Adapter类的定义：
Adapter对象是AdapterView和底层数据见的桥梁。Adapter用于访问数据项，并且负责为数据项生成视图
AdapterView是一个抽象类，用于那些需要通过Adapter填充自身的视图，其常见子类是ListView。显示AdapterView时会调用Adapter的getView()方法创建并添加每个子条目的视图。Adapter的getView()方法就是用来创建这些视图的，Adapter并不会为每行数据都创建一个新视图，而是提供了回收旧视图的方法。运行机制简单说就是当getView()方法被调用是，如果convertView参数不为null,就使用convertView，不用新建视图，通过convertView.findViewById()方法获取每个UI控件的引用，然后使用与当前项的位置绑定的数据来填充视图
为了优化，使用ViewHolder模式，ViewHolder是一个静态类，可以用于保存每行的视图以避免每次调用getView时都会调用findViewById()
public class Hack25Activity extends ListActivity {
private static final int MODEL_COUNT = 30;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setListAdapter(new ModelAdapter(this, 0, buildModels()));
}
private List buildModels() {
final ArrayList ret = new ArrayList(MODEL_COUNT);
for (int i = 0; i
Model.java
public class Model {
private String mText1;
private String mText2;
private int mImageResId;
public String getText1() {
return mText1;
}
public void setText1(String text1) {
mText1 = text1;
}
public String getText2() {
return mText2;
}
public void setText2(String text2) {
mText2 = text2;
}
public int getImage() {
return mImageResId;
}
public void setImage(int imageResId) {
mImageResId = imageResId;
}
}
ModelAdapter.java
public class ModelAdapter extends ArrayAdapter{ private LayoutInflater mInflater; public ModelAdapter(Context context, int textViewResourceId, List objects) { super(context, textViewResourceId, objects); mInflater = LayoutInflater.from(context); } @Override public View getView(int position, View convertView, ViewGroup parent) { final ViewHolder viewHolder; if (cOnvertView== null) { cOnvertView= mInflater.inflate(R.layout.row_layout, parent, false); viewHolder = new ViewHolder(); viewHolder.imageView = (ImageView) convertView .findViewById(R.id.image); viewHolder.text1 = (TextView) convertView .findViewById(R.id.text1); viewHolder.text2 = (TextView) convertView .findViewById(R.id.text2); convertView.setTag(viewHolder); } else { viewHolder = (ViewHolder) convertView.getTag(); } Model model = getItem(position); viewHolder.imageView.setImageResource(model.getImage()); viewHolder.text1.setText(model.getText1()); viewHolder.text2.setText(model.getText2()); return convertView; } private static class ViewHolder { public ImageView imageView; public TextView text1; public TextView text2; } }
row_layout.xml
<&＃63;xml version="1.0" encoding="utf-8"&＃63;>
以上代码就基本实现了功能
不过每次都自定义ViewHolder比较繁琐，在网上找了一个工具类，共享一下
ViewHolder.java
public class ViewHolder {
public static T get(View view, int id) {
SparseArray viewHolder = (SparseArray) view.getTag();
if (viewHolder == null) {
viewHolder = new SparseArray();
view.setTag(viewHolder);
}
View childView = viewHolder.get(id);
if (childView == null) {
childView = view.findViewById(id);
viewHolder.put(id, childView);
}
return (T) childView;
}
}
使用方法：
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (cOnvertView== null) {
cOnvertView= LayoutInflater.from(context)
.inflate(R.layout.banana_phone, parent, false);
}
ImageView bananaView = ViewHolder.get(convertView, R.id.banana);
TextView phOneView= ViewHolder.get(convertView, R.id.phone);
BananaPhone bananaPhOne= getItem(position);
phoneView.setText(bananaPhone.getPhone());
bananaView.setImageResource(bananaPhone.getBanana());
return convertView;
}
以上这篇Android 通过ViewHolder优化适配器的实现方法(必看)就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持。
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