在android开发中有很多地方要用到数据填充器,也就是Adpter填充器的知识,关于Adpter的继承关系大家可以参考我转载的一篇文章:
http://www.cnblogs.com/tanlon/archive/2011/05/21/2053009.html
相关的属性以及方法可以参考API,如果英语不好的看不懂API的可以参考一下农民伯伯的博客,这个里面翻译的和推荐的文章都不错:
http://home.cnblogs.com/over140
对于他们的继承与实现之间的关系,大家可以在我上面提到的文章里面可以很清楚的看到,在此基础上我还要对其进行扩展。
不论是那种适配器模式,也不管是Listview也好还是gridview也好,对他们填充数据,都是分三步走。
第一:创建一个数据填充的对象,可以是ListView, GridView, Gallery。
listView=(ListView) findViewById(R.id.listview_simple);
第二步:创建一个数据填充器,可以是BaseAdpter、SimpleAdapter,也可以是与数据库相关联的CursorAdpter。
例如:SimpleAdapter可以使用系统封装好的,你也可以自己去继承一个Simpleadpter,来重写其中的方法。继承 simpleadpter的好处在于,你可以对listitem中每个单一的控件设置监听事件等等一系列操作。如果用的是系统封装好的就有点爱莫能助了。
直接使用系统封装的:
SimpleAdapter simpleAdapter =new SimpleAdapter(
this,
data,
R.layout.simple_item,
new String[] { "name", "info" },
newint[] { R.id.simple_name, R.id.simple_info });
this,
data,
R.layout.simple_item,
new String[] { "name", "info" },
newint[] { R.id.simple_name, R.id.simple_info });
重写系统的simpleadpter:
publicclass ListSimpleAdpter extends SimpleAdapter{
//要使用到的数据源
private List<Map<String, Object>> data=new ArrayList<Map<String, Object>>();
//填充数据的资源文件
privateint resource;
private String[] from;
private Context context;
public ListSimpleAdpter(Context context,
List<Map<String, Object>> data, int resource, String[] from,
int[] to) {
super(context, data, resource, from, to);
this.context=context;
this.data=data;
this.resource=resource;
this.from=from;
}
//item的总行数
@Override
publicint getCount() {
// TODO Auto-generated method stub
return data==null?0:data.size();
}
//item对象
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return position;
}
//item的id
@Override
publiclong getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
//绘制每一个item
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
Holder holder =null;
if(convertView==null)
{
convertView=LayoutInflater.from(context).inflate(resource, null);
holder=new Holder();
holder.imageView=(ImageView) convertView.findViewById(R.id.listitem_pic);
holder.title=(TextView) convertView.findViewById(R.id.listitem_title);
holder.content=(TextView) convertView.findViewById(R.id.listitem_content);
convertView.setTag(holder);
}else
{
holder=(Holder) convertView.getTag();
}
holder.imageView.setImageResource(Integer.parseInt(data.get(position).get(from[0]).toString()));
holder.title.setText(data.get(position).get(from[1]).toString());
holder.content.setText(data.get(position).get(from[2]).toString());
return convertView;
}
class Holder{
ImageView imageView;
TextView title;
TextView content;
}
}
//要使用到的数据源
private List<Map<String, Object>> data=new ArrayList<Map<String, Object>>();
//填充数据的资源文件
privateint resource;
private String[] from;
private Context context;
public ListSimpleAdpter(Context context,
List<Map<String, Object>> data, int resource, String[] from,
int[] to) {
super(context, data, resource, from, to);
this.context=context;
this.data=data;
this.resource=resource;
this.from=from;
}
//item的总行数
@Override
publicint getCount() {
// TODO Auto-generated method stub
return data==null?0:data.size();
}
//item对象
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return position;
}
//item的id
@Override
publiclong getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
//绘制每一个item
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
Holder holder =null;
if(convertView==null)
{
convertView=LayoutInflater.from(context).inflate(resource, null);
holder=new Holder();
holder.imageView=(ImageView) convertView.findViewById(R.id.listitem_pic);
holder.title=(TextView) convertView.findViewById(R.id.listitem_title);
holder.content=(TextView) convertView.findViewById(R.id.listitem_content);
convertView.setTag(holder);
}else
{
holder=(Holder) convertView.getTag();
}
holder.imageView.setImageResource(Integer.parseInt(data.get(position).get(from[0]).toString()));
holder.title.setText(data.get(position).get(from[1]).toString());
holder.content.setText(data.get(position).get(from[2]).toString());
return convertView;
}
class Holder{
ImageView imageView;
TextView title;
TextView content;
}
}
这里对于Adapter的优化,用的很古老的ViewHolder、ViewCache办法:
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
Holder holder =null;
if(convertView==null)
{
convertView=LayoutInflater.from(context).inflate(resource, null);
holder=new Holder();
holder.imageView=(ImageView) convertView.findViewById(R.id.listitem_pic);
holder.title=(TextView) convertView.findViewById(R.id.listitem_title);
holder.content=(TextView) convertView.findViewById(R.id.listitem_content);
convertView.setTag(holder);
}else
{
holder=(Holder) convertView.getTag();
}
holder.imageView.setImageResource(Integer.parseInt(data.get(position).get(from[0]).toString()));
holder.title.setText(data.get(position).get(from[1]).toString());
holder.content.setText(data.get(position).get(from[2]).toString());
return convertView;
}
class Holder{
ImageView imageView;
TextView title;
TextView content;
}
// TODO Auto-generated method stub
Holder holder =null;
if(convertView==null)
{
convertView=LayoutInflater.from(context).inflate(resource, null);
holder=new Holder();
holder.imageView=(ImageView) convertView.findViewById(R.id.listitem_pic);
holder.title=(TextView) convertView.findViewById(R.id.listitem_title);
holder.content=(TextView) convertView.findViewById(R.id.listitem_content);
convertView.setTag(holder);
}else
{
holder=(Holder) convertView.getTag();
}
holder.imageView.setImageResource(Integer.parseInt(data.get(position).get(from[0]).toString()));
holder.title.setText(data.get(position).get(from[1]).toString());
holder.content.setText(data.get(position).get(from[2]).toString());
return convertView;
}
class Holder{
ImageView imageView;
TextView title;
TextView content;
}
或者使用HashMap做缓存的方法:
HashMap<Integer, View> m =new HashMap<Integer, View>();
public View getView(int position, View view, ViewGroup parent) {
View convertView = m.get(position);
if (convertView !=null) {
return convertView;
} else {
convertView=LayoutInflater.from(context).inflate(resource, null);
ImageView imageView=(ImageView) convertView.findViewById(R.id.listitem_pic);
TextView title=(TextView) convertView.findViewById(R.id.listitem_title);
TextViewcontent=(TextView) convertView.findViewById(R.id.listitem_content);
m.put(position, convertView);
}
}
public View getView(int position, View view, ViewGroup parent) {
View convertView = m.get(position);
if (convertView !=null) {
return convertView;
} else {
convertView=LayoutInflater.from(context).inflate(resource, null);
ImageView imageView=(ImageView) convertView.findViewById(R.id.listitem_pic);
TextView title=(TextView) convertView.findViewById(R.id.listitem_title);
TextViewcontent=(TextView) convertView.findViewById(R.id.listitem_content);
m.put(position, convertView);
}
}
第三步:将数据填充到对象中去
listView.setAdapter(simpleAdapter );
这样就完成了数据填充器的数据填充。还有ArrayAdapter, BaseAdapter, CursorAdapter, HeaderViewListAdapter, ListAdapter,
ResourceCursorAdapter, SimpleAdapter, SimpleCursorAdapter, SpinnerAdapter, WrapperListAdapter.SimpleCursorTreeAdapter、
二级树相关的SimpleExpandableListAdapter、BaseExpandableListAdapter等等。
sourceurl:http://www.cnblogs.com/tanlon/archive/2011/06/20/2084901.html