如何使用Retrofit库在Android下载文件？

时间：2015-10-01 02:22:00

标签： android download retrofit

我需要在我的应用程序中使用Retrofit库下载所有类型的文件（二进制文件，图像，文本等）。网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？

8 个答案:

答案 0 :(得分：9)

使用@Streaming

异步

编辑1 

//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();
}

<强>同步 

ls -R /Users/samuel/Apps/assets/images  | grep "*.jpg" > file_names.txt

答案 1 :(得分：8)

对于kotlin，请执行以下操作：

在您的服务添加方法中：

    @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 ""
    }

注意：

  1. 确保您的refrofit客户端的基本url和传递给downloadFile的url使得有效的文件url为：

Retrofit的基本url + downloadFile的方法url = File url

  1. 在这里，我在downloadFile之前使用suspend关键字从ViewModel调用它，我已经使用过viewModelScope.launch {}，可以根据调用者的端使用不同的协程范围。

  2. 现在pathWhereYouWantToSaveFile，如果要将文件存储到项目的文件目录中，可以执行以下操作：

val fileName=url.substring(url.lastIndexOf("/")+1)
val pathWhereYouWantToSaveFile = myApplication.filesDir.absolutePath+fileName
  1. 如果要将下载的文件存储在文件目录或缓存下，则无需获取许可，否则，对于公共存储，您知道此过程。

答案 2 :(得分：5)

这是如何在Retrofit 2中下载文件

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) {
                    }
                });
}

答案 3 :(得分：2)

如果您使用Retrofit 2.0.0，则可以在问题answer下引用我的Use retrofit to download image file。

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

并且您希望使用POST方法来获取文件，这很简单，只需将@GET更改为@POST，但这取决于您的服务器是否支持POST 1}}方法！

答案 4 :(得分：2)

您可以使用以下代码进行进度下载（Kotlin）

Retrofit Api服务

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

确保为大文件下载添加@ {Streming}

并将以下代码粘贴到“活动”或“片段”中

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.getFile("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)
}

答案 5 :(得分：1)

我使用以下代码使用改造来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;
    }
}

答案 6 :(得分：0)

在MainActivity.java中包含以下功能：

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

答案 7 :(得分：0)

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);

这样声明您的请求后

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");
    }
});

还可以实现此方法以将其归档到您的SD卡中。

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;
    }
}
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