Android 封装popwindow类，实现所有activity共用

来源：互联网发布：android 虚拟机 java 编辑：程序博客网时间：2024/06/18 15:51

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/detail/jdsjlzx/9583823

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。

定义公用类以便调用所有activity调用。

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();        };}

定义pop类

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;        }    }}

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" >     <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>

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"     android:cacheColorHint="#00000000"    android:divider="@drawable/line2"    android:dividerHeight="4.0dip"    android:focusable="true"    android:scrollbars="none" >    </ListView></LinearLayout>

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popwindowImageButton 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);

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