Java泛型应用之打造Android中ListView和GridView万能适配器【CommonAdapter】--超简洁写法

转载请注明出处：http://blog.csdn.net/linglongxin24/article/details/52813227 【DylanAndroid的csdn博客】

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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 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();        }        /**         * 普通适配器的方法         */        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 extends View> T get(View view, int id) {        SparseArray<View> viewHolder = (SparseArray<View>) view.getTag();        //如果根view没有用来缓存View的集合        if (viewHolder == null) {            viewHolder = new SparseArray<View>();            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<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<String> 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<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);            }        });    }  }

• 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