Android实现联动下拉框二级地市联动下拉框功能

日常使用软件中，为了方便且规范输入，会使用到下拉框进行输入，如注册时生日选项，购物时的地址输入，都会用到下拉框，今日笔者为了巩固已学的知识，实现了二级联动下拉框用作回顾及分享给求知的新手。

思路/步骤：

在实现联动下拉框之前，我们先对用到的ArrayAdapter和数据的封装作必要的了解，Android 中提供了很多适配器的实现类，其中ArrayAdapter就其中之一。它可以通过泛型来指定要适配的数据类型，然后在构造函数中把要适配的数据传入。如：

ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
  getApplicationContext(), 
  R.array.province,
   android.R.layout.simple_spinner_item)；

ArrayAdapter中比较常用的泛型是String，但此处用了CharSequence(字符序列)，通过指定泛型来装配适合的数据类型。

这段代码中有三个参数：

第一个参数Context是上下文，就是当前的Activity。
第二个参数是数据来源，R.array.province是存储在文件中的数据。
第三个参数是Android SDK中内置的一个TextView。(此文件中只有一个TextView)。

通过创建一个ArrayAdapter处理存储在中的省份地市数据，用Spinner控件处理ArrayAdapter处理好的数据，用TextView将数据显示出来形成一个list供用户点击选择。

主要实现代码： MainActivity.java

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.Toast;
public class MainActivity extends Activity {
 Spinner spinner1, spinner2;//声明两个下拉框
 String City, Province;
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 spinner1 = (Spinner) findViewById(R.id.spinner1);//绑定ID
 spinner2 = (Spinner) findViewById(R.id.spinner2);//绑定ID
 ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.province,
  android.R.layout.simple_spinner_item);//创建资源
 spinner1.setAdapter(adapter);//装配数据
 spinner1.setOnItemSelectedListener(new provinceClickListen());//监听事件
 spinner2.setOnItemSelectedListener(new CityClickListen());//监听事件
 }
class provinceClickListen implements OnItemSelectedListener {
 public void onItemSelected(AdapterView<?> parent, View v, int i, long l) {
  Spinner spinner = (Spinner) parent;
  String pro = (String) spinner.getItemAtPosition(i);//获取当前选中项
  ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.def,
   R.layout.item);//初始化
  Province = spinner1.getSelectedItem().toString();//当前选中的省份
  /** 根据省份，装配地市数据**/
  if (pro.equals(\"北京\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.北京, R.layout.item);
  } else if (pro.equals(\"天津\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.天津, R.layout.item);
  } else if (pro.equals(\"河北\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.河北, R.layout.item);
  } else if (pro.equals(\"山西\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.山西, R.layout.item);
  } else if (pro.equals(\"内蒙古\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.内蒙古, R.layout.item);
  } else if (pro.equals(\"辽宁\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.辽宁, R.layout.item);
  } else if (pro.equals(\"吉林\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.吉林, R.layout.item);
  } else if (pro.equals(\"黑龙江\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.黑龙江, R.layout.item);
  } else if (pro.equals(\"上海\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.上海, R.layout.item);
  } else if (pro.equals(\"江苏\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.江苏, R.layout.item);
  } else if (pro.equals(\"浙江\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.浙江, R.layout.item);
  } else if (pro.equals(\"安徽\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.安徽, R.layout.item);
  } else if (pro.equals(\"福建\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.福建, R.layout.item);
  } else if (pro.equals(\"江西\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.江西, R.layout.item);
  } else if (pro.equals(\"山东\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.山东, R.layout.item);
  } else if (pro.equals(\"河南\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.河南, R.layout.item);
  } else if (pro.equals(\"湖北\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.湖北, R.layout.item);
  } else if (pro.equals(\"湖南\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.湖南, R.layout.item);
  } else if (pro.equals(\"广东\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.广东, R.layout.item);
  } else if (pro.equals(\"广西\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.广西, R.layout.item);
  } else if (pro.equals(\"海南\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.海南, R.layout.item);
  } else if (pro.equals(\"重庆\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.重庆, R.layout.item);
  } else if (pro.equals(\"四川\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.四川, R.layout.item);
  } else if (pro.equals(\"贵州\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.贵州, R.layout.item);
  } else if (pro.equals(\"云南\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.云南, R.layout.item);
  } else if (pro.equals(\"西藏\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.西藏, R.layout.item);
  } else if (pro.equals(\"陕西\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.陕西, R.layout.item);
  } else if (pro.equals(\"甘肃\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.甘肃, R.layout.item);
  } else if (pro.equals(\"青海\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.青海, R.layout.item);
  } else if (pro.equals(\"宁夏\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.宁夏, R.layout.item);
  } else if (pro.equals(\"新疆\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.新疆, R.layout.item);
  } else if (pro.equals(\"台湾\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.台湾, R.layout.item);
  } else if (pro.equals(\"香港\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.香港, R.layout.item);
  } else if (pro.equals(\"澳门\")) {
  adapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.澳门, R.layout.item);
  }
  spinner2.setAdapter(adapter);//装配地市数据
 }
 public void onNothingSelected(AdapterView<?> parent) {

 }
 }
 class CityClickListen implements OnItemSelectedListener {

 public void onItemSelected(AdapterView<?> parent, View v, int i, long l) {
  City = spinner2.getSelectedItem().toString();//当前选中的地市
  if (City.equals(\"-城市-\")) {//当前还没选择地市
  } else {
  Toast.makeText(getApplicationContext(), Province+\"省\"+City, Toast.LENGTH_LONG).show();//Toast显示选中的省份城市
  }
 }
 public void onNothingSelected(AdapterView<?> parent) {}
 }
 public boolean onCreateOptionsMenu(Menu menu) {
 // Inflate the menu; this adds items to the action bar if it is present.
 getMenuInflater().inflate(R.menu.main, menu);
 return true;
 }
}

此外还有布局文件: activity_main.

<LinearLayout  ns:android=\"http://schemas.android.com/apk/res/android\"
   ns:tools=\"http://schemas.android.com/tools\"
  android:layout_width=\"match_parent\"
  android:layout_height=\"match_parent\"
  android:orientation=\"horizontal\"
  android:paddingBottom=\"@dimen/activity_vertical_margin\"
  android:paddingLeft=\"@dimen/activity_horizontal_margin\"
  android:paddingRight=\"@dimen/activity_horizontal_margin\"
  android:paddingTop=\"@dimen/activity_vertical_margin\"
  tools:context=\".MainActivity\" >
  <TextView
    android:id=\"@+id/province\"
    android:layout_width=\"match_parent\"
    android:layout_height=\"wrap_content\"
    android:layout_weight=\"1\"
    android:text=\"省份:\" />
  <Spinner
    android:id=\"@+id/spinner1\"
    android:layout_width=\"match_parent\"
    android:layout_height=\"wrap_content\"
    android:layout_weight=\"1\" />
  <TextView
    android:id=\"@+id/city\"
    android:layout_width=\"match_parent\"
    android:layout_height=\"wrap_content\"
    android:layout_weight=\"1\"
    android:text=\"城市:\" />
  <Spinner
    android:id=\"@+id/spinner2\"
    android:layout_width=\"match_parent\"
    android:layout_height=\"wrap_content\"
    android:layout_weight=\"1\" />
</LinearLayout>

item.

<?  version=\"1.0\" encoding=\"utf-8\"?>
  <TextView  ns:android=\"http://schemas.android.com/apk/res/android\"
    android:id=\"@+id/spinner_item\"
    android:layout_height=\"wrap_content\"
    android:layout_width=\"match_parent\"
    android:text=\"名称\"
    android:textColor=\"#000\"
    android:textSize=\"16dp\"/>

实现效果如下：

$\"在这里插入图片描述\"$
$\"在这里插入图片描述\"$
$\"在这里插入图片描述\"$
$\"在这里插入图片描述\"$
$\"完成选择后\"$