使用OkHttp的那些事儿(三)

2019-11-07 23:48:28

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本篇主要介绍文件的断点续传下载。原文来自:http://blog.csdn.net/KevinsCSDN/article/details/51934274

1.Gradle引入依赖:

compile 'com.squareup.okhttp3:okhttp:3.6.0' compile 'io.reactivex:rxjava:1.1.6' compile 'io.reactivex:rxandroid:1.2.1'

2.定义能够实现PRogress进度条显示功能的ResponseBody:

/** * Created by BeautifulSoup on 2017/2/24. */public class DownLoadResponse extends ResponseBody { private final ResponseBody responseBody; private final UpdateProgressListener progressListener; private BufferedSource bufferedSource; public DownLoadResponse (ResponseBody responseBody,UpdateProgressListener progressListener) { this.responseBody = responseBody; this.progressListener = progressListener; if(progressListener!=null){ progressListener.onPreExecute(contentLength()); } } @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; } public interface UpdateProgressListener { void onPreExecute(long contentLength); void update(long totalBytes, boolean done); } private Source source(Source source) { return new ForwardingSource(source) { long totalBytes = 0L; @Override public long read(Buffer sink, long byteCount) throws IOException { long bytesRead = super.read(sink, byteCount); totalBytes += bytesRead != -1 ? bytesRead : 0; if (null != progressListener) { progressListener.update(totalBytes, bytesRead == -1); } return bytesRead; } }; }}

3.定义带有进度响应的工具类:

public static final String TAG = "ProgressDownloader"; private ProgressListener progressListener; private String url; private OkHttpClient client; private File destination; private Call call; public ProgressDownloader(String url, File destination, ProgressListener progressListener) { this.url = url; this.destination = destination; this.progressListener = progressListener; //在下载、暂停后的继续下载中可复用同一个client对象 client = getProgressClient(); } //每次下载需要新建新的Call对象 private Call newCall(long startPoints) { Request request = new Request.Builder() .url(url) .header("RANGE", "bytes=" + startPoints + "-")//断点续传要用到的，指示下载的区间 .build(); return client.newCall(request); } public OkHttpClient getProgressClient() { // 拦截器，用上ProgressResponseBody Interceptor interceptor = new Interceptor() { @Override public Response intercept(Chain chain) throws IOException { Response originalResponse = chain.proceed(chain.request()); return originalResponse.newBuilder() .body(new ProgressResponseBody(originalResponse.body(), progressListener)) .build(); } }; return new OkHttpClient.Builder() .addNetworkInterceptor(interceptor) .build(); }// startsPoint指定开始下载的点 public void download(final long startsPoint) { call = newCall(startsPoint); call.enqueue(new Callback() { @Override public void onFailure(Call call, IOException e) { } @Override public void onResponse(Call call, Response response) throws IOException { save(response, startsPoint); } }); } public void pause() { if(call!=null){ call.cancel(); } } private void save(Response response, long startsPoint) { ResponseBody body = response.body(); InputStream in = body.byteStream(); FileChannel channelOut = null; // 随机访问文件，可以指定断点续传的起始位置 Random accessFile randomAccessFile = null; try { randomAccessFile = new RandomAccessFile(destination, "rwd"); //Chanel NIO中的用法，由于RandomAccessFile没有使用缓存策略，直接使用会使得下载速度变慢，亲测缓存下载3.3秒的文件，用普通的RandomAccessFile需要20多秒。 channelOut = randomAccessFile.getChannel(); // 内存映射，直接使用RandomAccessFile，是用其seek方法指定下载的起始位置，使用缓存下载，在这里指定下载位置。 MappedByteBuffer mappedBuffer = channelOut.map(FileChannel.MapMode.READ_WRITE, startsPoint, body.contentLength()); byte[] buffer = new byte[1024]; int len; while ((len = in.read(buffer)) != -1) { mappedBuffer.put(buffer, 0, len); } } catch (IOException e) { e.printStackTrace(); }finally { try { in.close(); if (channelOut != null) { channelOut.close(); } if (randomAccessFile != null) { randomAccessFile.close(); } } catch (IOException e) { e.printStackTrace(); } } }}

4.测试代码:

private File file; private long totalBytes; private long contentLength; private long breakPoints; private ProgressDownLoader downloader; public static final String PACKAGE_URL = "http://10.0.2.2:8088/filedownload/download.txt"; private ProgressBar progressBar; public void downLoadFile(View view){ // 新下载前清空断点信息 breakPoints = 0L; file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "aaaa.txt"); downloader = new ProgressDownLoader(PACKAGE_URL, file, this); downloader.download(0L); } public void downPauseFile(View view){ downloader.pause(); Toast.makeText(this, "下载暂停", Toast.LENGTH_SHORT).show(); // 存储此时的totalBytes，即断点位置。 breakPoints = totalBytes; } public void CountinueDownLoadFile(View view){ downloader.download(breakPoints); } @Override public void onPreExecute(long contentLength) { // 文件总长只需记录一次，要注意断点续传后的contentLength只是剩余部分的长度 if (this.contentLength == 0L) { this.contentLength = contentLength; progressBar.setMax((int) (contentLength / 1024)); } } @Override public void update(long totalBytes, boolean done) { // 注意加上断点的长度 this.totalBytes = totalBytes + breakPoints; progressBar.setProgress((int) (totalBytes + breakPoints) / 1024); if (done) { // 切换到主线程 Observable .empty() .observeOn(AndroidSchedulers.mainThread()) .doOnCompleted(new Action0() { @Override public void call() { Toast.makeText(MainActivity.this, "下载完成", Toast.LENGTH_SHORT).show(); } }) .subscribe(); } }

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