I want to add a function for my button, but don't know how

That's my XML file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal" >
<Button
    android:id="@+id/btFinish"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="onClick"
    android:text="Finish" />
<Button
    android:id="@+id/btClicked"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="onClick"
    android:text="Clicked" />
</LinearLayout>

And that's my method: public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    final Button bt = (Button) findViewById(R.id.btClicked);
    bt.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            switch (v.getId()) {
                case R.id.btFinish:
                    finish();
                    break;

                case R.id.btClicked:
                    bt.setText("UnClicked");

            }
        }
    });
 }
}

I want to add a function that if clicked again, the text reverts to "Clicked".