关于ListView （2）——SimpleAdapter源码解析与ViewBinders的用法
如题，这里主要讲解SimpleAdapter的源码，ViewBinders只是作为该类的一个知识点。
说到android源码，很多人看下去可能会开始觉得头越来越晕，最后就不了了之。不过理解源码确实能让自己更深入的了解android的运作，更顺手的写出优秀的代码。其实看android源码，一开始不一定就立即从重要或者核心开始下手，即使能够看下去，也会很累，浪费的时间也多。就如解剖一只牛，让我来，我就会先一刀一刀去掉外层的肉（因为我不是那种经验丰富的人），先从简单的，一层一层剥开，牛肉慢慢的去掉，开始可以看到整个骨架了。这样既不会很快失去耐心，又能挑起自己继续学习下去的欲望，虽然这种方法是很慢的，但是过程明白了，以后就可以快。当然剩下的骨头也不容易啃 :），不过至少轻松很多。
这里讲解的例子主要是跟别人的结合在一起说，引用的文章链接：http://mgmblog.com/2008/12/29/simpleadapter-viewbinders/
SimpleAdapter toolsAdapter =
new SimpleAdapter(
this,
_activityNames,
R.layout.row,
new String[] { ACTIVITY_NAME_ENTRY },
new int[] { R.id.text1 } );
这是创建SimpleAdapter的一段代码，先不要理那些变量。当运行这段代码时，会有如下操作：
public SimpleAdapter(Context context, List<? extends Map<String, ?>> data,
int resource, String[] from, int[] to) {
mData = data;
mResource = mDropDownResource = resource;
mFrom = from;
mTo = to;
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
SimpleAdapter下面的源码跟继承重写BaseAdapter里面的方法差不多。
/**
* @see android.widget.Adapter#getCount()
*/
public int getCount() {
return mData.size();
}
/**
* @see android.widget.Adapter#getItem(int)
*/
public Object getItem(int position) {
return mData.get(position);
}
/**
* @see android.widget.Adapter#getItemId(int)
*/
public long getItemId(int position) {
return position;
}
/**
* @see android.widget.Adapter#getView(int, View, ViewGroup)
*/
public View getView(int position, View convertView, ViewGroup parent) {
return createViewFromResource(position, convertView, parent, mResource);
}
//这里提高listview的效率
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;
}
// bindView是重点，主要是将你前面传入给item的xml文件解析，然后判断是Checkable还是TextView或者是ImageView，做出相应的处理。
private void bindView(int position, View view) {
final Map dataSet = mData.get(position);
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]);
if (v != null) {
final Object data = dataSet.get(from[i]);
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) {
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);
} 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");
}
}
}
}
}
这段代码主要是针对特殊数据做处理
boolean bound = false;
if (binder != null) {
bound = binder.setViewValue(v, data, text);
}
SimpleAdapter的基本解析就到这里。
现在结合那篇文章说说剩下的一点（ViewBinders）。
重写TextView，触发按键会跳转到另一个intent
/////ToolNameView.java
public class ToolNameView extends TextView
{
private Intent _intentToLaunch;
public ToolNameView(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
setupView();
}
public ToolNameView(Context context, AttributeSet attrs)
{
super(context, attrs);
setupView();
}
public ToolNameView(Context context)
{
super(context);
setupView();
}
private void setupView()
{
this.setOnClickListener( new OnClickListener()
{
public void onClick(View v)
{
getContext().startActivity( _intentToLaunch );
}
});
}
public void setIntentToLaunch( Intent intent )
{
_intentToLaunch = intent;
}
}
///// layout/row.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/vw1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<com.mgm.android.toolbox.ToolNameView
android:id="@+id/text1"
android:textSize="16sp"
android:textStyle="bold"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="3dip"/>
</LinearLayout>
//////类
class ToolboxRow
{
private Intent _intentToLaunch;
private String _name;
public ToolboxRow( Intent intentToLaunch, String name )
{
_intentToLaunch = intentToLaunch;
_name = name;
}
public Intent getIntentToLaunch()
{
return _intentToLaunch;
}
public String getName()
{
return _name;
}
}
ArrayList<HashMap<String, ToolboxRow>> _activityNames;
////添加name和intent到数据源_activityNames
/**
* DON'T FORGET TO ALSO ADD ACTIVITY TO MANIFEST!!
*
* @param name
* @param intentToLaunch
*/
private void addActivityToList( String name, Intent intentToLaunch )
{
HashMap entry = new HashMap();
ToolboxRow row = new ToolboxRow( intentToLaunch, name );
entry.put( ACTIVITY_NAME_ENTRY, row );
_activityNames.add( entry );
}
////// ToolBinder,这里将重写ViewBinder里面的方法setViewValue，给textview设置onclick事件。这里其实跟重写BaseAapter的做法差不多，都是一样的设置事件。
class ToolBinder implements ViewBinder
{
public boolean setViewValue(View view, Object data, String textRepresentation)
{
ToolNameView tool = (ToolNameView)view;
ToolboxRow row = (ToolboxRow)data;
tool.setIntentToLaunch( row.getIntentToLaunch() );
tool.setText( row.getName() );
return true;
}
}
主要代码：
public class Toolbox extends ListActivity
{
private static final String ACTIVITY_NAME_ENTRY = "activity_name";
ArrayList<HashMap<String, ToolboxRow>> _activityNames;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// define the list which holds the information of the list
_activityNames = new ArrayList<HashMap<String, ToolboxRow>>();
addActivityToList( "Data Roaming", new Intent( this, DataRoamingSetting.class ) );
addActivityToList( "Expanding Example", new Intent( this, Expando.class ) );
SimpleAdapter toolsAdapter =
new SimpleAdapter(
this,
_activityNames,
R.layout.row,
new String[] { ACTIVITY_NAME_ENTRY },
new int[] { R.id.text1 } );
toolsAdapter.setViewBinder( new ToolBinder() );
setListAdapter( toolsAdapter );
}
}
toolsAdapter.setViewBinder( new ToolBinder() );
这里给SimpleAdapter设置setViewBinder方法，当执行到
if (binder != null) {
bound = binder.setViewValue(v, data, text);
}
会去里面执行，返回true。这样就是完成给item设置监听事件。
