【Android架构】基于MVP模式的Retrofit2+RXjava封装之文件下载（二）

上篇中我们介绍了基于MVP的Retrofit2+RXjava封装，还没有看的点击这里，这一篇我们来说说文件下载的实现。

首先，我们先在ApiServer定义好调用的接口

 @GET Observable<ResponseBody> downloadFile(@Url String fileUrl); 

接着定义一个接口，下载成功后用来回调

public interface FileView extends BaseView { void onSuccess(File file); } 

接着是Observer，建议与处理普通接口的Observer区分处理

public abstract class FileObsever extends BaseObserver<ResponseBody> { private String path; public FileObsever(BaseView view, String path) { super(view); this.path = path; } @Override protected void onStart() { } @Override public void onComplete() { } @Override public void onSuccess(ResponseBody o) { } @Override public void onError(String msg) { } @Override public void onNext(ResponseBody o) { File file = FileUtil.saveFile(path, o); if (file != null && file.exists()) { onSuccess(file); } else { onErrorMsg("file is null or file not exists"); } } @Override public void onError(Throwable e) { onErrorMsg(e.toString()); } public abstract void onSuccess(File file); public abstract void onErrorMsg(String msg); } 

FileUtil 注：如果需要写入文件的进度，可以在将这段方法放在onNext中，在FileObsever这个类写个方法，然后回调。

public static File saveFile(String filePath, ResponseBody body) { InputStream inputStream = null; OutputStream outputStream = null; File file = null; try { if (filePath == null) { return null; } file = new File(filePath); if (file == null || !file.exists()) { file.createNewFile(); } long fileSize = body.contentLength(); long fileSizeDownloaded = 0; byte[] fileReader = new byte[4096]; inputStream = body.byteStream(); outputStream = new FileOutputStream(file); while (true) { int read = inputStream.read(fileReader); if (read == -1) { break; } outputStream.write(fileReader, 0, read); fileSizeDownloaded += read; } outputStream.flush(); } catch (Exception e) { e.printStackTrace(); } finally { if (inputStream != null) { try { inputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (outputStream != null) { try { outputStream.close(); } catch (IOException e) { e.printStackTrace(); } } } return file; } 

下来是FilePresenter

public class FilePresenter extends BasePresenter<FileView> { public FilePresenter(FileView baseView) { super(baseView); } public void downFile(String url, final String path) { addDisposable(apiServer.downloadFile(url), new FileObsever(baseView, path) { @Override public void onSuccess(File file) { if (file != null && file.exists()) { baseView.onSuccess(file); } else { baseView.showError("file is null"); } } @Override public void onErrorMsg(String msg) { baseView.showError(msg); } }); } } 

最后在Activity中调用

private void downFile() { String url = "http://download.sdk.mob.com/apkbus.apk"; String state = Environment.getExternalStorageState(); if (state.equals(Environment.MEDIA_MOUNTED)) {// 检查是否有存储卡 dir = Environment.getExternalStorageDirectory() + "/ceshi/"; File dirFile = new File(dir); if (!dirFile.exists()) { dirFile.mkdirs(); } } presenter.downFile(url, dir + "app-debug.apk"); } 

就在我以为万事大吉的时候，APP崩溃了，错误信息如下：

[图片上传失败...(image-39e2a7-1532052138950)]

原来是加入日志监听器，会导致每次都把整个文件加载到内存，那我们就去掉这个

修改FilePresenter#downFile如下：

 public void downFile(String url, final String path) { OkHttpClient client = new OkHttpClient.Builder().build(); Retrofit retrofit = new Retrofit.Builder().client(client) .addCallAdapterFactory(RxJava2CallAdapterFactory.create()) .baseUrl("https://wawa-api.vchangyi.com/").build(); apiServer = retrofit.create(ApiServer.class); addDisposable(apiServer.downloadFile(url), new FileObsever(baseView, path) { @Override public void onSuccess(File file) { if (file != null && file.exists()) { baseView.onSuccess(file); } else { baseView.showError("file is null"); } } @Override public void onErrorMsg(String msg) { baseView.showError(msg); } }); } 

这次倒是下载成功了，不过官方建议10M以上的文件用Streaming标签，我们加上Streaming标签试试

修改ApiServer

 @Streaming @GET /** * 大文件官方建议用 @Streaming 来进行注解，不然会出现IO异常，小文件可以忽略不注入 */ Observable<ResponseBody> downloadFile(@Url String fileUrl); 

这次又崩溃了，错误信息如下：

[图片上传失败...(image-fc8c28-1532052138951)]

这是怎么回事，我们网络请求是在子线程啊。无奈之下只得翻翻官方文档，原来使用该注解表示响应用字节流的形式返回.如果没使用该注解,默认会把数据全部载入到内存中。我们可以在主线程中处理写入文件（不建议），但不能在主线程中处理字节流。所以，我们需要将处理字节流、写入文件都放在子线程中。

于是，修改FilePresenter#downFile如下：

 OkHttpClient client = new OkHttpClient.Builder().build(); Retrofit retrofit = new Retrofit.Builder().client(client) .addCallAdapterFactory(RxJava2CallAdapterFactory.create()) .baseUrl("https://wawa-api.vchangyi.com/").build(); apiServer = retrofit.create(ApiServer.class); apiServer .downloadFile(url) .map(new Function<ResponseBody, String>() { @Override public String apply(ResponseBody body) throws Exception { File file = FileUtil.saveFile(path, body); return file.getPath(); } }).subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribeWith(new FileObserver(baseView) { @Override public void onSuccess(File file) { baseView.onSuccess(file); } @Override public void onError(String msg) { baseView.showError(msg); } }); 

这样，下载文件算是完成了，好像还缺点什么？对，缺个下载进度，还记得拦截器吗，我们可以从这里入手：

public class ProgressResponseBody extends ResponseBody { private ResponseBody responseBody; private BufferedSource bufferedSource; private ProgressListener progressListener; public ProgressResponseBody(ResponseBody responseBody, ProgressListener progressListener) { this.responseBody = responseBody; this.progressListener = progressListener; } @Nullable @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; @Override public long read(Buffer sink, long byteCount) throws IOException { long bytesRead = super.read(sink, byteCount); totalBytesRead += bytesRead; progressListener.onProgress(responseBody.contentLength(), totalBytesRead); return bytesRead; } }; } public interface ProgressListener { void onProgress(long totalSize, long downSize); } } 

在BaseView 中定义接口，个人建议放在BaseView 中，在BaseActivity中实现BaseView，方便复用

 /** * 下载进度 * * @param totalSize * @param downSize */ void onProgress(long totalSize, long downSize); 

再次修改FilePresenter#downFile如下：

 public void downFile(final String url, final String path) { OkHttpClient client = new OkHttpClient.Builder() .addNetworkInterceptor(new Interceptor() { @Override public Response intercept(Chain chain) throws IOException { Response response = chain.proceed(chain.request()); return response.newBuilder().body(new ProgressResponseBody(response.body(), new ProgressResponseBody.ProgressListener() { @Override public void onProgress(long totalSize, long downSize) { baseView.onProgress(totalSize, downSize); } })).build(); } }).build(); Retrofit retrofit = new Retrofit.Builder().client(client) .addCallAdapterFactory(RxJava2CallAdapterFactory.create()) .baseUrl("https://wawa-api.vchangyi.com/").build(); apiServer = retrofit.create(ApiServer.class); apiServer .downloadFile(url) .map(new Function<ResponseBody, String>() { @Override public String apply(ResponseBody body) throws Exception { File file = FileUtil.saveFile(path, body); return file.getPath(); } }).subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribeWith(new FileObserver(baseView) { @Override public void onSuccess(File file) { baseView.onSuccess(file); } @Override public void onError(String msg) { baseView.showError(msg); } }); } 

至此，使用Retrofit下载文件暂时告一段落。

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