前言
前面介紹了很多關(guān)于Retrofit2的基本使用硕淑，下面就單獨(dú)介紹一下如何使用Retrofit2實(shí)現(xiàn)文件上傳和文件下載，并且做了一點(diǎn)拓展笋额，重點(diǎn)介紹了一下上傳和下載過(guò)程中進(jìn)度的顯示元暴。
文件上傳
定義接口
@Multipart
@POST("url")
Call<Result> uploadFile(@Part RequestBody file);
構(gòu)造所要上傳的RequestBody
File file = new File(filePath);
RequestBody body = RequestBody.create(MediaType.parse("multipart/form-data"), file);
Call<String> call = fileService.uploadFile(body);
call.enqueue(callback);
通過(guò)Retrofit提供的方法就可以很簡(jiǎn)單的將文件上傳到服務(wù)器，但通常上傳文件時(shí)兄猩，都會(huì)加上文件的上傳進(jìn)度茉盏，這樣交互會(huì)顯得更加友好。而Retrofit本身是不支持文件上傳進(jìn)度顯示的枢冤，所以就需要我們自己擴(kuò)展OkHttp來(lái)實(shí)現(xiàn)文件上傳進(jìn)度鸠姨。
我的做法是直接擴(kuò)展一個(gè)RequestBody來(lái)實(shí)現(xiàn)進(jìn)度顯示，實(shí)現(xiàn)完成之后只需要將上面body進(jìn)行包裝轉(zhuǎn)換即可淹真。
首先封裝一個(gè)RetrofitCallback讶迁，用于進(jìn)度的回調(diào)。
public abstract class RetrofitCallback<T> implements Callback<T> {
@Override
public void onResponse(Call<T> call, Response<T> response) {
if(response.isSuccessful()) {
onSuccess(call, response);
} else {
onFailure(call, new Throwable(response.message()));
}
}
public abstract void onSuccess(Call<T> call, Response<T> response);
//用于進(jìn)度的回調(diào)
public abstract void onLoading(long total, long progress) ;
}
第二步核蘸，擴(kuò)展OkHttp的請(qǐng)求體巍糯，編寫(xiě)包裝類FileRequestBody，對(duì)RequestBody進(jìn)行包裝
public final class FileRequestBody<T> extends RequestBody {
/**
* 實(shí)際請(qǐng)求體
*/
private RequestBody requestBody;
/**
* 上傳回調(diào)接口
*/
private RetrofitCallback<T> callback;
/**
* 包裝完成的BufferedSink
*/
private BufferedSink bufferedSink;
public FileRequestBody(RequestBody requestBody, RetrofitCallback<T> callback) {
super();
this.requestBody = requestBody;
this.callback = callback;
}
@Override
public long contentLength() throws IOException {
return requestBody.contentLength();
}
@Override
public MediaType contentType() {
return requestBody.contentType();
}
@Override
public void writeTo(BufferedSink sink) throws IOException {
bufferedSink = Okio.buffer(sink(sink));
//寫(xiě)入
requestBody.writeTo(bufferedSink);
//必須調(diào)用flush客扎，否則最后一部分?jǐn)?shù)據(jù)可能不會(huì)被寫(xiě)入
bufferedSink.flush();
}
/**
* 寫(xiě)入祟峦，回調(diào)進(jìn)度接口
* @param sink Sink
* @return Sink
*/
private Sink sink(Sink sink) {
return new ForwardingSink(sink) {
//當(dāng)前寫(xiě)入字節(jié)數(shù)
long bytesWritten = 0L;
//總字節(jié)長(zhǎng)度，避免多次調(diào)用contentLength()方法
long contentLength = 0L;
@Override
public void write(Buffer source, long byteCount) throws IOException {
super.write(source, byteCount);
if (contentLength == 0) {
//獲得contentLength的值宅楞，后續(xù)不再調(diào)用
contentLength = contentLength();
}
//增加當(dāng)前寫(xiě)入的字節(jié)數(shù)
bytesWritten += byteCount;
//回調(diào)
callback.onLoading(contentLength, bytesWritten);
}
};
}
}
最后，通過(guò)onLoading(long total, long progress) 袱吆，更新上傳進(jìn)度
RetrofitCallback< String > callback = new RetrofitCallback< Result >() {
@Override
public void onSuccess(Call< String > call, Response< String > response) {
runOnUIThread(activity, response.body().toString());
//進(jìn)度更新結(jié)束
}
@Override
public void onFailure(Call< String > call, Throwable t) {
runOnUIThread(activity, t.getMessage());
//進(jìn)度更新結(jié)束
}
@Override
public void onLoading(long total, long progress) {
super.onLoading(total, progress);
//此處進(jìn)行進(jìn)度更新
}
};
RequestBody resquestBody = RequestBody.create(MediaType.parse("multipart/form-data"), file);
//通過(guò)該行代碼將RequestBody轉(zhuǎn)換成特定的FileRequestBody
FileRequestBody body = new FileRequestBody(resquestBody, callback);
Call<String> call = fileService.uploadOneFile(body);
call.enqueue(callback);
文件下載
接口定義
文件下載請(qǐng)求與普通的Get和Post請(qǐng)求是一樣的绞绒，只是他們的返回值不一樣而已蓬衡，文件下載請(qǐng)求的返回值一般定義成ResponseBody
//這里只舉例POST方式進(jìn)行文件下載
@FormUrlEncoded
@POST("fileService")
Call<ResponseBody> downloadFile(@Field("param") String param);
發(fā)起請(qǐng)求
RetrofitCallback<ResponseBody> callback = new RetrofitCallback<ResponseBody>() {
@Override
public void onSuccess(Call<ResponseBody> call, Response<ResponseBody> response) {
try {
InputStream is = response.body().byteStream();
String path = Util.getSdCardPath();
File file = new File(path, "download.jpg");
FileOutputStream fos = new FileOutputStream(file);
BufferedInputStream bis = new BufferedInputStream(is);
byte[] buffer = new byte[1024];
int len;
while ((len = bis.read(buffer)) != -1) {
fos.write(buffer, 0, len);
}
fos.flush();
fos.close();
bis.close();
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void onFailure(Call<ResponseBody> call, Throwable t) {
runOnUIThread(activity, t.getMessage());
}
@Override
public void onLoading(long total, long progress){
//更新下載進(jìn)度
}
};
Call<ResponseBody> call = getRetrofitService(callback).downloadFile(param);
call.enqueue(callback);
下載進(jìn)度顯示
通過(guò)OkHttp設(shè)置攔截器將ResponseBody進(jìn)行轉(zhuǎn)換成我們擴(kuò)展后的ResponseBody
** 擴(kuò)展ResponseBody設(shè)置OkHttp攔截器**
private <T> RetrofitService getRetrofitService(final RetrofitCallback<T> callback) {
OkHttpClient.Builder clientBuilder = new OkHttpClient.Builder();
clientBuilder.addInterceptor(new Interceptor() {
@Override
public okhttp3.Response intercept(Chain chain) throws IOException {
okhttp3.Response response = chain.proceed(chain.request());
//將ResponseBody轉(zhuǎn)換成我們需要的FileResponseBody
return response.newBuilder().body(new FileResponseBody<T>(response.body(), callback)).build();
}
});
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.client(clientBuilder.build())
.addConverterFactory(GsonConverterFactory.create())
.build();
RetrofitService service = retrofit.create(RetrofitService.class);
return service ;
}
//通過(guò)上面的設(shè)置后家肯，我們需要在回調(diào)RetrofitCallback中實(shí)現(xiàn)onLoading方法來(lái)進(jìn)行進(jìn)度的更新操作龄砰，與上傳文件的方法相同
FileResponseBody
/**
* 擴(kuò)展OkHttp的請(qǐng)求體，實(shí)現(xiàn)上傳時(shí)的進(jìn)度提示
*
* @param <T>
*/
public final class FileResponseBody<T> extends ResponseBody {
/**
* 實(shí)際請(qǐng)求體
*/
private ResponseBody mResponseBody;
/**
* 下載回調(diào)接口
*/
private RetrofitCallback<T> mCallback;
/**
* BufferedSource
*/
private BufferedSource mBufferedSource;
public FileResponseBody(ResponseBody responseBody, RetrofitCallback<T> callback) {
super();
this.mResponseBody = responseBody;
this.mCallback = callback;
}
@Override
public BufferedSource source() {
if (mBufferedSource == null) {
mBufferedSource = Okio.buffer(source(mResponseBody.source()));
}
return mBufferedSource;
}
@Override
public long contentLength() {
return mResponseBody.contentLength();
}
@Override
public MediaType contentType() {
return mResponseBody.contentType();
}
/**
* 回調(diào)進(jìn)度接口
* @param source
* @return Source
*/
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 != -1 ? bytesRead : 0;
mCallback.onLoading(mResponseBody.contentLength(), totalBytesRead);
return bytesRead;
}
};
}
}
總結(jié)
依照慣例讨衣，最后都要有一個(gè)總結(jié)换棚，先感嘆一下retrofit的強(qiáng)大。ok反镇，再來(lái)說(shuō)一下使用過(guò)程中的感受固蚤，從本文中也感受的到立帖，就是retrofit大量的引入了對(duì)okhttp 應(yīng)用香椎，所以要想用好retrofit 缓淹，學(xué)好okhttp 也是必須的肴掷，不說(shuō)了铝噩，啃代碼去了其屏。
