Java 如何在Android上使用反应式扩展下载带有进度更新的文件
我目前正在编写一个需要进行大量api调用组合的应用程序,因此第一次使用rxjava,因为它似乎更便于处理异步事件和Android生命周期 不过,该应用程序有时还需要加载打包在zip存档中的静态数据集。为了保持一致性,我尝试使用rx进行此操作,它工作得很好,但我没有真正掌握如何订阅进度事件以使用文件下载进度更新UI 这是我现在用来下载使用okhttp库的文件的代码:Java 如何在Android上使用反应式扩展下载带有进度更新的文件,java,android,rx-java,lifecycle,okhttp,Java,Android,Rx Java,Lifecycle,Okhttp,我目前正在编写一个需要进行大量api调用组合的应用程序,因此第一次使用rxjava,因为它似乎更便于处理异步事件和Android生命周期 不过,该应用程序有时还需要加载打包在zip存档中的静态数据集。为了保持一致性,我尝试使用rx进行此操作,它工作得很好,但我没有真正掌握如何订阅进度事件以使用文件下载进度更新UI 这是我现在用来下载使用okhttp库的文件的代码: downloadService.downloadFile(filename) .flatMap(new Func1<R
downloadService.downloadFile(filename)
.flatMap(new Func1<Response<ResponseBody>, Observable<File>>()
{
@Override
public Observable<File> call(final Response<ResponseBody> responseBodyResponse)
{
return Observable.create(new Observable.OnSubscribe<File>()
{
@Override
public void call(Subscriber<? super File> subscriber)
{
try
{
File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getAbsoluteFile(), filename);
BufferedSink sink = Okio.buffer(Okio.sink(file));
sink.writeAll(responseBodyResponse.body().source());
sink.close();
subscriber.onNext(file);
subscriber.onCompleted();
}
catch (IOException e)
{
e.printStackTrace();
subscriber.onError(e);
}
}
});
}
})
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer<File>()
{
@Override
public void onCompleted()
{
Log.d("downloadZipFile", "onCompleted");
}
@Override
public void onError(Throwable e) {
e.printStackTrace();
Log.d("downloadZipFile", "Error " + e.getMessage());
}
@Override
public void onNext(File file) {
Log.d("downloadZipFile", "File downloaded to " + file.getAbsolutePath());
}
});
downloadService.downloadFile(文件名)
.flatMap(新函数1()
{
@凌驾
公共可观察呼叫(最终响应-响应-响应)
{
返回Observable.create(newobservable.OnSubscribe()
{
@凌驾
public void call(订阅方首先:永远不要使用Observable.create()
,除非您知道自己在做什么,并且准备好处理背压和Observable应该处理的所有事情。(更新:如果您使用RxJava2,您可以安全地使用create()
方法)
也就是说,首先创建一个类来保存进度信息
public class DownloadProgress<DATA> {
private final float progress;
private final DATA data;
public DownloadProgress(float progress) {
this.progress = progress;
this.data = null;
}
public DownloadProgress(@NonNull DATA data) {
this.progress = 1f;
this.data = data;
}
public float getProgress() {
return progress;
}
public boolean isDone() {
return data != null;
}
public DATA getData() {
return data;
}
}
这应该可以工作(我没有测试过),但如果您取消订阅,它不会让您取消正在进行的http调用
如果您可以修改您的下载服务,我宁愿通过OkHttp来处理它,其灵感来自配方示例:
用法:
String filename = "yourFileName";
String url = "http://your.url.here";
File saveLocation = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getAbsoluteFile(), filename);
downloadFile(url, saveLocation)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.doOnNext(fileDownloadProgress -> {
float progress = fileDownloadProgress.getProgress();
// TODO update UI
})
.filter(DownloadProgress::isDone)
.map(DownloadProgress::getData)
.subscribe(file -> {
// file downloaded
}, throwable -> {
// error
});
哇,非常感谢您花时间提供如此详细的示例。谢谢。@Markus您能为上述答案发布工作示例吗?这将非常有用。有人使用此解决方案吗?看起来非常棒。谢谢@Markus!一些更新:RxJava2 create方法的工作原理类似于fromEmitter()
很好。我很遗憾我建议使用doOnNext()
:在订阅时处理一切。如果你需要单独处理进度和完成,请使用share()
并使用合适的筛选器订阅两次。顺便说一句,我编辑了帖子:onError
应该是tryOnError()
。否则,它可能会在处理下游时尝试发出错误,从而导致异常无法传递和->崩溃。
String filename = "yourFileName";
downloadFile(filename)
.observeOn(AndroidSchedulers.mainThread())
.doOnNext(fileDownloadProgress -> {
float progress = fileDownloadProgress.getProgress();
// TODO update UI
})
.filter(DownloadProgress::isDone)
.map(DownloadProgress::getData)
.subscribe(file -> {
// file downloaded
}, throwable -> {
// error
});
public Observable<DownloadProgress<File>> downloadFile(@NonNull final String url, @NonNull final File saveLocation) {
return Observable.fromEmitter(emitter -> {
Request request = new Request.Builder()
.url(url)
.build();
final ProgressListener progressListener = (bytesRead, contentLength, done) -> {
// range [0,1]
float progress = done ? 1f : (float) bytesRead / contentLength;
emitter.onNext(new DownloadProgress<>(progress));
};
OkHttpClient client = new OkHttpClient.Builder()
.addNetworkInterceptor(chain -> {
Response originalResponse = chain.proceed(chain.request());
return originalResponse.newBuilder()
.body(new ProgressResponseBody(originalResponse.body(), progressListener))
.build();
})
.build();
final Call call = client.newCall(request);
emitter.setCancellation(() -> call.cancel());
try {
Response response = call.execute();
BufferedSink sink = Okio.buffer(Okio.sink(saveLocation));
sink.writeAll(response.body().source());
sink.close();
emitter.onNext(new DownloadProgress<>(saveLocation));
emitter.onCompleted();
} catch (IOException e) {
emitter.onError(e);
}
}, Emitter.BackpressureMode.LATEST);
}
public static class ProgressResponseBody extends ResponseBody {
private final ResponseBody responseBody;
private final ProgressListener progressListener;
private BufferedSource bufferedSource;
public ProgressResponseBody(ResponseBody responseBody, ProgressListener progressListener) {
this.responseBody = responseBody;
this.progressListener = progressListener;
}
@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);
// read() returns the number of bytes read, or -1 if this source is exhausted.
totalBytesRead += bytesRead != -1 ? bytesRead : 0;
progressListener.update(totalBytesRead, responseBody.contentLength(), bytesRead == -1);
return bytesRead;
}
};
}
}
interface ProgressListener {
void update(long bytesRead, long contentLength, boolean done);
}
String filename = "yourFileName";
String url = "http://your.url.here";
File saveLocation = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getAbsoluteFile(), filename);
downloadFile(url, saveLocation)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.doOnNext(fileDownloadProgress -> {
float progress = fileDownloadProgress.getProgress();
// TODO update UI
})
.filter(DownloadProgress::isDone)
.map(DownloadProgress::getData)
.subscribe(file -> {
// file downloaded
}, throwable -> {
// error
});