Android自定义Spinner

项目中用到Spinner，什么都好，就是内含的popup无法限制高度。当我展示的数据较多时，
spinner会自动计算屏高，尽可能多的展示，导致item列表时高时矮，不甚美观。耗费了很多时间和精力
在网上查找解决方法，并仔细看了Spinner源码，发现真的没有提供限制高度这一方法。无奈只能尝试自己写一个类似功能的
MySpinner。
我们知道Spinner有DropdownPopup，DialogPopup两种展示模式，这里只用到DropDown模式，所以MySpinner中只用到了
TextView,PopupWindow和ListView。思路是点击TextView,显示包含ListView的PopupWindow和ListView，
然后设置 一系列点击事件和监听，满足需求。特点就在于可灵活设置PopupWindow宽高和Spinner常见功能。但因为只用到了基本的ArrayAdapter,所以功能有点受限。

代码如下：

public class MySpinner extends AppCompatTextView {

    private PopupWindow popupWindow;
    private int popupWindowWidth = 50;
    private int popupWindowHeight = 50;
    private int listviewDividerHeight = 0;
    private int selectedItemPosition = 0;
    private ListView listView;
    private ListAdapter adapter;
    private MySpinnerListener listener;//可监听listview Item点击，回调结果

    public MySpinner(Context context) {
        super(context);
        initView(context);
        initListener();
    }

    public MySpinner(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        initView(context);
        initListener();
    }

    public MySpinner(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initView(context);
        initListener();
    }

    private void initView(Context context) {
        popupWindow = new PopupWindow(this);
        listView = new ListView(context);
    }

    private void initListener() {
        setOnItemClickListener();
        popupWindowShowAsDropDown(MySpinner.this);
    }

    public void setPopupWindowParams(int windowWidth,int windowHeight) {
        this.popupWindowWidth = windowWidth;
        this.popupWindowHeight = windowHeight;
    }

    public void setPopupWindowWidth(int windowWidth) {
        this.popupWindowWidth = windowWidth;
    }

    public void setPopupWindowHeight(int windowHeight) {
        this.popupWindowHeight = windowHeight;
    }

    public void setListviewDividerHeight(int listviewDividerHeight) {
        this.listviewDividerHeight = listviewDividerHeight;
    }

    public void setAdapter(ListAdapter adapter) {
        this.adapter = adapter;
    }

    //listview 点击事件
    private void setOnItemClickListener() {
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                selectedItemPosition = position;
                String itemselect = (String) parent.getItemAtPosition(position);
                MySpinner.this.setText(itemselect);
                popupWindow.dismiss();
                //回调
                if (listener != null)
                    listener.onItemSelected(itemselect, position);
            }
        });
    }

    //作用同 listview setOnItemSelectedListener
    public void setMySpinnerOnItemSelectedListener(MySpinnerListener listener) {
        this.listener = listener;
    }

    public void popupWindowShowAsDropDown(View anchor) {
        popupWindowShowAsDropDown(anchor, 0, 0);
    }

    public void popupWindowShowAsDropDown(View anchor, int xoff, int yoff) {
        popupWindowShowAsDropDown(anchor, xoff, yoff, Gravity.TOP | Gravity.START);
    }

    public void popupWindowShowAsDropDown(final View anchor, final int xoff, final int yoff, final int gravity) {
        //popupwindow显示事件
        this.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                popupWindow.showAsDropDown(anchor, xoff, yoff, gravity);
            }
        });
    }

    public void show() {
        listView.setBackgroundResource(R.drawable.shape_bg_test);
        listView.setDividerHeight(listviewDividerHeight);
        listView.setAdapter(adapter);

        popupWindow.setWidth(popupWindowWidth);
        popupWindow.setHeight(popupWindowHeight);
        popupWindow.setContentView(listView);
        popupWindow.setBackgroundDrawable(new ColorDrawable(0x00000000));
        popupWindow.setOutsideTouchable(false);
        popupWindow.setFocusable(true);

        setSelection(0);
    }

    public void setSelection(int i) {
        if (adapter != null && adapter.getCount() > i) {
            selectedItemPosition = i;
            listView.setSelection(i);
            MySpinner.this.setText((String) adapter.getItem(i));
        }
    }

    public String getSelectedItem() {
        return (String) listView.getItemAtPosition(selectedItemPosition);
    }

    public int getSelectedItemPosition() {
        return selectedItemPosition;
    }
}

public interface MySpinnerListener {
    public void onItemSelected(String item,int position);
}

调用如下：

    myspinner.setPopupWindowParams(dip2px(getActivity(), 70), dip2px(getActivity(), 26*7));
    myspinner.setAdapter(new ArrayAdapter<String>(getActivity(), R.layout.simple_spinner_dropdown_item, getDays()));
    myspinner.show();