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android spinner 一般預設是選中第一項

但是有時我們需要一開始是  [未選取] 或 [請選擇]

點選spinner後出現選項，點了某個選項後就顯示他。

要達到此目的須自己另外撰寫 spiiner adapter

adapter:

import android.content.Context;
import android.database.DataSetObserver;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListAdapter;
import android.widget.SpinnerAdapter;
 
/**
 * Decorator Adapter to allow a Spinner to show a 'Nothing Selected...' initially displayed instead
 * of the first choice in the Adapter.
 */
public class NothingSelectedSpinnerAdapter implements SpinnerAdapter, ListAdapter {
 
protected static final int EXTRA = 1;
protected SpinnerAdapter adapter;
protected Context context;
protected int nothingSelectedLayout;
protected int nothingSelectedDropdownLayout;
protected LayoutInflater layoutInflater;
 
/**
 * Use this constructor to have NO 'Select One...' item, instead use the standard prompt or nothing at all
 * @param spinnerAdapter wrapped Adapter.
 * @param nothingSelectedLayout layout for nothing selected, perhaps you want text grayed out like a prompt...
 * @param context
 */
public NothingSelectedSpinnerAdapter(SpinnerAdapter spinnerAdapter,  
        int nothingSelectedLayout, Context context) {
    this(spinnerAdapter, nothingSelectedLayout, -1, context);
}
 
/**
 * Use this constructor to Define your 'Select One...' layout as the first row in the returned choices.
 * If you do this, you probably don't want a prompt on your spinner or it'll have two 'Select' rows.
 * @param spinnerAdapter wrapped Adapter. Should probably return false for isEnabled(0)
 * @param nothingSelectedLayout layout for nothing selected, perhaps you want text grayed out like a prompt...
 * @param nothingSelectedDropdownLayout layout for your 'Select an Item...' in the dropdown
 * @param context
 */
public NothingSelectedSpinnerAdapter(SpinnerAdapter spinnerAdapter,  
        int nothingSelectedLayout, int nothingSelectedDropdownLayout, Context context) {
    this.adapter = spinnerAdapter;
    this.context = context;
    this.nothingSelectedLayout = nothingSelectedLayout;
    this.nothingSelectedDropdownLayout = nothingSelectedDropdownLayout;
    layoutInflater = LayoutInflater.from(context);
}
 
@Override
public final View getView(int position, View convertView, ViewGroup parent) {
    // This provides the View for the Selected Item in the Spinner, not the dropdown (unless dropdownView not set)
    if (position == 0) {
        return getNothingSelectedView(parent);
    }
    return adapter.getView(position - EXTRA, null, parent); // could re-use the convertView if possible
}
 
/**
 * View to show in Spinner with Nothing Selected
 * Override this to do something dynamic... e.g. "37 Options Found"
 * @param parent
 * @return
 */
protected View getNothingSelectedView(ViewGroup parent) {
    return layoutInflater.inflate(nothingSelectedLayout, parent, false);
}
 
@Override
public View getDropDownView(int position, View convertView, ViewGroup parent) {
    // BUG! Vote to fix!! http://code.google.com/p/android/issues/detail?id=17128 - Spinner does not support multiple view types
    if (position == 0) {
        return nothingSelectedDropdownLayout == -1 ? new View(context) : getNothingSelectedDropdownView(parent);
    }
 
    return adapter.getDropDownView(position - EXTRA, null, parent);  // could re-use the convertView if possible, utilize setTag...
}
 
/**
 * Override this to do something dynamic... e.g. "Pick your Favorite of these 37"  
 * @param parent
 * @return
 */
protected View getNothingSelectedDropdownView(ViewGroup parent) {
    return layoutInflater.inflate(nothingSelectedDropdownLayout, parent, false);
}
 
@Override
public int getCount() {
    int count = adapter.getCount();
    return count == 0 ? 0 : count + EXTRA;
}
 
@Override
public Object getItem(int position) {
    return position == 0 ? null : adapter.getItem(position - EXTRA);
}
 
@Override
public int getItemViewType(int position) {
    // doesn't work!! Vote to Fix! http://code.google.com/p/android/issues/detail?id=17128 - Spinner does not support multiple view types
    // This method determines what is the convertView, this should return 1 for pos 0 or return 0 otherwise.
    return position == 0 ? getViewTypeCount() - EXTRA : adapter.getItemViewType(position - EXTRA);
}
 
@Override
public int getViewTypeCount() {
    return adapter.getViewTypeCount() + EXTRA;
}
 
@Override
public long getItemId(int position) {
    return adapter.getItemId(position - EXTRA);
}
 
@Override
public boolean hasStableIds() {
    return adapter.hasStableIds();
}
 
@Override
public boolean isEmpty() {
    return adapter.isEmpty();
}
 
@Override
public void registerDataSetObserver(DataSetObserver observer) {
    adapter.registerDataSetObserver(observer);
}
 
@Override
public void unregisterDataSetObserver(DataSetObserver observer) {
    adapter.unregisterDataSetObserver(observer);
}
 
@Override
public boolean areAllItemsEnabled() {
    return false;
}
 
@Override
public boolean isEnabled(int position) {
    return position == 0 ? false : true; // don't allow the 'nothing selected' item to be picked
}
 
}

呼叫:

Spinner spinner = (Spinner) findViewById(R.id.spinner);
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.planets_array, android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setPrompt("选项：");
 
    spinner.setAdapter(new NothingSelectedSpinnerAdapter(
            adapter,
            R.layout.contact_spinner_row_nothing_selected,
                    // R.layout.contact_spinner_nothing_selected_dropdown, // optional
            this));

layout:

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@android:id/text1"
  style="?android:attr/spinnerItemStyle"
  android:singleLine="true"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:ellipsize="marquee"
  android:textSize="18sp"
  android:textColor="#808080"
  android:text="[ 请选择：]" />

轉自:http://www.eoeandroid.com/thread-271812-1-1.html