在Android中弹出？

import android.app.*;
import android.os.bundle;
import android.view.Gravity;
import android.view.View;
import android.view.View.onClickListener;
import android.view.ViewGroup.LayoutParams;
import android.widget.*;

public class ShowPopUp extends Activity {

PopupWindow popUp;
LinearLayout layout;
TextView tv;
LayoutParams params;
LinearLayout mainLayout;
Button but;
Boolean click = true;


public void onCreate(Bundle savedInstanceStatE) {
    super.onCreate(savedInstanceStatE);
    popUp = new PopupWindow(this);
    layout = new LinearLayout(this);
    mainLayout = new LinearLayout(this);
    tv = new TextView(this);
    but = new Button(this);
    but.setText("Click Me");
    but.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {
            if (click) {
                popUp.showAtLOCATIOn(mainLayout,Gravity.bOTTOM,10,10);
                popUp.update(50,50,300,80);
                click = false;
            } else {
                popUp.dismiss();
                click = true;
            }
        }

    });
    params = new LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
    layout.setOrientation(LinearLayout.VERTICAL);
    tv.setText("Hi this is a sample text for popup window");
    layout.addView(tv,params);
    popUp.setContentView(layout);
    // popUp.showAtLOCATIOn(layout,10);
    mainLayout.addView(but,params);
    setContentView(mainLayout);
       }
   }