Java泛型應用之打造Android中ListView和GridView萬能介面卡【CommonAdapter】--超簡潔寫法
阿新 • • 發佈:2019-01-26
在android中使用最多的就是ListView,GridView,用到這兩個控制元件那麼肯定要用到介面卡,那就是定義一個類繼承BaseAdapter,讓後覆寫它裡面的getCount(),getView()等方法,下面來寫一個demo。
1.我們來實現一個普通的ListView的Demo
主佈局檔案:activity_main.xml
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools
ListView的item佈局:item.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout
ListView的介面卡程式碼:MyAdapter.java
/** * * Created by yuandl on 2016-10-14. * *listView的介面卡 */ public class MyAdapter extends BaseAdapter { private Context context; private List<String> datas; public MyAdapter(Context context, List<String> datas) { this.context = context; this.datas = datas; } @Override public int getCount() { return datas == null ? 0 : datas.size(); } @Override public String getItem(int position) { return datas.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder viewHolder; if (convertView == null) { convertView = LayoutInflater.from(context).inflate(R.layout.item, null); viewHolder = new ViewHolder(); viewHolder.textView = (TextView) convertView.findViewById(R.id.textView); convertView.setTag(viewHolder); } else { viewHolder = (ViewHolder) convertView.getTag(); } String name = datas.get(position); viewHolder.textView.setText(name); return convertView; } private class ViewHolder { public TextView textView; } }
- 使用:MainActivity.java
public class MainActivity extends Activity {
private WebView webView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myAdapterTest();
}
/**
* 普通介面卡的方法
*/
private void myAdapterTest() {
setContentView(R.layout.activity_main);
ListView listView= (ListView) findViewById(R.id.listview);
List<String> datas=new ArrayList<>();
datas.add("普通介面卡測試1");
datas.add("普通介面卡測試2");
datas.add("普通介面卡測試3");
datas.add("普通介面卡測試4");
listView.setAdapter(new MyAdapter(context,datas));
}
}
看效果圖
2.打造萬能介面卡第一步,萬能ViewHolder–CommonViewHolder
import android.util.SparseArray;
import android.view.View;
/**
* Created by yuandl on 2016-10-13.
* 萬能的ViewHolder
*
* @author
*/
public class CommonViewHolder {
/**
* @param view 所有快取View的根View
* @param id 快取View的唯一標識
* @return
*/
public static <T extends View> T get(View view, int id) {
SparseArray<View> viewHolder = (SparseArray<View>) view.getTag();
//如果根view沒有用來快取View的集合
if (viewHolder == null) {
viewHolder = new SparseArray<View>();
view.setTag(viewHolder);//建立集合和根View關聯
}
View chidlView = viewHolder.get(id);//獲取根View儲存在集合中的孩紙
if (chidlView == null) {//如果沒有改孩紙
//找到該孩紙
chidlView = view.findViewById(id);
viewHolder.put(id, chidlView);//儲存到集合
}
return (T) chidlView;
}
}
3.打造萬能介面卡的最後封裝–CommonAdapter
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import java.util.List;
/**
* Created by yuandl on 2016-10-13.
* 萬能介面卡
*/
public abstract class CommonAdapter<T> extends BaseAdapter {
private Context context;
private List<T> datas;
private int layoutId;
public CommonAdapter(Context context, List<T> datas, int layoutId) {
this.context = context;
this.datas = datas;
this.layoutId = layoutId;
}
@Override
public int getCount() {
return datas == null ? 0 : datas.size();
}
@Override
public T getItem(int position) {
return datas.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = LayoutInflater.from(context).inflate(layoutId, null);
}
T t = getItem(position);
convertView(convertView, t);
return convertView;
}
/**
* 需要去實現的對item中的view的設定操作
* @param item
* @param t
*/
protected abstract void convertView(View item, T t);
}
4.萬能介面卡CommonAdapter的超簡潔用法
- 使用程式碼
public class MainActivity extends Activity {
private WebView webView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myAdapterTest();
}
/**
* 萬能介面卡的方法
*/
private void commonAdapterTest() {
setContentView(R.layout.activity_main);
ListView listView= (ListView) findViewById(R.id.listview);
List<String> datas=new ArrayList<>();
datas.add("萬能介面卡測試1");
datas.add("萬能介面卡測試2");
datas.add("萬能介面卡測試3");
datas.add("萬能介面卡測試4");
listView.setAdapter(new CommonAdapter<String>(context,datas,R.layout.item) {
@Override
protected void convertView(View item, String s) {
TextView textView= CommonViewHolder.get(item,R.id.textView);
textView.setText(s);
}
});
}
}