本文主要是介绍Android中封装自己的BaseAdapter,希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!
android项目开发中经常会用到listview、gridview等组件去显示数据,这些组件都需要绑定adapter,androidsdk中提供了adapter和baseadapter可用于作为自定义adapter的基类进行扩展。
以BaseAdapter作为基类自定义一个Adapter如下:
```
public class ParkAdapter extends BaseAdapter {
private Context context;
private List<ParkItem> data;
public ParkAdapter(Context context, List<ParkItem> data) {
this.context = context;
this.data = data;
}
private boolean isDataEmpty() {
return data == null || data.isEmpty();
}
@Override
public int getCount() {
return isDataEmpty() ? 0 : data.size();
}
@Override
public Object getItem(int arg0) {
return isDataEmpty() ? null : data.get(arg0);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (isDataEmpty()) {
return null;
}
ParkItem curItem = data.get(position);
ViewHolder holder;
if (convertView == null) {
convertView = LayoutInflater.from(context).inflate(R.layout.park_item, null);
holder = new ViewHolder(convertView);
convertView.setTag(R.string.firstparm, holder);
} else {
holder = (ViewHolder) convertView.getTag(R.string.firstparm);
}
if (curItem != null) {
//todo
}
convertView.setTag(R.string.secondparm, curItem);
return convertView;
}
@Override
public int getItemViewType(int position) {
}
}
```
做了几个页面之后就会发现,直接如果每个Adapter都从BaseAdapter直接继承的话,每次都要写很多重复的代码:
```
private boolean isDataEmpty() {
return data == null || data.isEmpty();
}
@Override
public int getCount() {
return isDataEmpty() ? 0 : data.size();
}
@Override
public Object getItem(int arg0) {
return isDataEmpty() ? null : data.get(arg0);
}
@Override
public long getItemId(int position) {
return position;
}
```
这里的逻辑每个Adapter中都是相同的,没有必要每个Adapter中都写一遍,那么既然是重复的,那我们就把这些重复的部分抽出来,另外List中的数据类型可以使用泛型来替代,当然也会存在有些adaper布局中有按钮等可以操作的组件需要响应用户操作(点击、滑动等),那我们就可以定义一个接口去回调用户操作,这样我们就可以重新定义一个Adapter的基类供自定义的Adapter继承:
```
public abstract class MyBaseAdapter<T> extends BaseAdapter {
public Context context;
public List<T> list;
public interface MyClickListener {
void onClick(View view, int position);
}
protected MyClickListener listener;
public MyBaseAdapter() {
super();
}
public MyBaseAdapter(Context context, List<T> list) {
super();
this.context = context;
this.list = list;
}
public MyBaseAdapter(Context context, List<T> list, MyClickListener listener) {
super();
this.context = context;
this.list = list;
this.listener = listener;
}
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int position) {
return list.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
public void setListener(MyClickListener listener) {
this.listener = listener;
}
}
```
其他自定义Adapter使用的话就可以直接继承了:
public class AreaListAdapter extends MyBaseAdapter<Region> {
AreaListAdapter(Context context, List<Region> list) {
super(context, list);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
AreaItemBinding binding;
if (convertView == null) {
binding = DataBindingUtil.inflate(LayoutInflater.from(parent.getContext()), R.layout.area_item, parent, false);
convertView = binding.getRoot();
} else {
binding = DataBindingUtil.getBinding(convertView);
}
Region curItem = list.get(position);
if (curItem != null) {
binding.setItem(curItem);
}
return convertView;
}
}
怎么样, 再自定义adapter就只需要关注布局和操作了, 重复的代码根本就不用管了,代码也精简明了。
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