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。
对我来说,它是这样工作的。有改进,只改变文本在某些选项,而不是全部。
首先,我采用旋转器的名称并创建带有自定义视图的arrayadapter,但现在这并不重要,关键是覆盖getView,并在内部更改你需要更改的值。在我的情况下只有第一个,其余的我离开原来的
public void rellenarSpinnerCompeticiones(){
spinnerArrayCompeticiones = new ArrayList<String>();
for(Competicion c: ((Controlador)getApplication()).getCompeticiones()){
spinnerArrayCompeticiones.add(c.getNombre());
}
//ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(this,R.layout.spinner_item_competicion,spinnerArrayCompeticiones);
ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(this, R.layout.spinner_item_competicion, spinnerArrayCompeticiones){
@Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
final View v = vi.inflate(R.layout.spinner_item_competicion, null);
final TextView t = (TextView)v.findViewById(R.id.tvCompeticion);
if(spinnerCompeticion.getSelectedItemPosition()>0){
t.setText(spinnerArrayCompeticiones.get(spinnerCompeticion.getSelectedItemPosition()));
}else{
t.setText("Competiciones");
}
return v;
}
};
spinnerArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerCompeticion.setAdapter(spinnerArrayAdapter);
}