这个需要配合PHP使用

 //需要在build.gradle添加
 implementation 'com.squareup.okhttp3:okhttp:3.7.0'
 implementation 'com.squareup.okio:okio:1.13.0'

 File file = new File(picturePath);
 //上传文件的格式
 String img_format = "image/*";
 //封装文件格式
 RequestBody requestFormat = RequestBody.create(MediaType.parse(img_format),file);
 //文件内容
 RequestBody requestBody = new MultipartBody.Builder()
             .setType(MultipartBody.FORM)
             .addFormDataPart("file",file.getName(),requestFormat)
             .build();
             //Okhttp网络数据传递
OkHttpClient client = new OkHttpClient.Builder()
             .build();
Request request = new Request.Builder()
            .url(链接)
            .post(requestBody)
            .build();
             Call call = client.newCall(request);
             call.enqueue(new Callback() {
             @Override
             public void onFailure(Call call, IOException e) {
             Log.i("onFailure",e.getMessage());
             }
             @Override
             public void onResponse(Call call, Response response) throws IOException {
             Log.i("上传至服务器成功",response.body().string());
          }
});