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);