于我们使用的是RxJava,而且没有特别多复杂的方法,所以就没单独写接口,而是谢了一个Observer对象来作为回调,接下来是DownLoadObserver的代码

package com.lanou3g.downdemo;

import io.reactivex.Observer;
import io.reactivex.disposables.Disposable;

/**
 * Created by 陈丰尧 on 2017/2/2.
 */

public  abstract class DownLoadObserver implements Observer<DownloadInfo> {
    protected Disposable d;//能够用于取消注冊的监听者
    protected DownloadInfo downloadInfo;
    @Override
    public void onSubscribe(Disposable d) {
        this.d = d;
    }

    @Override
    public void onNext(DownloadInfo downloadInfo) {
        this.downloadInfo = downloadInfo;
    }

    @Override
    public void onError(Throwable e) {
        e.printStackTrace();
    }


}

在RxJava2中 这个Observer有点变化,当注冊观察者的时候,会调用onSubscribe方法,而该方法參数就是用来取消注冊的,这种修改能够更灵活的有监听者来取消监听了,我们的进度信息会一直的传送的onNext方法里,这里将下载所须要的内容封了一个类叫DownloadInfo

package com.lanou3g.downdemo;

/**
 * Created by 陈丰尧 on 2017/2/2.
 * 下载信息
 */

public class DownloadInfo {
    public static final long TOTAL_ERROR = -1;//获取进度失败
    private String url;
    private long total;
    private long progress;
    private String fileName;
    
    public DownloadInfo(String url) {
        this.url = url;
    }

    public String getUrl() {
        return url;
    }

    public String getFileName() {
        return fileName;
    }

    public void setFileName(String fileName) {
        this.fileName = fileName;
    }

    public long getTotal() {
        return total;
    }

    public void setTotal(long total) {
        this.total = total;
    }

    public long getProgress() {
        return progress;
    }

    public void setProgress(long progress) {
        this.progress = progress;
    }
}

这个类就是一些基本信息,total就是须要下载的文件的总大小,而progress就是当前下载的进度了,这样就能够计算出下载的进度信息了

接着看DownloadManager的download方法,首先通过url生成一个Observable对象,然后通过filter操作符过滤一下,假设当前正在下载这个url相应的内容,那么就不下载它,

接下来调用createDownInfo又一次生成Observable对象,这里应该用map也是能够的,createDownInfo这种方法里会调用getContentLength来获取server上的文件大小,能够看一下这种方法的代码,

 /**
     * 获取下载长度
     *
     * @param downloadUrl
     * @return
     */
    private long getContentLength(String downloadUrl) {
        Request request = new Request.Builder()
                .url(downloadUrl)
                .build();
        try {
            Response response = mClient.newCall(request).execute();
            if (response != null && response.isSuccessful()) {
                long contentLength = response.body().contentLength();
                response.close();
                return contentLength == 0 ? DownloadInfo.TOTAL_ERROR : contentLength;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return DownloadInfo.TOTAL_ERROR;
    }

能够看到,事实上就是在通过OK进行了一次网络请求,而且从返回的头信息里拿到文件的大小信息,一般这个信息都是能够拿到的,除非下载网址不是直接指向资源文件的,而是自己手写的Servlet,那就得跟后台人员沟通好了.注意,这次网络请求并没有真正的去下载文件,而是请求个大小就结束了,详细原因会在后面真正请求数据的时候解释

接着download方法

获取完文件大小后,就能够去硬盘里找文件了,这里调用了getRealFileName方法

private DownloadInfo getRealFileName(DownloadInfo downloadInfo) {
        String fileName = downloadInfo.getFileName();
        long downloadLength = 0, contentLength = downloadInfo.getTotal();
        File file = new File(MyApp.sContext.getFilesDir(), fileName);
        if (file.exists()) {
            //找到了文件,代表已经下载过,则获取其长度
            downloadLength = file.length();
        }
        //之前下载过,须要又一次来一个文件
        int i = 1;
        while (downloadLength >= contentLength) {
            int dotIndex = fileName.lastIndexOf(".");
            String fileNameOther;
            if (dotIndex == -1) {
                fileNameOther = fileName + "(" + i + ")";
            } else {
                fileNameOther = fileName.substring(0, dotIndex)
                        + "(" + i + ")" + fileName.substring(dotIndex);
            }
            File newFile = new File(MyApp.sContext.getFilesDir(), fileNameOther);
            file = newFile;
            downloadLength = newFile.length();
            i++;
        }
        //设置改变过的文件名称/大小
        downloadInfo.setProgress(downloadLength);
        downloadInfo.setFileName(file.getName());
        return downloadInfo;
    }

这种方法就是看本地是否有已经下载过的文件,假设有,再推断一次本地文件的大小和server上数据的大小,假设是一样的,证明之前下载全了,就再成一个带(1)这种文件,而假设本地文件大小比server上的小的话,那么证明之前下载了一半断掉了,那么就把进度信息保存上,并把文件名称也存上,看完了再回到download方法

之后就開始真正的网络请求了,这里写了一个内部类来实现ObservableOnSubscribe接口,这个接口也是RxJava2的,东西和之前一样,好像仅仅改了名字,看一下代码

private class DownloadSubscribe implements ObservableOnSubscribe<DownloadInfo> {
        private DownloadInfo downloadInfo;

        public DownloadSubscribe(DownloadInfo downloadInfo) {
            this.downloadInfo = downloadInfo;
        }

        @Override
        public void subscribe(ObservableEmitter<DownloadInfo> e) throws Exception {
            String url = downloadInfo.getUrl();
            long downloadLength = downloadInfo.getProgress();//已经下载好的长度
            long contentLength = downloadInfo.getTotal();//文件的总长度
            //初始进度信息
            e.onNext(downloadInfo);

            Request request = new Request.Builder()
                    //确定下载的范围,加入此头,则server就能够跳过已经下载好的部分
                    .addHeader("RANGE", "bytes=" + downloadLength + "-" + contentLength)
                    .url(url)
                    .build();
            Call call = mClient.newCall(request);
            downCalls.put(url, call);//把这个加入到call里,方便取消
            Response response = call.execute();

            File file = new File(MyApp.sContext.getFilesDir(), downloadInfo.getFileName());
            InputStream is = null;
            FileOutputStream fileOutputStream = null;
            try {
                is = response.body().byteStream();
                fileOutputStream = new FileOutputStream(file, true);
                byte[] buffer = new byte[2048];//缓冲数组2kB
                int len;
                while ((len = is.read(buffer)) != -1) {
                    fileOutputStream.write(buffer, 0, len);
                    downloadLength += len;
                    downloadInfo.setProgress(downloadLength);
                    e.onNext(downloadInfo);
                }
                fileOutputStream.flush();
                downCalls.remove(url);
            } finally {
                //关闭IO流
                IOUtil.closeAll(is, fileOutputStream);

            }
            e.onComplete();//完毕
        }
    }

主要看subscribe方法

首先拿到url,当前进度信息和文件的总大小,然后開始网络请求,注意这次网络请求的时候须要加入一条头信息

.addHeader("RANGE", "bytes=" + downloadLength + "-" + contentLength)

这条头信息的意思是下载的范围是多少,downloadLength是从哪開始下载,contentLength是下载到哪,当要断点续传的话必须加入这个头,让输入流跳过多少字节的形式是不行的,所以我们要想能成功的加入这条信息那么就必须对这个url请求2次,一次拿到总长度,来方便推断本地是否有下载一半的数据,第二次才開始真正的读流进行网络请求,我还想了一种思路,当文件没有下载完毕的时候加入一个自己定义的后缀,当下载完毕再把这个后缀取消了,应该就不须要请求两次了.

接下来就是正常的网络请求,向本地写文件了,而写文件到本地这,网上大多用的是RandomAccessFile这个类,可是假设不涉及到多个部分拼接的话是不是必需的,直接使用输出流就好了,在输出流的构造方法上加入一个true的參数,代表是在原文件的后面加入数据就可以,而在循环里,不断的调用onNext方法发送进度信息,当写完了之后别忘了关流,同一时候把call对象从hashMap中移除了.这里写了一个IOUtil来关流

package com.lanou3g.downdemo;

import java.io.Closeable;
import java.io.IOException;

/**
 * Created by 陈丰尧 on 2017/2/2.
 */

public class IOUtil {
    public static void closeAll(Closeable... closeables){
        if(closeables == null){
            return;
        }
        for (Closeable closeable : closeables) {
            if(closeable!=null){
                try {
                    closeable.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

事实上就是挨一个推断是否为空,并关闭罢了

这样download方法就完毕了,剩下的就是切换线程,注冊观察者了

MainActivity

最后是aty的代码

package com.lanou3g.downdemo;

import android.net.Uri;
import android.support.annotation.IdRes;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private Button downloadBtn1, downloadBtn2, downloadBtn3;
    private Button cancelBtn1, cancelBtn2, cancelBtn3;
    private ProgressBar progress1, progress2, progress3;
    private String url1 = "http://192.168.31.169:8080/out/dream.flac";
    private String url2 = "http://192.168.31.169:8080/out/music.mp3";
    private String url3 = "http://192.168.31.169:8080/out/code.zip";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        downloadBtn1 = bindView(R.id.main_btn_down1);
        downloadBtn2 = bindView(R.id.main_btn_down2);
        downloadBtn3 = bindView(R.id.main_btn_down3);

        cancelBtn1 = bindView(R.id.main_btn_cancel1);
        cancelBtn2 = bindView(R.id.main_btn_cancel2);
        cancelBtn3 = bindView(R.id.main_btn_cancel3);

        progress1 = bindView(R.id.main_progress1);
        progress2 = bindView(R.id.main_progress2);
        progress3 = bindView(R.id.main_progress3);

        downloadBtn1.setOnClickListener(this);
        downloadBtn2.setOnClickListener(this);
        downloadBtn3.setOnClickListener(this);

        cancelBtn1.setOnClickListener(this);
        cancelBtn2.setOnClickListener(this);
        cancelBtn3.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.main_btn_down1:
                DownloadManager.getInstance().download(url1, new DownLoadObserver() {
                    @Override
                    public void onNext(DownloadInfo value) {
                        super.onNext(value);
                        progress1.setMax((int) value.getTotal());
                        progress1.setProgress((int) value.getProgress());
                    }

                    @Override
                    public void onComplete() {
                        if(downloadInfo != null){
                            Toast.makeText(MainActivity.this,
                                    downloadInfo.getFileName() + "-DownloadComplete",
                                    Toast.LENGTH_SHORT).show();
                        }
                    }
                });
                break;
            case R.id.main_btn_down2:
                DownloadManager.getInstance().download(url2, new DownLoadObserver() {
                    @Override
                    public void onNext(DownloadInfo value) {
                        super.onNext(value);
                        progress2.setMax((int) value.getTotal());
                        progress2.setProgress((int) value.getProgress());
                    }

                    @Override
                    public void onComplete() {
                        if(downloadInfo != null){
                            Toast.makeText(MainActivity.this,
                                    downloadInfo.getFileName() + Uri.encode("下载完毕"),
                                    Toast.LENGTH_SHORT).show();
                        }
                    }
                });
                break;
            case R.id.main_btn_down3:
                DownloadManager.getInstance().download(url3, new DownLoadObserver() {
                    @Override
                    public void onNext(DownloadInfo value) {
                        super.onNext(value);
                        progress3.setMax((int) value.getTotal());
                        progress3.setProgress((int) value.getProgress());
                    }

                    @Override
                    public void onComplete() {
                        if(downloadInfo != null){
                            Toast.makeText(MainActivity.this,
                                    downloadInfo.getFileName() + "下载完毕",
                                    Toast.LENGTH_SHORT).show();
                        }
                    }
                });
                break;
            case R.id.main_btn_cancel1:
                DownloadManager.getInstance().cancel(url1);
                break;
            case R.id.main_btn_cancel2:
                DownloadManager.getInstance().cancel(url2);
                break;
            case R.id.main_btn_cancel3:
                DownloadManager.getInstance().cancel(url3);
                break;
        }
    }
    
    private <T extends View> T bindView(@IdRes int id){
        View viewById = findViewById(id);
        return (T) viewById;
    }
}

Activity里没什么了,就是注冊监听,開始下载,取消下载这些了,以下我们来看看效果吧

执行效果

能够看到 多个下载,断点续传什么的都已经成功了,最后我的文件网址是我自己的局域网,大家写的时候别忘了换了..

代码

http://download.csdn.net/detail/cfy137000/9746583