Develop Reference

Change attributes of items on an Android Actionbar

I have an Actionbar displayed on my maps fragment to which I have added a zoom-in button. When selected I would like to replace it with a zoom-out button.
When zoom-in is selected the it is obviously pases in to onOptionsItemSelected as the menu item, so it is easy to set it's attributes like this: viewZoomIn.setVisibility(viewZoomIn.GONE); My problem is, how do I get a reference to the zoom-out button on the action bar to set it as as I would like to viewZoomOut.setVisibility(viewZoomOut.VISIBLE);?
I thought I may be able to store the zoom-in and zoom-out views as instance variables and capture them when I inflate the Actionbar, like this:
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main_menu, menu);
viewZoomIn = findViewById(R.id.zoom_in);
viewZoomOut = findViewById(R.id.zoom_out);
return super.onCreateOptionsMenu(menu);
This does not work.
Any help on getting hold of thes buttons, or advice on a better way of toggling my zoom-in/zoom-out buttons would be appreciated.
It probably shows, but I am pretty new to Java, so it would be preferable is any assistance were communicated in a simple manner.
Thank you.

You have to apply your visibility logic in onPrepareOptionsMenu(Menu) not in onCreateOptionsMenu(Menu) if you want to toggle MenuItem state.
private boolean currentlyZoomedIn;
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main_menu, menu);
return super.onCreateOptionsMenu(menu);
}
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
// called the first time and after each "invalidateOptionsMenu()"
// if tha Activity is in the "zoomedIn" state, the zoomOut button will be visible
menu.findItem(R.id.zoom_in).setVisible(!currentlyZoomedIn);
menu.findItem(R.id.zoom_out).setVisible(currentlyZoomedIn);
return super.onPrepareOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()){
case R.id.zoom_in:
// do your logic when zoom_in is clicked
currentlyZoomedIn = true;
break;
case R.id.zoom_out:
// do your logic when zoom_out is clicked
currentlyZoomedIn = false;
break;
}
// force the redraw of the menu
invalidateOptionsMenu();
return super.onOptionsItemSelected(item);
}
By the way, I suggest you to use only one button and move your logic only in onOptionsItemSelected(MenuItem) to avoid an instance variable and the call to invalidateOptionsMenu() in a way like this:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// zoom_out_in_id is the id for the common button
if (item.getItemId() == R.id.zoom_out_in_id) {
// get the curren title
final CharSequence title = item.getTitle();
// if the current title is the one of zoom_in button, you have to change its infos to zoom_out ones
if (title.equals("zoom_in_title")) {
// do your logic when zoom_in is clicked
item.setIcon(R.drawable.zoom_out_icon);
item.setTitle("zoom_out_title");
} else if (title.equals("zoom_out_title")) {
// do your logic when zoom_out is clicked
item.setIcon(R.drawable.zoom_in_icon);
item.setTitle("zoom_in_title");
}
}
return super.onOptionsItemSelected(item);
}

how can i change the visibility of a menu item inside onOptionsItemSelected(..)

i have three menu items "enable, diable, exit". what i want to do is, when the R.id.menu_enable_bt is chosen, i want to disable it using
menu.findItem(R.id.menu_enable_bt).setVisible(false);
but i can not call
menu.findItem(R.id.menu_enable_bt).setVisible(false);
from inside the onOptionsItemSelected(..) method.
how can i change the visibility of a menu item inside onOptionsItemSelected(..)
CODE:
#Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
Log.w(TAG, SubTag.msg("onCreateOptionsMenu"));
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
if (this.mBTAdapter.isEnabled()) {
menu.findItem(R.id.menu_enable_bt).setVisible(false);
menu.findItem(R.id.menu_disable_bt).setVisible(true);
} else {
menu.findItem(R.id.menu_enable_bt).setVisible(true);
menu.findItem(R.id.menu_disable_bt).setVisible(false);
}
return super.onCreateOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);
Log.w(TAG, SubTag.msg("onOptionsItemSelected"));
switch (item.getItemId()) {
case R.id.menu_enable_bt:
Log.d(TAG, SubTag.bullet("onOptionsItemSelected", "menu_enable_bt"));
//menu.findItem(R.id.menu_enable_bt).setVisible(false); **how to do this**
this.mATEnableBT = new ATEnableBT();
this.mATEnableBT.execute();
break;
case R.id.menu_disable_bt:
Log.d(TAG, SubTag.bullet("onOptionsItemSelected", "menu_disable_bt"));
break;
case R.id.menu_exit:
Log.d(TAG,SubTag.bullet("onOptionsItemSelected", "menu_exit"));
finish();
break;
}
return super.onOptionsItemSelected(item);
}

you can use invalidateOptionsMenu() which will forse onCreateOptionsMenu to be called again.
From the documentation
Declare that the options menu has changed, so should be recreated. The
onCreateOptionsMenu(Menu) method will be called the next time it needs
to be displayed.
There you can check your conditions and undertake the needed actions

See the javadoc for onPrepareOptionsMenu. This is your opportunity to make changes to a menu just before it becomes visible to the user. So you should maintain some member variables describing what should be visible and use that to modify the menu items here.

Menu doesn't show up in android

I have the below code and I can't understand why my code doesn't show up menu. If the activity containing data, condition_true = true otherwise condition_true = false. I can clearly see the control going to menutag and the condition is true too. Even I am getting Inflated string too in log. But still menu doesn't show up. I have seen lot of posts on these like link 1, link2 etc., but that didn't solve my problem. Can someone please help me on this issue?
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
menu.clear(); //Clear view of previous menu
MenuInflater inflater = getSupportMenuInflater();
Log.d("menutag", condition_true);
if(condition_true)
{
inflater.inflate(R.layout.menu, menu);
Log.d("menutag","Inflated");
}
return super.onPrepareOptionsMenu(menu); // replaced this with true, but no use.
}

You have to add the options attributes in xml.. Otherwise you can do it programmatically like this:
public boolean onCreateOptionsMenu(Menu menu){
getMenuInflater().inflate(R.menu.yourmenuxmlfilename, menu);
return true;
}
public boolean onOptionsItemSelected(MenuItem item){
switch(item.getItemId){
case R.id.item1:
// what you want to do with first button
break;
case .....
break;
}
return true;
}

Maybe you're overriding onKeyDown and it always returns true? This can cause the problem, because it will catch the menu button pressed event too.

Android - Enabling MenuItems by code

I need to enable a MenuItem when a previous screen (Activity) returns.
I tried this code:
...
((MenuItem)findViewById(R.id.menu_how)).setEnabled(true);
...
but a null pointer exception is launched.
BTW, the menu_how is set to false in xml; and the code is part of onActivityResult(int requestCode, int resultCode, Intent data) call.

Try using menu.findItem(R.id.menu_how) in onCreateOptionsMenu and save a reference for later use.
This should work fine with enabled, however, I've found that setting a menu item to invisible in the XML means you can't show/hide it programmatically.

I found something at the android dev site that might be helpful (look for the section "Changing menu items at runtime")
It said that the onCreateOptionsMenu() method fired only when the the menu for the activity is created, and it happens when this activity starts. So if you want to change the menu items after the menu/activity was created, you need to override the onPrepareOptionsMenu() method instead. search the link for full details.
EDIT:
Just made it and it's working fine. I'm using one boolean var per menuItem which represents if this item should be enabled or not. This is my code:
/*************************************Game Menu**************************************/
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.game_menu, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId())
{
case R.id.gm_new_game:
//newGame();
return true;
case R.id.gm_stand_up:
//some code when "gm_stand_up" button clicked..
return true;
case R.id.gm_forfeit:
//some code when "gm_forfeit" button clicked..
return true;
case R.id.gm_surrender:
//some code when "gm_surrender" button clicked..
return true;
case R.id.gm_exit_table:
exitTableCommand();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
#Override
public boolean onPrepareOptionsMenu(Menu menu)
{
menu.findItem(R.id.gm_forfeit).setEnabled(forfeitMenuButtonIsEnabled);
menu.findItem(R.id.gm_surrender).setEnabled(surrenderMenuButtonIsEnabled);
menu.findItem(R.id.gm_new_game).setEnabled(newGameMenuButtonIsEnabled);
menu.findItem(R.id.gm_stand_up).setEnabled(standUpMenuButtonIsEnabled);
return super.onPrepareOptionsMenu(menu);
}

where are you calling this? (Sorry, didn't read carefully) I think you need to call it after the menu is inflated (usually in OnCreateOptionsMenu). To do this, you can set a variable to true when the other Activity returns, then do ((MenuItem)findViewById(R.id.menu_how)).setEnabled(mMyBooleanField) in OnCreateOptionsMenu after the call to inflater.inflate.
Edit: To accomplish this in code, it might look something like this:
At the top of the class (along with all the other class members):
Boolean mEnableMenuItem = false;
In OnCreateOptionsMenu:
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.options_main, menu);
((MenuItem)findViewById(R.id.menu_how)).setEnabled(mEnableMenuItem );
In OnActivityResult:
mEnableMenuItem = true;

Keep a reference to Menu in your activity:
private Menu mMenu;
Then:
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_note, menu);
mMenu = menu;
return true;
}
Now, to access menu items anywhere in your activity use similar code to this:
mMenu.findItem(R.id.menu_how).setVisible(false);
or
mMenu.findItem(R.id.menu_how).setEnabled(true);

Optionsmenu in an TabActivity for a specific Tab

My problem is, that I have got a TabActivity, which has 4 Tabs right now. The first Tab is a special Details-Tab, where the user could modify some data.
The problem is, that if I add a OptionsMenu for the Activity, that the OptionsMenu is appearing on every Tab.
I tried to check the current mTabHost.getCurrentTabTag() in the onCreateOptionsMenu but that changed nothing.
So, how to do that?
(The following code, which still shows the OptionsMenu on every Tab)
public boolean onCreateOptionsMenu(Menu menu) {
if(mTabHost.getCurrentTabTag()==getString(R.string.tab_details)) {
boolean result = super.onCreateOptionsMenu(menu);
menu.add(0, EDIT_ID, 0, R.string.menu_edit).setIcon(R.drawable.edit);
return result;
}
return true;
}
public boolean onMenuItemSelected(int featureId, MenuItem item) {
switch (item.getItemId()) {
case EDIT_ID: {
Toast.makeText(this, "o.O", Toast.LENGTH_LONG).show();
}
}
return super.onMenuItemSelected(featureId, item);
}

I see that you are comparing strings (tags in fact) with ==, usually, this is nicer to do that with .equals() method. Maybe it will solve your issue.
To dynamically update an option menu (from the documentation) :
If you want to change the Options
Menu each time it opens, you must
override the onPrepareOptionsMenu()