Android Case 1: Dialer

package org.dreamtech.helloworld;

import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

    private EditText et_number;

    @Override
    protected  void onCreate (Bundle savedInstanceState) {
         super .onCreate (savedInstanceState);
        setContentView(R.layout.activity_main);
        et_number = (EditText) findViewById(R.id.editText1);
        Button btn_call = (Button) findViewById(R.id.button1);
        btn_call.setOnClickListener(new MyClickListener());
    }
    
    private class MyClickListener implements OnClickListener{

        @Override
        public void onClick(View v) {
            //get
            String number = et_number.getText().toString().trim();
            if("".equals(number)){
                Toast.makeText(MainActivity.this , "can't be empty" , Toast.LENGTH_LONG ).show();
                 return ;
            }
            
            Intent intent = new Intent();
            intent.setAction(Intent.ACTION_CALL);
            intent.setData(Uri.parse("tel:"+number));
            startActivity(intent);
        }
        
    }
}

 

Pay attention to setting permissions:

 

layout: