Android PopupWindow & some problems

1====main.xml.

 

Define a Show_button

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView 
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"
    />
    <Button android:id="@+id/show_button"
     android:layout_width="fill_parent"
     android:layout_height="40dp"
     android:text="Show"
    />
</LinearLayout>

 

2====popupwindow.xml

Define the Content to Popup Window

<?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="vertical">
  <TextView
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="NIhao,woahiaffaafaf!!@@@##"
   android:textSize="20sp"
   android:textColor="#FF0000"
  />
  <EditText
   android:layout_width="fill_parent"
   android:layout_height="30dp"
   android:id="@+id/name_edit"
  />
  <Button
   android:layout_width="100dp"
   android:layout_height="50dp"
   android:layout_gravity="center_horizontal"
   android:text="Enter Name"
   android:id="@+id/name_button"
  />
  <Button
   android:layout_width="100dp"
   android:layout_height="50dp"
   android:layout_gravity="center_horizontal"
   android:text="Cancel"
   android:id="@+id/cancel_button"
  />
</LinearLayout>

3====MainActivity.java

package com.android.tian;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.PopupWindow;

public class MainActivity extends Activity {
    /** Called when the activity is first created. */
 Button mShowBtn;
 Button mNameBtn;
 Button mCancelBtn;
 EditText mNameEdit;
 View vPopupWindowView;
 LayoutInflater inflater;
 PopupWindow mPopupWindow;
 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //获取控件
        mShowBtn = (Button)findViewById(R.id.show_button);
        mNameBtn = (Button)findViewById(R.id.name_button);
       
        //响应按钮事件
        mShowBtn.setOnClickListener(new ClickEvent());
       //??!!mCancelBtn.setOnClickListener(new ClickEvent());
    }

  public void showPopWindow(Context context,View parent){
   inflater = (LayoutInflater)     
          context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
   mCancelBtn = (Button)findViewById(R.id.cancel_button);
      mNameEdit=(EditText)findViewById(R.id.name_edit);
      //!!mNameBtn.setOnClickListener(new ClickEvent());
      mCancelBtn.setOnClickListener(new Button.OnClickListener(){
   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    mPopupWindow.dismiss();
   }
      });
   vPopupWindowView = inflater.inflate(R.layout.popupwindow,null,false);
   mPopupWindow = new PopupWindow(vPopupWindowView,300,300,true);
   //mPopupWindow.showAtLocation(parent,Gravity.LEFT,0,0);
   mPopupWindow.showAsDropDown(parent);
  }
 //统一处理的按钮事件类
  class ClickEvent implements OnClickListener {
  @Override
  public void onClick(View v) {
   // TODO Auto-generated method stub
   if((Button)v==mShowBtn){
    showPopWindow(MainActivity.this,MainActivity.this.findViewById(R.id.show_button));
   }else if((Button)v==mNameBtn){
    mNameEdit = (EditText)MainActivity.this.findViewById(R.id.name_edit);
    mNameEdit.setText("What");
   }else if((Button)v==mCancelBtn){
    mPopupWindow.dismiss();
   }
  }
 }
}

 

Problems:

 为什么出错！！！！

好像是mCancleBtn的响应事件的错误？？？可我不知道为什么，高手指教！