In Android 3.0, when you select some text for example, the ActionBar switches to a ContextMenu-like mode, which enables you to do actions with the selected text: copy/share/etc, and a "Done" button appears on the left side to enable the user to leave this mode.
How can I switch the ActionBar into this mode in my app (with my menu items of course)? I just couldn't find this in the docs.
Yeah, I couldn't find it either -- I had to ask at Google I|O.
Use startActionMode()
. Here is one of their samples that demonstrates it. I need to do more work in this area myself.
To use the new contextual action bar, see "Enabling the contextual action mode for individual views". It states:
If you want to invoke the contextual action mode only when the user selects specific views, you should:
- Implement the
ActionMode.Callback
interface. In its callback methods, you can specify the actions for the contextual action bar, respond to click events on action items, and handle other lifecycle events for the action mode. - Call
startActionMode()
when you want to show the bar (such as when the user long-clicks the view).
For example:
- Implement the
ActionMode.Callback
interface:private ActionMode.Callback mActionModeCallback = new ActionMode.Callback() { // Called when the action mode is created; startActionMode() was called @Override public boolean onCreateActionMode(ActionMode mode, Menu menu) { // Inflate a menu resource providing context menu items MenuInflater inflater = mode.getMenuInflater(); inflater.inflate(R.menu.context_menu, menu); return true; } // Called each time the action mode is shown. Always called after onCreateActionMode, but // may be called multiple times if the mode is invalidated. @Override public boolean onPrepareActionMode(ActionMode mode, Menu menu) { return false; // Return false if nothing is done } // Called when the user selects a contextual menu item @Override public boolean onActionItemClicked(ActionMode mode, MenuItem item) { switch (item.getItemId()) { case R.id.menu_share: shareCurrentItem(); mode.finish(); // Action picked, so close the CAB return true; default: return false; } } // Called when the user exits the action mode @Override public void onDestroyActionMode(ActionMode mode) { mActionMode = null; } };
Notice that these event callbacks are almost exactly the same as the callbacks for the options menu, except each of these also pass the
ActionMode
object associated with the event. You can useActionMode
APIs to make various changes to the CAB, such as revise the title and subtitle withsetTitle()
andsetSubtitle()
(useful to indicate how many items are selected).Also notice that the above sample sets the
mActionMode
variable null when the action mode is destroyed. In the next step, you'll see how it's initialized and how saving the member variable in your activity or fragment can be useful. - Call
startActionMode()
to enable the contextual action mode when appropriate, such as in response to a long-click on aView
:someView.setOnLongClickListener(new View.OnLongClickListener() { // Called when the user long-clicks on someView public boolean onLongClick(View view) { if (mActionMode != null) { return false; } // Start the CAB using the ActionMode.Callback defined above mActionMode = getActivity().startActionMode(mActionModeCallback); view.setSelected(true); return true; } });
When you call
startActionMode()
, the system returns theActionMode
created. By saving this in a member variable, you can make changes to the contextual action bar in response to other events. In the above sample, theActionMode
is used to ensure that theActionMode
instance is not recreated if it's already active, by checking whether the member is null before starting the action mode.
If you have a collection of items in a ListView
or GridView
(or another extension of AbsListView
) and want to
allow users to perform batch actions, you should:
- Implement the
AbsListView.MultiChoiceModeListener
interface and set it for the view group withsetMultiChoiceModeListener()
. In the listener's callback methods, you can specify the actions for the contextual action bar, respond to click events on action items, and handle other callbacks inherited from theActionMode.Callback
interface. - Call
setChoiceMode()
with theCHOICE_MODE_MULTIPLE_MODAL
argument.
For example:
ListView listView = getListView();
listView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE_MODAL);
listView.setMultiChoiceModeListener(new MultiChoiceModeListener() {
@Override
public void onItemCheckedStateChanged(ActionMode mode, int position,
long id, boolean checked) {
// Here you can do something when items are selected/de-selected,
// such as update the title in the CAB
}
@Override
public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
// Respond to clicks on the actions in the CAB
switch (item.getItemId()) {
case R.id.menu_delete:
deleteSelectedItems();
mode.finish(); // Action picked, so close the CAB
return true;
default:
return false;
}
}
@Override
public boolean onCreateActionMode(ActionMode mode, Menu menu) {
// Inflate the menu for the CAB
MenuInflater inflater = mode.getMenuInflater();
inflater.inflate(R.menu.context, menu);
return true;
}
@Override
public void onDestroyActionMode(ActionMode mode) {
// Here you can make any necessary updates to the activity when
// the CAB is removed. By default, selected items are deselected/unchecked.
}
@Override
public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
// Here you can perform updates to the CAB due to
// an invalidate()
request
return false;
}
});
That's it. Now when the user selects an item with a long-click, the system calls the onCreateActionMode()
method and displays the contextual action bar with the specified actions. While the contextual
action bar is visible, users can select additional items.
In some cases in which the contextual actions provide common action items, you might
want to add a checkbox or a similar UI element that allows users to select items, because they
might not discover the long-click behavior. When a user selects the checkbox, you
can invoke the contextual action mode by setting the respective list item to the checked
state with setItemChecked()
.
Maybe a bit late but here's a tutorial for the actionmode: http://www.vogella.com/articles/AndroidListView/article.html#listview_actionbar
来源:https://stackoverflow.com/questions/6162595/how-to-invoke-the-actionbars-contextmenu-like-behavior