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前面一篇文章介绍了Retrofit2的基本使用，这篇文章接着介绍使用Retrofit2实现文件上传和文件下载，以及上传下载过程中如何实现进度的显示。
文件上传
定义接口
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Call<User> uploadFile(@Part MultipartBody.Part file);
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构造请求体上传
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File file = new File(filePath);
RequestBody body = RequestBody.create(MediaType.parse("application/otcet-stream"), file);
MultipartBody.Part part = MultipartBody.Part.createFormData("file", file.getName(), body);
Call<User> call = getRetrofitService().uploadOneFile(part);
call.enqueue(callback);
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这样就可以将这个文件上传到服务器，但就这样上传操作不够友好，最好加上文件上传进度。而Retrofit本身是不支持文件上传进度显示的，所以就需要我们自己扩展OkHttp来实现文件上传进度。
我的做法是直接扩展一个RequestBody来实现进度显示，实现完成之后只需要将上面body进行包装转换即可
上传进度显示
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RetrofitCallback<User> callback = new RetrofitCallback<User>() {
public void onSuccess(Call<User> call, Response<User> response) {
runOnUIThread(activity, response.body().toString());
//进度更新结束
}
public void onFailure(Call<User> call, Throwable t) {
runOnUIThread(activity, t.getMessage());
//进度更新结束
}
public void onLoading(long total, long progress) {
super.onLoading(total, progress);
//此处进行进度更新
}
};
RequestBody body1 = RequestBody.create(MediaType.parse("application/otcet-stream"), file);
//通过该行代码将RequestBody转换成特定的FileRequestBody
FileRequestBody body = new FileRequestBody(body1, callback);
MultipartBody.Part part = MultipartBody.Part.createFormData("file", file.getName(), body);
Call<User> call = getRetrofitService().uploadOneFile(part);
call.enqueue(callback);
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回调RetrofitCallback
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public abstract class RetrofitCallback<T> implements Callback<T> {
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);
public void onLoading(long total, long progress) {
}
}
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FileRequestBody
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/**
* 扩展OkHttp的请求体，实现上传时的进度提示
*
* @param <T>
*/
public final class FileRequestBody<T> extends RequestBody {
/**
* 实际请求体
*/
private RequestBody requestBody;
/**
* 上传回调接口
*/
private RetrofitCallback<T> callback;
/**
* 包装完成的BufferedSink
*/
private BufferedSink bufferedSink;
public FileRequestBody(RequestBody requestBody, RetrofitCallback<T> callback) {
super();
this.requestBody = requestBody;
this.callback = callback;
}
public long contentLength() throws IOException {
return requestBody.contentLength();
}
public MediaType contentType() {
return requestBody.contentType();
}
public void writeTo(BufferedSink sink) throws IOException {
if (bufferedSink == null) {
//包装
bufferedSink = Okio.buffer(sink(sink));
}
//写入
requestBody.writeTo(bufferedSink);
//必须调用flush，否则最后一部分数据可能不会被写入
bufferedSink.flush();
}
/**
* 写入，回调进度接口
* @param sink Sink
* @return Sink
*/
private Sink sink(Sink sink) {
return new ForwardingSink(sink) {
//当前写入字节数
long bytesWritten = 0L;
//总字节长度，避免多次调用contentLength()方法
long contentLength = 0L;
public void write(Buffer source, long byteCount) throws IOException {
super.write(source, byteCount);
if (contentLength == 0) {
//获得contentLength的值，后续不再调用
contentLength = contentLength();
}
//增加当前写入的字节数
bytesWritten += byteCount;
//回调
callback.onLoading(contentLength, bytesWritten);
}
};
}
}
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文件下载
接口定义
文件下载请求与普通的Get和Post请求是一样的，只是他们的返回值不一样而已，文件下载请求的返回值一般定义成ResponseBody
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//这里只举例POST方式进行文件下载
Call<ResponseBody> downloadFile(@Field("param") String param);
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发起请求
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RetrofitCallback<ResponseBody> callback = new RetrofitCallback<ResponseBody>() {
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();
}
}
public void onFailure(Call<ResponseBody> call, Throwable t) {
runOnUIThread(activity, t.getMessage());
}
};
Call<ResponseBody> call = getRetrofitService(callback).downloadFile(param);
call.enqueue(callback);
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下载进度显示
下载进度显示有两种方式实现，一种是通过OkHttp设置拦截器将ResponseBody进行转换成我们扩展后的ResponseBody（稍后介绍），另外一种则是在上面的回调Callback中将ResponseBody的流写入到文件时进行进度处理，下面分别进行介绍。
扩展ResponseBody设置OkHttp拦截器
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private <T> RetrofitService getRetrofitService(final RetrofitCallback<T> callback) {
OkHttpClient.Builder clientBuilder = new OkHttpClient.Builder();
clientBuilder.addInterceptor(new Interceptor() {
public okhttp3.Response intercept(Chain chain) throws IOException {
okhttp3.Response response = chain.proceed(chain.request());
//将ResponseBody转换成我们需要的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 ;
}
//通过上面的设置后，我们需要在回调RetrofitCallback中实现onLoading方法来进行进度的更新操作，与上传文件的方法相同
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FileResponseBody
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/**
* 扩展OkHttp的请求体，实现上传时的进度提示
*
* @param <T>
*/
public final class FileResponseBody<T> extends ResponseBody {
/**
* 实际请求体
*/
private ResponseBody mResponseBody;
/**
* 下载回调接口
*/
private RetrofitCallback<T> mCallback;
/**
* BufferedSource
*/
private BufferedSource mBufferedSource;
public FileResponseBody(ResponseBody responseBody, RetrofitCallback<T> callback) {
super();
this.mResponseBody = responseBody;
this.mCallback = callback;
}
public BufferedSource source() {
if (mBufferedSource == null) {
mBufferedSource = Okio.buffer(source(mResponseBody.source()));
}
return mBufferedSource;
}
public long contentLength() {
return mResponseBody.contentLength();
}
public MediaType contentType() {
return mResponseBody.contentType();
}
/**
* 回调进度接口
* @param source
* @return Source
*/
private Source source(Source source) {
return new ForwardingSource(source) {
long totalBytesRead = 0L;
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;
}
};
}
}
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直接在回调中进行进度更新
上面介绍了通过扩展ResponseBody同时设置OkHttp拦截器来实现进度条更新显示，另外也可以直接在请求回调onSuccess中将流转换成文件时实现进度更新，下面给出大致实现
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RetrofitCallback<ResponseBody> callback = new RetrofitCallback<ResponseBody>() {
public void onSuccess(Call<ResponseBody> call, Response<ResponseBody> response) {
try {
InputStream is = response.body().byteStream();
//获取文件总长度
long totalLength = is.available();
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);
//此处进行更新操作
//len即可理解为已下载的字节数
//onLoading(len, totalLength);
}
fos.flush();
fos.close();
bis.close();
is.close();
//此处就代表更新结束
} catch (IOException e) {
e.printStackTrace();
}
}
public void onFailure(Call<ResponseBody> call, Throwable t) {
runOnUIThread(activity, t.getMessage());
}
};
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以上就是Retrofit中文件上传下载及其进度更新显示的实现