1. 导入依赖包
// retrofit, 基于Okhttp，考虑到项目中经常会用到retrofit，就导入这个了。 compile 'com.squareup.retrofit2:retrofit:2.1.0' // ButterKnife compile 'com.jakewharton:butterknife:7.0.1' // rxjava 本例中线程切换要用到，代替handler compile 'io.reactivex:rxjava:1.1.6' compile 'io.reactivex:rxandroid:1.2.1'
2. 继承ResponseBody，生成带进度监听的ProgressResponseBody
// 参考okhttp的官方demo，此类当中我们主要把注意力放在ProgressListener和read方法中。在这里获取文件总长我写在了构造方法里，这样免得在source的read方法中重复调用或判断。读者也可以根据个人需要定制自己的监听器。 public class ProgressResponseBody extends ResponseBody { public interface ProgressListener { void onPreExecute(long contentLength); void update(long totalBytes, boolean done); } private final ResponseBody responseBody; private final ProgressListener progressListener; private BufferedSource bufferedSource; public ProgressResponseBody(ResponseBody responseBody, ProgressListener 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; } 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); // read() returns the number of bytes read, or -1 if this source is exhausted. totalBytes += bytesRead != -1 ? bytesRead : 0; if (null != progressListener) { progressListener.update(totalBytes, bytesRead == -1); } return bytesRead; } }; } }
3.创建ProgressDownloader
//带进度监听功能的辅助类 public class ProgressDownloader { 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 RandomAccessFile 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demo
清单文件中添加网络权限和文件访问权限
<uses-permission android:name="android.permission.INTERNET"/> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
MainActivity
public class MainActivity extends AppCompatActivity implements ProgressResponseBody.ProgressListener { public static final String TAG = "MainActivity"; public static final String PACKAGE_URL = "http://gdown.baidu.com/data/wisegame/df65a597122796a4/weixin_821.apk"; @Bind(R.id.progressBar) ProgressBar progressBar; private long breakPoints; private ProgressDownloader downloader; private File file; private long totalBytes; private long contentLength; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ButterKnife.bind(this); } @OnClick({R.id.downloadButton, R.id.cancel_button, R.id.continue_button}) public void onClick(View view) { switch (view.getId()) { case R.id.downloadButton: // 新下载前清空断点信息 breakPoints = 0L; file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "sample.apk"); downloader = new ProgressDownloader(PACKAGE_URL, file, this); downloader.download(0L); break; case R.id.pause_button: 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; break; case R.id.continue_button: downloader.download(breakPoints); break; } } @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(); } } }
最后是动态效果图
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脚本之家。