王学岗ListView和源码解析(二)

在本文中我们介绍ListView第二个的适配器——SimpleAdapter；
与ArrayAdapter只能显示单列的不同，SimpleAdapter可以显示多列。
下面我们使用SimpleAdapter在ListView中显示一个人的信息，包括name,number。
下面看下源码：

package com.example.listview;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import android.app.Activity;import android.os.Bundle;import android.widget.ArrayAdapter;import android.widget.ListView;import android.widget.SimpleAdapter;public class MainActivity extends Activity {    private ListView lv_list;    private List<Map<String, String>> data;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        lv_list = (ListView) findViewById(R.id.lv_list);        data = new ArrayList<Map<String, String>>();        intData();        // 创建适配器        SimpleAdapter adapter = new SimpleAdapter(this,// 上下文，不多解释                data,// 填充到listView里面的数据                R.layout.list_item,// 每一行的布局文件                new String[] {"name","number"}, //根据每一行的map里面的key,得到里面的值                new int[] {R.id.tv_name,R.id.tv_number}//根据ID，去吧每一个数据填充到对应的个控件上        );        lv_list.setAdapter(adapter);    }    // 初始化数据    private void intData() {        for (int i = 0; i < 150; i++) {            Map<String, String> item = new HashMap<String, String>();            item.put("name", "周瑜帅" + "-" + i);            item.put("number", String.valueOf(36+i));            data.add(item);        }    }}

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="horizontal" >    <TextView        android:id="@+id/tv_name"        android:layout_width="120dp"        android:layout_height="wrap_content"          />    <TextView        android:id="@+id/tv_number"        android:layout_width="140dp"        android:layout_height="wrap_content"         /></LinearLayout>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:id="@+id/LinearLayout1"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context=".MainActivity" >    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/hello_world" />    <ListView        android:id="@+id/lv_list"        android:layout_width="match_parent"        android:layout_height="wrap_content" >    </ListView></LinearLayout>

源码解析：与arraydapter极为类似，也是BaseAdapter的子类

我们直接看getView方法，其他的方法参考(一)；

public View getView(int position, View convertView, ViewGroup parent) {    return createViewFromResource(position, convertView, parent, mResource);}private View createViewFromResource(int position, View convertView,        ViewGroup parent, int resource) {    View v;    if (convertView == null) {        v = mInflater.inflate(resource, parent, false);    } else {        v = convertView;    }    bindView(position, v);    return v;}

多了一行代码bindView(position, v);
我们仔细来分析

private void bindView(int position, View view) {    final Map dataSet = mData.get(position);//根据行号，得到对应的map    if (dataSet == null) {        return;    }    final ViewBinder binder = mViewBinder;    final String[] from = mFrom;    final int[] to = mTo;    final int count = to.length;    for (int i = 0; i < count; i++) {        final View v = view.findViewById(to[i]);//根据对应的ID找到对应的控件        if (v != null) {            final Object data = dataSet.get(from[i]);//根据K(name,number)的值拿到相应的数据            String text = data == null ? "" : data.toString();            if (text == null) {                text = "";            }            boolean bound = false;            if (binder != null) {                bound = binder.setViewValue(v, data, text);            }            if (!bound) {                if (v instanceof Checkable) {//对控件的类型进行判断                    if (data instanceof Boolean) {                        ((Checkable) v).setChecked((Boolean) data);                    } else if (v instanceof TextView) {                        // Note: keep the instanceof TextView check at the bottom of these                        // ifs since a lot of views are TextViews (e.g. CheckBoxes).                        setViewText((TextView) v, text);                    } else {                        throw new IllegalStateException(v.getClass().getName() +                                " should be bound to a Boolean, not a " +                                (data == null ? "<unknown type>" : data.getClass()));                    }                } else if (v instanceof TextView) {                    // Note: keep the instanceof TextView check at the bottom of these                    // ifs since a lot of views are TextViews (e.g. CheckBoxes).                   setViewText((TextView) v, text);//调用该方法赋值                } else if (v instanceof ImageView) {                    if (data instanceof Integer) {                        setViewImage((ImageView) v, (Integer) data);                                                } else {                        setViewImage((ImageView) v, text);                    }                } else {                    throw new IllegalStateException(v.getClass().getName() + " is not a " +                            " view that can be bounds by this SimpleAdapter");                }            }        }    }}