Android:具有两种不同视图的 EfficientAdapter [英] Android: EfficientAdapter with two different Views
问题描述
我正在使用基于 EfficientAdapter 示例 来自 SDK 演示示例.
I'm using an extended version of BaseAdapter based on the EfficientAdapter example from the SDK demo samples.
我的数据基本上是一个对象 (ListPlaces)，它包含一个带有实际地点列表的 ArrayList，可通过 listPlaces.getValues().此 ArrayList 数据按范围排序，ArrayList 由一些特殊项(分隔符)组成，没有数据，但 separator 标志设置为 true.
My data is basically an object (ListPlaces) which holds an ArrayList with the actual list of places, accessible via listPlaces.getValues(). This ArrayList data is sorted by range and the ArrayList consist of some special items (separators), with no data, but a separator flag set to true.
现在，每当我的 EfficientAdapter 获得一个作为分隔符的数据对象时，它都会为 public boolean isEnabled(int position) 和 返回 根据当前数据对象是由真实数据组成还是只是一个分隔符虚拟，膨胀了两种不同的布局.false>public View getView(int position, View convertView, ViewGroup parent)
Now whenever my EfficientAdapter gets a data object which is a separator it returns false for public boolean isEnabled(int position) and public View getView(int position, View convertView, ViewGroup parent) inflates two different layouts depending on if the current data object consists of real data or is just a separator dummy.
这很好用，如果我每次都夸大布局.然而，每次都增加布局并调用 findViewById 使得 ListView 几乎无法使用.
This works great, if I inflate the layout every time. However, inflating the layout every time and calling findViewById makes the ListView almost unusabely slow.
所以我尝试使用带有 ViewHolder 方法的 EfficientAdapter.但这并不是开箱即用的，因为我尝试访问两种不同的视图.因此，每当我的 convertView != null(其他情况)通过我们的 ViewHolder 访问布局上的项目时，当前一个 View 是分隔符时，它当然不会努力访问那里的 TextView，它仅在真实"项目布局上可用.
So I tried to use the EfficientAdapter with ViewHolder approach. But that didn't work right out of the box, because of the two different views I try to access. So whenever my convertView != null (the else-case) accesses the items on the layout via our ViewHolder and when the previous View was a separator it of course doesn't work to access a TextView there which is only available on the "real" items layout.
所以我还强制我的 getView() 不仅在 convertView == null 时膨胀布局，而且在前一个 listRow 与当前列表行不同时:if (convertView == null || (listRow != listRow_previous)) { [....] }
So I also force my getView() to inflate the layout not only when convertView == null, but also when the previous listRow is different than the current one: if (convertView == null || (listRow != listRow_previous)) { [....] }
这似乎现在几乎可以工作了.或者至少它不会从一开始就崩溃.但它仍然崩溃，我不知道我必须做些什么不同的事情.我曾尝试研究 convertView.getID() 和 convertView.getResources()，但到目前为止这并没有真正的帮助.也许其他人知道如何检查我当前的 convertView 是否与列表项布局或列表分隔符布局匹配.谢谢.
This seems to almost work now. Or at least it doesn't crash right from the beginning. But it still crashes and I don't know what I've to do different. I've tried to look into convertView.getID() and convertView.getResources(), but that wasn't really helpful so far. Maybe someone else has an idea how I can check whether my current convertView matches with the list item layout or the list separator layout. Thanks.
这是代码.凡是有 [...] 的地方，我都删除了一些不太重要的代码，以便于阅读和理解:
Here's the code. Where ever there is a [...] I took out some less important code to make it easier to read and understand:
private class EfficientAdapter extends BaseAdapter {
private LayoutInflater mInflater;
private ListPlaces listPlaces;
private ListRow listRow;
private ListRow listRow_previous;
public EfficientAdapter(Context context, ListPlaces listPlaces) {
// Cache the LayoutInflate to avoid asking for a new one each time.
mInflater = LayoutInflater.from(context);
// Data
this.listPlaces = listPlaces;
}
/**
* The number of items in the list is determined by the number of items
* in our ArrayList
*
* @see android.widget.ListAdapter#getCount()
*/
public int getCount() {
return listPlaces.getValues().size();
}
/**
* Since the data comes from an array, just returning the index is
* sufficent to get at the data. If we were using a more complex data
* structure, we would return whatever object represents one row in the
* list.
*
* @see android.widget.ListAdapter#getItem(int)
*/
public Object getItem(int position) {
return position;
}
/**
* Use the array index as a unique id.
*
* @see android.widget.ListAdapter#getItemId(int)
*/
public long getItemId(int position) {
return position;
}
@Override
public boolean isEnabled(int position) {
// return false if item is a separator:
if(listPlaces.getValues().get(position).separator >= 0)
return false;
else
return true;
}
@Override
public boolean areAllItemsEnabled() {
return false;
}
/**
* Make a view to hold each row.
*
* @see android.widget.ListAdapter#getView(int, android.view.View,
* android.view.ViewGroup)
*/
public View getView(int position, View convertView, ViewGroup parent) {
// Get the values for the current list element
ListPlacesValues curValues = listPlaces.getValues().get(position);
if (curValues.separator >= 0)
listRow = ListRow.SEPARATOR;
else
listRow = ListRow.ITEM;
Log.i(TAG,"Adapter: getView("+position+") " + listRow + " (" + listRow_previous + ") -> START");
// A ViewHolder keeps references to children views to avoid unneccessary calls
// to findViewById() on each row.
ViewHolder holder;
// When convertView is not null, we can reuse it directly, there is no need
// to reinflate it. We only inflate a new View when the convertView supplied
// by ListView is null.
if (convertView == null || (listRow != listRow_previous)) {
Log.i(TAG, "--> (convertView == null) at position: " + position);
// Creates a ViewHolder and store references to the two children views
// we want to bind data to.
holder = new ViewHolder();
if (listRow == ListRow.SEPARATOR) {
convertView = mInflater.inflate(R.layout.taxonomy_list_separator, null);
holder.separatorText = (TextView) convertView.findViewById(R.id.separatorText);
convertView.setTag(holder);
Log.i(TAG," CREATE SEPARATOR: convertView ID: " + convertView.getId() + " Resource: " + convertView.getResources());
}
else {
convertView = mInflater.inflate(R.layout.taxonomy_listitem, null);
holder.name = (TextView) convertView.findViewById(R.id.name);
holder.category = (TextView) convertView.findViewById(R.id.category);
// [...]
convertView.setTag(holder);
Log.i(TAG," CREATE ITEM: convertView ID: " + convertView.getId() + " Resource: " + convertView.getResources());
}
} else {
// Get the ViewHolder back to get fast access to the TextView
// and the ImageView.
Log.i(TAG," convertView ID: " + convertView.getId() + " Resource: " + convertView.getResources());
holder = (ViewHolder) convertView.getTag();
convertView.setAnimation(null);
}
/* Bind the data efficiently with the holder */
if (listRow == ListRow.SEPARATOR) {
String separatorText;
switch (curValues.separator) {
case 0: separatorText="case 0"; break;
case 1: separatorText="case 1"; break;
case 2: separatorText="case 2"; break;
// [...]
default: separatorText="[ERROR]"; break;
}
holder.separatorText.setText(separatorText);
}
else {
// Set the name:
holder.name.setText(curValues.name);
// Set category
String cat = curValues.classification.toString();
cat = cat.substring(1,cat.length()-1); // removing "[" and "]"
if (cat.length() > 35) {
cat = cat.substring(0, 35);
cat = cat + "...";
}
holder.category.setText(cat);
// [...] (and many more TextViews and ImageViews to be set)
}
listRow_previous = listRow;
Log.i(TAG,"Adapter: getView("+position+") -> DONE");
return convertView;
}
private class ViewHolder {
TextView name;
TextView category;
// [...] -> many more TextViews and ImageViews
TextView separatorText;
}
}
这里是我的 Logcat 输出:
755 ListPlaces_Activity I onPostExecute: notifyDataSetChanged()
755 ListPlaces_Activity I Adapter: getView(0) SEPARATOR (null) -> START
755 ListPlaces_Activity I --> (convertView == null) at position: 0
755 ListPlaces_Activity I CREATE SEPARATOR: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(0) -> DONE
755 ListPlaces_Activity I Adapter: getView(1) ITEM (SEPARATOR) -> START
755 ListPlaces_Activity I --> (convertView == null) at position: 1
755 ListPlaces_Activity I CREATE ITEM: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(1) -> DONE
755 ListPlaces_Activity I Adapter: getView(2) SEPARATOR (ITEM) -> START
755 ListPlaces_Activity I --> (convertView == null) at position: 2
755 ListPlaces_Activity I CREATE SEPARATOR: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(2) -> DONE
755 ListPlaces_Activity I Adapter: getView(3) ITEM (SEPARATOR) -> START
755 ListPlaces_Activity I --> (convertView == null) at position: 3
755 ListPlaces_Activity I CREATE ITEM: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(3) -> DONE
755 ListPlaces_Activity I Adapter: getView(4) ITEM (ITEM) -> START
755 ListPlaces_Activity I convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(4) -> DONE
755 ListPlaces_Activity I Adapter: getView(5) ITEM (ITEM) -> START
755 ListPlaces_Activity I convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(5) -> DONE
755 ListPlaces_Activity I Adapter: getView(6) ITEM (ITEM) -> START
755 ListPlaces_Activity I convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(6) -> DONE
755 ListPlaces_Activity I Adapter: getView(0) SEPARATOR (ITEM) -> START
755 ListPlaces_Activity I --> (convertView == null) at position: 0
755 ListPlaces_Activity I CREATE SEPARATOR: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(0) -> DONE
755 ListPlaces_Activity I Adapter: getView(1) ITEM (SEPARATOR) -> START
755 ListPlaces_Activity I --> (convertView == null) at position: 1
755 ListPlaces_Activity I CREATE ITEM: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(1) -> DONE
755 ListPlaces_Activity I Adapter: getView(2) SEPARATOR (ITEM) -> START
755 ListPlaces_Activity I --> (convertView == null) at position: 2
755 ListPlaces_Activity I CREATE SEPARATOR: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(2) -> DONE
755 ListPlaces_Activity I Adapter: getView(3) ITEM (SEPARATOR) -> START
755 ListPlaces_Activity I --> (convertView == null) at position: 3
755 ListPlaces_Activity I CREATE ITEM: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(3) -> DONE
755 ListPlaces_Activity I Adapter: getView(4) ITEM (ITEM) -> START
755 ListPlaces_Activity I convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 ListPlaces_Activity I Adapter: getView(4) -> DONE
755 ListPlaces_Activity I Adapter: getView(5) ITEM (ITEM) -> START
755 ListPlaces_Activity I convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0
755 AndroidRuntime D Shutting down VM
755 dalvikvm W threadid=3: thread exiting with uncaught exception (group=0x4001aa28)
755 AndroidRuntime E Uncaught handler: thread main exiting due to uncaught exception
755 AndroidRuntime E java.lang.NullPointerException
755 AndroidRuntime E at com.tato.main.ListPlaces_Activity$EfficientAdapter.getView(ListPlaces_Activity.java:330)
755 AndroidRuntime E at android.widget.HeaderViewListAdapter.getView(HeaderViewListAdapter.java:191)
755 AndroidRuntime E at android.widget.AbsListView.obtainView(AbsListView.java:1255)
755 AndroidRuntime E at android.widget.ListView.makeAndAddView(ListView.java:1658)
755 AndroidRuntime E at android.widget.ListView.fillDown(ListView.java:637)
755 AndroidRuntime E at android.widget.ListView.fillFromTop(ListView.java:694)
755 AndroidRuntime E at android.widget.ListView.layoutChildren(ListView.java:1502)
755 AndroidRuntime E at android.widget.AbsListView.onLayout(AbsListView.java:1112)
755 AndroidRuntime E at android.view.View.layout(View.java:6569)
755 AndroidRuntime E at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119)
755 AndroidRuntime E at android.widget.LinearLayout.layoutVertical(LinearLayout.java:998)
755 AndroidRuntime E at android.widget.LinearLayout.onLayout(LinearLayout.java:918)
755 AndroidRuntime E at android.view.View.layout(View.java:6569)
755 AndroidRuntime E at android.widget.FrameLayout.onLayout(FrameLayout.java:333)
755 AndroidRuntime E at android.view.View.layout(View.java:6569)
755 AndroidRuntime E at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119)
755 AndroidRuntime E at android.widget.LinearLayout.layoutVertical(LinearLayout.java:998)
755 AndroidRuntime E at android.widget.LinearLayout.onLayout(LinearLayout.java:918)
755 AndroidRuntime E at android.view.View.layout(View.java:6569)
755 AndroidRuntime E at android.widget.FrameLayout.onLayout(FrameLayout.java:333)
755 AndroidRuntime E at android.view.View.layout(View.java:6569)
755 AndroidRuntime E at android.view.ViewRoot.performTraversals(ViewRoot.java:979)
755 AndroidRuntime E at android.view.ViewRoot.handleMessage(ViewRoot.java:1613)
755 AndroidRuntime E at android.os.Handler.dispatchMessage(Handler.java:99)
755 AndroidRuntime E at android.os.Looper.loop(Looper.java:123)
755 AndroidRuntime E at android.app.ActivityThread.main(ActivityThread.java:4203)
755 AndroidRuntime E at java.lang.reflect.Method.invokeNative(Native Method)
755 AndroidRuntime E at java.lang.reflect.Method.invoke(Method.java:521)
755 AndroidRuntime E at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
755 AndroidRuntime E at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
755 AndroidRuntime E at dalvik.system.NativeStart.main(Native Method)
推荐答案
您忘记了几个需要重写的方法:getViewTypeCount() 和 getItemViewType().所有行都相同的列表不需要这些，但它们对于您的场景非常重要.正确实施这些，Android 将为您的标题和详细信息行维护单独的对象池.
You forgot a couple of methods you need to override: getViewTypeCount() and getItemViewType(). These are not needed for lists where all rows are the same, but they are very important for your scenario. Implement these properly, and Android will maintain separate object pools for your headers and detail rows.
或者，你可以看看:
- Jeff Sharkey 的原始 SeparatedListAdapter (GPL)
- 我的更新版本 (GPL)
- 我的MergeAdapter，也可用于此场景(Apache)
- Jeff Sharkey's original SeparatedListAdapter (GPL)
- My updated rendition (GPL)
- My MergeAdapter, which can be used for this scenario as well (Apache)
这篇关于Android:具有两种不同视图的 EfficientAdapter的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
