[JAVA] Programming from 51 years old Note Android Asynchronous communication callback Processing after AsyncTask ends Further generalization / standardization

Asynchronous communication callback

It is used when you want to do something after the processing of AsyncTask is completed.

MainActivity

public class MainActivity extends AppCompatActivity{

    TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = findViewById(R.id.tv);

        AsyncCallBack asyncCallBack = new AsyncCallBack();
        MyAsyncTask myAsyncTask = new MyAsyncTask(asyncCallBack);
        myAsyncTask.execute();
    }

    public class AsyncCallBack{
        public void callBack(String s){
            //Describe the process you want to do after the AsyncTask ends
            tv.setText(s);
        }
    }
}

MyAsyncTask

public class MyAsyncTask extends AsyncTask<Void,Void,String> {

    private MainActivity.AsyncCallBack callBack = null;

    public MyAsyncTask(MainActivity.AsyncCallBack callBack){
        this.callBack = callBack;
    }

    @Override
    protected String doInBackground(Void... aVoid) {
        return "success";
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
        callBack.callBack(s);
    }
}

SampleCode that generalizes / standardizes AnsycTask

It would be very difficult to write AsyncTask code every time asynchronous communication is performed.

From the caller

AsyncCallBack callBack  = new AsyncCallBack();
AsyncTask     asyncTask = new AsyncTask(callback);

I want to be able to call it from anywhere.

With the above "CallBack for asynchronous communication" method, in the constructor of AsyncTask I received an argument with \ <MainActivity.AsyncCallBack asyncCallBack>, but I can't generalize with this. So using Interface to be able to declare the AsyncCallBack type Generalize by accepting arguments with \ .

I will also use HashMap to make the parameters portable.
Then the interface!

CallBack.interface

interface CallBack{
   public void Receiver(Map<String,String> map);
}

Now you can use CallBack type arguments!

AsyncTaskSample.java

public class AsyncTaskSample extends AsyncTask<Map<String,String>,Void,Map<String,String>{

   AsyncTaskCallBack callback;

   public AsyncTaskSample(AsyncTaskCallBack callBack){
      this.callback = callBack;
   }
   
   @Override 
   protected Map<String,String> doInBackground(Map<String,String>... map){
      return map[0];
   }

   @Override 
   protected void onPostExecute(Map<String,String> map){
      super.onPostExecute(map);
      callback.Receiver(map);
   }
}

MainActivity.java

public class MainActivity extends AppCompatActivity implements CallBack{ //Extend CallBack

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

      AsyncTaskSample  async = new AsyncTaskSample(this);
      Map<String,String> map = new HashMap<String,String>();
         map.put("key","MainActivity");
      async.execute(map);

      new SampleClass.SampleClass();
   }

   @Override 
   public void Receiver(Map<String,String> map) {
      Log.d("=====>",map.get("key");
   }

SampleClass.java

public class SampleClass implemants CallBack{ //Extend CallBack

   void SampleClass(){
      AsyncTaskSample  async = new AsyncTaskSample(this);
      Map<String,String> map = new HashMap<String,String>();
         map.put("key","SampleClass");
      async.execute(map); 
   }
   
   @Override 
   public void Receiver(Map<String,String> map){
      Log.d("=====>",map.get("key");
   }
}