Android uses OkHttp to download and upload pictures

public class MainActivity extends AppCompatActivity {

  private String Path = "/eth/ajNVdqHZLLAxibwnrOxXSzIxA76ichutwMCcOpA45xjiapneMZsib7eY4wUxF6XDmL2FmZEVYsf86iaw/";
  private static final int SUCCESS = 993;
  private static final int FALL = 814;
  Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
      switch () {
        //The network is loaded successfully, the UI is updated, and the obtained image resources are processed        case SUCCESS:
          //Get the byte array through message          byte[] Picture = (byte[]) ;
          //Use the BitmapFactory factory to convert the byte array into bitmap          Bitmap bitmap = (Picture, 0, );
          //Set the picture through ImageView          mImageView_okhttp.setImageBitmap(bitmap);
          break;
        // When the network loading fails, the logical code executed        case FALL:
          (, "Network exception", Toast.LENGTH_SHORT).show();
          break;

        default:
          break;
      }
    }
  };
  private ImageView mImageView_okhttp;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    (savedInstanceState);
    setContentView(.activity_main);
    //Initialize the control    initView();
  }

  private void initView() {
    mImageView_okhttp = (ImageView) findViewById(.imageView_okhttp);
  }

  /**
    * Obtain the image resources on the network based on the click event, using the OKhttp framework
    *
    * @param view
    */
  public void Picture_okhttp_bt(View view) {
    //1. Create OKhttpClient object    OkHttpClient okHttpClient = new OkHttpClient();
    //2. Create a Request object, set parameters, and if the request method is get, you don't need to set it. The default is get    Request request = new ()
        .url(Path)//Set the request URL        .build();//Create a request object    //3. Create a Call object with the parameter request object and send a request    Call call = (request);
    //4. Asynchronous request, request to join the schedule    (new Callback() {
      @Override//Request failed callback      public void onFailure(Call call, IOException e) {
        (FALL);
      }

      @Override//Request successfully callback      public void onResponse(Call call, Response response) throws IOException {
        //Get to get resources from the Internet and convert them to the type we want        byte[] Picture_bt = ().bytes();
        //Update the UI through handler        Message message = ();
         = Picture_bt;
         = SUCCESS;
        (message);

      }
    });
  }

  //When the button is clicked, use OKhttp to upload the image to the server (/tangxl2008008/article/details/51777355)  //Note: Sometimes the upload of images fails, and the server stipulates that a key must be uploaded. If there is a problem with the network during development, communicate more with the interviewer.  public void uploading(View view) {
    //Picture upload interface address    String url = "https:///sell/";
    //Create upload file object    File file = new File((), "");

    //Create RequestBody encapsulation parameters    RequestBody fileBody = (("application/octet-stream"), file);
    //Create MultipartBody and set RequestBody    MultipartBody multipartBody = new ()
        .setType()
        .addFormDataPart("image", "", fileBody)
        .build();
    //Create Request    Request request = new ()
        .url(url)
        .post(multipartBody)
        .build();

    //Create an okhttp object    OkHttpClient okHttpClient = new ()
        .connectTimeout(10, )
        .readTimeout(10, )
        .writeTimeout(10, )
        .build();

    //After uploading the picture, you will get the server feedback data    (request).enqueue(new Callback() {
      @Override
      public void onFailure(Call call, IOException e) {
        ("ff", "uploadMultiFile() e=" + e);
      }

      @Override
      public void onResponse(Call call, Response response) throws IOException {
        ("ff", "uploadMultiFile() response=" + ().string());
      }
    });


  }

}

<RelativeLayout
  xmlns:andro
  xmlns:tools="/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context=".picture_okhttp.MainActivity">


  <Button
    android:
    android:onClick="Picture_okhttp_bt"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Download Picture"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="59dp"/>

  <Button
    android:text="Upload pictures"
    android:onClick="uploading"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:
    android:layout_alignParentTop="true"
    android:layout_alignLeft="@+id/button"
    android:layout_alignStart="@+id/button"/>

  <ImageView
    android:
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"/>

</RelativeLayout>

implementation '.okhttp3:okhttp:3.4.2'