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");
}
}
}
}
}