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?
String[] listAges = getResources().getStringArray(R.array.ages);
// Creating adapter for spinner
ArrayAdapter<String> dataAdapter =
new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, listAges);
// Drop down layout style - list view with radio button
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// attaching data adapter to spinner
spinner_age.getBackground().setColorFilter(ContextCompat.getColor(this, R.color.spinner_icon), PorterDuff.Mode.SRC_ATOP);
spinner_age.setAdapter(dataAdapter);
spinner_age.setSelection(0);
spinner_age.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
String item = parent.getItemAtPosition(position).toString();
if(position > 0){
// get spinner value
Toast.makeText(parent.getContext(), "Age..." + item, Toast.LENGTH_SHORT).show();
}else{
// show toast select gender
Toast.makeText(parent.getContext(), "none" + item, Toast.LENGTH_SHORT).show();
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
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) {
}
});
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);
}
}
}
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。
