Develop Reference

Change the icon to Toolbar Android

How can I get an icon from the toolbar to be changed to a new one that I get with a method that is seen in a bbdd.
The problem is that I can not access the event that updates the activity to be able to change the icon.
I tried with the onPrepareOptionsMenu method, but I can not make it work.
I have not been able to do this by putting the code in onStart because it tells me that the menu object is empty or invalid.
public boolean onPrepareOptionsMenu(Menu menu) {
menu.clear();
Drawable iconoMenu = obtenerIconoMenuCarro();
getMenuInflater().inflate(R.menu.menu_categorias, menu);
menu.getItem(0).setIcon(iconoMenu);
return super.onPrepareOptionsMenu(menu);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_categorias, menu);
Drawable iconoMenu = obtenerIconoMenuCarro();
menu.getItem(0).setIcon(iconoMenu);
return true;
}
My activities are extended by AppCompactActivity and loaded through an AdapterView.
And I have the problem when I go back to the fragmentDialog or since the next activity.
Thanks.

For me the simplest way was to keep a reference to the MenuItem for later use.
Obtain when the menu item is inflated.
MenuItem menuItem;
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main_menu, menu);
//find the menu item from the id
menuItem = menu.findItem(R.id.myMenuItem);
return true;
}
Then change the image where you need to with mipmap resource or #drawable.
menuItem.setIcon(R.mipmap.ic_other_icon);

How to change the menu bar item by oncreate() method

In here I am having list of colleges. I favourite the particular college by using menu bar Favourite_icon.Then the Favourite_icon changed as Favourite_icon1 When the college is viewed by some other time that menu bar Favourite_icon should as Favourite_icon1. So that I am checking Whether the college is already favourited by using server API. So how can I set the menu bar Icon from oncreate() method.

If you mean the Android menu bar, you shouldn't try and change it in onCreate(), because it hasn't been instantiated, and will always throw a NullPointerException.
If you are waiting for an API response to find the favorites, you will need to create a local menu variable to access it.
Menu myMenu;
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
myMenu = menu;
return super.onPrepareOptionsMenu(menu);
}
Then, whatever your server API's callback method should do something like this:
void callback(boolean favorite) {
if (favorite) {
myMenu.findItem(R.id.myMenuItem).setIcon(R.drawable.Favourite_icon1);
}
}

Something like this:
#Override
protected void onCreate (Bundle savedInstanceState){
...
isSomethingInMenu = true;
invalidateOptionsMenu();
...
}
#Override
public boolean onCreateOptionsMenu (Menu menu){
getMenuInflater().inflate(R.menu.menu, menu);
menu.findItem(R.id.action_something).setVisible(isSomethingInMenu);
...
}

Android: Can't toggle MenuItem icon

I'm tring to change a menuitem icon, but the icon is not being changed.
Here is how I find the MenuItem (works fine):
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu items for use in the action bar
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.activity_location_actions, menu);
mActionLocation = menu.findItem(R.id.action_location);
return super.onCreateOptionsMenu(menu);
}
Method UpdateIcon: I took a screenshot so you can see (in the red frame) that the images have been found by the system.
The mActionLocation is a MenuItem which is initialized before this Method is called and is not null.
Anyone has an idea?
UPDATE (solution by help from #vinitius)
The UpdateIcon method:
private void UpdateIcon(boolean locationOn) {
mActionLocation = locationOn; // mActionLocation is a global boolean
invalidateOptionsMenu();
}
The onPrepareOptionsMenu override:
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
// Toggle location icon
if (mActionLocation) {
menu.findItem(R.id.action_location).setIcon(R.drawable.ic_location_on_white_24dp);
} else {
menu.findItem(R.id.action_location).setIcon(R.drawable.ic_location_off_white_24dp);
}
return super.onPrepareOptionsMenu(menu);
}

You need to use onPrepareOptionsMenu(Menu menu):
This is called right before the menu is shown, every time it is shown.You can use this method to efficiently enable/disable items or otherwise dynamically modify the contents.
Inside this method, retrieve your item as you do in onCreateOtionsMenu and check whether your gps in os or not to modify your item icon.

Android: Change menu item from Log in to Log out

My menu has a item to Log in, but when you are logged in I want it to say Log out.
How?
If I'm going to change the item after its created, its probably through this method
#Override
public boolean onCreateOptionsMenu( Menu menu ) {
MenuInflater inflater = getMenuInflater();
inflater.inflate( R.menu.menu_main, menu );
return true;
}
Afaik the onCreateOptionsMenu() happens after the onCreate so putting any getItemId() for the menu there will give me a NullPointerException right away.
I want the app to find out if its supposed to use the string R.string.Logout if its logged in.
I dont even know what to search for for this issue. All I found was how to make a string implement names, like this answer https://stackoverflow.com/a/7646689/3064486

You should use onPrepareOptionsMenu(Menu menu) instead to update menu items
#Override
public boolean onPrepareOptionsMenu(Menu menu){
super.onPrepareOptionsMenu(menu);
MenuItem someMenuItem = menu.findItem(R.id.some_menu_item);
someMenuItem.setTitle("Log out");
return super.onPrepareOptionsMenu(menu);
}
To refresh Menu items call invalidateOptionsMenu();from Activity
From Android API guides: "If you want to modify the options menu based on events that occur during the activity lifecycle, you can do so in the onPrepareOptionsMenu() method. This method passes you the Menu object as it currently exists so you can modify it, such as add, remove, or disable items. (Fragments also provide an onPrepareOptionsMenu() callback.)"

After you inflate a menu, you can customize its items. To get each one, you must call findItem() with the item's id. In particular, you can use setTitle() to change the displayed string.
For example:
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
if (mIsLoggedIn)
menu.findItem(R.id.action_login).setTitle("Log out");
return true;
}
where action_login is the id you set for this particular menu item in the menu's xml file.

private void updateUI() {
runOnUiThread(new Runnable() {
#Override
public void run() {
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
Menu menu = navigationView.getMenu();
MenuItem nav_signin = menu.findItem(R.id.nav_signin);
nav_signin.setTitle(MyApp.signedIn ? "Sign out" : "Sign in");
}
});
}

Interaction between Activity and Fragments

In my application the main activity hosts two fragments and attached to acticity as ActionBarTabs. using the following code. NOTE: activity and the 2 fragments are defined in seperate xml layout files (See the picture at the bottom)
private void createActionTabs() {
ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
//Status Tab
String strStatus = getResources().getString(R.string.lblStatus);
ActionBar.Tab statusTab = actionBar.newTab();
statusTab.setText(strStatus);
TabListener<SFrag> sFTabListener = new TabListener<SFrag>(this, strStatus, SFrag.class);
statusTab.setTabListener(sFTabListener);
actionBar.addTab(statusTab);
//Controller Tab attached the same way
.....
}
The ActionBar Items (start and refresh) are added using
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main_menu, menu);
return true;
}
Now coming to my problem:
I want to update the data shown on the Status Fragment at application load, fragment resume and click of refresh menu item from the action bar. Now when I try to access the Status fragment from Main Activity using the following code
SFrag frag = (SFrag) getFragmentManager().findFragmentById(R.id.st_frag);
Log.d(TAG, "In Activity SFrag is " + (frag == null ? "null" : "not null"));
if (frag != null) {
//calls the method to update data
fragment.updateStatusData(statusInformation);
}
The getFragmentManager().findFragmentById methods always returns null. I even tried the onResume method of the activity, the fragment objects is still returned as null. So how do I access the fragment and thus accessa method of that fragment from host acticty.
Secondly, I am trying to use the action_service (its shown as Start button just for this mockup) in action bar as a toggle for satrting or stopping a background service. I can easily update the title/icon for start menu item from onOptionsItemSelected method (I save the current status running/stoppede in shared-preferences). but when I try to accees the menuItem at onStart/onResume of the activity by using
MenuItem mi = (MenuItem) findViewById (R.id.action_service);
it always returns null. So How Can I access action_service menu Item in onResume/onStart to update it.
My Application looks like this

First of all if you want to declare MenuItem, you should do it in this way :
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getSupportMenuInflater().inflate(R.menu.main_activity, menu);
MenuItem mRefresh = menu.findItem(R.id.refresh_menu_item);
return true;
}
About updating your Fragment on applications load or Activity's start, just set selected the tab which holds your Fragment and put the code which will load the data in your Fragment on it's onStart() or onActivityCreated() method. You can override onOptionsItemSelected() in your Fragment, so you can update your views not from your Activity which holds your Fragment, but from it's own class.
Edit: Here is an example how you should handle menu from your Fragment :
public class MyFragment extends Fragment {
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setHasOptionsMenu(true); // Do not forget this!!!
}
#Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
inflater.inflate(R.menu.first_fragment, menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);
switch (item.getItemId()) {
case R.id.action_refresh:
// Do You stuff here
break;
}
return super.onOptionsItemSelected(item);
}
}
Using this you can add and use MenuItem's in your Fragment.
Hope this helps!

I can answer the MenuItem part just not the other part.
for the menu item as per the docs You can safely hold on to menu (and any items created from it), making modifications to it as desired, until the next time onCreateOptionsMenu() is called.
for example
#Override
public boolean onCreateOptionsMenu(Menu menu) {
actionMenu = menu;
return true;
}
so basically anytime you want to change one of the items you can do this
MenuItem item = actionMenu.getItem(0);