Doubt with ArrayAdapter,ArrayAdapterView

[vinoth vino]

I'm new to Android programming....Please anyone explain me in detail...

I don't know some code i'll explain list of things....

1. what is this "spin.setOnItemSelectedListener(this); " ? (I understood that this line will call the AdapterView.OnItemSelectedListener when selecting any country from country strings ) is this right ?
2. What is ArrayAdapter and AdapterView ?
3.AdapterView<?> arg0, View arg1, int position,long id ( please explain it one by one... what is AdapterView<?> arg0 ? , what is View arg1 ? and position,id ? why should i construct onItemSelectedListener with these things) ?
4. what is this <?> ?
5.Shall i change parent instead of arg0 and view instead of arg1 ?

    package com.example.spinner;  
    import android.app.Activity;  
    import android.os.Bundle;  
    import android.view.Menu;  
    import android.view.View;  
    import android.widget.AdapterView;  
    import android.widget.ArrayAdapter;  
    import android.widget.Spinner;  
    import android.widget.TextView;  
    import android.widget.Toast;  
      
    public class MainActivity extends Activity implements  
    AdapterView.OnItemSelectedListener {  
      
        String[] country = { "India", "USA", "China", "Japan", "Other",  };  
      
        @Override  
        protected void onCreate(Bundle savedInstanceState) {  
            super.onCreate(savedInstanceState);  
            setContentView(R.layout.activity_main);  
            //Getting the instance of Spinner and applying OnItemSelectedListener on it  
            Spinner spin = (Spinner) findViewById(R.id.spinner1);  
            spin.setOnItemSelectedListener(this);  
              
            //Creating the ArrayAdapter instance having the country list  
            ArrayAdapter aa = new ArrayAdapter(this,android.R.layout.simple_spinner_item,country);  
            aa.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);  
            //Setting the ArrayAdapter data on the Spinner  
            spin.setAdapter(aa);  
        }  
      
          
        //Performing action onItemSelected and onNothing selected  
        @Override  
        public void onItemSelected(AdapterView<?> arg0, View arg1, int position,long id) {  
            Toast.makeText(getApplicationContext(),country[position] ,Toast.LENGTH_LONG).show();  
        }  
      
        @Override  
        public void onNothingSelected(AdapterView<?> arg0) {  
            // TODO Auto-generated method stub  
              
        }  
      
        @Override  
        public boolean onCreateOptionsMenu(Menu menu) {  
            // Inflate the menu; this adds items to the action bar if it is present.  
            getMenuInflater().inflate(R.menu.activity_main, menu);  
            return true;  
        }  
    }  

Please anyone explain me this program fully

[Giovanni Montano]

vinoth vino wrote:I'm new to Android programming....Please anyone explain me in detail...

also java I guess. the question you ask are also java oriented in my opinion, I am junior as well but here are my replies, is good you are curious, but I would buy head first java where all these curiosities are really dealt in detail and in an humorous way, like slowing breaking a toy ..

1)
this is a listener. you can find milions of replies on google, is difficult to understand, because I guess you do not know the observer pattern.
when the button is pressed it trigs onItemSelected. How this happens? Because the class implements
AdapterView.OnItemSelectedListener that is an interface that obliges to implement the methods
2) this can be found on internet! what did you not understand from the documentation?
3)these are parameters..please look for : java parameters. If you learn the basis of java you can understand these concept really easily or you can do a search on java beginner forum in this site, there are ton of post explaining these things, but if you do not get conceptually does not have sense to explain it briefly.
4)<?> means any type, you should deal with generics before to understand how it works in the API like that. in head first java is well explained, also looking in the internet question mark java and wildcard java