Android：下拉框

image.png

主要是用PopupWindow实现，PopupWindow一个弹出窗口，可用于显示任意视图。弹出窗口是一个浮动容器，显示在当前活动的顶部。
具体使用看API https://www.android-doc.com/reference/android/widget/PopupWindow.html

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {
    private EditText et_con;
    private ImageButton btn;
    private PopupWindow popupWindow;
    private ListView listView;
    private List<String> list;
    private RelativeLayout rl;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        et_con = findViewById(R.id.et_con);
        btn = findViewById(R.id.btn);
        rl = findViewById(R.id.rl);
        //下拉图标点击事件
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                initListView();
                //弹窗，下拉列表(listview,宽,高)
                popupWindow = new PopupWindow(listView, rl.getWidth(), 400);
                //点击外部隐藏
                popupWindow.setOutsideTouchable(true);
                // 设置空的背景, 响应点击事件
                popupWindow.setBackgroundDrawable(new BitmapDrawable());
                //设置获取焦点
                popupWindow.setFocusable(true);
                //显示在指定控件下面
                popupWindow.showAsDropDown(et_con, 0, 0);
            }
        });
    }

    private void initListView() {
        listView = new ListView(this);
        listView.setDividerHeight(0);
        listView.setBackgroundResource(R.drawable.listview_background);
        listView.setOnItemClickListener(this);
        list = new ArrayList<>();
        //创建一些数据
        for (int i = 0; i < 20; i++) {
            list.add(10086 + i + "");
        }
        listView.setAdapter(new MyAdatper());
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        String tv = list.get(position);
        et_con.setText(tv);
        popupWindow.dismiss();
    }

    class MyAdatper extends BaseAdapter {

        @Override
        public int getCount() {
            return list.size();
        }

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

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

        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {
            View view1;
            if (view == null) {
                view1 = View.inflate(viewGroup.getContext(), R.layout.spinnerlist, null);
            }else {
                view1 = view;
            }
            TextView textView = view1.findViewById(R.id.text);
            textView.setText(list.get(i));

            view1.findViewById(R.id.del).setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    list.remove(i);
                    notifyDataSetChanged();
                    if (list.size() == 0){
                        popupWindow.dismiss();
                    }
                }
            });
            return view1;
        }
    }
}

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

    <RelativeLayout
        android:id="@+id/rl"
        android:layout_width="200dp"
        android:layout_height="50dp"
        android:background="@drawable/bg">

        <EditText
            android:id="@+id/et_con"
            android:layout_width="170dp"
            android:layout_height="50dp"
            android:background="@null" />

        <ImageButton
            android:id="@+id/btn"
            android:layout_width="20dp"
            android:layout_height="match_parent"
            android:layout_alignParentRight="true"
            android:layout_marginRight="10dp"
            android:background="@null"
            android:src="@drawable/down_arrow" />


    </RelativeLayout>

</LinearLayout>

<?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:orientation="horizontal">

    <ImageView

        android:layout_width="0dp"
        android:layout_height="30dp"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="5dp"
        android:layout_weight="1"
        android:src="@drawable/user" />

    <TextView
        android:id="@+id/text"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="10dp"
        android:layout_weight="9"
        android:text="1234"
        android:textColor="#000"
        android:textSize="20dp" />

    <ImageView
        android:id="@+id/del"
        android:layout_width="0dp"
        android:layout_height="30dp"
        android:layout_gravity="center_vertical"
        android:layout_marginRight="5dp"
        android:layout_weight="1"
        android:padding="-10dp"
        android:src="@drawable/delete" />
</LinearLayout>