android ListView中自定义adapter的封装

【声明】 

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生命壹号：http://www.cnblogs.com/smyhvae/

文章来源：http://www.cnblogs.com/smyhvae/p/4477079.html

 

 

【正文】

【引入】

我们一般编写listView的时候顺序是这样的：

• 需要展示的数据集List<T>
• 为这个数据集编写一个ListView
• 为这个ListView编写一个Adapter，一般继承自BaseAdapter
• 在BaseAdapter内部编写一个ViewHolder类，对应ListView里面的item控件，提高控件的查询效率

分析：

List<T>:ListView --> Adapter extends BaseAdapter --> ViewHolder

一般情况下，一个ListView对应一个Adapter类，对应一个ViewHolder类，那如果一个app中有20个ListView，我们岂不是要写20遍？所以的做法是：

• 抽取ViewHolder，作为公共的类。
• 将Adapter封装成CommonAdapter，作为公共的类。

 

一、传统方式编写适配器：

（1）activity_main.xml:

<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">

<ListView
    android:id="@+id/listView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"></ListView>

</RelativeLayout>

 

(2)item_listview.xml:单个item的布局文件

 

其对应的布局效果如下：

<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:padding="10dp">

    <TextView
        android:id="@+id/titleTv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:singleLine="true"
        android:text="Android新技能"
        android:textColor="#444"
        android:textSize="16sp" />

    <TextView
        android:id="@+id/descTv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/titleTv"
        android:layout_marginTop="10dp"
        android:maxLines="2"
        android:minLines="1"
        android:text="Android为ListView和GridView打造万能适配器"
        android:textColor="#898989"
        android:textSize="16sp" />

    <TextView
        android:id="@+id/timeTv"
        android:paddingTop="3dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/descTv"
        android:layout_marginTop="10dp"
        android:text="2015-05-04"
        android:textColor="#898989"
        android:textSize="12sp" />

    <TextView
        android:padding="2dp"
        android:id="@+id/phoneTv"
        android:gravity="center"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/descTv"
        android:layout_marginTop="10dp"
        android:background="#2ED667"
        android:drawableLeft="@mipmap/phone"
        android:drawablePadding="5dp"
        android:text="10086"
        android:textColor="#ffffff"
        android:textSize="12sp"
        android:layout_alignParentRight="true" />


</RelativeLayout>

 

 

（3）Bean.java:ListView的数据集

package com.smyhvae.baseadapter.entities;

/**
 * Created by smyhvae on 2015/5/4.
 */
public class Bean {
    private String title;
    private String desc;
    private String time;
    private String phone;

    public Bean() {
    }

    public Bean(String title, String desc, String time, String phone) {
        this.title = title;
        
        this.desc = desc;
        this.time = time;
        this.phone = phone;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }
}

 

（4）MyAdapter.java:自定义适配器，继承自BaseAdapter

package com.smyhvae.baseadapter;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

import com.smyhvae.baseadapter.entities.Bean;

import java.util.List;

/**
 * Created by smyhvae on 2015/5/4.
 */
public class MyAdapter extends BaseAdapter {
    private LayoutInflater mInflater;
    private List<Bean> mDatas;

    //MyAdapter需要一个Context，通过Context获得Layout.inflater，然后通过inflater加载item的布局
    public MyAdapter(Context context, List<Bean> datas) {

        mInflater = LayoutInflater.from(context);
        mDatas = datas;
    }

    //返回数据集的长度
    @Override
    public int getCount() {
        return mDatas.size();
    }

    @Override
    public Object getItem(int position) {
        return mDatas.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    //这个方法才是重点，我们要为它编写一个ViewHolder
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.item_listview, parent, false); //加载布局
            holder = new ViewHolder();

            holder.titleTv = (TextView) convertView.findViewById(R.id.titleTv);
            holder.descTv = (TextView) convertView.findViewById(R.id.descTv);
            holder.timeTv = (TextView) convertView.findViewById(R.id.timeTv);
            holder.phoneTv = (TextView) convertView.findViewById(R.id.phoneTv);

            convertView.setTag(holder);
        } else {   //else里面说明，convertView已经被复用了，说明convertView中已经设置过tag了，即holder
            holder = (ViewHolder) convertView.getTag();
        }

        Bean bean = mDatas.get(position);
        holder.titleTv.setText(bean.getTitle());
        holder.descTv.setText(bean.getDesc());
        holder.timeTv.setText(bean.getTime());
        holder.phoneTv.setText(bean.getPhone());

        return convertView;
    }

    //这个ViewHolder只能服务于当前这个特定的adapter，因为ViewHolder里会指定item的控件，不同的ListView，item可能不同，所以ViewHolder写成一个私有的类
    private class ViewHolder {
        TextView titleTv;
        TextView descTv;
        TextView timeTv;
        TextView phoneTv;
    }

}

 

(5)MainActivity.java:

package com.smyhvae.baseadapter;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;

import com.smyhvae.baseadapter.entities.Bean;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends Activity {

    private ListView listView;
    private List<Bean> mDatas;
    private MyAdapter mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initView();
        initData();

    }

    //方法：初始化View
    private void initView() {
        listView = (ListView) findViewById(R.id.listView);
    }

    //方法；初始化Data
    private void initData() {
        mDatas = new ArrayList<Bean>();

        //将数据装到集合中去
        Bean bean = new Bean("Android新技能1", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
        mDatas.add(bean);

        bean = new Bean("Android新技能2", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
        mDatas.add(bean);

        bean = new Bean("Android新技能3", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
        mDatas.add(bean);

        bean = new Bean("Android新技能4", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
        mDatas.add(bean);

        //为数据绑定适配器
        mAdapter = new MyAdapter(this,mDatas);

        listView.setAdapter(mAdapter);
    }

}

 

运行效果如下：

【工程文件】

2015-05-04-BaseAdapter的传统写法.rar

 

二、ListView中自定义adapter的封装（万能的写法来编写适配器）：

完整版代码如下：

(1)activity_main.xml:

<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">

<ListView
    android:id="@+id/listView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"></ListView>

</RelativeLayout>

 

（2）item_listview.xml.xml:（ListView中单个item的布局）

<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:padding="10dp">

    <TextView
        android:id="@+id/titleTv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:singleLine="true"
        android:text="Android新技能"
        android:textColor="#444"
        android:textSize="16sp" />

    <TextView
        android:id="@+id/descTv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/titleTv"
        android:layout_marginTop="10dp"
        android:maxLines="2"
        android:minLines="1"
        android:text="Android为ListView和GridView打造万能适配器"
        android:textColor="#898989"
        android:textSize="16sp" />

    <TextView
        android:id="@+id/timeTv"
        android:paddingTop="3dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/descTv"
        android:layout_marginTop="10dp"
        android:text="2015-05-04"
        android:textColor="#898989"
        android:textSize="12sp" />

    <TextView
        android:padding="2dp"
        android:id="@+id/phoneTv"
        android:gravity="center"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/descTv"
        android:layout_marginTop="10dp"
        android:background="#2ED667"
        android:drawableLeft="@mipmap/phone"
        android:drawablePadding="5dp"
        android:text="10086"
        android:textColor="#ffffff"
        android:textSize="12sp"
        android:layout_alignParentRight="true" />


</RelativeLayout>

 

其对应的布局效果如下：

（3）Bean.java:数据集

package com.smyhvae.baseadapter.entities;

/**
 * Created by smyhvae on 2015/5/4.
 */
public class Bean {
    private String title;
    private String desc;
    private String time;
    private String phone;

    public Bean() {
    }

    public Bean(String title, String desc, String time, String phone) {
        this.title = title;

        this.desc = desc;
        this.time = time;
        this.phone = phone;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }
}

 

（4）【可复用的代码】ViewHolder.java:

package com.smyhvae.baseadapter.utils;

import android.content.Context;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by smyhvae on 2015/5/4.
 */
public class ViewHolder {

    private SparseArray<View> mViews;
    private int mPosition;
    private View mConvertView;

    public ViewHolder(Context context, ViewGroup parent, int layoutId, int position) {
        this.mPosition = position;
        this.mViews = new SparseArray<View>();

        mConvertView = LayoutInflater.from(context).inflate(layoutId, parent, false);

        mConvertView.setTag(this);

    }

    public static ViewHolder get(Context context, View convertView, ViewGroup parent, int layoutId, int position) {
        if (convertView == null) {
            return new ViewHolder(context, parent, layoutId, position);
        } else {
            ViewHolder holder = (ViewHolder) convertView.getTag();
            holder.mPosition = position; //即时ViewHolder是复用的，但是position记得更新一下
            return holder;
        }
    }

    /*
    通过viewId获取控件
     */
    //使用的是泛型T,返回的是View的子类
    public <T extends View> T getView(int viewId) {
        View view = mViews.get(viewId);

        if (view == null) {
            view = mConvertView.findViewById(viewId);
            mViews.put(viewId, view);
        }

        return (T) view;
    }

    public View getConvertView() {
        return mConvertView;
    }

}

 

（5）【可复用的代码】ListViewAdapter.java:自定义的通用适配器，继承自BaseAdapter。以后如果是自定义ListView的adapter，继承它就行了

package com.smyhvae.baseadapter.utils;

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 smyhvae on 2015/5/4.
 * 通用的ListView的BaseAdapter，所有的ListView的自定义adapter都可以继承这个类哦
 */
public abstract class ListViewAdapter<T> extends BaseAdapter {

    //为了让子类访问，于是将属性设置为protected
    protected Context mContext;
    protected List<T> mDatas;
    protected LayoutInflater mInflater;
    private int layoutId; //不同的ListView的item布局肯能不同，所以要把布局单独提取出来

    public ListViewAdapter(Context context, List<T> datas, int layoutId) {
        this.mContext = context;
        mInflater = LayoutInflater.from(context);
        this.mDatas = datas;
        this.layoutId = layoutId;
    }

    @Override
    public int getCount() {
        return mDatas.size();
    }

    @Override
    public T getItem(int position) {
        return mDatas.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        //初始化ViewHolder,使用通用的ViewHolder，一样代码就搞定ViewHolder的初始化咯
        ViewHolder holder = ViewHolder.get(mContext, convertView, parent, layoutId, position);//layoutId就是单个item的布局

        convert(holder, getItem(position));
        return holder.getConvertView(); //这一行的代码要注意了
    }

    //将convert方法公布出去
    public abstract void convert(ViewHolder holder, T t);

}

 

（6）ListViewAdapterWithViewHolder.java:继承自ListViewAdapter

package com.smyhvae.baseadapter;

import android.content.Context;
import android.widget.TextView;

import com.smyhvae.baseadapter.entities.Bean;
import com.smyhvae.baseadapter.utils.ListViewAdapter;
import com.smyhvae.baseadapter.utils.ViewHolder;

import java.util.List;

/**
 * Created by smyhvae on 2015/5/4.
 */
public class ListViewAdapterWithViewHolder extends ListViewAdapter<Bean> {

    //MyAdapter需要一个Context，通过Context获得Layout.inflater，然后通过inflater加载item的布局
    public ListViewAdapterWithViewHolder(Context context, List<Bean> datas) {
        super(context, datas, R.layout.item_listview);
    }

    @Override
    public void convert(ViewHolder holder, Bean bean) {

        ((TextView) holder.getView(R.id.titleTv)).setText(bean.getTitle());
        ((TextView) holder.getView(R.id.descTv)).setText(bean.getDesc());
        ((TextView) holder.getView(R.id.timeTv)).setText(bean.getTime());
        ((TextView) holder.getView(R.id.phoneTv)).setText(bean.getPhone());

/*
        TextView tv = holder.getView(R.id.titleTv);
        tv.setText(...);

       ImageView view = getView(viewId);
       Imageloader.getInstance().loadImag(view.url);
*/
    }
}

 

（7）MainActivity.java:

package com.smyhvae.baseadapter;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;

import com.smyhvae.baseadapter.entities.Bean;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends Activity {

    private ListView listView;
    private List<Bean> mDatas;

    private ListViewAdapterWithViewHolder listViewAdapterWithViewHolder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initView();
        initData();
    }


    //方法：初始化View
    private void initView() {
        listView = (ListView) findViewById(R.id.listView);
    }

    //方法；初始化Data
    private void initData() {
        mDatas = new ArrayList<Bean>();

        //将数据装到集合中去
        Bean bean = new Bean("Android新技能1", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
        mDatas.add(bean);

        bean = new Bean("Android新技能2", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
        mDatas.add(bean);

        bean = new Bean("Android新技能3", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
        mDatas.add(bean);

        bean = new Bean("Android新技能4", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
        mDatas.add(bean);

        //为数据绑定适配器
        listViewAdapterWithViewHolder = new ListViewAdapterWithViewHolder(this, mDatas);

        listView.setAdapter(listViewAdapterWithViewHolder);

    }
}

 

运行效果：

这样的话，以后每写个ListView，就这么做：直接导入ViewHolder.java和ListViewAdapter，然后写一个自定义adapter继承自ListViewAdapter就行了。

【工程文件】

2015-05-04-BaseAdapter的封装.rar

 

三、常见问题：

1、item控件抢占焦点：

假设item里有一个checkbox，那运行程序之后，发现只有checkBox能被点击，而item中的其他位置不能被点击，这是由于checkbox抢占了整个item的焦点。办法是:：

办法1：为该checkBox设置属性：

android:focusable = "false" 

办法二：为该item设置属性：

android:descendantFocusability = "blocksDescendants" 

不让这个item的焦点从上往下传。

2、ListView复用导致内容错乱。