我想使用一个微调器,最初(当用户还没有做出选择时)显示文本“Select One”。当用户单击微调器时,将显示项目列表,用户可以选择其中一个选项。用户做出选择后,所选项目将显示在微调器中,而不是“Select One”。

我有以下代码来创建一个旋转器:

String[] items = new String[] {"One", "Two", "Three"};
Spinner spinner = (Spinner) findViewById(R.id.mySpinner);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_spinner_item, items);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);

使用这段代码,最初会显示项目“One”。我可以在项目中添加一个新项目“Select One”,但“Select One”也会作为第一项显示在下拉列表中,这不是我想要的。

我该如何解决这个问题?


当前回答

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

其他回答

似乎是一个平庸的解决方案,但我通常把简单的TextView在纺纱器的前面。整个Xml是这样的。(嘿,伙计们,别朝我开枪,我知道你们有些人不喜欢这种婚姻):

<FrameLayout
    android:id="@+id/selectTypesLinear"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >

    <Spinner
        android:id="@+id/spinnerExercises"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:entries="@array/exercise_spinner_entries"
        android:prompt="@string/exercise_spinner_prompt"
     />                         
    <TextView
        android:id="@+id/spinnerSelectText"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Hey! Select this guy!"
        android:gravity="center"
        android:background="#FF000000" />


</FrameLayout>

然后我隐藏TextView时,一个项目被选中。显然,TextView的背景颜色应该与旋转器相同。适用于Android 4.0。不知道旧版本。

是的。因为Spinner在开始时调用setOnItemSelectedListener,隐藏textview可能有点棘手,但可以这样做:

    Boolean controlTouched;

    exerciseSpinner.setOnTouchListener(new OnTouchListener() {


        @Override
        public boolean onTouch(View v, MotionEvent event) {
            controlTouched = true; // I touched it but but not yet selected an Item.
            return false;
        }

    });
    exerciseSpinner.setOnItemSelectedListener(new OnItemSelectedListener() {

        @Override
        public void onItemSelected(AdapterView<?> arg0, View arg1,
                int arg2, long arg3) {
            if (controlTouched) { // Are you sure that I touched it with my fingers and not someone else  ?
                spinnerSelText.setVisibility(View.GONE);
            }
        }

        @Override
        public void onNothingSelected(AdapterView<?> arg0) {
        }

    });

对于那些使用Xamarin的人,下面是与上面aaronvargas的答案相当的c#版本。

using Android.Content;
using Android.Database;
using Android.Views;
using Android.Widget;
using Java.Lang;

namespace MyNamespace.Droid
{ 
  public class NothingSelectedSpinnerAdapter : BaseAdapter, ISpinnerAdapter, IListAdapter
  {
    protected static readonly int EXTRA = 1;
    protected ISpinnerAdapter adapter;
    protected Context context;
    protected int nothingSelectedLayout;
    protected int nothingSelectedDropdownLayout;
    protected LayoutInflater layoutInflater;

    public NothingSelectedSpinnerAdapter(ISpinnerAdapter spinnerAdapter, int nothingSelectedLayout, Context context) : this(spinnerAdapter, nothingSelectedLayout, -1, context)
    {
    }

    public NothingSelectedSpinnerAdapter(ISpinnerAdapter spinnerAdapter, int nothingSelectedLayout, int nothingSelectedDropdownLayout, Context context)
    {
      this.adapter = spinnerAdapter;
      this.context = context;
      this.nothingSelectedLayout = nothingSelectedLayout;
      this.nothingSelectedDropdownLayout = nothingSelectedDropdownLayout;
      layoutInflater = LayoutInflater.From(context);
    }

    protected View GetNothingSelectedView(ViewGroup parent)
    {
      return layoutInflater.Inflate(nothingSelectedLayout, parent, false);
    }

    protected View GetNothingSelectedDropdownView(ViewGroup parent)
    {
      return layoutInflater.Inflate(nothingSelectedDropdownLayout, parent, false);
    }

    public override Object GetItem(int position)
    {
      return position == 0 ? null : adapter.GetItem(position - EXTRA);
    }

    public override long GetItemId(int position)
    {
      return position >= EXTRA ? adapter.GetItemId(position - EXTRA) : position - EXTRA;
    }

    public override 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);
      }

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

    public override int Count
    {
      get
      {
        int count = this.adapter.Count;
        return count == 0 ? 0 : count + EXTRA;
      }
    }

    public override 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);
    }

    public override int GetItemViewType(int position)
    {
      return 0;
    }

    public override int ViewTypeCount => 1;

    public override bool HasStableIds => this.adapter.HasStableIds;

    public override bool IsEmpty => this.adapter.IsEmpty;

    public override void RegisterDataSetObserver(DataSetObserver observer)
    {
      adapter.RegisterDataSetObserver(observer);
    }

    public override void UnregisterDataSetObserver(DataSetObserver observer)
    {
      adapter.UnregisterDataSetObserver(observer);
    }

    public override bool AreAllItemsEnabled()
    {
      return false;
    }

    public override bool IsEnabled(int position)
    {
      return position > 0;
    }
  }
}

我昨天遇到了同样的问题,不想向ArrayAdapter添加隐藏项或使用反射,这工作得很好,但有点脏。

在阅读了许多帖子和尝试之后,我通过扩展ArrayAdapter和覆盖getView方法找到了一个解决方案。

import android.content.Context;
import android.support.annotation.NonNull;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;

/**
 * A SpinnerAdapter which does not show the value of the initial selection initially,
 * but an initialText.
 * To use the spinner with initial selection instead call notifyDataSetChanged().
 */
public class SpinnerAdapterWithInitialText<T> extends ArrayAdapter<T> {

    private Context context;
    private int resource;

    private boolean initialTextWasShown = false;
    private String initialText = "Please select";

    /**
     * Constructor
     *
     * @param context The current context.
     * @param resource The resource ID for a layout file containing a TextView to use when
     *                 instantiating views.
     * @param objects The objects to represent in the ListView.
     */
    public SpinnerAdapterWithInitialText(@NonNull Context context, int resource, @NonNull T[] objects) {
        super(context, resource, objects);
        this.context = context;
        this.resource = resource;
    }

    /**
     * Returns whether the user has selected a spinner item, or if still the initial text is shown.
     * @param spinner The spinner the SpinnerAdapterWithInitialText is assigned to.
     * @return true if the user has selected a spinner item, false if not.
     */
    public boolean selectionMade(Spinner spinner) {
        return !((TextView)spinner.getSelectedView()).getText().toString().equals(initialText);
    }

    /**
     * Returns a TextView with the initialText the first time getView is called.
     * So the Spinner has an initialText which does not represent the selected item.
     * To use the spinner with initial selection instead call notifyDataSetChanged(),
     * after assigning the SpinnerAdapterWithInitialText.
     */
    @Override
    public View getView(int position, View recycle, ViewGroup container) {
        if(initialTextWasShown) {
            return super.getView(position, recycle, container);
        } else {
            initialTextWasShown = true;
            LayoutInflater inflater = LayoutInflater.from(context);
            final View view = inflater.inflate(resource, container, false);

            ((TextView) view).setText(initialText);

            return view;
        }
    }
}

Android在初始化Spinner时所做的,是在为T[]对象中的所有项目调用getView之前为所选项目调用getView。 SpinnerAdapterWithInitialText在第一次调用时返回带有initialText的TextView。 其他时间都调用super。getView是ArrayAdapter的getView方法如果你正常使用Spinner,它会被调用。

要找出用户是否选择了一个微调项,或者微调器是否仍然显示initialText,请调用selectionMade并移交适配器分配给的微调器。

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:

我有一个旋转器在我的main.xml和它的id是@+id/spinner1

这是我在OnCreate函数中写的:

spinner1 = (Spinner)this.findViewById(R.id.spinner1);
final String[] groupes = new String[] {"A", "B", "C", "D", "E", "F", "G", "H"};
ArrayAdapter<CharSequence> featuresAdapter = new ArrayAdapter<CharSequence>(this, android.R.layout.simple_spinner_item, new ArrayList<CharSequence>());
featuresAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner1.setAdapter(featuresAdapter);
for (String s : groupes) featuresAdapter.add(s);

spinner1.setOnItemSelectedListener(new OnItemSelectedListener() {
     public void onItemSelected(AdapterView<?> arg0, View arg1, int position, long id) {
         // Here go your instructions when the user chose something
         Toast.makeText(getBaseContext(), groupes[position], 0).show();
     }
     public void onNothingSelected(AdapterView<?> arg0) { }
});

它不需要类中的任何实现。