在我们的应用程序中，我使用此代码下载图像文件。我需要在用户界面上显示下载进度（下载的字节数百分比）。如何在此代码中获取下载进度？我寻找解决方案，但仍然无法自己完成。
Observable<String> downloadObservable = Observable.create(
sub -> {
Request request = new Request.Builder()
.url(media.getMediaUrl())
.build();
Response response = null;
try {
response = http_client.newCall(request).execute();
if (response.isSuccessful()) {
Log.d(TAG, "response.isSuccessful()");
String mimeType = MimeTypeMap.getFileExtensionFromUrl(media.getMediaUrl());
File file = new File(helper.getTmpFolder() + "/" + helper.generateUniqueName() + "test." + mimeType);
BufferedSink sink = Okio.buffer(Okio.sink(file));
sink.writeAll(response.body().source());
sink.close();
sub.onNext(response.toString());
sub.onCompleted();
} else {
sub.onError(new IOException());
}
} catch (IOException e) {
e.printStackTrace();
}
}
);
Subscriber<String> mySubscriber = new Subscriber<String>() {
@Override
public void onNext(String responseString) {
Log.d(TAG, "works: " + responseString);
}
};
downloadObservable
.subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(mySubscriber);
这就是我会做的来显示进度。
Observable<String> downloadObservable = Observable.create(
sub -> {
InputStream input = null;
OutputStream output = null;
try {
Response response = http_client.newCall(request).execute();
if (response.isSuccessful()) {
input = response.body().byteStream();
long tlength= response.body().contentLength();
output = new FileOutputStream("/pathtofile");
byte data[] = new byte[1024];
sub.onNext("0%");
long total = 0;
int count;
while ((count = input.read(data)) != -1) {
total += count;
sub.onNext(String.valueOf(total*100/tlength) + "%");
output.write(data, 0, count);
}
output.flush();
output.close();
input.close();
}
} catch(IOException e){
sub.onError(e);
} finally {
if (input != null){
try {
input.close();
}catch(IOException ioe){}
}
if (out != null){
try{
output.close();
}catch (IOException e){}
}
}
sub.onCompleted();
}
);
并使用具有完整抽象方法的订阅者。
Subscriber<String> mySubscriber = new Subscriber<String>() {
@Override
public void onCompleted() {
// hide progress bar
}
@Override
public void onError(Throwable e) {
// hide progress bar
}
@Override
public void onNext(String percentProgress) {
// show percentage progress
}
};
接受的答案仅显示保存下载文件的进度，而不显示实际的下载进度。
在 Kotlin 上创建了带有进度解决方案的 Rx 下载文件，希望有帮助：
private const val FULL_PROGRESS = 100L
class DownloadWithProgress {
fun start(url: String, directory: File, fileName: String) =
Observable.create<Download> { emitter ->
try {
val request = Request.Builder()
.url(url)
.build()
OkHttpClient.Builder()
.addNetworkInterceptor { chain: Interceptor.Chain ->
val originalResponse = chain.proceed(chain.request())
originalResponse.newBuilder()
.body(originalResponse.body()?.let { responseBody ->
ProgressResponseBody(responseBody) { emitter.onNext(Download(it)) }
})
.build()
}
.build()
.newCall(request).execute().use { response ->
if (!response.isSuccessful) throw IOException("Unexpected code $response")
val bufferedSource = response.body()?.source() ?: throw NullPointerException("Response is null")
try {
val packageFile = File(directory, fileName).apply {
sink().buffer().run {
writeAll(bufferedSource)
close()
}
}
emitter.onNext(Download(FULL_PROGRESS, packageFile))
} catch (ioException: Exception) {
throw AppUpdateException("Io exception: " + ioException.localizedMessage)
}
emitter.onComplete()
}
} catch (exception: Exception) {
emitter.onError(exception)
}
}
private class ProgressResponseBody(
private val responseBody: ResponseBody,
private val onProgress: (progress: Long) -> Unit
) : ResponseBody() {
private var bufferedSource: BufferedSource? = null
override fun contentType() = responseBody.contentType()
override fun contentLength() = responseBody.contentLength()
override fun source() = bufferedSource ?: source(responseBody.source()).buffer().also { bufferedSource = it }
private fun source(source: Source): Source {
return object : ForwardingSource(source) {
var totalBytesRead = 0L
override fun read(sink: Buffer, byteCount: Long): Long {
return super.read(sink, byteCount).apply {
val bytesRead = this
totalBytesRead += if (bytesRead != -1L) bytesRead else 0
if (bytesRead != -1L) {
val progress = FULL_PROGRESS * totalBytesRead / responseBody.contentLength()
onProgress(progress)
}
}
}
}
}
}
}
data class Download(
val progress: Long,
val file: File? = null
) {
val isDownloaded = progress == FULL_PROGRESS && file != null
}
这就是我和 Okio 一起做的：
new SingleFromCallable<>(() -> {
Request.Builder requestBuilder = new Request.Builder();
BufferedSink sink=null; BufferedSource source=null;
try(Response response = okHttpClient.newCall(requestBuilder.url(downloadUrl).build()).execute()){
if(response.isSuccessful()){
ResponseBody responseBody = response.body(); assert responseBody != null;
long totalSize = responseBody.contentLength();
source = responseBody.source();
File downloadFile = new File(filePath);
sink = Okio.buffer(Okio.sink(downloadFile));
int bufferSize = 8*1024; long downloadedSize=0;
for(long bytesRead; (bytesRead= source.read(sink.getBuffer(),bufferSize))!=-1;){
sink.emit(); downloadedSize+=bytesRead;
publishProgress(downloadedSize*100/totalSize);
}
Log.d(TAG, "File successfully downloaded and saved to storage.");
return CODE_SUCCESS;
}
}
catch (IOException e) {e.printStackTrace();}
finally {if(sink!=null){sink.flush(); sink.close();} if(source!=null)source.close();}
return CODE_ERROR;
}).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribe(new SingleObserver<Long>() {
@Override public void onSubscribe(@NonNull Disposable d) {Log.d(TAG, "Subscribed");}
@Override public void onSuccess(@NonNull Long c) {Log.d(TAG, "Execution completed. Code:"+c);}
@Override public void onError(@NonNull Throwable e) {e.printStackTrace();}
});
您可以使用以下方法更新主线程上的 UI：
Handler handler = new Handler(Looper.getMainLooper());
handler.post(()-> {
publishProgress(); //do UI stuff
});