Spinner的实现

曾经终败给现在 2022-03-11 17:40 268阅读 0赞

1.dropdowm mode：

使用的是ListPopupWindow：

设置ListPopupWindow的ListView的OnItemClickListener：

public DropdownPopup(
                    Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
                super(context, attrs, defStyleAttr, defStyleRes);
    
                setAnchorView(Spinner.this);
                setModal(true);
                setPromptPosition(POSITION_PROMPT_ABOVE);
                setOnItemClickListener(new OnItemClickListener() {
                    public void onItemClick(AdapterView parent, View v, int position, long id) {//调用该方法后，requestLayout(),重新布局将调用Spinner的layout()方法，方法中将根据position，把selected item的view从ListView中取出，addView到Spinner中。因为执行layout时，该List View已经从PupupWindow中解绑，窗口也移除了。Spinner算是废物利用，但是不明白的是，为什么PopupWindow用一次ListView就不用了。
                        Spinner.this.setSelection(position);
                        if (mOnItemClickListener != null) {
                            Spinner.this.performItemClick(v, position, mAdapter.getItemId(position));//调用Spinner.setOnItemClickListener设置的
                        }
                        dismiss();//wm.removeView()
                    }
                });
            }

2.dialogMode:

使用的是AlertDialog的singleIchoice样式的ListView。

public void show(int textDirection, int textAlignment) {
                if (mListAdapter == null) {
                    return;
                }
                AlertDialog.Builder builder = new AlertDialog.Builder(getPopupContext());
                if (mPrompt != null) {
                    builder.setTitle(mPrompt);
                }
                mPopup = builder.setSingleChoiceItems(mListAdapter,
                        getSelectedItemPosition(), this).create();
                final ListView listView = mPopup.getListView();
                listView.setTextDirection(textDirection);
                listView.setTextAlignment(textAlignment);
                mPopup.show();
            }
    
            public void onClick(DialogInterface dialog, int which) {//该类实现了DialogInterface.OnClickListener
                setSelection(which);
                if (mOnItemClickListener != null) {
                    performItemClick(null, which, mListAdapter.getItemId(which));
                }
                dismiss();
            }