3.自定义控件：PopupWindow小案例

案例展示：

PopupWindow.gif

1. 思路很简单：

在PopupWindow中添加ListView即可；

popupWindow=new PopupWindow(listView,et_print.getWidth(),400);
popupWindow.showAsDropDown(et_print,0,-5);

2. 最主要有1个关键点：

PopupWindow界面中如果存在Button或者ImageButton等按钮控件会抢夺所在Layout的焦点，导致其他区域点击不生效，解决办法是==在其所在的布局界面==添加以下例句：

android:descendantFocusability="blocksDescendants"

并设置PopupWindow的焦点为true

 //获取焦点，点击事件生效
popupWindow.setFocusable(true);

3.PopupWindow点击空白处取消：

//点击空白处取消PopupWindow
popupWindow.setOnDismissListener(new PopupWindow.OnDismissListener() {
       @Override
       public void onDismiss() {
            popupWindow.dismiss();
       }
});

3.完整代码：

public class ListActivity extends AppCompatActivity {
    private  EditText et_print;
    private ListView listView;
    private List<String> dataList;
    private PopupWindow popupWindow;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list);
        initViews();
        initData();
    }

    private void initData() {
        dataList=new ArrayList<>();
        for (int i=0;i<5;i++){
            dataList.add((1000+i)+"");
        }
    }

    private void showPopupWindow() {
        initListViews();
        popupWindow=new PopupWindow(listView,et_print.getWidth(),400);
        //获取焦点，点击事件生效
        popupWindow.setFocusable(true);
        //显示在指定位置下：
        popupWindow.showAsDropDown(et_print,0,-5);
        //点击空白处取消PopupWindow
        popupWindow.setOnDismissListener(new PopupWindow.OnDismissListener() {
            @Override
            public void onDismiss() {
                popupWindow.dismiss();
            }
        });
    }

    private void initListViews() {
        listView=new ListView(this);
        listView.setAdapter(new ListAdapter(dataList));
        //去除分割线：
        listView.setDividerHeight(0);

        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                et_print.setText(dataList.get(position));
                popupWindow.dismiss();
            }
        });
    }

    private void initViews() {
        et_print=findViewById(R.id.et_print);
        ImageButton ib_select=findViewById(R.id.ib_select);
        ib_select.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showPopupWindow();
            }
        });
    }

    class ListAdapter extends BaseAdapter{
        private List<String> dataList;
        public ListAdapter(List<String> dataList){
            this.dataList=dataList;
        }

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

        @Override
        public Object getItem(int position) {
            return dataList.get(position);
        }

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

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            View view;
            ViewHolder viewHolder=null;
            if (convertView==null){
                view= LayoutInflater.from(ListActivity.this).inflate(R.layout.item_list,null,false);
                viewHolder=new ViewHolder();
                viewHolder.tv_text=view.findViewById(R.id.tv_text);
                viewHolder.ib_delete=view.findViewById(R.id.ib_delete);
                view.setTag(viewHolder);
            }else{
                view=convertView;
               viewHolder= (ViewHolder) convertView.getTag();
            }
            viewHolder.tv_text.setText(dataList.get(position));
            viewHolder.ib_delete.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    dataList.remove(position);
                    notifyDataSetChanged();
                    if (dataList.size()==0){
                        popupWindow.dismiss();
                    }
                }
            });
            return view;
        }
        class ViewHolder{
            TextView tv_text;
            ImageButton ib_delete;
        }
    }

}