封装popwindow类，实现所有activity共用

popwindow是一个弹出window，在此对其进行封装，使这个popwindow可以在所有页面都显示。

在CSDN上有类似的封装类供下载，可以去自行下载然后做修改。附上地址：http://download.csdn.net/download/duanyu218/5045677

这样一来就会出现一个问题，定义popwindow上的item的点击事件做相应的动作的时候，就会提示空指针异常，从而强制退出程序。如下将分析如何解决：

1、定义公用类 以便调用所有activity调用

package com.ytumobilelibrary.common;

import com.ytumobilelibrary.readerservice.LoginActivity;

import android.app.Activity;

import android.content.Context;

import android.content.Intent;

import android.content.SharedPreferences;

import android.os.Bundle;

import android.view.View;

import android.widget.AdapterView;

import android.widget.ImageButton;

import android.widget.Toast;

import android.widget.AdapterView.OnItemClickListener;

public class CommonPopWindowActivity extends Activity {

private PopMenu popMenu; //此popmenu是2中定义的popwindow生成类

private Context context;

private Context current_activity;

private static CommonPopWindowActivity instance;

public synchronized static CommonPopWindowActivity getInstance() {

if (null == instance) {

instance = new CommonPopWindowActivity();

}

return instance;

}

public void buildPopWindow(Activity activity, ImageButton popWind) {

this.context = activity;

popMenu = new PopMenu(context);

popMenu.addItems(new String[] { "登录", "注销","使用说明", "关于软件" });

// 菜单项点击监听器

popMenu.setOnItemClickListener(popmenuItemClickListener);

popWind.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

popMenu.showAsDropDown(v);

}

});

}

// 弹出菜单监听器

OnItemClickListener popmenuItemClickListener = new OnItemClickListener() {

@Override

public void onItemClick(AdapterView<?> parent, View view, int position,

long id) {

current_activity = view.getContext();

// current_activity 的定义是为了取得调用此方Activity

//的本身实例，这样才不会报空指针异常。

System.out.println("下拉菜单点击" + position);

// 取得item上的值

// HashMap<String, Object> item = (HashMap<String, Object>)

// adapterView

// .getItemAtPosition(position);

Intent intent = new Intent();

intent.putExtra("Flag", RS_FLAG);
intent.setClass(current_activity, LoginActivity.class);
((Activity) current_activity).startActivityForResult(

intent, 5);

popMenu.dismiss();

};

}

2、定义pop类

package com.ytumobilelibrary.common;

import java.util.ArrayList;

import com.ytumobilelibrary.R;

import android.content.Context;

import android.graphics.drawable.BitmapDrawable;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.AdapterView.OnItemClickListener;

import android.widget.BaseAdapter;

import android.widget.ListView;

import android.widget.PopupWindow;

import android.widget.TextView;

public class PopMenu {

private ArrayList<String> itemList;

private Context context;

private PopupWindow popupWindow;

private ListView listView;

// private OnItemClickListener listener;

public PopMenu(Context context) {

this.context = context;

itemList = new ArrayList<String>(5);

View view = LayoutInflater.from(context)

.inflate(R.layout.popmenu, null);

// 设置 listview

listView = (ListView) view.findViewById(R.id.popwin_listView);

listView.setAdapter(new PopAdapter());

listView.setFocusableInTouchMode(true);

listView.setFocusable(true);

// popupWindow = new PopupWindow(view, 100, LayoutParams.WRAP_CONTENT);

popupWindow = new PopupWindow(view,context.getResources()

.getDimensionPixelSize(R.dimen.popmenu_width),

context.getResources()

.getDimensionPixelSize(R.dimen.popmenu_height));

// context.getResources()

// .getDimensionPixelSize(R.dimen.popmenu_width)

// 这个是为了点击“返回Back”也能使其消失，并且并不会影响你的背景（很神奇的）

popupWindow.setBackgroundDrawable(new BitmapDrawable());

}

// 设置菜单项点击监听器

public void setOnItemClickListener(OnItemClickListener listener) {

// this.listener = listener;

listView.setOnItemClickListener(listener);

}

// 批量添加菜单项

public void addItems(String[] items) {

for (String s : items)

itemList.add(s);

}

// 单个添加菜单项

public void addItem(String item) {

itemList.add(item);

}

// 下拉式 弹出 pop菜单 parent 右下角

public void showAsDropDown(View parent) {

popupWindow.showAsDropDown(parent,

10,

// 保证尺寸是根据屏幕像素密度来的

context.getResources().getDimensionPixelSize(

R.dimen.popmenu_yoff));

// 使其聚集

popupWindow.setFocusable(true);

// 设置允许在外点击消失

popupWindow.setOutsideTouchable(true);

// // 刷新状态

popupWindow.update();

}

// 隐藏菜单

public void dismiss() {

popupWindow.dismiss();

}

// 适配器

private final class PopAdapter extends BaseAdapter {

@Override

public int getCount() {

// TODO Auto-generated method stub

return itemList.size();

}

@Override

public Object getItem(int position) {

// TODO Auto-generated method stub

return itemList.get(position);

}

@Override

public long getItemId(int position) {

// TODO Auto-generated method stub

return position;

}

@Override

public View getView(int position, View convertView, ViewGroup parent) {

// TODO Auto-generated method stub

ViewHolder holder;

if (convertView == null) {

convertView = LayoutInflater.from(context).inflate(

R.layout.pomenu_item, null);

holder = new ViewHolder();

convertView.setTag(holder);

holder.groupItem = (TextView) convertView

.findViewById(R.id.popwin_textView);

} else {

holder = (ViewHolder) convertView.getTag();

}

holder.groupItem.setText(itemList.get(position));

return convertView;

}

private final class ViewHolder {

TextView groupItem;

}

}

}

3、pomenu_item.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="120.0dip"

android:layout_height="wrap_content"

android:orientation="vertical"

android:gravity="center_vertical"
android:background="@drawable/bg_pop_item" > //点击item的变化图片 如5所示

<TextView

android:id="@+id/popwin_textView"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:layout_marginTop="10.0dip"

android:gravity="center"

android:text="测试"

android:textColor="#FFFFFF"

android:textSize="17.0dip" />

</LinearLayout>

4、pomenu.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:id="@+id/popup_view_cont"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical"

>

<ListView

android:id="@+id/popwin_listView"

android:layout_width="fill_parent"

android:layout_height="0.0dip"

android:layout_weight="1.0"
android:background="@drawable/map_tips" //图片可以自己定义，popwindow的背景图片

android:cacheColorHint="#00000000"

android:divider="@drawable/line2"

android:dividerHeight="4.0dip"

android:focusable="true"

android:scrollbars="none" >

</ListView>

</LinearLayout>

5、bg_pop_item.xml

<?xml version="1.0" encoding="utf-8"?>

<selector xmlns:android="http://schemas.android.com/apk/res/android">

<item android:drawable="@drawable/home_btn_bg_s"

android:state_pressed="true"/>

<item android:drawable="@drawable/home_btn_bg_s"

android:state_enabled="true"

android:state_focused="true"/>

<item android:drawable="@drawable/home_btn_bg_s"

android:state_checked="true"

android:state_enabled="true"

></item>

</selector>

在所有Activity中调用公用类CommonPopWindowActivity 的方法如下：

// ImageButton 是所有activity中定义的ImageButton，点击此bt可以弹出popwindow

ImageButton popWind = (ImageButton) findViewById(R.id.radio_button4);

//加载popwindow this就是该activity的实例，这样在CommonPopWindowActivity类中跳转页面或者弹出toast才不会报空指针异常

CommonPopWindowActivity.getInstance().buildPopWindow(this,popWind);