使用Spinner实现下拉列表

首先在布局文件中创建Spinner 控件，一个最简单的Spinner 控件如下：

<Spinner
android:id="@+id/spinner"
android:layout_width="match_parent"
android:layout_height="wrap_content" />

然后再在JAVA代码中初始化Spinner，为其设置适配器和监听事件。

1. 首先用findViewById() 的方法初始化Spinner

public class MainActivity extends Activity {

<strong>private Spinner spinner;</strong>
...

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
<strong>spinner = (Spinner)findViewById(R.id.spinner);</strong>
...
}

}


2. 为其设置适配器。
这里有两种方法，第一种是使用ArrayAdapter，第二种是使用SimpleAdapter，两种适配器的使用方法与在ListView 中基本相同

1）使用ArrayAdapter

准备数据源，创建适配器，绑定适配器

public class MainActivity extends Activity {

...

private ArrayAdapter<String> adapter1;
private List<String> dataList1;
private String[] cities = {"北京", "上海", "深圳", "广州"};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
...

dataList1 = new ArrayList<String>();
for(int i = 0; i < cities.length; i++){
dataList1.add(cities[i]);
}
adapter1 = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, dataList1);
adapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter2);
...
}

}
注意到，这里使用适配器多了一条方法adapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)这个方法专门用来给Spinner配置下来的样式，这里选择使用了系统的样式。
2）使用SimpleAdapter

准备目标项布局，准备数据源，创建适配器，绑定适配器

spinner_item.xml

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

<ImageView
android:id="@+id/image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:src="@drawable/ic_launcher" />

<TextView
android:id="@+id/spinner_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginLeft="5dp"
android:text="text" />

</LinearLayout>

MainActivity.java
public class MainActivity extends Activity {

...

private SimpleAdapter adapter2;
private List<Map<String, Object>> dataList2;
private String[] cities = {"北京", "上海", "深圳", "广州"};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
...

dataList2 = new ArrayList<Map<String, Object>>();
for(int i = 0; i < cities.length; i++){
Map<String, Object> map = new HashMap<String, Object>();
map.put("image", R.drawable.ic_launcher);
map.put("text", cities[i]);
dataList2.add(map);
}
adapter2 = new SimpleAdapter(this, dataList2, R.layout.spinner_item, new String[]{"image", "text"}, new int[]{R.id.image, R.id.spinner_text});
spinner.setAdapter(adapter2);
...
}

}SimpleAdapter也可以用setDropDownViewResource方法给适配器设置下拉的样式，不过必须要使用自定义的样式。

3. 设置监听器

设置监听器使用SetOnItemSelectedListener 方法和OnItemSelectedListener 接口

spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

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

@Override
public void onNothingSelected(AdapterView<?> parent) {
...
}
});

一个完整的示例代码如下

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
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="com.example.spinnerdemo.MainActivity" >

<TextView
android:id="@+id/text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="24sp" />

<Spinner
android:id="@+id/spinner"
android:layout_width="match_parent"
android:layout_height="wrap_content" />

</LinearLayout>

spinner_item.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <ImageView android:id="@+id/image" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:src="@drawable/ic_launcher" /> <TextView android:id="@+id/spinner_text" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:layout_marginLeft="5dp" android:text="text" /> </LinearLayout>

MainActivity.java
public class MainActivity extends Activity {

private TextView text;
private Spinner spinner;

// private ArrayAdapter<String> adapter1;
private SimpleAdapter adapter2;
// private List<String> dataList1;
private List<Map<String, Object>> dataList2;

private String[] cities = {"北京", "上海", "深圳", "广州"};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
text = (TextView)findViewById(R.id.text);
spinner = (Spinner)findViewById(R.id.spinner);
text.setText("您选择的是北京");

// dataList1 = new ArrayList<String>();
// for(int i = 0; i < cities.length; i++){
// dataList1.add(cities[i]);
// }
// adapter1 = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, dataList1);

dataList2 = new ArrayList<Map<String, Object>>();
for(int i = 0; i < cities.length; i++){
Map<String, Object> map = new HashMap<String, Object>();
map.put("image", R.drawable.ic_launcher);
map.put("text", cities[i]);
dataList2.add(map);
}
adapter2 = new SimpleAdapter(this, dataList2, R.layout.spinner_item, new String[]{"image", "text"}, new int[]{R.id.image, R.id.spinner_text});
//adapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter2);
//adapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

@Override
public void onItemSelected(AdapterView<?> parent, View view,
int position, long id) {
text.setText("您选择的是" + adapter2.getItem(position));
}

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

}
});
}

}

效果如下：