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?
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) {
}
});
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
我得到了同样的问题旋转，与一个空的选择，我找到了一个更好的解决方案。看看这段简单的代码。
Spinner lCreditOrDebit = (Spinner)lCardPayView.findViewById(R.id.CARD_TYPE);
spinneradapter lAdapter =
new spinneradapter(
BillPayScreen.this,
ndroid.R.layout.simple_spinner_item,getResources().getStringArray(R.array.creditordebit));
lAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
lCreditOrDebit.setAdapter(lAdapter);
这里spinneradapter是对arrayadapter的一个小定制。它是这样的:
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
public class spinneradapter extends ArrayAdapter<String>{
private Context m_cContext;
public spinneradapter(Context context,int textViewResourceId, String[] objects) {
super(context, textViewResourceId, objects);
this.m_cContext = context;
}
boolean firsttime = true;
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if(firsttime){
firsttime = false;
//Just return some empty view
return new ImageView(m_cContext);
}
//Let the array adapter take care of it this time.
return super.getView(position, convertView, parent);
}
}
对此，我找到了很多好的解决方案。大多数是通过在适配器的末尾添加一个项来工作的，并且不在下拉列表中显示最后一个项。
对我来说最大的问题是旋转器下拉列表将从列表的底部开始。所以用户看到的最后一个项目，而不是第一个项目(在情况下有许多项目显示)，触摸转轮后，第一次。
所以我把提示项放在列表的开头。并在下拉列表中隐藏第一项。
private void loadSpinner(){
HintArrayAdapter hintAdapter = new HintArrayAdapter<String>(context, 0);
hintAdapter.add("Hint to be displayed");
hintAdapter.add("Item 1");
hintAdapter.add("Item 2");
.
.
hintAdapter.add("Item 30");
spinner1.setAdapter(hintAdapter);
//spinner1.setSelection(0); //display hint. Actually you can ignore it, because the default is already 0
//spinner1.setSelection(0, false); //use this if don't want to onItemClick called for the hint
spinner1.setOnItemSelectedListener(yourListener);
}
private class HintArrayAdapter<T> extends ArrayAdapter<T> {
Context mContext;
public HintArrayAdapter(Context context, int resource) {
super(context, resource);
this.mContext = context
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
View view = inflater.inflate(android.R.layout.simple_spinner_item, parent, false);
TextView texview = (TextView) view.findViewById(android.R.id.text1);
if(position == 0) {
texview.setText("");
texview.setHint(getItem(position).toString()); //"Hint to be displayed"
} else {
texview.setText(getItem(position).toString());
}
return view;
}
@Override
public View getDropDownView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
View view;
if(position == 0){
view = inflater.inflate(R.layout.spinner_hint_list_item_layout, parent, false); // Hide first row
} else {
view = inflater.inflate(android.R.layout.simple_spinner_dropdown_item, parent, false);
TextView texview = (TextView) view.findViewById(android.R.id.text1);
texview.setText(getItem(position).toString());
}
return view;
}
}
在@Override getDropDownView()中设置下面的布局，当position为0时，隐藏第一个提示行。
R.layout.spinner_hint_list_item_layout:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</LinearLayout>
我最终使用了Button。虽然Button不是旋转器，但其行为很容易自定义。
首先像往常一样创建适配器:
String[] items = new String[] {"One", "Two", "Three"};
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_dropdown_item, items);
注意，我使用simple_spinner_dropdown_item作为布局id。这将有助于创建一个更好的外观时，创建警报对话框。
在onClick处理我的按钮，我有:
public void onClick(View w) {
new AlertDialog.Builder(this)
.setTitle("the prompt")
.setAdapter(adapter, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO: user specific action
dialog.dismiss();
}
}).create().show();
}
就是这样!
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) {
}
});
