没有默认的API来设置微调提示。为了添加它，我们需要一个小的解决方案，而不是安全反射实现

List<Object> objects = new ArrayList<Object>();
objects.add(firstItem);
objects.add(secondItem);
// add hint as last item
objects.add(hint);

HintAdapter adapter = new HintAdapter(context, objects, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

Spinner spinnerFilmType = (Spinner) findViewById(R.id.spinner);
spinner.setAdapter(adapter);

// show hint
spinner.setSelection(adapter.getCount());

适配器来源:

public class HintAdapter
        extends ArrayAdapter<Objects> {

    public HintAdapter(Context theContext, List<Object> objects) {
        super(theContext, android.R.id.text1, android.R.id.text1, objects);
    }

    public HintAdapter(Context theContext, List<Object> objects, int theLayoutResId) {
        super(theContext, theLayoutResId, android.R.id.text1, objects);
    }

    @Override
    public int getCount() {
        // don't display last item. It is used as hint.
        int count = super.getCount();
        return count > 0 ? count - 1 : count;
    }
}

原始来源

这是我最后一个“all in”按钮旋转器的例子

在activity_my_form.xml

    <Button
        android:id="@+id/btnSpinnerPlanets"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="left|center_vertical"
        android:singleLine="true"
        android:text="@string/selectAPlanet"
        android:textSize="10sp"
        android:background="@android:drawable/btn_dropdown">
    </Button>

在strings.xml

<string name="selectAPlanet">Select planet&#8230;</string>

<string-array name="planets__entries">
    <item>The Sun with a name very long so long long long long longThe Sun with a name very long so long long long long longThe Sun with a name very long so long long long long long</item>
    <item>Mercury</item>
    <item>Venus</item>
    <item>Earth</item>
    <item>Mars</item>
    <item>Jupiter</item>
    <item>Saturn</item>
    <item>Uranus</item>
    <item>Neptune</item>
</string-array>

在MyFormActivity.java

public class MyFormActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        ((Button) findViewById(R.id.btnSpinnerPlanets)).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                final String[] items = view.getResources().getStringArray(R.array.planets__entries);
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(MyFormActivity.this, android.R.layout.simple_spinner_dropdown_item, items);
                new AlertDialog.Builder(MyFormActivity.this).setTitle("the prompt").setAdapter(adapter, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        ((Button) findViewById(R.id.btnSpinnerPlanets)).setText(items[which]);
                        dialog.dismiss();
                    }
                }).create().show();
            }
        });     

    }

}   

最后我获得了一个字体大小可配置无第一项可选择的按钮旋转器!! 感谢HRJ

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。

public AdapterView.OnItemSelectedListener instructorSpinnerListener = new AdapterView.OnItemSelectedListener() {
    @Override
    public void onItemSelected(AdapterView << ? > adapterView, View view, int i, long l) {
        String selectedInstructorName = adapterView.getItemAtPosition(i).toString();
        if (selectedInstructorName.equals("[Select Instructor]")) {
            instructorSpinnerAdapter.clear();
            for (Offering offering: allOfferingsList)
                instructorSpinnerAdapter.add(offering);
        } else {
            instructorSpinnerAdapter.clear();
        }
    }

    @Override
    public void onNothingSelected(AdapterView<< ? > adapterView) {
        adapterView.setSelection(0);

        // Toast.makeText(getApplicationContext(), "Why?", Toast.LENGTH_SHORT).show();
    }
};

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;
        }
    }

//...
}

看到答案与轻量级和高可定制的库:

https://stackoverflow.com/a/73085435/6694920

<com.innowisegroup.hintedspinner.HintedSpinner
android:id="@+id/hintedSpinner"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginHorizontal="20dp"
app:hintTextSize="24sp"
app:hintTextColor="@color/red"
app:hint="Custom hint"
app:withDivider="true"
app:dividerColor="@color/dark_green"
app:arrowDrawable="@drawable/example_arrow_4"
app:arrowTint="@color/colorAccent"
app:popupBackground="@color/light_blue"
app:items="@array/text" />

倒塌的微调器:

扩大转轮: