我有一个ExpandableListActivity(使用SimpleCursorTreeAdapter),当用户点击子元素时,它会启动另一个活动。在新活动中按后退按钮时,所有列表项都会再次折叠。如何保存ExpandableListActivity的展开状态并再次将其恢复。
我已经尝试过像这样实现onSaveInstanceState()和onRestoreInstanceState()......
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
Parcelable listState = getExpandableListView().onSaveInstanceState();
outState.putParcelable("ListState", listState);
}
@Override
protected void onRestoreInstanceState(Bundle state) {
super.onRestoreInstanceState(state);
Parcelable listState = state.getParcelable("ListState");
getExpandableListView().onRestoreInstanceState(listState);
}
...但是onRestoreInstanceState()从未被调用过。我也尝试在onCreate()方法中恢复状态,但也没有调用它:
if (savedInstanceState != null) {
Parcelable listState = savedInstanceState.getParcelable("ListState");
getExpandableListView().onRestoreInstanceState(listState);
}
答案 0 :(得分:11)
不幸的是,只要焦点丢失,扩展状态总会重置,并且当再次获得焦点但onStart()时不调用onCreate()。所以我现在的解决方法是手动存储所有扩展项的ID,并再次在onStart()中展开它们。我实现了ExpandableListActivity的子类来重用该行为。
public class PersistentExpandableListActivity extends ExpandableListActivity {
private long[] expandedIds;
@Override
protected void onStart() {
super.onStart();
if (this.expandedIds != null) {
restoreExpandedState(expandedIds);
}
}
@Override
protected void onStop() {
super.onStop();
expandedIds = getExpandedIds();
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
this.expandedIds = getExpandedIds();
outState.putLongArray("ExpandedIds", this.expandedIds);
}
@Override
protected void onRestoreInstanceState(Bundle state) {
super.onRestoreInstanceState(state);
long[] expandedIds = state.getLongArray("ExpandedIds");
if (expandedIds != null) {
restoreExpandedState(expandedIds);
}
}
private long[] getExpandedIds() {
ExpandableListView list = getExpandableListView();
ExpandableListAdapter adapter = getExpandableListAdapter();
if (adapter != null) {
int length = adapter.getGroupCount();
ArrayList<Long> expandedIds = new ArrayList<Long>();
for(int i=0; i < length; i++) {
if(list.isGroupExpanded(i)) {
expandedIds.add(adapter.getGroupId(i));
}
}
return toLongArray(expandedIds);
} else {
return null;
}
}
private void restoreExpandedState(long[] expandedIds) {
this.expandedIds = expandedIds;
if (expandedIds != null) {
ExpandableListView list = getExpandableListView();
ExpandableListAdapter adapter = getExpandableListAdapter();
if (adapter != null) {
for (int i=0; i<adapter.getGroupCount(); i++) {
long id = adapter.getGroupId(i);
if (inArray(expandedIds, id)) list.expandGroup(i);
}
}
}
}
private static boolean inArray(long[] array, long element) {
for (long l : array) {
if (l == element) {
return true;
}
}
return false;
}
private static long[] toLongArray(List<Long> list) {
long[] ret = new long[list.size()];
int i = 0;
for (Long e : list)
ret[i++] = e.longValue();
return ret;
}
}
可能有人有更好的解决方案。
答案 1 :(得分:2)
这应该有效
Parcelable state = exercisesList.onSaveInstanceState();
exercisesList.setAdapter(....);
exercisesList.onRestoreInstanceState(state);
答案 2 :(得分:0)
试试这个。这将解决问题,部分
yourlist.setSaveEnabled(true);