When extending SpinnerAdapter, you override two View-producing methods, getView(int, View, ViewGroup) and getDropDownView(int, View, ViewGroup). The first one supplies the View inserted into the Spinner itself; the second supplies the View in the drop-down list (as the name suggests). You can override the getView(...) so that, until an item has been selected, it displays a TextView containing a prompt; then, when you detect an item has been selected, you change it to display a TextView corresponding to that.

public class PromptingAdapter extends SpinnerAdapter {

    //... various code ...

    private boolean selectionmade = false;

    //call this method from the OnItemSelectedListener for your Spinner
    public setSelectionState(boolean b) {
        selectionmade = b;
    }

    @Override
    public View getView(int position, View recycle, ViewGroup container) {
        if(selectionmade) {
            //your existing code to supply a View for the Spinner
            //you could even put "return getDropDownView(position, recycle, container);"
        }
        else {
            View output;
            if(recycle instanceof TextView) {
                 output = recycle;
            }
            else {
                 output = new TextView();
                 //and layout stuff
            }
            output.setText(R.string.please_select_one);
            //put a string "please_select_one" in res/values/strings.xml
            return output;
        }
    }

//...
}

首先，您可能对Spinner类的prompt属性感兴趣。如下图所示，“Choose a Planet”是可以用android在XML中设置的提示符:prompt=""。

我建议子类化Spinner，在这里您可以在内部维护两个适配器。一个适配器有“选择一个”选项，另一个真正的适配器(有实际的选项)，然后使用OnClickListener在选项对话框显示之前切换适配器。然而，在尝试实现这个想法后，我得出的结论是，你不能接收小部件本身的OnClick事件。

您可以将旋转器包装在不同的视图中，拦截视图上的单击，然后告诉CustomSpinner切换适配器，但这似乎是一种糟糕的hack。

你真的需要显示“选择一”吗?

之前提交的答案都没有真正按照我想要的方式解决这个问题。对我来说，理想的解决方案是在旋转器第一次显示时提供“Select One”(或任何初始文本)。当用户点击转轮时，初始文本不应该是显示的下拉框的一部分。

为了使我的特定情况更加复杂，我的旋转器数据来自通过LoaderManager回调加载的游标。

经过大量的实验，我想出了以下解决方案:

public class MyFragment extends Fragment implements
LoaderManager.LoaderCallbacks<Cursor>{

private static final String SPINNER_INIT_VALUE = "Select A Widget";
private Spinner mSpinner;
private int mSpinnerPosition;
private boolean mSpinnerDropDownShowing = false;
private View mSpinnerDropDown;

private MyCursorAdapter mCursorAdapter;

...

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
...

mCursorAdapter = new MyCursorAdapter(getActivity());

mSpinner = (Spinner) rootView.findViewById(R.id.theSpinner);
mSpinner.setOnTouchListener(mSpinnerTouchListener);
mSpinner.setAdapter(mCursorAdapter);

...
}

//Capture the touch events to toggle the spinner's dropdown visibility
private OnTouchListener mSpinnerTouchListener = new View.OnTouchListener() {
    @Override
    public boolean onTouch(View view, MotionEvent motionEvent) {
        if(mSpinnerDropDown != null && mSpinnerDropDownShowing == false){
            mSpinnerDropDownShowing = true;
            mSpinnerDropDown.setVisibility(View.VISIBLE);
        }
        return false;
    }
};

//Capture the click event on the spinner drop down items
protected OnClickListener spinnerItemClick = new OnClickListener(){

    @Override
    public void onClick(View view) {
        String widget = ((TextView) view.findViewById(android.R.id.text1)).getText().toString();

        if(!widget.equals(SPINNER_INIT_VALUE)){
            if(mCursorAdapter != null){
                Cursor cursor = mCursorAdapter.getCursor();
                if(cursor.moveToFirst()){
                    while(!cursor.isAfterLast()){
                        if(widget.equals(cursor.getString(WidgetQuery.WIDGET_NAME))){

                            ...

                            //Set the spinner to the correct item
                            mSpinnerPosition = cursor.getPosition() + 1;
                            mSpinner.setSelection(mSpinnerPosition);
                            break;
                        }
                        cursor.moveToNext();
                    }
                }
            }
        }

        //Hide the drop down. Not the most elegent solution but it is the only way I could hide/dismiss the drop down
        mSpinnerDropDown = view.getRootView();
        mSpinnerDropDownShowing = false;
        mSpinnerDropDown.setVisibility(View.GONE);
    }
};

private class MyCursorAdapter extends CursorAdapter {

    private final int DISPLACEMENT = 1;
    private final int DEFAULT_ITEM_ID = Integer.MAX_VALUE;

    private Activity mActivity;

    public MyCursorAdapter(Activity activity) {
            super(activity, null, false);
            mActivity = activity;
    }

    //When loading the regular views, inject the defualt item
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if(position == 0){
            if(convertView == null){
                convertView = mActivity.getLayoutInflater().inflate(R.layout.list_item_widget, parent, false);
            }
            return getDefaultItem(convertView);
        }
        return super.getView(position - DISPLACEMENT, convertView, parent);
    }

    //When loading the drop down views, set the onClickListener for each view
    @Override
    public View getDropDownView(int position, View convertView, ViewGroup parent){
        View view = super.getDropDownView(position, convertView, parent);
        view.setOnClickListener(spinnerItemClick);
        return view;
    }

    //The special default item that is being injected
    private View getDefaultItem(View convertView){
        TextView text = (TextView) convertView.findViewById(android.R.id.text1);
        text.setText(SPINNER_INIT_VALUE);
        return convertView;
    }

    @Override
    public long getItemId(int position) {
        if (position == 0) {
            return DEFAULT_ITEM_ID;
        }
        return super.getItemId(position - DISPLACEMENT);
    }

    @Override
    public boolean isEnabled(int position) {
        return position == 0 ? true : super.isEnabled(position - DISPLACEMENT);
    }

    @Override
    public int getViewTypeCount() {
        return super.getViewTypeCount() + DISPLACEMENT;
    }

    @Override
    public int getItemViewType(int position) {
        if (position == 0) {
            return super.getViewTypeCount();
        }

        return super.getItemViewType(position - DISPLACEMENT);
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        return mActivity.getLayoutInflater().inflate(R.layout.list_item_widget, parent, false);
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor){

        if(cursor.isAfterLast()){
            return;
        }

        TextView text = (TextView) view.findViewById(android.R.id.text1);
        String WidgetName = cursor.getString(WidgetQuery.WIDGET_NAME);
        text.setText(WidgetName);
    }
}
}

你可以做的是装饰你的SpinnerAdapter与一个显示“选择选项…”视图，以便旋转器显示时不选择任何内容。

这里是一个工作的例子测试Android 2.3，和4.0(它不使用兼容性库，所以它应该是好的一段时间)，因为它是一个装饰器，它应该很容易改造现有的代码，它与CursorLoaders工作也很好。(当然是在包装的cursorAdapter上交换光标…)

有一个Android漏洞使得重用视图有点困难。(所以你必须使用setTag或其他东西来确保你的convertView是正确的。)Spinner不支持多种视图类型

代码注释:2个构造函数

这允许您使用标准提示符或定义您自己的“nothing selected”作为第一行，或两者都有，或没有。(注意:有些主题为旋转器显示下拉菜单，而不是对话框。下拉菜单通常不会显示提示)

你定义了一个“看起来”像提示符的布局，例如，灰色…

使用标准提示符(注意没有选择任何内容):

或者加上提示符和动态的东西(也可以没有提示符):

上面例子中的用法

Spinner spinner = (Spinner) findViewById(R.id.spinner);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.planets_array, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setPrompt("Select your favorite Planet!");

spinner.setAdapter(
      new NothingSelectedSpinnerAdapter(
            adapter,
            R.layout.contact_spinner_row_nothing_selected,
            // R.layout.contact_spinner_nothing_selected_dropdown, // Optional
            this));

contact_spinner_row_nothing_selected.xml

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/text1"
    style="?android:attr/spinnerItemStyle"
    android:singleLine="true"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:ellipsize="marquee"
    android:textSize="18sp"
    android:textColor="#808080"
    android:text="[Select a Planet...]" />

NothingSelectedSpinnerAdapter.java

import android.content.Context;
import android.database.DataSetObserver;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListAdapter;
import android.widget.SpinnerAdapter;

/**
 * Decorator Adapter to allow a Spinner to show a 'Nothing Selected...' initially
 * displayed instead of the first choice in the Adapter.
 */
public class NothingSelectedSpinnerAdapter implements SpinnerAdapter, ListAdapter {

    protected static final int EXTRA = 1;
    protected SpinnerAdapter adapter;
    protected Context context;
    protected int nothingSelectedLayout;
    protected int nothingSelectedDropdownLayout;
    protected LayoutInflater layoutInflater;

    /**
     * Use this constructor to have NO 'Select One...' item, instead use
     * the standard prompt or nothing at all.
     * @param spinnerAdapter wrapped Adapter.
     * @param nothingSelectedLayout layout for nothing selected, perhaps
     * you want text grayed out like a prompt...
     * @param context
     */
    public NothingSelectedSpinnerAdapter(
      SpinnerAdapter spinnerAdapter,
      int nothingSelectedLayout, Context context) {

        this(spinnerAdapter, nothingSelectedLayout, -1, context);
    }

    /**
     * Use this constructor to Define your 'Select One...' layout as the first
     * row in the returned choices.
     * If you do this, you probably don't want a prompt on your spinner or it'll
     * have two 'Select' rows.
     * @param spinnerAdapter wrapped Adapter. Should probably return false for isEnabled(0)
     * @param nothingSelectedLayout layout for nothing selected, perhaps you want
     * text grayed out like a prompt...
     * @param nothingSelectedDropdownLayout layout for your 'Select an Item...' in
     * the dropdown.
     * @param context
     */
    public NothingSelectedSpinnerAdapter(SpinnerAdapter spinnerAdapter,
            int nothingSelectedLayout, int nothingSelectedDropdownLayout, Context context) {
        this.adapter = spinnerAdapter;
        this.context = context;
        this.nothingSelectedLayout = nothingSelectedLayout;
        this.nothingSelectedDropdownLayout = nothingSelectedDropdownLayout;
        layoutInflater = LayoutInflater.from(context);
    }

    @Override
    public final View getView(int position, View convertView, ViewGroup parent) {
        // This provides the View for the Selected Item in the Spinner, not
        // the dropdown (unless dropdownView is not set).
        if (position == 0) {
            return getNothingSelectedView(parent);
        }
        return adapter.getView(position - EXTRA, null, parent); // Could re-use
                                                 // the convertView if possible.
    }

    /**
     * View to show in Spinner with Nothing Selected
     * Override this to do something dynamic... e.g. "37 Options Found"
     * @param parent
     * @return
     */
    protected View getNothingSelectedView(ViewGroup parent) {
        return layoutInflater.inflate(nothingSelectedLayout, parent, false);
    }

    @Override
    public View getDropDownView(int position, View convertView, ViewGroup parent) {
        // Android BUG! http://code.google.com/p/android/issues/detail?id=17128 -
        // Spinner does not support multiple view types
        if (position == 0) {
            return nothingSelectedDropdownLayout == -1 ?
              new View(context) :
              getNothingSelectedDropdownView(parent);
        }

        // Could re-use the convertView if possible, use setTag...
        return adapter.getDropDownView(position - EXTRA, null, parent);
    }

    /**
     * Override this to do something dynamic... For example, "Pick your favorite
     * of these 37".
     * @param parent
     * @return
     */
    protected View getNothingSelectedDropdownView(ViewGroup parent) {
        return layoutInflater.inflate(nothingSelectedDropdownLayout, parent, false);
    }

    @Override
    public int getCount() {
        int count = adapter.getCount();
        return count == 0 ? 0 : count + EXTRA;
    }

    @Override
    public Object getItem(int position) {
        return position == 0 ? null : adapter.getItem(position - EXTRA);
    }

    @Override
    public int getItemViewType(int position) {
        return 0;
    }

    @Override
    public int getViewTypeCount() {
        return 1;
    }

    @Override
    public long getItemId(int position) {
        return position >= EXTRA ? adapter.getItemId(position - EXTRA) : position - EXTRA;
    }

    @Override
    public boolean hasStableIds() {
        return adapter.hasStableIds();
    }

    @Override
    public boolean isEmpty() {
        return adapter.isEmpty();
    }

    @Override
    public void registerDataSetObserver(DataSetObserver observer) {
        adapter.registerDataSetObserver(observer);
    }

    @Override
    public void unregisterDataSetObserver(DataSetObserver observer) {
        adapter.unregisterDataSetObserver(observer);
    }

    @Override
    public boolean areAllItemsEnabled() {
        return false;
    }

    @Override
    public boolean isEnabled(int position) {
        return position != 0; // Don't allow the 'nothing selected'
                                             // item to be picked.
    }

}

如果你只有三个选择，我只会使用带有RadioButtons的RadioGroup，你可以在一开始让它们都未选中。

你可以把它变成一个文本视图，并使用这个:

android:style="@android:style/Widget.DeviceDefault.Light.Spinner"

然后定义android:text属性。