1.导入依赖 

  //Retrofit 核心库
    implementation("com.squareup.retrofit2:retrofit:2.9.0")
    //响应数据自动序列化
    //JSON
    implementation("com.squareup.retrofit2:converter-gson:2.9.0")
    //String类型
    implementation("com.squareup.retrofit2:converter-scalars:2.9.0")
    //拦截器 logging
    implementation("com.squareup.okhttp3:logging-interceptor:3.14.+")

2.需要配置清单文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android">

    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.OkHttp"
        android:networkSecurityConfig="@xml/network_security_config">
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <provider

            android:authorities="${applicationId}.provider"
            android:name="androidx.core.content.FileProvider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/provider_paths"/>
        </provider>
    </application>

</manifest>

3.网络权限和 provider

provider_paths.xml

<?xml version="1.0" encoding="utf-8" ?>
<paths>
    <external-path
        name="aaa"
        path="."/>
    
</paths>

network_security_config.xml

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
    <base-config cleartextTrafficPermitted="true" />
</network-security-config>

4.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/upload"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="上传图片"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

5.ApiService

package com.tiger.retrofel.api;

import java.util.List;
import java.util.Map;

import okhttp3.MultipartBody;
import retrofit2.Call;
import retrofit2.http.Field;
import retrofit2.http.FormUrlEncoded;
import retrofit2.http.GET;
import retrofit2.http.Multipart;
import retrofit2.http.POST;
import retrofit2.http.Part;
import retrofit2.http.Query;

public interface ApiService {

    @POST("findList")
    @FormUrlEncoded
    Call<Map<String,Object>> test(
            @Field("start") Integer start,
            @Field("count") Integer count
    );

    @POST("uploadPic")
    @Multipart
    Call<Map<String,Object>> upload(
            @Part MultipartBody.Part part
            );




}

6.权限工具类

package com.tiger.retrofel;

import android.Manifest;
import android.app.Activity;
import android.content.pm.PackageManager;
import android.os.Build;

import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

public class PermissionUtil {

    public static final String[] PERMISSIONS_EXTERNAL_STORAGE = new String[]{
            Manifest.permission.READ_EXTERNAL_STORAGE,
            Manifest.permission.WRITE_EXTERNAL_STORAGE
    };


    public static final int PERMISSIONS_EXTERNAL_STORAGE_TAG = 1;

 
    //检查多个权限。返回true表示已完全启用权限，返回false 表示 未完全启用权限
    public static boolean checkPermission(Activity act, String[] permissions, int requestCode) {
 
        //Android 6.0之后开始采用动态权限管理
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            int check = PackageManager.PERMISSION_GRANTED;
            for (String permission : permissions) {
                check = ContextCompat.checkSelfPermission(act, permission);
                if (check != PackageManager.PERMISSION_GRANTED) {
                    break;
                }
            }
            //未开启该权限，则请求系统弹窗，好让用户选择 是否立即开启权限
            if (check != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(act, permissions, requestCode);
                return false;
            }
 
        }
 
        return true;
    }
 
 
    public static boolean checkGrant(int[] grantResults) {
        if (grantResults != null) {
            for (int grantResult : grantResults) {
                if (grantResult != PackageManager.PERMISSION_GRANTED) {
                    return false;
                }
            }
            return true;
        } else {
            return false;
        }
    }
}

7.Activity

package com.tiger.retrofel;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.tiger.retrofel.api.ApiService;
import com.tiger.retrofel.api.Subject;

import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.Map;

import okhttp3.MediaType;
import okhttp3.MultipartBody;
import okhttp3.OkHttpClient;
import okhttp3.RequestBody;
import okhttp3.logging.HttpLoggingInterceptor;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;
import retrofit2.converter.scalars.ScalarsConverterFactory;

public class MainActivity extends AppCompatActivity {
    Retrofit retrofit;
    private OkHttpClient client;
    private ApiService apiService;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        HttpLoggingInterceptor httpLoggingInterceptor = new HttpLoggingInterceptor(new HttpLoggingInterceptor.Logger() {
            @Override
            public void log(String message) {
                Log.i("TAG", message);
            }
        }).setLevel(HttpLoggingInterceptor.Level.BASIC);

        client = new OkHttpClient.Builder()
                .addInterceptor(httpLoggingInterceptor)
                .build();
        retrofit = new Retrofit.Builder()
                .baseUrl("http://192.168.202.55:8999/")
                .client(client)
//                .addConverterFactory(ScalarsConverterFactory.create())
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        apiService = retrofit.create(ApiService.class);

        Button viewById = findViewById(R.id.upload);
        viewById.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showPhoto();
            }
        });

        syncRequest();

    }

    //同步的请求
    private void syncRequest() {
        //同步
        new Thread(() -> {

            Response<Map<String,Object>> execute = null;
            try {
                execute = apiService.test(0, 2).execute();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
            Map<String,Object> body = execute.body();
                Log.i("ning", "run:response：" + body);

        }).start();

    }


    //异步的请求
    private void ayncRequest() {
        //同步

            try {
                 apiService.test(0, 2).enqueue(new Callback<Map<String,Object>>() {
                     @Override
                     public void onResponse(Call<Map<String,Object>> call, Response<Map<String,Object>> response) {

                     }

                     @Override
                     public void onFailure(Call<Map<String,Object>> call, Throwable t) {

                     }
                 });

            } catch (Exception e) {
              e.printStackTrace();
            }


    }
    private void showPhoto() {

        if (PermissionUtil.checkPermission(this, PermissionUtil.PERMISSIONS_EXTERNAL_STORAGE, PermissionUtil.PERMISSIONS_EXTERNAL_STORAGE_TAG)) {
            //有权限
            // 跳转到系统相册，选择图片，并返回
            Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);

            startActivityForResult(intent,1);
        }


    }


    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
//        Log.d("ning","进来了"+resultCode+":"+resultCode);
        //获取图片路径
        if (requestCode==1 && resultCode == Activity.RESULT_OK &&data!=null){
            Uri selectedImage = data.getData();
            String[] filePathColumns ={MediaStore.Images.Media.DATA};
            Cursor query = getContentResolver().query(selectedImage, filePathColumns, null, null, null);
            query.moveToFirst();
            int columnIndex = query.getColumnIndex(filePathColumns[0]);
            String string = query.getString(columnIndex);
            Log.d("ning",string);
            uploadFile(string);
            query.close();
        }
    }



    public void uploadFile(String path){
        File file = new File(path);
        RequestBody requestBody = RequestBody.create(MediaType.parse("image/jp"),file);

        MultipartBody.Part part = MultipartBody.Part.createFormData("pic",file.getName(),requestBody);

     apiService.upload(part).enqueue(new Callback<Map<String, Object>>() {
         @Override
         public void onResponse(Call<Map<String, Object>> call, Response<Map<String, Object>> response) {
             Log.d("ning",response.body().get("result").toString());
         }

         @Override
         public void onFailure(Call<Map<String, Object>> call, Throwable t) {

         }
     });


    }

}

8.实体类

public class Subject {
    private String episodes_info;
    private String rate;
    private Integer cover_x;
    private String title;
    private String url;
    private Boolean playable;
    private String cover;
    private String id;
    private Integer cover_y;
    private Boolean is_new;