Android下拉列表框

        周末翻了翻书，发现才歇了一两个月没看Android，好多看的东西又都还给书了，遂决定将所学的写到博客中，权当笔记（代码为主），巩固所学知识。

        整理的下拉列表框示例代码中，主要分为以下部分：静态绑定下拉框数据、动态绑定下拉框数据、选择时触发的事件以及获得所选的值；

        1、静态绑定下拉框数据

        需要将数据写在xml中，然后设置下拉框的entries属性，则数据自动加载到下拉框中。具体如下：

        在value文件夹中新建cityInfo.xml，xml中写入

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="cityArray">
        <item>北京</item>
        <item>江苏</item>        
        <item>浙江</item>
        <item>上海</item>        
    </string-array>
</resources>

        设计页面控件代码：

    <Spinner android:id="@+id/spinnerCityStatic"
	     android:layout_width="wrap_content"
	     android:layout_height="wrap_content"
	     android:entries="@array/cityArray"/>

        2、动态绑定下拉框数据

        主要三个步骤，1.获得数据列表；2.填充数据适配器；3.设置下拉框的适配器；

private Spinner spCity = null;
private ArrayAdapter<CharSequence> adapterCity = null;
private static String[] cityInfo={"北京","江苏","浙江","上海"};
//初始化函数中代码如下
this.spCity = (Spinner) super.findViewById(R.id.spinnerCity);
//将数据cityInfo填充到适配器adapterCity中
this.adapterCity = new ArrayAdapter<CharSequence>(this,
	android.R.layout.simple_spinner_dropdown_item, cityInfo);
//设置下拉框的数据适配器adapterCity
this.spCity.setAdapter(adapterCity);

        3、选择时触发的事件

        需要实现OnItemSelectedListener接口的onItemSelected方法，代码如下

//下拉框选择事件
private class OnItemSelectedListenerImpl implements OnItemSelectedListener {
	@Override
	public void onItemSelected(AdapterView<?> parent, View view,
			int position, long id) {
		String city = parent.getItemAtPosition(position).toString();
		Toast.makeText(MainActivity.this, "选择的城市是：" + city,
				Toast.LENGTH_LONG).show();
	}

	@Override
	public void onNothingSelected(AdapterView<?> parent) {
		// TODO Auto-generated method stub
	}

}

        4、获得下拉框所选的值

String cityStatic = spCityStatic.getSelectedItem().toString();

       项目完整代码：

       前台设计页面activity_main.xml如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Spinner 
        android:id="@+id/spinnerCityStatic"
	    android:layout_width="wrap_content"
	    android:layout_height="wrap_content"
	    android:entries="@array/cityArray"/>
     <Spinner 
        android:id="@+id/spinnerCity"
	    android:layout_width="wrap_content"
	    android:layout_height="wrap_content"/>
     <Button 
        android:id="@+id/btnShowCity"
	    android:layout_width="wrap_content"
	    android:layout_height="wrap_content"
	    android:text="查看选择的结果"/>
</LinearLayout>

        后台页面MainActivity.java代码：

package com.example.spinner0803;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.Toast;

public class MainActivity extends Activity {
	private Button btnShowCity = null;
	private Spinner spCityStatic = null;
	private Spinner spCity = null;
	private ArrayAdapter<CharSequence> adapterCity = null;
	private static String[] cityInfo={"北京","江苏","浙江","上海"};
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		//按钮相关
		btnShowCity = (Button) super.findViewById(R.id.btnShowCity);
		btnShowCity.setOnClickListener(new OnClickListenerImpl());
		//静态实现的下拉框，数据写在cityInfo.xml文件中
		this.spCityStatic = (Spinner) super
				.findViewById(R.id.spinnerCityStatic);
		this.spCityStatic
				.setOnItemSelectedListener(new OnItemSelectedListenerImpl());
		//动态实现的下拉框，数据在程序中获得，实际项目可能来自数据库等
		this.spCity = (Spinner) super.findViewById(R.id.spinnerCity);
		this.adapterCity = new ArrayAdapter<CharSequence>(this,
				android.R.layout.simple_spinner_dropdown_item, cityInfo);
		this.spCity.setAdapter(adapterCity);
		this.spCity.setOnItemSelectedListener(new OnItemSelectedListenerImpl());
	}
	//按钮点击事件
	private class OnClickListenerImpl implements OnClickListener {
		@Override
		public void onClick(View v) {
			String cityStatic = spCityStatic.getSelectedItem().toString();
			String city = spCity.getSelectedItem().toString();
			String selectInfo = "第一个选择的城市是：" + city + "，第二个选择的城市是："
					+ cityStatic;
			Toast.makeText(MainActivity.this, selectInfo, Toast.LENGTH_LONG)
					.show();
		}

	}
	//下拉框选择事件
	private class OnItemSelectedListenerImpl implements OnItemSelectedListener {
		@Override
		public void onItemSelected(AdapterView<?> parent, View view,
				int position, long id) {
			String city = parent.getItemAtPosition(position).toString();
			Toast.makeText(MainActivity.this, "选择的城市是：" + city,
					Toast.LENGTH_LONG).show();
		}

		@Override
		public void onNothingSelected(AdapterView<?> parent) {
			// TODO Auto-generated method stub
		}

	}
}

        项目运行截图：

        项目源码下载