为了理解这个技巧,首先要了解适配器的一般工作原理以及特别是ArrayAdapter。
适配器:是可以将数据结构绑定到小部件上的对象,然后这些小部件在列表或下拉列表中显示该数据。
因此,适配器回答的两个问题是:
1. 对于某个索引,应将哪个小部件或复合视图与数据结构(您类的对象)关联起来?
2. 如何从数据结构(您类的对象)中提取数据,并如何根据这些数据设置小部件或复合视图的字段,例如
EditText
?
ArrayAdapter的回答是:
1. 任何索引的每个小部件(例如
row.xml
或
android.R.layout.simple_spinner_item
)都是相同的,并且从传递给ArrayAdapter构造函数的资源中膨胀而来。
2. 每个小部件都应该是TextView(或其子类)的实例。使用支持数据结构中项目的字符串格式调用小部件的
.setText()
方法。该字符串格式将通过对项目调用
.toString()
获得。
CustomListViewDemo.java
public class CustomListViewDemo extends ListActivity {
private EfficientAdapter adap;
private static String[] data = new String[] { "0", "1", "2", "3", "4" };
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.main);
adap = new EfficientAdapter(this);
setListAdapter(adap);
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
Toast.makeText(this, "Click-" + String.valueOf(position), Toast.LENGTH_SHORT).show();
}
public static class EfficientAdapter extends BaseAdapter implements Filterable {
private LayoutInflater mInflater;
private Bitmap mIcon1;
private Context context;
int firstpos=0;
public EfficientAdapter(Context context) {
mInflater = LayoutInflater.from(context);
this.context = context;
}
public View getView(final int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = mInflater.inflate(R.layout.adaptor_content, null);
holder = new ViewHolder();
holder.sp = (Spinner) convertView.findViewById(R.id.spinner1);
holder.ArrayAdapter_sp = new ArrayAdapter(parent.getContext(),android.R.layout.simple_spinner_item,data);
holder.ArrayAdapter_sp.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
holder.sp.setAdapter( holder.ArrayAdapter_sp);
holder.sp.setOnItemSelectedListener(new OnItemSelectedListener()
{
private int pos = position;
@Override
public void onItemSelected(AdapterView<?> arg0, View arg1,
int p, long arg3)
{
Toast.makeText(context, "select spinner " + String.valueOf(pos)+" with value ID "+p, Toast.LENGTH_SHORT).show();
}
@Override
public void onNothingSelected(AdapterView<?> arg0)
{
}
});
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
return convertView;
}
static class ViewHolder
{
Spinner sp;
ArrayAdapter ArrayAdapter_sp;
}
@Override
public Filter getFilter() {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public int getCount() {
return data.length;
}
@Override
public Object getItem(int position) {
return data[position];
}
}
}
adaptor_content.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/lineItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_vertical" >
<Spinner
android:id="@+id/spinner1"
android:layout_width="314dp"
android:layout_height="wrap_content" />
</LinearLayout>
main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="fill_parent" android:layout_width="fill_parent"
>
<ListView
android:id="@+id/android:list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_marginBottom="60dip"
android:layout_marginTop="10dip"
android:cacheColorHint="#00000000"
android:drawSelectorOnTop="false" />
</RelativeLayout>
它正常工作,我希望它有用。