为什么OnItemSelectedListener仅在项目更改时调用,而不是在每个用户选择时调用？

Question

我在Android应用程序中使用微调控件,我通过onItemSelectedListener()方法处理用户选择.当与当前选项不同时,这似乎可以正常工作.我想在某些条件下将所有微调器重置为默认值并确保onItemSelectedListener()为所有调整器调用.

它是Android的语义的一部分,onItemSelectedListener()仅在用户选择更改时调用.有没有办法强制onItemSelectedListener()被召唤？

Answer 1

如果要激活Spinner的"onItemSelected",即使选择了微调器中的项目/选择了项目并再次单击它.然后使用这个扩展微调器的自定义类,这对我有用

然后用像这样的微调器编辑你的活动,我改变了

  static Spinner spinner1;

至

  static NDSpinner spinner1;

和

   variables.spinner1 = (Spinner) findViewById(R.id.spinner1); 

至

   variables.spinner1 = (NDSpinner ) findViewById(R.id.spinner1); 

我还改变了微调器所在的xml布局

    <Spinner
    android:id="@+id/spinner1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="@string/place" />

至

    <com.yourpackagename.NDSpinner 
     android:id="@+id/spinner1"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:text="@string/place" />

Spinner扩展类:

 package com.yourpackagename;
 import android.content.Context;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.widget.Spinner;
 import android.widget.Toast;
 import java.lang.reflect.Field;

     /** Spinner extension that calls onItemSelected even when the selection is the same as       its previous value. 
       *   ie This is extended "Customized class of Spinner" to  get the "onItemSelected"      event even if the item in the
     *  Spinner is already  selected by the user*/
    public class NDSpinner extends Spinner {

      public NDSpinner(Context context)
      { super(context); }

      public NDSpinner(Context context, AttributeSet attrs)
      { super(context, attrs); }

      public NDSpinner(Context context, AttributeSet attrs, int defStyle)
      { super(context, attrs, defStyle); }


      private void ignoreOldSelectionByReflection() {
            try {
                Class<?> c = this.getClass().getSuperclass().getSuperclass().getSuperclass();
                Field reqField = c.getDeclaredField("mOldSelectedPosition");
                reqField.setAccessible(true);
                reqField.setInt(this, -1);
            } catch (Exception e) {
                Log.d("Exception Private", "ex", e);
                // TODO: handle exception
            }
        }

      @Override
      public void  setSelection(int position, boolean animate)
      {
        boolean sameSelected = position == getSelectedItemPosition();
        ignoreOldSelectionByReflection();
        super.setSelection(position, animate);
        if (sameSelected) {
          // Spinner does not call the OnItemSelectedListener if the same item is selected, so do it manually now
          getOnItemSelectedListener().onItemSelected(this, getSelectedView(), position, getSelectedItemId());


        }
      }
      @Override
      public void setSelection(int position) {
          ignoreOldSelectionByReflection();
          super.setSelection(position);
      }

    }

Answer 2

当您选择与当前所选项目相同的项目时，默认微调器不会触发任何事件。为此，您需要制作一个自定义 Spinner。看当当前选定的项目再次被选择时，如何在 Android Spinner 中获取事件？