Android使用OKHttp3实现下载(断点续传、显示进度).doc

Android使用OKHttp3实现下载(断点续传、显示进度)OKHttp3是如今非常流行的Android网络请求框架,那么如何利用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实现线程切换非常方便,而且数据流的形式也非常舒服,同时Lambda和RxJava配合食用味道更佳打开我们的app Module下的build.gradle,代码如下plain view plain copy 在CODE上查看代码片派生到我的代码片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), /开启Java1.8 能够使用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,并且配置开启了Java8布局文件接着开始书写布局文件html view plain copy 在CODE上查看代码片派生到我的代码片 大概是这个样子的3个ProgressBar就是为了显示进度的,每个ProgressBar对应2个Button,一个是开始下载,一个是暂停(取消)下载,这里需要说明的是,对下载来说暂停和取消没有什么区别,除非当取消的时候,会顺带把临时文件都删除了,在本例里是不区分他俩的.Application我们这里需要用到一些文件路径,有一个全局Context会比较方便, 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Applicationjava view plain copy 在CODE上查看代码片派生到我的代码片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; 可以看到,我们就是要获得一个全局的Context对象的我们在AndroidManifest中注册一下我们的Application,同时再把我们所需要的权限给上html view plain copy 在CODE上查看代码片派生到我的代码片 我们只需要一个网络权限,在application标签下,添加name属性,来指向我们的ApplicationDownloadManager接下来是核心代码了,就是我们的DownloadManager,先上代码java view plain copy 在CODE上查看代码片派生到我的代码片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 INSTANCE = new AtomicReference(); private HashMap 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(); /* * 开始下载 * * 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)/检测本地文件夹,生成新的文件名 .flatMap(downloadInfo - Observable.create(new DownloadSubscribe(downloadInfo)/下载 .observeOn(AndroidSchedulers.mainThread()/在主线程回调 .subscribeOn(Schedulers.io()/在子线程执行 .subscribe(downLoadObserver);/添加观察者 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,需要重新来一个文件 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/大小 downloadInfo.setProgress(downloadLength); downloadInfo.setFileName(file.getName(); return downloadInfo; private class DownloadSubscribe implements ObservableOnSubscribe private DownloadInfo downloadInfo; public DownloadSubscribe(DownloadInfo downloadInfo) this.downloadInfo = downloadInfo; Override public void subscribe(ObservableEmitter 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,添加此头,则服务器就可以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);/把这个添加到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 byte2048;/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();/完成 /* * 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; 代码稍微有点长,关键部位我都加了注释了,我们挑关键地方看看首先我们这个类是单例类,我们下载只需要一个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可以的,然后我们在构造方法里初始化我们的HttpClient,并且初始化一个HashMap,用来放所有的网络请求的,这样当我们取消下载的时候,就可以找到url对应的网络请求然后把它取消掉就可以了接下来就是核心的download方法了,首先是参数,第一个参数url不用多说,就是请求的网址,第二个参数是一个Observer对象,因为我们使用的是RxJava,并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java view plain copy 在CODE上查看代码片派生到我的代码片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 protected Disposable d;/可以用于取消注册的监听者 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,当注册观察者的时候,会调用onSubscribe方法,而该方法参数就是用来取消注册的,这样的改动可以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,这里将下载所需要的内容封了一个类叫DownloadInfojava view plain copy 在CODE上查看代码片派生到我的代码片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) gress = progress; 这个类就是一些基本信息,total就是需要下载的文件的总大小,而progress就是当前下载的进度了,这样就可以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,如果当前正在下载这个url对应的内容,那么就不下载它,接下来调用createDownInfo重新生成Observable对象,这里应该用map也是可以的,createDownInfo这个方法里会调用getContentLength来获取服务器上的文件大小,可以看一下这个方法的代码,java view plain copy 在CODE上查看代码片派生到我的代码片/* * 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; 可以看到,其实就是在通过OK进行了一次网络请求,并且从返回的头信息里拿到文件的大小信息,一般这个信息都是可以拿到的,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,具体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,就可以去硬盘里找文件了,这里调用了getRealFileName方法java view plain copy 在CODE上查看代码片派生到我的代码片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,需要重新来一个文件 int i = 1; while (downloadLength = contentLength) int dotIndex = fileName.lastIndexOf(.); String fileNameOther; if (dotIndex = -1) fileNameOther = fileName + ( + i + ); else fileNameOther = fileName.subst