Android practical tutorial: Simple implementation of call function

<LinearLayout xmlns:andro 
 xmlns:tools="/tools" 
 android:layout_width="match_parent" 
 android:layout_height="match_parent" 
 tools:context=".MainActivity" 
 android:orientation="vertical" 
 > 
 
 <TextView 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
  android:text="Please enter a number" /> 
 <EditText 
  android: 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content" 
  /> 
 <Button 
  android: 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
  android:text="Call" 
  /> 
 
</LinearLayout> 

package ; 
 
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public class MainActivity extends Activity { 
 
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
  (savedInstanceState); 
  setContentView(.activity_main); 
   
  //Set the button to listen click  //1. Get the button object  Button bt = (Button) findViewById(.bt_call);//Button class is a subclass of View, and it is necessary to transform downward.  //2. Set listening  (new MyListener()); 
 } 
 
 class MyListener implements OnClickListener{ 
 
  //This method is called when the button is clicked  @Override 
  public void onClick(View v) { 
   //Get the number entered by the user   EditText et = (EditText) findViewById(.et_phone); 
   String phone = ().toString(); 
    
   //We need to tell the system, our actions: I want to call   //Create an intent object   Intent intent = new Intent(); 
   //Encapsulate the call action ACTION_CALL into the intent object   (Intent.ACTION_CALL); 
   //Set to whom   (("tel:" + phone));//This tel: It must be added, indicating that I want to call.  Otherwise, there will be no call function, because this "protocol" is set in the call list file.    
   //Tell the action of the system and start the system calling function.   startActivity(intent); 
  } 
   
 } 
  
}