动态的多个旋转器状态/城市选择

Question

我需要开发一个Android视图，其中包含两个下拉框控件，一个用于选择州，另一个用于选择城市。

我的问题是，当选择一个州时，如何自动填充城市下拉框？

这背后的逻辑是什么？

我的string.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="spinner_category"></string>
<string-array name="category_state">
    <item >kerala</item>
    <item >tamil nadu</item>
    <item >Andra Pradesh</item>
    <item >karnataka</item>
</string-array>
</resources>

我的main.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical">

    <LinearLayout android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
        <TextView android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="10dip"
            android:text="Select : "/>
        <Spinner android:layout_width="250dip"
            android:layout_height="wrap_content"
            android:id="@+id/spinner_state"/>
    </LinearLayout>

<LinearLayout android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
        <TextView android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="10dip"
            android:text="Select : "/>
        <Spinner android:layout_width="250dip"
            android:layout_height="wrap_content"
            android:id="@+id/spinner_state"/>
    </LinearLayout>
</LinearLayout>

我的 activity.java 文件:

package com.converter;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

public class ConverterActivity extends Activity 
{
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Spinner spinner_s = (Spinner)findViewById(R.id.spinner_state);
        ArrayAdapter<CharSequence> category_adapter = ArrayAdapter.createFromResource(
                this, R.array.category_array, android.R.layout.simple_spinner_item);
        category_adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner_s.setAdapter(category_adapter);

    }
}

- Dil Se...

Answer 1

例子：

    Spinner city=(Spinner)findViewById(R.id.citySpinner);
    Spinner state=(Spinner)findViewById(R.id.stateSpinner);

    final ArrayList<String> state_options=new ArrayList<String>();
    final ArrayList<String> city_options=new ArrayList<String>();

    state_options.add("state_1");
    state_options.add("state_2");
    state_options.add("state_3");
    // Here you can also get a cursor and add Strings as options to state_options instead of what i have done

    city_options.add("city_1_state_1");
    city_options.add("city_2_state_1");
    city_options.add("city_3_state_1");
    // Here you can also get a cursor and add Strings as options to city_options instead of what i have done

    ArrayAdapter<String> cityAdapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_spinner_item,city_options);
    city.setAdapter(cityAdapter);   

    ArrayAdapter<String> stateAdapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_spinner_item,state_options);
    state.setAdapter(stateAdapter);

    state.setOnItemSelectedListener(new OnItemSelectedListener() {

        @Override
        public void onItemSelected(AdapterView<?> arg0, View view,
                        int position, long id) {

            String stateName=state_options.get(position).toString();
                resetCity(stateName);                               
        }

        @Override
        public void onNothingSelected(AdapterView<?> arg0) {

        }
   });

现在，

public void resetCity(String stateName)
{      
      city_options.removeAll(city_options);//i haven't checked this.
      if(stateName.eqauls("state_1"))
      {
          city_option.add("city_1_state_1");
          city_options.add("city_2_state_1");
          city_options.add("city_3_state_1");
          //you can also get a cursor and add Strings as options to city_options instead of what i have done
      }
      else if(stateName.eqauls("state_2"))
      {
          city_option.add("city_1_state_2");
          city_options.add("city_2_state_2");
          city_options.add("city_3_state_2");
          // you can also get a cursor and add Strings as options to city_options instead of what i have done
      } 
      else
      {
          city_option.add("city_1_state_3");
          city_options.add("city_2_state_3");
          city_options.add("city_3_state_3");
          //you can also get a cursor and add Strings as options to city_options instead of what i have done
      }

      ArrayAdapter<String> cityAdapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_spinner_item,city_options);
      city.setAdapter(cityAdapter);
}

这是最简单的例子。您可以从数据库中设置您的 city_options 和 state_options，然后您可以使用它来填充相应的下拉框。

- Hiral Vadodaria

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其实我是这个网站的新手。有人能告诉我如何接受答案吗？ - Dil Se...

你需要在答案左侧的投票标志下方检查正确的标记。 - Hiral Vadodaria

我已经放置了对我有效的确切代码。我认为它会起作用。 - Dil Se...

Answer 2

亲爱的，这是正确的方法……

我已将所有必要的州和城市写在字符串数组中……

例如

<string-array name="State_array">
            <item >s1</item>
            <item >s2</item>
            <item >s3</item>
            <item >s4</item>
    </string-array>
//then cities array for each states, like 
<string-array name="State1Cities_array">
            <item >c11</item>
            <item >c12</item>
            <item >c15</item>
            <item >c13</item>
    </string-array>
<string-array name="State2Cities_array">
            <item >c1</item>
            <item >c2</item>
            <item >c5</item>
            <item >c3</item>
    </string-array>

// and so on for all the states

然后在主xml中为两者都添加了2个下拉框。我相信所有人都能简单地完成，对吧？

然后我的main.xml如下...

spinner_states_activity = (Spinner)findViewById(R.id.spinner_states_main);
        spinner_states_activity.setOnItemSelectedListener(this);
        adapter = ArrayAdapter.createFromResource(
                this, R.array.state_array, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(R.layout.myspinner);
// my layout for spinners u can use urs or defalut. k?
        spinner_states_activity.setAdapter(adapter);

spinner_cities_activity = (Spinner)findViewById(R.id.spinner_cities_main);
        spinner_cities_activity.setOnItemSelectedListener(this);

//and in function onItemSelected

        int pos,pos2;
        pos = spinner_states_activity.getSelectedItemPosition();
        int iden=parent.getId();
        if(iden==R.id.spinner_states_main)
        {
            pos2 = 0;
            switch (pos) 
            {
                case 0: unit_adapter= ArrayAdapter.createFromResource(
                            this, R.array.States1Cities_array, android.R.layout.simple_spinner_item);
                        break;
                case 1: unit_adapter= ArrayAdapter.createFromResource(
                            this, R.array.States3Cities_array, android.R.layout.simple_spinner_item);
                        break;
                        // all the StatesxCities entires....
                default:
                        break;
            }

            spinner_cities_activity.setAdapter(unit_adapter);
            unit_adapter.setDropDownViewResource(R.layout.myspinner);
        }

只需看一眼，自己动手做... 希望这能对你有所帮助...

亲爱的朋友们， Sujith

- Dil Se...

Answer 3

public class ConverterActivity extends Activity {

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Spinner citySpinner = (Spinner)findViewById(R.id.spinner_city);
        final ArrayAdapter<String> cityAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, new String[]); // starts empty
        city_adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner_city.setAdapter(city_adapter);

        Spinner categorySpinner = (Spinner)findViewById(R.id.spinner_state);
        final ArrayAdapter<String> categoryAdapter = ArrayAdapter.createFromResource(
                this, R.array.category_array, android.R.layout.simple_spinner_item);
        categoryAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        categorySpinner.setAdapter(category_adapter);
        categorySpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                String selectedState = parent.getItemAtPosition(position);
                cityAdapter.clear(); // remove previous entries
                // look up your cities for the state selectedState, using your own method
                cityAdapter.add(the cities you want); // do that in a loop for all your cities
                cityAdapter.notifyDataSetChanged();
            };
            @Override
            public void onNothingSelected(AdapterView<?> parent) {
                // do nothing
            }
        });
    }
} 

注意：在StackOverflow编辑器中编码时，可能会出现一些语法错误 :)

要查找每个州的城市，可以使用任何方法：您可以在多个字符串数组资源中定义它们，也可以从数据库中获取它们等。

- Guillaume

Answer 4

你需要完成以下步骤：

1. 创建城市数据源（可以是数据库或哈希映射表（“州”，“城市”））。

2. 将setOnItemSelectedListener(listener)设置为包含州的下拉列表。

3. 上述监听器的onItemSelected()方法从第一步创建的数据源中获取数据，并将其附加到城市下拉列表中。

就这样。

- School Boy

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请查看我的回答，其中详细说明了步骤2和3。注意，步骤1存在错误：它需要是一个HashMap<state，List<city>> ;) - Guillaume