Spinner使用方法

Android中的Spinner和VC中的列表框很类似。这里做个小例子，是为笔记。

示例效果

下拉的效果：

布局文件

Activity的布局my_layout.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="vertical" >

<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >

<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="@string/spinner_hint" />

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

</LinearLayout>

<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" >

<TextView
android:id="@+id/result_hint"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="@string/result_hint" />

<!-- android:hint="@string/result" -->
<EditText
android:id="@+id/result"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="none"
android:textAppearance="?android:attr/textAppearanceLarge"/>

</LinearLayout>

</LinearLayout>

Spinner显示的布局spinner_layout.xml

这里直接简化了，显示一个简单的TextView。

<?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="vertical" >

<TextView
android:id="@+id/calculate_result"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"/>

</LinearLayout>

注：可以增加padding属性，优化显示效果。如：

<!--
android:layout_marginBottom="6dip"
android:layout_marginLeft="10dip"
android:layout_marginTop="6dip"
android:layout_marginRight="2dip"
-->

<!--
android:paddingBottom="3dip"
android:paddingEnd="4dip"
android:paddingStart="4dip"
android:paddingTop="3dip"
-->

代码

省略一些自动生成的代码。

public static final String TAG = "MainActivity";

private int[] values = {1, 3, 5, 7, 9};

private Spinner spinner = null;
private EditText result = null;
private TextView result_hint = null;

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

spinner = (Spinner) this.findViewById(R.id.spinner);
spinner.setAdapter(new MySpinnerAdapter());
spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

public void onItemSelected(AdapterView<?> parent, View view,
int position, long id) {
int value = values[position];
int cal_result = value * value;
result.setText("" + cal_result);

result_hint.setText(value + " * " + value + "=");
}

public void onNothingSelected(AdapterView<?> parent) {
}

});

result = (EditText) this.findViewById(R.id.result);
result.setInputType(InputType.TYPE_NULL);
result.setTextColor(Color.GRAY);

result_hint = (TextView) this.findViewById(R.id.result_hint);
}

private class MySpinnerAdapter extends BaseAdapter {
public int getCount() {
return values.length;
}

public Object getItem(int position) {
return values[position];
}

public long getItemId(int position) {
return position;
}

public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = LayoutInflater.from(MainActivity.this)
.inflate(R.layout.spinner_layout,
null);
}

TextView textView = (TextView) convertView.findViewById(R.id.calculate_result);
textView.setText("" + values[position]);

return convertView;
}

}

要点

在布局文件中增加Spinner

为Spinner定义一个布局文件

为Spinner定义一个Adapter，实现数据和视图的映射（MVC）

为Spinner定义事件处理，通常即为OnItemSelectedListener。

ArrayAdapter

使用场景

在上面的例子中，使用的数据源是一个数组，而且只是让每个数字显示在Spinner的layout（spinner_layout.xml）的一个TextView中。

对于这种情况，直接使用ArrayAdapter以及android.R.layout.simple_spinner_item就够了。但需要修改values的类型为Integer[]：

private Integer[] values = {1, 3, 5, 7, 9};

适配器部分改为：

spinner = (Spinner) this.findViewById(R.id.spinner);

ArrayAdapter<Integer> arrayAdapter = new ArrayAdapter<Integer>(this,
android.R.layout.simple_spinner_item,
values);
arrayAdapter.setDropDownViewResource(
android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(arrayAdapter);

//spinner.setAdapter(new MySpinnerAdapter());

simple_spinner_item

android.R.layout.simple_spinner_item是Android平台提供的，定义如下：

<?xml version="1.0" encoding="utf-8"?>
<!--
/* //device/apps/common/assets/res/any/layout/simple_spinner_item.xml
**
** Copyright 2006, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
**     http://www.apache.org/licenses/LICENSE-2.0 **
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
-->
<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:textAlignment="inherit"/>

simple_spinner_dropdown_item

R.layout.simple_spinner_dropdown_item也是Android平台定义的，如下：

<CheckedTextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/text1"
style="?android:attr/spinnerDropDownItemStyle"
android:singleLine="true"
android:layout_width="match_parent"
android:layout_height="?android:attr/dropdownListPreferredItemHeight"
android:ellipsize="marquee"
android:textAlignment="inherit"/>