下拉选择框，PopupWindow的使用

实现下拉选择框

直接上代码

Activity.java

package com.example.shaofei.customerviewdemo1;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.PopupWindow;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;

public class ShowDownMenuDemoActivity extends AppCompatActivity {

    private EditText mEt_input;
    private ImageButton mIb_show_down;
    private ArrayList<String> mListData;
    private PopupWindow mPopupWindow;
    private boolean isShow = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_popup_window_demo);


        initView();
    }

    private void initView() {
        mEt_input = (EditText) findViewById(R.id.et_input);
        mIb_show_down = (ImageButton) findViewById(R.id.ib_show_down);


        mIb_show_down.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                if (isShow) {
                    mPopupWindow.dismiss();
                    isShow = false;
                } else {
                    showPopupWindow();
                    isShow = true;
                }
            }
        });
    }

    /**
     * 显示PopupWindow
     */
    private void showPopupWindow() {
        ListView listView = new ListView(this);

        mListData = new ArrayList<>();
        for (int i = 0; i < 30; i++) {
            mListData.add("10000" + i);
        }

        //设置数据适配器
        listView.setAdapter(new MyAdapter());
        listView.setDividerHeight(0);

        mPopupWindow = new PopupWindow(listView, mEt_input.getWidth(), 800);

        //设置点击空白处隐藏
        mPopupWindow.setOutsideTouchable(true);

        //在哪个位置，x偏移多少，y偏移多少
        mPopupWindow.showAsDropDown(mEt_input, 0, 0);



        //让Popupwindown可以获取焦点
        mPopupWindow.setFocusable(true);


        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                mEt_input.setText(mListData.get(i));
                mPopupWindow.dismiss();
                isShow = false;
            }
        });


    }

    private class MyAdapter extends BaseAdapter {
        @Override
        public int getCount() {
            return mListData.size();
        }

        @Override
        public Object getItem(int i) {
            return mListData.get(i);
        }

        @Override
        public long getItemId(int i) {
            return i;
        }

        @Override
        public View getView(final int i, View view, ViewGroup viewGroup) {
            ViewHolder holder = null;

            if (view == null) {
                holder = new ViewHolder();

                view = View.inflate(viewGroup.getContext(), R.layout.item_popup, null);

                holder.mTextView = view.findViewById(R.id.tv_center);
                holder.mImageButton = view.findViewById(R.id.ib_delete);

                view.setTag(holder);
            }

            holder = (ViewHolder) view.getTag();

            holder.mTextView.setText(mListData.get(i));


            holder.mImageButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Toast.makeText(ShowDownMenuDemoActivity.this, "点击删除", Toast.LENGTH_SHORT).show();

                    mListData.remove(mListData.get(i));

                    notifyDataSetChanged();

                    if(mListData.size()==0) {
                        //如果删除到空集合，那么就隐藏
                        mPopupWindow.dismiss();
                        isShow = false;
                    }

                }
            });


            return view;
        }
    }

    class ViewHolder {
        TextView mTextView;
        ImageButton mImageButton;
    }
}

xml文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">


    <RelativeLayout
        android:layout_width="300dp"
        android:layout_height="60dp"
        android:layout_gravity="center">

        <EditText
            android:id="@+id/et_input"
            android:layout_width="match_parent"
            android:layout_height="60dp"
            android:hint="点击输入"/>

        <ImageButton
            android:id="@+id/ib_show_down"
            android:layout_width="60dp"
            android:layout_height="60dp"
            android:layout_alignParentRight="true"
            android:background="@null"
            android:src="@mipmap/arrow_down"/>

    </RelativeLayout>


</LinearLayout>

ListView中的item布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="50dp"
    android:descendantFocusability="blocksDescendants"
    android:layout_margin="20dp"
    android:gravity="center"
    android:orientation="horizontal">


    <ImageView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:src="@mipmap/arrow_constant"/>

    <TextView
        android:id="@+id/tv_center"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="10"
        android:gravity="center"
        android:text="1000101"
        android:textColor="#a000"/>

    <ImageButton
        android:id="@+id/ib_delete"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:background="@null"
        android:src="@mipmap/arrow_delete"/>

</LinearLayout>

遇到的问题
PopupWindow中的ListView的item获取不到点击事件，原因是，item中的ImageButton抢占了item的焦点。我们可以在item的根布局中设置如下属性：
android:descendantFocusability=”blocksDescendants”
将其布局的焦点分块进行区分。就可以获取到焦点了。如果还是不能获取焦点的话，那么就在代码中再添加一行代码；
//让Popupwindown可以获取焦点
mPopupWindow.setFocusable(true);