android studio Spinner下拉菜单多选源码实现

Spinner控件本身不支持多选功能，但可以通过自定义适配器来实现多选下拉菜单。

以下是一个示例代码：

public class MultiSpinnerAdapter extends ArrayAdapter<String> implements OnItemClickListener {
    private List<String> items;
    private boolean[] selected;
    private Spinner spinner;
 
    public MultiSpinnerAdapter(Context context, int textViewResourceId, List<String> items, Spinner spinner) {
        super(context, textViewResourceId, items);
        this.items = items;
        this.selected = new boolean[items.size()];
        this.spinner = spinner;
        spinner.setOnItemClickListener(this);
    }
 
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = super.getView(position, convertView, parent);
        TextView textView = (TextView) view.findViewById(android.R.id.text1);
        if (selected[position]) {
            textView.setTextColor(Color.RED);
        } else {
            textView.setTextColor(Color.BLACK);
        }
        return view;
    }
 
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        selected[position] = !selected[position];
        getView(position, view, parent);
    }
 
    public List<String> getSelectedItems() {
        List<String> selectedItems = new ArrayList<>();
        for (int i = 0; i < items.size(); i++) {
            if (selected[i]) {
                selectedItems.add(items.get(i));
            }
        }
        return selectedItems;
    }
}

在Activity中使用该适配器：

Spinner spinner = (Spinner) findViewById(R.id.spinner);
List<String> items = Arrays.asList("Item 1", "Item 2", "Item 3", "Item 4");
MultiSpinnerAdapter adapter = new MultiSpinnerAdapter(this, android.R.layout.simple_spinner_item, items, spinner);
spinner.setAdapter(adapter);

// 获取选中的项
List<String> selectedItems = adapter.getSelectedItems();

以上代码实现了一个多选下拉菜单，当用户点击列表项时，会切换该项的选中状态，并且选中状态的文本颜色将变为红色。getSelectedItems()方法可以获取选中的项。