Android Başlangıç basit bir soru

setContentView(R.layout.layout_adi)

TextView txt = (TextView) findViewById(R.id.tvSonuc); 
  TextView et = (EditText) findViewById(R.id.etGiris); 
  Button btn = (Button) findViewById(R.id.btnIslem);

<Button 
          android:id="@+id/btnIslem" 
          style="?android:attr/buttonStyleSmall" 
          android:layout_width="match_parent" 
          android:layout_height="wrap_content" 
          android:layout_margin="20dp" 
          android:text="Button" />

    <Button 
          android:id="@+id/btnIslem" 
          style="?android:attr/buttonStyleSmall" 
          android:layout_width="match_parent" 
          android:layout_height="wrap_content" 
          android:layout_margin="20dp" 
          android:onClick="sifreKontrol" 
          android:text="Button" />

public void sifreKontrol(View v) 
  { 
      // Kullanıcının Edittext'e Girdigi Degeri Alalim 
      String val = et.getText().toString(); 
      // Sifre Kontrolunu Yapalim 
      if (va.equals("12345")) 
          txt.setText("Şifre Doğru"); 
      else 
          txt.setText("Şifre Yanlış"); 
  }

public class App extends Activity 
  { 
      TextView tv; 
      EditText et; 
   
     onCReate(..) {...} 
  } 
  

package com.example.yeni; 
   
  import android.support.v7.app.ActionBarActivity; 
  import android.content.Intent; 
  import android.media.MediaPlayer; 
  import android.os.Bundle; 
  import android.view.Menu; 
  import android.view.MenuItem; 
  import android.view.View; 
  import android.widget.Button; 
  import android.widget.EditText; 
  import android.widget.TextView; 
   
   
   
  public class MainActivity extends ActionBarActivity { 
   
  	//MediaPlayer ses; 
      @Override 
      protected void onCreate(Bundle savedInstanceState) { 
          super.onCreate(savedInstanceState); 
          setContentView(R.layout.activity_main); 
       
  		 
  		MediaPlayer ses=MediaPlayer.create(MainActivity.this,R.raw.sess); 
  		ses.start(); 
           
      final TextView goster = (TextView)findViewById(R.id.textView1);   
      final EditText al = (EditText)findViewById(R.id.editText1); 
      Button b=(Button)findViewById(R.id.button1);    
      Button b2=(Button)findViewById(R.id.button2); 
      b.setOnClickListener(new View.OnClickListener(){ 
      	 
       
      	public void sifreKontrol(View v) 
      	{ 
      	    // Kullanıcının Edittext'e Girdigi Degeri Alalim 
      	    String val = al.getText().toString(); 
      	    // Sifre Kontrolunu Yapalim 
      	    if (val.equals("12345")) 
      	        goster.setText("Şifre Doğru"); 
      	    else 
      	        goster.setText("Şifre Yanlış"); 
      	} 
      	 
      	 
    
      b2.setOnClickListener(new View.OnClickListener() { 
  		 
  		@Override 
  		public void onClick(View v) { 
  			 
  			startActivity(new Intent("android.intent.action.DIGER")); 
  		} 
  	}); 
       
       
      } 
   
   
      @Override 
      public boolean onCreateOptionsMenu(Menu menu) { 
          // Inflate the menu; this adds items to the action bar if it is present. 
          getMenuInflater().inflate(R.menu.main, menu); 
          return true; 
      } 
   
      @Override 
      public boolean onOptionsItemSelected(MenuItem item) { 
          // Handle action bar item clicks here. The action bar will 
          // automatically handle clicks on the Home/Up button, so long 
          // as you specify a parent activity in AndroidManifest.xml. 
          int id = item.getItemId(); 
          if (id == R.id.action_settings) { 
              return true; 
          } 
          return super.onOptionsItemSelected(item); 
      } 
  }