上一篇博客中介绍了基于Ok+Rxjava实现断点续传下载，这一篇给大家介绍下基于Ok+Rxjava+Retrofit实现断点续传下载，demo下载地址，效果图跟上一篇图片一样，哈哈
说下我的大致思路吧（跟上一篇略有不同）:根据文件下载url按照自己定义的规则生成文件名，判断本地同路径下是否存在此文件，如果存在，文件大小与服务器上获取的文件大小一致的情况下，则覆盖本地文件重新下载；如果文件比服务器获取的文件大小小，则执行断点下载，从本地文件长度处开始下载。如果文件不存在，则从0字节开始下载。
还有的不同是，这里需要重新ResponseBody的source()方法，在这里监听文件下载的进度，然后通过我么自定义的Downloadinterceptor把我们重新的DownloadResponseBody给设置进去，从而完成我们的进度监听工作。
下面还是上主要代码：
首先重写ResponseBody
public class DownloadResponseBody extends ResponseBody {
private ResponseBody responseBody;
//进度回调接口
private DownFileCallback downFileCallback;
private BufferedSource bufferedSource;
private String downUrl;
public DownloadResponseBody(ResponseBody responseBody, DownFileCallback downFileCallback, String downUrl) {
this.responseBody = responseBody;
this.downFileCallback = downFileCallback;
this.downUrl = downUrl;
}
@Override
public MediaType contentType() {
return responseBody.contentType();
}
@Override
public long contentLength() {
return responseBody.contentLength();
}
@Override
public BufferedSource source() {
if (bufferedSource == null) {
bufferedSource = Okio.buffer(source(responseBody.source()));
}
return bufferedSource;
}
private Source source(Source source) {
return new ForwardingSource(source) {
long totalBytesRead = 0L;
File file = new File(DownloadManager.getInstance().getTemporaryName(downUrl));
@Override
public long read(Buffer sink, long byteCount) throws IOException {
long bytesRead = super.read(sink, byteCount);
totalBytesRead += bytesRead != -1 ? bytesRead : 0;
if (null != downFileCallback) {
if (bytesRead != -1) {
long loacalSize = file.length();//本地已下载的长度
long trueTotal = loacalSize + responseBody.contentLength() - totalBytesRead;//文件真实长度
downFileCallback.onProgress(trueTotal,loacalSize);
} else {
}
}
return bytesRead;
}
};
}
}
重写Interceptor
public class Downloadinterceptor implements Interceptor {
private DownFileCallback downFileCallback;
private String downUrl;
public Downloadinterceptor(DownFileCallback listener,String downUrl) {
this.downFileCallback = listener;
this.downUrl = downUrl;
}
@Override
public Response intercept(Chain chain) throws IOException {
Response response = chain.proceed(chain.request());
return response.newBuilder()
.body(new DownloadResponseBody(response.body(), downFileCallback,downUrl))
.build();
}
}
然后我们的service
public interface HttpService {
/*大文件需要加入Streaming这个判断，防止下载过程中写入到内存中,造成oom*/
@Streaming
@GET
Observable<ResponseBody> download(@Header("range") String start, @Url String url);
}
接下来我们的DownloadManager中download方法
/**
* 开始下载
* @param url 下载地址
* @param downFileCallback 进度回调接口
*/
public void download(final String url, final DownFileCallback downFileCallback) {
/*正在下载不处理*/
if (url == null || submap.get(url) != null) {
return;
}
Downloadinterceptor interceptor = new Downloadinterceptor(downFileCallback, url);
okHttpClient = new OkHttpClient.Builder()
.addInterceptor(interceptor)
.build();
Retrofit retrofit = new Retrofit.Builder()
.client(okHttpClient)
.baseUrl("http://imtt.dd.qq.com")
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
.build();
final HttpService httpservice = retrofit.create(HttpService.class);
ProgressDownSubscriber subscriber =
Observable.just(url)
.flatMap(new Function<String, ObservableSource<DownloadInfo>>() {
@Override
public ObservableSource<DownloadInfo> apply(String s) throws Exception {
return Observable.just(createDownInfo(s));
}
})
.map(new Function<DownloadInfo, DownloadInfo>() {
@Override
public DownloadInfo apply(DownloadInfo s) throws Exception {
return getRealFileName(s);
}
})
.flatMap(new Function<DownloadInfo, Observable<ResponseBody>>() {
@Override
public Observable<ResponseBody> apply(DownloadInfo downInfo) throws Exception {
return httpservice.download("bytes=" + downInfo.getProgress() + "-", downInfo.getUrl());
}
})//下载
.map(new Function<ResponseBody, DownloadInfo>() {
@Override
public DownloadInfo apply(ResponseBody responsebody) {
try {
return writecache(responsebody, url);
} catch (IOException e) {
//*失败抛出异常*//
e.printStackTrace();
}
return null;
}
})
.observeOn(AndroidSchedulers.mainThread())//在主线程回调
.subscribeOn(Schedulers.io())//在子线程执行
.subscribeWith(new ProgressDownSubscriber<DownloadInfo>() {
@Override
public void onNext(DownloadInfo downInfo) {
downFileCallback.onSuccess(downInfo);
submap.remove(downInfo.getUrl());
}
@Override
public void onError(Throwable t) {
downFileCallback.onFail(t.getMessage());
submap.remove(url);
}
});
submap.put(url, subscriber);
}
然后暂停操作：
/**
* 暂停下载
*/
public void stop(String url) {
if (url == null) return;
if (submap.containsKey(url)) {
ProgressDownSubscriber subscriber = submap.get(url);
subscriber.dispose();
submap.remove(url);
}
}
从服务器获取文件长度
/**
* 从服务器获取文件长度
*
* @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;
}
从服务器获取文件长度的时候注意一下，Android P之后，也就是api 28以上禁止明文网络传输。需要在你的AndroidManifest中的application标签中声明"android:usesCleartextTraffic="true",允许应用进行明文传输。
使用方法：首先要获取sd卡权限
DownloadManager.getInstance().downloadPath(本地存放地址).download(url1, new DownFileCallback() {
@Override
public void onSuccess(DownloadInfo info) {
Toast.makeText(MainActivity.this, url1 + "下载完成", Toast.LENGTH_SHORT).show();
}
@Override
public void onFail(String msg) {
Toast.makeText(MainActivity.this, url1 + "下载失败", Toast.LENGTH_SHORT).show();
}
@Override
public void onProgress(final long totalSize, final long downSize) {
// 需要注意的是，如果文件总大小为50M，已下载的大小为10M，
// 再次下载时onProgress返回的totalSize是文件总长度
// 减去 已下载大小 10M， 即40M，downSize为本次下载的已下载量
// 好消息是，我已经在内部做过处理，放心使用吧，但是这个问题大家还是要知道的
runOnUiThread(new Runnable() {
@Override
public void run() {
int progress = (int) (downSize * 100 / totalSize);
progress1.setProgress(progress);
}
});
}
});
好了今天就到这里，希望能帮到大家，这对我来说也是一种加深印象的笔记。
github地址：DownManager 欢迎star
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。