如何使用 Retrofit 库下载 Android 中的文件？

Question

我需要在我的应用程序中使用 Retrofit 库下载所有类型的文件（二进制、图像、文本等）。网络上的所有示例都使用 HTML GET 方法。我需要使用 POST 来防止自动缓存。

我的问题是如何在 Retrofit 中使用 POST 方法下载文件？

Answer 1

使用@Streaming

异步

编辑 1

//On your api interface
@POST("path/to/your/resource")
@Streaming
void apiRequest(Callback<POJO> callback);

restAdapter.apiRequest(new Callback<POJO>() {
        @Override
        public void success(POJO pojo, Response response) {
            try {
                //you can now get your file in the InputStream
                InputStream is = response.getBody().in();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void failure(RetrofitError error) {

        }
    });

同步

//On your api interface
@POST("path/to/your/resource")
@Streaming
Response apiRequest();

Response response = restAdapter.apiRequest();

try {
    //you can now get your file in the InputStream
    InputStream is = response.getBody().in();
} catch (IOException e) {
    e.printStackTrace();
}

Answer 2

如果你用的是Retrofit 2.0.0，可以参考我的answer under the question -- Use retrofit to download image file.

关键点是使用 okhttp3.ReponseBody 接收原始二进制数据，而不是任何 POJO。

而你想用POST方式获取文件，很简单，把@GET改成@POST就可以了，不过要看你的服务器是否支持POST ]方法！

Answer 3

这是在 Retrofit 2 中下载文件的方法

public interface ServerAPI {
        @GET
        Call<ResponseBody> downlload(@Url String fileUrl);

        Retrofit retrofit =
                new Retrofit.Builder()
                        .baseUrl("http://192.168.43.135/retro/") // REMEMBER TO END with /
                        .addConverterFactory(GsonConverterFactory.create())
                 .build();

}

    //How To Call
public void download(){
        ServerAPI api = ServerAPI.retrofit.create(ServerAPI.class);
        api.downlload("http://192.168.43.135/retro/pic.jpg").enqueue(new Callback<ResponseBody>() {
                    @Override
                    public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
                        try {
                            File path = Environment.getExternalStorageDirectory();
                            File file = new File(path, "file_name.jpg");
                            FileOutputStream fileOutputStream = new FileOutputStream(file);
                            IOUtils.write(response.body().bytes(), fileOutputStream);
                        }
                        catch (Exception ex){
                        }
                    }

                    @Override
                    public void onFailure(Call<ResponseBody> call, Throwable t) {
                    }
                });
}

Answer 4

在MainActivity.java中包含以下函数：

void getRetrofitImage() {

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(url)
            .addConverterFactory(GsonConverterFactory.create())
            .build();

    RetrofitImageAPI service = retrofit.create(RetrofitImageAPI.class);

    Call<ResponseBody> call = service.getImageDetails();

    call.enqueue(new Callback<ResponseBody>() {
        @Override
        public void onResponse(Response<ResponseBody> response, Retrofit retrofit) {

            try {

                Log.d("onResponse", "Response came from server");

                boolean FileDownloaded = DownloadImage(response.body());

                Log.d("onResponse", "Image is downloaded and saved ? " + FileDownloaded);

            } catch (Exception e) {
                Log.d("onResponse", "There is an error");
                e.printStackTrace();
            }

        }

        @Override
        public void onFailure(Throwable t) {
            Log.d("onFailure", t.toString());
        }
    });
}

图像下载的文件处理部分将是：

private boolean DownloadImage(ResponseBody body) {

    try {
        Log.d("DownloadImage", "Reading and writing file");
        InputStream in = null;
        FileOutputStream out = null;

        try {
            in = body.byteStream();
            out = new FileOutputStream(getExternalFilesDir(null) + File.separator + "AndroidTutorialPoint.jpg");
            int c;

            while ((c = in.read()) != -1) {
                out.write(c);
            }
        }
        catch (IOException e) {
            Log.d("DownloadImage",e.toString());
            return false;
        }
        finally {
            if (in != null) {
                in.close();
            }
            if (out != null) {
                out.close();
            }
        }

        int width, height;
        ImageView image = (ImageView) findViewById(R.id.imageViewId);
        Bitmap bMap = BitmapFactory.decodeFile(getExternalFilesDir(null) + File.separator + "AndroidTutorialPoint.jpg");
        width = 2*bMap.getWidth();
        height = 6*bMap.getHeight();
        Bitmap bMap2 = Bitmap.createScaledBitmap(bMap, width, height, false);
        image.setImageBitmap(bMap2);

        return true;

    } catch (IOException e) {
        Log.d("DownloadImage",e.toString());
        return false;
    }
}

您可以查看完整教程：Image Download using Retrofit 2.0

Answer 5

我使用以下代码通过改造下载任何类型的文件...

 File file = new File("Your_File_path/name");

  private void startDownload() {

    if (!NetWorkUtils.getInstance(context).isNetworkAvailable()) {
        Toast.makeText(context, "No data connection available", Toast.LENGTH_SHORT).show();
        return;
    }

    showProgressDialog();

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(FILE_BASE_URL)
            .build();

    FileHandlerService handlerService = retrofit.create(FileHandlerService.class);

    Call<ResponseBody> call = handlerService.downloadFile(mFileName);
    call.enqueue(new Callback<ResponseBody>() {
        @Override
        public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
            dismissProgressDialog();
            if (response.isSuccessful()) {
                if (writeResponseBodyToDisk(response.body())) {
                    listener.onFileLoaded(file);
                }
            } else {
                listener.onDownloadFailed("Resource not Found");
            }
        }

        @Override
        public void onFailure(Call<ResponseBody> call, Throwable t) {
            dismissProgressDialog();
            listener.onDownloadFailed("Download Failed");
            t.printStackTrace();
        }
    });

}


interface FileHandlerService {

    @GET("uploads/documents/{file_name}")
    Call<ResponseBody> downloadFile(
            @Path("file_name") String imageName);
}

private boolean writeResponseBodyToDisk(ResponseBody body) {
    try {

        InputStream inputStream = null;
        OutputStream outputStream = null;

        try {
            byte[] fileReader = new byte[4096];

            long fileSize = body.contentLength();
            long fileSizeDownloaded = 0;

            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;

                Log.d(TAG, "file download: " + fileSizeDownloaded + " of " + fileSize);
            }

            outputStream.flush();

            return true;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        } finally {
            if (inputStream != null) {
                inputStream.close();
            }
            if (outputStream != null) {
                outputStream.close();
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
        return false;
    }
}

Answer 6

下载文件的请求声明如下所示

// option 1: a resource relative to your base URL
@GET("/resource/example.zip")
Call<ResponseBody> downloadFileWithFixedUrl();

// option 2: using a dynamic URL
@GET
Call<ResponseBody> downloadFileWithDynamicUrlSync(@Url String fileUrl);

像这样声明请求调用后

FileDownloadService downloadService = ServiceGenerator.create(FileDownloadService.class);

Call<ResponseBody> call = downloadService.downloadFileWithDynamicUrlSync(fileUrl);

call.enqueue(new Callback<ResponseBody>() {  
    @Override
    public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
        if (response.isSuccess()) {
            Log.d(TAG, "server contacted and has file");

            boolean writeToDisk = writeToDisk(response.body());

            Log.d(TAG, "file downloaded " + writtenToDisk);
        } else {
            Log.d(TAG, "server error");
        }
    }

    @Override
    public void onFailure(Call<ResponseBody> call, Throwable t) {
        Log.e(TAG, "error");
    }
});

同样实现这个方法，将文件存入你的sdcard。

private boolean writeToDisk(ResponseBody body) {  
    try { File mediaStorageDir = new File(
                Environment
                        .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
                "ProfileImage");

        // Create the storage directory if it does not exist
        if (!mediaStorageDir.exists()) {
            if (!mediaStorageDir.mkdirs()) {
                Log.e("ProfileImage", "Oops! Failed create "
                        + "ProfileImage" + " directory");
            }
        }
        File futureStudioIconFile = new File(mediaStorageDir.getPath() + File.separator
                + "userImage.png");

        InputStream inputStream = null;
        OutputStream outputStream = null;

        try {
            byte[] fileReader = new byte[4096];

            long fileSize = body.contentLength();
            long fileSizeDownloaded = 0;

            inputStream = body.byteStream();
            outputStream = new FileOutputStream(futureStudioIconFile);

            while (true) {
                int read = inputStream.read(fileReader);

                if (read == -1) {
                    break;
                }

                outputStream.write(fileReader, 0, read);

                fileSizeDownloaded += read;

                Log.d(TAG, "file download: " + fileSizeDownloaded + " of " + fileSize);
            }

            outputStream.flush();

            return true;
        } catch (IOException e) {
            return false;
        } finally {
            if (inputStream != null) {
                inputStream.close();
            }

            if (outputStream != null) {
                outputStream.close();
            }
        }
    } catch (IOException e) {
        return false;
    }
}

Answer 7

您可以使用以下代码进行进度下载 (Kotlin)

改造Api服务

@Streaming
@GET
fun downloadFile(@Url fileUrl: String): Observable<Response<ResponseBody>>

确保为大文件下载添加 @Streaming

并将以下代码粘贴到您的 Activity 或 Fragment

fun downloadfileFromRetrofit() {
    val retrofit = Retrofit.Builder()
        .baseUrl("ENTER_YOUR_BASE_URL")
        .client(OkHttpClient.Builder().build())
        .addCallAdapterFactory(RxJava2CallAdapterFactory.create()).build()
    val downloadService = retrofit.create(RetrofitApi::class.java)

   downloadService.downloadFile("FILE_URL_PATH").observeOn(AndroidSchedulers.mainThread())
        .subscribeOn(Schedulers.io()).subscribe({
            val task = object : AsyncTask<Void, Integer, Void>() {
                override fun doInBackground(vararg voids: Void): Void? {
                    val writtenToDisk =writeResponseBodyToDisk(it.body()!!)
                    println("file download was a success? $writtenToDisk")
                    return null
                }
            }
            task.execute()
        }, {
            print(it.message)
        })
}

下面是 writeResponseBodyToDisk 方法

fun writeResponseBodyToDisk(body: ResponseBody): Boolean {
    val appDirectoryName = "YOUR_DIRECTORY_NAME"
    val filename = "YOUR_FILE_NAME"
    val apkFile = File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), filename)
    try {

        var inputStream: InputStream? = null
        var outputStream: OutputStream? = null
        try {
            val fileReader = ByteArray(4096)
            val fileSize = body.contentLength()
            var fileSizeDownloaded: Long = 0
            inputStream = body.byteStream()
            outputStream = FileOutputStream(apkFile)
            while (true) {
                val read = inputStream!!.read(fileReader)
                if (read == -1) {
                    break
                }
                outputStream.write(fileReader, 0, read)
                fileSizeDownloaded += read.toLong()

           calulateProgress(fileSize.toDouble(),fileSizeDownloaded.toDouble()
                println("file downloading $fileSizeDownloaded of $fileSize")

            outputStream.flush()

            return true
        } catch (e: Exception) {
            println(e.toString())
            return false
        } finally {
            if (inputStream != null) {
                inputStream!!.close()
            }
            outputStream?.close()
        }
    } catch (e: Exception) {
        println(e.toString())
        return false
    }

}

以下方法用于计算进度

 fun calulateProgress(totalSize:Double,downloadSize:Double):Double{
    return ((downloadSize/totalSize)*100)
}

Answer 8

在 kotlin 中，执行此操作：

在您的服务中添加方法：

    @Streaming
    @GET
    suspend fun downloadFile(@Url fileUrl:String): Response<ResponseBody>

要从 ViewModel 调用此方法：

viewModelScope.launch {
     val responseBody=yourServiceInstance.downloadFile(url).body()
     saveFile(responseBody,pathWhereYouWantToSaveFile)
}

要保存文件：

fun saveFile(body: ResponseBody?, pathWhereYouWantToSaveFile: String):String{
        if (body==null)
            return ""
        var input: InputStream? = null
        try {
            input = body.byteStream()
            //val file = File(getCacheDir(), "cacheFileAppeal.srl")
            val fos = FileOutputStream(pathWhereYouWantToSaveFile)
            fos.use { output ->
                val buffer = ByteArray(4 * 1024) // or other buffer size
                var read: Int
                while (input.read(buffer).also { read = it } != -1) {
                    output.write(buffer, 0, read)
                }
                output.flush()
            }
            return pathWhereYouWantToSaveFile
        }catch (e:Exception){
            Log.e("saveFile",e.toString())
        }
        finally {
            input?.close()
        }
        return ""
    }

注：

确保您的 refrofit 客户端的基础 url 和传递给 downloadFile 的 url 使文件有效 url:

Retrofit's Base url + downloadFile's method url = File url

这里我在 downloadFile 之前使用 suspend 关键字从 ViewModel 调用它，我已经使用 viewModelScope.launch {} 你可以根据你的调用端使用不同的协程范围。
现在pathWhereYouWantToSaveFile，如果你想把文件存入项目的文件目录，你可以这样做：

val fileName=url.substring(url.lastIndexOf("/")+1)
val pathWhereYouWantToSaveFile = myApplication.filesDir.absolutePath+fileName

如果是将下载的文件存放在file或cache目录下，则不需要获取权限，否则public存放，过程你懂的。

Answer 9

使用 Kotlin，这有点简单。

API 服务

@GET
@Streaming
fun download(@Url url: String): Call<ResponseBody>

API 客户端

object ApiClient {
    private val retrofit = ...

    val service: ApiService = retrofit.create(ApiService::class.java)
}

下载函数

fun download(urlString: String, target: File) {
    val response = ApiClient.service.download(urlString).execute()
    response.body()?.byteStream()?.use {
        target.parentFile?.mkdirs()
    
        FileOutputStream(target).use { targetOutputStream ->
            it.copyTo(targetOutputStream)
        }
    } ?: throw RuntimeException("failed to download: $urlString")
}

如何使用 Retrofit 库下载 Android 中的文件？

How to download file in Android using Retrofit library?

android

download

retrofit