我使用的是baseadapter的扩展版本,它基于sdk演示示例中的efficientadapter示例。
我的数据基本上是一个对象( ListPlaces
)它有一个 ArrayList
实际位置列表,可通过 listPlaces.getValues()
. 此arraylist数据按范围和 ArrayList
由一些特殊项目(分隔符)组成,没有数据,但是 separator
标志设置为 true
.
现在每当我 EfficientAdapter
获取数据对象,该对象是它返回的分隔符 false
为了 public boolean isEnabled(int position)
以及 public View getView(int position, View convertView, ViewGroup parent)
根据当前数据对象是由真实数据组成还是只是分隔符虚拟对象,对两种不同的布局进行充气。
如果我每次都膨胀布局的话,效果会很好。但是,每次都会膨胀布局并调用 findViewById
使 ListView
几乎慢得无法形容。
所以我试着用efficientadapter ViewHolder
接近。但这并不是开箱即用的,因为我尝试访问两种不同的视图。所以每当我 convertView != null
(else情况)通过我们的 ViewHolder
当前面的视图是一个分隔符时,访问textview当然不起作用,它只在“real”items布局上可用。
所以我也强迫自己 getView()
不仅在 convertView == null
,但当前一个listrow与当前listrow不同时: if (convertView == null || (listRow != listRow_previous)) { [....] }
现在看来差不多可以了。或者至少它不会从一开始就崩溃。但它仍然崩溃,我不知道我要做什么不同。我试着调查 convertView.getID()
以及 convertView.getResources()
,但到目前为止这并没有什么帮助。也许有人知道我该怎么检查我的电流 convertView
与列表项布局或列表分隔符布局匹配。谢谢。
这是密码。在有[…]的地方,我拿出一些不太重要的代码,以便更容易阅读和理解:
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,"\tCREATE 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,"\tCREATE 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,"\tconvertView 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)
2条答案
按热度按时间2ic8powd1#
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。正确地实现这些,android将为您的header和detail行维护单独的对象池。
或者,你可以看看:
jeff sharkey最初的separatedlistadapter(gpl)
我更新的格式副本(gpl)
我的mergeadapter,也可以用于此场景(apache)
ddarikpa2#
多亏了getviewtypecount()和getitemviewtype()的提示,它现在可以完美地工作了。
实现这两种方法非常简单:
正如commonware在他的回答中提到的那样,android将为不同的列表项维护不同的对象池,这也意味着您可以删除对
listRow_previous
在我的例子中if (convertView == null || (listRow != listRow_previous))
至if (convertView == null)
只是。