The following code shows how to update Button text when clicking.
import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.Button; import java.util.Date; public class MainActivity extends Activity implements View.OnClickListener { Button btn; @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); btn = new Button(this); btn.setOnClickListener(this); updateTime(); setContentView(btn); } public void onClick(View view) { updateTime(); } private void updateTime() { btn.setText(new Date().toString()); } }