android开发实例06：popwindow实现下拉菜单

夜未眠，popwindow很好用一种控件，实现一些自定义效果很方便。要想在不同屏幕尺寸的手机上显示的话，就要在代码中设置dip的长度值，很多人都会在代码中用方法转换

// px转换成dip
    public int dip2px(Context context, float dipValue){  
                   final float scale = context.getResources().getDisplayMetrics().density;  
                   return ( int)(dipValue * scale + 0.5f);   
  }

但是有很多机器偏差很大，其实android资源文件中还有dimens.xml这种资源文件。可能这个dimens.xml大家不经常用，它和 strings.xml一样，只不过strings.xml放置字符串而 dimens.xml 放置长度值。dimens引用方法 getResources().getDimension(R.dimen.pop_y)；在代码中引用dip，sp.....类型不会变，也不要转换，很方便。代码已经整理打包；

 

package com.johnson.popwindow;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

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.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.PopupWindow;
import android.widget.PopupWindow.OnDismissListener;
import android.widget.SimpleAdapter;
import android.widget.Toast;

public class PopwindowActivity extends Activity {

   private ImageView arrow;
   private boolean isOpenPop = false;
   private PopupWindow window;
   private ListView list;
   private LinearLayout title_layout;
   public static final String KEY = "key";
  ArrayList<Map<String, Object>> items = new ArrayList<Map<String, Object>>();
  Context mContext;
  @Override
   protected void onCreate(Bundle savedInstanceState) {
     // TODO Auto-generated method stub
     super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    mContext= this;
    arrow = (ImageView) findViewById(R.id.arrow);
    title_layout = (LinearLayout) findViewById(R.id.title_layout);
    title_layout.setOnClickListener( new OnClickListener() {

      @Override
       public void onClick(View v) {
         // TODO Auto-generated method stub
    
        changPopState(v);

      }
    });
  }

   /**
    * 更改Pop状态
    * */

   public void changPopState(View v) {

    isOpenPop = !isOpenPop;
     if (isOpenPop) {
      arrow.setBackgroundResource(R.drawable.icon_arrow_up);
      popAwindow(v);

    } else {
      arrow.setBackgroundResource(R.drawable.icon_arrow_down);
       if (window != null) {
        window.dismiss();

      }
    }
  }

   private void popAwindow(View parent) {
     if (window == null) {
      LayoutInflater lay = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
      View v = lay.inflate(R.layout.pop, null);
      list = (ListView) v.findViewById(R.id.pop_list);

      SimpleAdapter adapter = new SimpleAdapter( this, CreateData(),
          R.layout.pop_list_item, new String[] { KEY },
           new int[] { R.id.title });

      list.setAdapter(adapter);
      list.setItemsCanFocus( false);
      list.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
      list.setOnItemClickListener(listClickListener);
       // window = new PopupWindow(v, 260, 300);
       int x = ( int) getResources().getDimension(R.dimen.pop_x);
       int y = ( int) getResources().getDimension(R.dimen.pop_y);
      window = new PopupWindow(v, x, y);
    }
    window.setBackgroundDrawable(getResources().getDrawable(
        R.drawable.pop_bg));
    window.setFocusable( true);
    window.setOutsideTouchable( false);
    window.setOnDismissListener( new OnDismissListener() {

      @Override
       public void onDismiss() {
         // TODO Auto-generated method stub
        isOpenPop = false;
        arrow.setBackgroundResource(R.drawable.icon_arrow_down);
      }
    });
    window.update();
    window.showAtLocation(parent, Gravity.CENTER_HORIZONTAL | Gravity.TOP,
        0, ( int) getResources().getDimension(R.dimen.pop_layout_y));

  }

  OnItemClickListener listClickListener = new OnItemClickListener() {
    @Override
     public void onItemClick(AdapterView<?> parent, View view, int position,
         long id) {
      Map<String, Object> map=(Map<String, Object>) parent.getItemAtPosition(position);
      Toast.makeText(mContext,map.get(KEY)+"", Toast.LENGTH_SHORT).show();
       if (window != null) {
        window.dismiss();

      }

    }
  };

   public ArrayList<Map<String, Object>> CreateData() {

    
    Map<String, Object> map;

    map = new HashMap<String, Object>();
    map.put(KEY, "锅包肉");
    items.add(map);
    map = new HashMap<String, Object>();
    map.put(KEY, "一品酱骨");
    items.add(map);
    map = new HashMap<String, Object>();
    map.put(KEY, "香辣小河虾");
    items.add(map);
    map = new HashMap<String, Object>();
    map.put(KEY, "川白肉");
    items.add(map);
    map = new HashMap<String, Object>();
    map.put(KEY, "莼菜汤");
    items.add(map);

     return items;

  }
}