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?
我试过的方法如下。取一个按钮并将单击事件赋予它。通过改变按钮背景，它似乎是一个旋转器。
声明为全局变量alertdialog和默认值..
AlertDialog d;
static int default_value = 0;
final Button btn = (Button) findViewById(R.id.button1);
btn .setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v)
{
//c.show();
final CharSequence str[] = {"Android","Black Berry","Iphone"};
AlertDialog.Builder builder =
new AlertDialog.Builder(TestGalleryActivity.this).setSingleChoiceItems(
str, default_value,new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int position)
{
Toast.makeText(TestGalleryActivity.this,
"" + position,
Toast.LENGTH_SHORT).show();
default_value = position;
btn.setText(str[position]);
if(d.isShowing())
d.dismiss();
}
}).setTitle("Select Any");
d = builder.create();
d.show();
}
});
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);
}
}
}
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
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;
}
}
//...
}
