Android开发：仿美团下拉列表菜单，帮助类，复用简单

public class MenuHelper {
	private PopupWindow popupWindow;
	private ListView listView;
	private List<String> data;
	private Context mContext;
	private View topView;
	private ListAdapter adapter;
	private int i = 0;
	private FrameLayout container;

	public MenuHelper(Context context, View topView, final OnMenuClick clickListener, List<String> data, FrameLayout containerView) {
		mContext = context;
		this.topView = topView;
		this.data = data;
		
		this.container = containerView;
		container.getForeground().setAlpha(0);
		topView.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				showMenu();
			}
		});
		
		initListView(clickListener);
		initPopupWindow();
		
	}
	
	private void initListView(final OnMenuClick clickListener) {
		listView = new ListView(mContext);
		listView.setDivider(null);
		listView.setDividerHeight(0);
		listView.setBackgroundColor(Color.WHITE);
		adapter = new ListAdapter(mContext);
		listView.setAdapter(adapter);
		
		listView.setOnItemClickListener(new OnItemClickListener() {
			@Override
			public void onItemClick(AdapterView<?
> parent, View view,					int position, long id) {				i = position;				clickListener.onPopupMenuClick(position);				popupWindow.dismiss();			}		});	}		private void initPopupWindow() {		popupWindow = new PopupWindow(listView, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT, true);		popupWindow.setOutsideTouchable(true);		popupWindow.setBackgroundDrawable(new ColorDrawable(Color.WHITE));				popupWindow.setOnDismissListener(new OnDismissListener() {			@Override			public void onDismiss() {				if (container != null) {					container.getForeground().setAlpha(0);				}			}		});	}		public void showMenu() {		adapter.notifyDataSetChanged();		if (popupWindow.isShowing()) {			popupWindow.dismiss();		}else {			popupWindow.setOutsideTouchable(true);			popupWindow.setTouchable(true);			popupWindow.showAsDropDown(topView, 0, 0);			if (container != null) {				container.getForeground().setAlpha(120);			}		}	}	private class ListAdapter extends ArrayAdapter<String> {		public ListAdapter(Context context) {			super(context, R.layout.item_text, data);		}				private Holder getHolder(final View view) {	        Holder holder = (Holder) view.getTag();	        if (holder == null) {	            holder = new Holder(view);	            view.setTag(holder);	        }	        return holder;	    }				@Override		public View getView(final int position, View convertView, ViewGroup parent) {			View rowView = convertView;			if (rowView == null) {				LayoutInflater inflater = LayoutInflater.from(mContext);				rowView = inflater.inflate(R.layout.item_text, null);			}			final Holder holder = getHolder(rowView);						holder.textview.setText(data.get(position));			if (position == i) {				holder.textview.setBackgroundColor(mContext.getResources().getColor(R.color.item_press));			}else {				holder.textview.setBackgroundColor(Color.TRANSPARENT);			}						return rowView;		}		private class Holder {			public TextView textview;						public Holder(View view) {				textview = (TextView) view.findViewById(R.id.textView);			}		}  	}}

public interface OnMenuClick {
	public void onPopupMenuClick(int position);
}

最后，是MainActivity的代码：

public class MainActivity extends Activity implements OnMenuClick{	private MenuHelper mMenuHelper;	private Button button;	private FrameLayout container;	private List<String> menuData;		@Override	protected void onCreate(Bundle savedInstanceState) {		super.onCreate(savedInstanceState);		setContentView(R.layout.activity_main);				container = (FrameLayout) findViewById(R.id.container);		button = (Button) findViewById(R.id.button);				menuData = new ArrayList<String>();		menuData.add("ladfj");		menuData.add("ladfj");		menuData.add("ladfj");		menuData.add("ladfj");		menuData.add("ladfj");				mMenuHelper = new MenuHelper(this, button, this, menuData, container);				button.setOnClickListener(new OnClickListener() {			@Override			public void onClick(View v) {				mMenuHelper.showMenu();			}		});			}	@Override	public void onPopupMenuClick(int position) {		Log.d("debug", "click position " + position);	}	}