Java泛型应用之打造Android中ListView和GridView万能适配器【CommonAdapter】--超简洁写法
16lz
2021-01-23
转载请注明出处：http://blog.csdn.net/linglongxin24/article/details/52813227 【DylanAndroid的csdn博客】
在android中使用最多的就是ListView，GridView，用到这两个控件那么肯定要用到适配器，那就是定义一个类继承BaseAdapter，让后覆写它里面的getCount(),getView()等方法，下面来写一个demo。
1.我们来实现一个普通的ListView的Demo
主布局文件:activity_main.xml
<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:paddingBottom="@dimen/activity_vertical_margin"android:paddingLeft="@dimen/activity_horizontal_margin"android:paddingRight="@dimen/activity_horizontal_margin"android:paddingTop="@dimen/activity_vertical_margin"tools:context="com.kejiang.yuandl.fastdev.MainActivity"><ListView android:id="@+id/listview" android:layout_width="wrap_content" android:layout_height="wrap_content" />RelativeLayout>ListView的item布局:item.xml
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical" android:layout_width="match_parent"android:layout_height="match_parent"><TextView android:text="万能适配器测试" android:layout_width="match_parent" android:layout_height="100px" android:gravity="center" android:id="@+id/textView" />LinearLayout>ListView的适配器代码:MyAdapter.java
/** * * Created by yuandl on 2016-10-14. * *listView的适配器 */ public class MyAdapter extends BaseAdapter { private Context context; private Listdatas; public MyAdapter(Context context, List 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(); } /** * 普通适配器的方法 */ private void myAdapterTest() { setContentView(R.layout.activity_main); ListView listView= (ListView) findViewById(R.id.listview); List datas=new ArrayList<>(); datas.add("普通适配器测试1"); datas.add("普通适配器测试2"); datas.add("普通适配器测试3"); datas.add("普通适配器测试4"); listView.setAdapter(new MyAdapter(context,datas)); } } 看效果图
2.打造万能适配器第一步，万能ViewHolder–CommonViewHolder
import android.util.SparseArray;import android.view.View;/** * Created by yuandl on 2016-10-13. * 万能的ViewHolder * * @author */public class CommonViewHolder { /** * @param view 所有缓存View的根View * @param id 缓存View的唯一标识 * @return */ public static T get(View view, int id) { SparseArray viewHolder = (SparseArray) view.getTag(); //如果根view没有用来缓存View的集合 if (viewHolder == null) { viewHolder = new SparseArray(); view.setTag(viewHolder);//创建集合和根View关联 } View chidlView = viewHolder.get(id);//获取根View储存在集合中的孩纸 if (chidlView == null) {//如果没有改孩纸 //找到该孩纸 chidlView = view.findViewById(id); viewHolder.put(id, chidlView);//保存到集合 } return (T) chidlView; }} 3.打造万能适配器的最后封装–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. * 万能适配器 */public abstract class CommonAdapter<T> extends BaseAdapter { private Context context; private List datas; private int layoutId; public CommonAdapter(Context context, List 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; } /** * 需要去实现的对item中的view的设置操作 * @param item * @param t */ protected abstract void convertView(View item, T t);} 4.万能适配器CommonAdapter的超简洁用法
- 使用代码
public class MainActivity extends Activity { private WebView webView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); myAdapterTest(); } /** * 万能适配器的方法 */ private void commonAdapterTest() { setContentView(R.layout.activity_main); ListView listView= (ListView) findViewById(R.id.listview); List datas=new ArrayList<>(); datas.add("万能适配器测试1"); datas.add("万能适配器测试2"); datas.add("万能适配器测试3"); datas.add("万能适配器测试4"); listView.setAdapter(new CommonAdapter(context,datas,R.layout.item) { @Override protected void convertView(View item, String s) { TextView textView= CommonViewHolder.get(item,R.id.textView); textView.setText(s); } }); } } 运行效果
GitHub源码地址：https://github.com/linglongxin24/ListViewUpdate/blob/master/app/src/main/java/cn/bluemobi/dylan/listviewupdate/adapter/CommonAdapter.java
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