Android : Can not access button

Good Day

I want to try some stuff with Android Studio (im oretty new in java) So what I want to do is a Tic-Tac-Toe. I have created a button and want to assign this button a function.

public class TicTacToe extends ActionBarActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_tic_tac_toe);
    /*Button i created*/
    Button btn1 = (Button)findViewById(R.id.button1);
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_tic_tac_toe, 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();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

public void onClick(View view){
    btn1 /*is not recognized. and here i want the button to do something. but its 
    not possible. Where is the mistake?*/
}
}

Here the xml

    <TextView
    android:layout_width="60dp"
    android:layout_height="60dp"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:id="@+id/text1"
    android:onClick="changeText"
    android:layout_alignBottom="@+id/button1"
    android:layout_toLeftOf="@+id/button2"
    android:layout_alignLeft="@+id/button1"
    android:layout_alignStart="@+id/button1"
    android:layout_alignTop="@+id/button1" />

Do you guys have any idea? Am I doing errors in reasoning? Thanks in advance FIISHxMAN