Question

popupwindow怎么实现下拉菜单

Answer 1

PopupWindow是一种比较好用的控件，通过它来实现一些自定义效果非常简便。如果需要在不同屏幕尺寸的手机上显示时，就有必要在程序中设置dip的长度值。很多人都会在代码中像下面这样转换。
Java代码
//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。也许这个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的引用方法：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。下面上代码。
Java代码
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;
}
}