1 抽取Adapter 共性的方法
2 把getView方法里 和holder相关的逻辑 摘取到Holder代码中
3 把Holder 相关的代码 抽取到BaseHolder中
4 把adapter 中getVIew 方法 抽取到了DefaultAdpater中, 其中每个子类getView方法中holder不太一样,所以定义了抽象方法getHolder 要求子类去实现holder
- BaseHolder 所有holder的基类
- DefaultAdapter 所有adapter 的基类
BaseHolder
public abstract class BaseHolder<T> {
protected View contentView;
protected T data;
public BaseHolder(){
contentView=initView();
contentView.setTag(this); // 在这个位置设置的标签
}
public void setData(T data) {
this.data=data;
refreshView(data);
}
/**
* 当Holder中的view对象显示到界面上的时候调用，即getview返回这个
* @return
*/
public View getContentView() {
return contentView;
}
/**
* 当setData调用的时候 会调用该方法 根据数据 显示界面
*/
protected abstract void refreshView(T data);
/**
* 初始化View对象 及其控件
* @return
*/
protected abstract View initView();
}
子类只需要填充数据和设置控件显示的数据就可以
DefaultAdapter
public abstract class DefaultAdapter<T> extends BaseAdapter {
private List<T> datas;
public DefaultAdapter(List<T> datas){
this.datas=datas;
}
@Override
public int getCount() {
return datas.size();
}
@Override
public Object getItem(int position) {
return datas.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
//convertView 划出屏幕的view对象
@Override
public View getView(int position, View convertView, ViewGroup parent) {
BaseHolder<T> holder;／／和adapter的泛型一样
if(convertView==null){
holder=getHolder();
}else{
holder=(BaseHolder<T>)convertView.getTag();
}
T string = datas.get(position);
//holder.refreshView(string);
holder.setData(string);
return holder.getContentView();
}
protected abstract BaseHolder<T> getHolder();
}
MainActivity
public class MainActivity extends Activity {
private ListView lv;
private List<String> datas;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
datas=new ArrayList<String>();
for(int i=0;i<100;i++){
datas.add("aabbbcc"+i);
}
lv=(ListView) findViewById(R.id.lv);
lv.setAdapter(new MainAdapter(datas));
}
public void click(View v){
Intent intent=new Intent(getApplicationContext(), SecondActivity.class);
startActivity(intent);
}
private class MainAdapter extends DefaultAdapter<String>{
public MainAdapter(List<String> datas) {
super(datas);
// TODO Auto-generated constructor stub
}
@Override
protected BaseHolder<String> getHolder() {
return new MainHolder();
}
}
class MainHolder extends BaseHolder<String>{
private TextView tv;
// 在adapter里list.get（position），然后调用了holer的setdate，而setdata调用了refresh，这样就把data传过来了
@Override
protected void refreshView(String data) {
this.tv.setText(data);
}
@Override
protected View initView() {
View view=View.inflate(getApplicationContext(), R.layout.item_main, null);
this.tv=(TextView) view.findViewById(R.id.tv);
return view;
}
}
}
SecondActivity
public class SecondActivity extends Activity {
private ListView lv_second;
private List<Drawable> datas;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
lv_second=(ListView) findViewById(R.id.lv_second);
datas=new ArrayList<Drawable>();
for(int i=0;i<100;i++){
Drawable drawable = getResources().getDrawable(R.drawable.ic_launcher);
datas.add(drawable);
}
lv_second.setAdapter(new SecondAdapter(datas));
}
private class SecondAdapter extends DefaultAdapter<Drawable>{
public SecondAdapter(List<Drawable> datas) {
super(datas);
}
@Override
protected BaseHolder<Drawable> getHolder() {
return new SecondHolder();
}
}
class SecondHolder extends BaseHolder<Drawable>{
ImageView iv;
@Override
protected void refreshView(Drawable data) {
iv.setImageDrawable(data);
}
@Override
protected View initView() {
View view=View.inflate(getApplicationContext(), R.layout.item_second, null);
this.iv=(ImageView) view.findViewById(R.id.iv);
return view;
}
}
}