【Android架構】基於MVP模式的Retrofit2+RXjava封裝之檔案下載（二）

Retrofit RxJava · 發表 2019-03-01 18:44:57

摘要：上篇中我們介紹了基於MVP的Retrofit2+RXjava封裝，這一篇我們來說說檔案下載的實現。【Android架構】基於MVP模式的Retrofit2+RXjava封裝（一）【Android架構】基於MVP模式的Retrofi...

上篇中我們介紹了基於MVP的Retrofit2+RXjava封裝，這一篇我們來說說檔案下載的實現。

我們先在ApiServer定義好呼叫的介面

@GET
Observable<ResponseBody> downloadFile(@Url String fileUrl);
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接著定義一個介面，下載成功後用來回調

public interface FileView extends BaseView {

void onSuccess(File file);
}
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接著是Observer，建議與處理普通介面的Observer區分處理

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);
}

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FileUtil 注：如果需要寫入檔案的進度，可以在將這段方法放在onNext中，在FileObsever這個類寫個方法，然後回撥。

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;
}
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下來是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);

}
});

}
}
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最後在Activity中呼叫

private void downFile() {
String url = "http://download.sdk.mob.com/apkbus.apk";

String state = Environment.getExternalStorageState();
if (state.equals(Environment.MEDIA_MOUNTED)) {// 檢查是否有儲存卡
dir = Environment.getExternalStorageDirectory() + "/ceshi/";
File dirFile = new File(dir);
if (!dirFile.exists()) {
dirFile.mkdirs();
}
}
presenter.downFile(url, dir + "app-debug.apk");
}
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就在我以為萬事大吉的時候，APP崩潰了，錯誤資訊如下： [圖片上傳失敗...(image-39e2a7-1532052138950)]

原來是加入日誌監聽器，會導致每次都把整個檔案載入到記憶體，那我們就去掉這個

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);

}
});
}
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這次倒是下載成功了，不過官方建議10M以上的檔案用Streaming標籤，我們加上Streaming標籤試試修改ApiServer

@Streaming
@GET
/**
* 大檔案官方建議用 @Streaming 來進行註解，不然會出現IO異常，小檔案可以忽略不注入
*/
Observable<ResponseBody> downloadFile(@Url String fileUrl);
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這次又崩潰了，錯誤資訊如下： [圖片上傳失敗...(image-fc8c28-1532052138951)]

這是怎麼回事，我們網路請求是在子執行緒啊。無奈之下只得翻翻官方文件，原來使用該註解表示響應用位元組流的形式返回.如果沒使用該註解,預設會把資料全部載入到記憶體中。我們可以在主執行緒中處理寫入檔案（不建議），但不能在主執行緒中處理位元組流。所以，我們需要將處理位元組流、寫入檔案都放在子執行緒中。

於是，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);
}
});
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這樣，下載檔案算是完成了，好像還缺點什麼？對，缺個下載進度，還記得攔截器嗎，我們可以從這裡入手：

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);
}
}

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在BaseView 中定義介面，個人建議放在BaseView 中，在BaseActivity中實現BaseView，方便複用

/**
* 下載進度
*
* @param totalSize
* @param downSize
*/

void onProgress(long totalSize, long downSize);
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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);
}
});


}
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至此，使用Retrofit下載檔案暫時告一段落。

【Android架構】基於MVP模式的Retrofit2+RXjava封裝之檔案下載（二）

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