如何将spinner中的第一个值(默认值)设置为空。意味着，在用户从列表中选择值之前，旋转控件将没有值。
list.add("");
但是，它不会工作。下面是我的代码:
if(values.contains("options")){
spinner.setOnItemSelectedListener(MyClass.this);
List<String> list = new ArrayList<String>();
list.add("");
list.add("Test");
list.add("Working");
ArrayAdapter<String> adapter = new ArrayAdapter<String>(mContext, android.R.layout.simple_spinner_item, list) {};
adapter.setDropDownViewResource(R.layout.custom_spinner_list);
spinner.setAdapter(adapter);
}
}
我找到路了。我们是这样做的，让最后一行是
list.add("");
并添加下面的代码:
ArrayAdapter<String> adapter = new ArrayAdapter<String>(mContext, android.R.layout.simple_spinner_item, list) {
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = super.getView(position, convertView, parent);
if (position == getCount()) {
((TextView)v.findViewById(android.R.id.text1)).setText("");
((TextView)v.findViewById(android.R.id.text1)).setHint(getItem(getCount())); //"Hint to be displayed"
}
return v;
}
@Override
public int getCount() {
return super.getCount()-1; // you don't display last item. It is used as hint.
}
};
adapter.setDropDownViewResource(R.layout.custom_spinner_list);
spinner.setAdapter(adapter);
spinner.setSelection(adapter.getCount()); //set the hint the default selection so it appears on launch.
spinner.setOnItemSelectedListener(this);
notifyDataSetChanged();
感谢上面user45678的回答，我写了这个
public class SpinnerNoDefault extends Spinner {
public void initialize(List<String> items) {
initialize(items, android.R.layout.simple_spinner_item, android.R.layout.simple_spinner_dropdown_item);
}
public void initialize(List<String> items, @LayoutRes int mItemResId, @LayoutRes int dropdownResId) {
List<String> itemsWithEmpty = new ArrayList<>(items);
itemsWithEmpty.add("");
String[] choicesArray = itemsWithEmpty.toArray(new String[itemsWithEmpty.size()]);
ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(getContext(), mItemResId, choicesArray) {
@NonNull
@Override
public View getView(int position, View convertView, @NonNull ViewGroup parent) {
View v = super.getView(position, convertView, parent);
if (position == getCount()) {
((TextView)v.findViewById(android.R.id.text1)).setText(null);
((TextView)v.findViewById(android.R.id.text1)).setHint(parent.getContext().getString(R.string.spinner_no_default_hint));
}
return v;
}
@Override
public int getCount() {
// Don't display last item. It is used as hint.
return super.getCount()-1;
}
};
spinnerArrayAdapter.setDropDownViewResource(dropdownResId);
setAdapter(spinnerArrayAdapter);
setSelection(itemsWithEmpty.size()-1);
}
}
List<String> allGoverNames = new ArrayList<String>();
allGoverNames.add(0, "");
allGoverNames.add(1,"Cricket");
allGoverNames.add(2,"FootBall");
allGoverNames.add(3,"Chess");
ArrayAdapter<String> GoverdataAdapter = new ArrayAdapter<String>
(context, android.R.layout.simple_spinner_item, allGoverNames);
GoverdataAdapter.setDropDownViewResource
(android.R.layout.simple_spinner_dropdown_item);
GovernorateSpinner.setAdapter(GoverdataAdapter);
在SearchableSpinner (com.toptoche.searchablespinnerlibrary.SearchableSpinner)中有一个参数叫做"app:hintText"-你可以用它来达到你的目的。例如:
<com.toptoche.searchablespinnerlibrary.SearchableSpinner
android:id="@+id/vehicle_name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/spinner_background"
android:layout_marginStart="20dp"
android:layout_marginEnd="20dp"
android:layout_marginBottom="20dp"
app:hintText=" "/>
提示将消失一旦某些东西将从微调器列表中选择。
一开始。初始化旋转控件时，添加
spinner.setSelection(0, false)
我创建了这个适配器，并选择了项目:
abstract class SpinnerSelectAdapter<T>(
context: Context,
private val resource: Int,
@ColorRes private val unselectedColorResource: Int,
@ColorRes private val selectedColorResource: Int,
open var objects: List<T>
) :
ArrayAdapter<T>(context, resource, objects) {
var selectedPosition = -1
override fun getView(position: Int, convertView: View?, parent: ViewGroup): View {
val view = convertView ?: LayoutInflater.from(parent.context)
.inflate(resource, parent, false)
if(selectedPosition != -1) {
setView(view, getItem(position)!!)
}
return view
}
override fun getDropDownView(position: Int, convertView: View?, parent: ViewGroup): View {
val view = convertView ?: LayoutInflater.from(parent.context)
.inflate(resource, parent, false)
if(selectedPosition == position){
view.setBackgroundResource(selectedColorResource)
}else {
view.setBackgroundResource(unselectedColorResource)
}
setView(view, getItem(position)!!)
return view
}
open fun setView(view: View, item: T) {
}
open fun setEmptyView(view: View){
}
override fun getItem(position: Int): T? {
return objects[position]
}
override fun getCount(): Int {
return objects.size
}
}
然后我为继承自SpinnerSelectAdapter的String Values创建适配器
class SpinnerStringAdapter(
context: Context,
resource: Int,
@ColorRes unselectedColorResource: Int,
@ColorRes selectedColorResource: Int,
override var objects: List<String>
) :
SpinnerSelectAdapter<String>(
context,
resource,
unselectedColorResource,
selectedColorResource,
objects
) {
override fun setView(view: View, item: String) {
val txt = view.findViewById<TextView>(android.R.id.text1)
txt.text = item
}
}
在你的片段或活动之后
val adapter = SpinnerStringAdapter(
requireContext(),
R.layout.spinner_item,
R.color.colorBG,
R.color.colorSubBG,
types
)
spinner.adapter = typeAdapter
spinner.setSelection(0, false)
spinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
override fun onItemSelected(
parent: AdapterView<*>?,
view: View?,
position: Int,
id: Long
) {
adapter.selectedPosition = position
adapter.notifyDataSetChanged()
}
``