Develop Reference

Android - Ques on order in which Fragment Options Menu called

I was reading the help section on google's android page on OptionsMenus and ActionsBars:
http://developer.android.com/guide/topics/ui/actionbar.html
And they included a note that stated that when using fragments, the activity's onOptionsItemSelected method would be called beforethe fragment's is called, their by making it necessary to include the default: return super.onOptionsItemSelected at the end of the onOptionsItemSelected method definition. They included the following method example but did not state if this was meant to be an example within an Activity definition or a Fragment definition. I was a little confused on this and wanted to ask for clearification. based on the use of "super" it would suggest it's inside the fragment getting passed up to the Activity, but this disagrees with their statement that the Activity gets called first. If it's meant to be an example in the Activity and "super" refers to the parent Application class, then I am not clear on how it gets referred back to the Fragment. Any notes of clearification would be appreciated.
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle presses on the action bar items
switch (item.getItemId()) {
case R.id.action_search:
openSearch();
return true;
case R.id.action_compose:
composeMessage();
return true;
default:
return super.onOptionsItemSelected(item);
}
}

Your MyActivity extends Activity and thus inherits its methods, one of which is onOptionsItemSelected() that you are overriding.
Calling super.whatever() says: I want to override this method whatever()from the superclass Activity, but still run the method as defined there. Basically, you are adding something to that method. It's what you typically do onCreate, for example.
In this case, returning false would mean that, if ID is different from the mentioned twos, we're done - menu managing can stop here. Obviously we are not, as we want the fragment to receive its call.
So: your activity overrides the superclass method to manage the first two menu items, then calls the superclass method to keep things running and say hey, there might be something that has not be managed here.

Menu onClick attribute and method argument

I'm practising adding menu items and trying to react to menu item clicks. According to the developer's guide, it says:
Tip: Android 3.0 adds the ability for you to define the on-click behavior for a menu item in XML, using the android:onClick attribute. The value for the attribute must be the name of a method defined by the activity using the menu. The method must be public and accept a single MenuItem parameter—when the system calls this method, it passes the menu item selected. For more information and an example, see the Menu Resource document.
However, the sample code in the same page doesn't follow the rule: the methods do not pass the MenuItem parameter. The sample code is:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId()) {
case R.id.new_game:
newGame();
return true;
case R.id.help:
showHelp();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
My question is: Shouldn't method calls be newGame(MenuItem item) and showHelp(MenuItem item), instead of newGame() and showHelp()? When I tested my own, (MenuItem item) argument was needed in fact, otherwise, the app was crashing, even though it compiles correctly.
Any help would be appreciated.

onOptionsItemSelected is the alternative to defining onClick attributes and what is available prior to Android 3.0 (important if you want to be backward compatible). It is simply a different way of providing the same process flow. Of course, onClick has the potential to crash your application on runtime, rather than onOptionsItemSelected not handling a menu item (simply causing it to do nothing).

handle click on iconmenu item

I see that it's possible to handle a tap on a icon menù item or by implementing
onOptionsItemSelected
inside the acivity, or by using
onMenuItemClickListener
like onclick listener on a button. When is better to use the fist one method, and when the second one?
Because for my opinion, using an external listener makes more modular the code, but create a new class, but using the first way don't create new class, but makes code less modular...

There are use cases other than the ones outlined below, but I'm putting in the general cases that come up regularly.
onOptionsItemSelected
If you're using Fragments, you may want to use onOptionsItemSelected and consider adding menu items to the Action Bar the way that is described in Adding items to the Action Bar.
What this describes is implementing onCreateOptionsMenu inside your Fragment. To make this happen, you must call setHasOptionsMenu in onCreate.
protected void onCreate(Bundle savedInstanceState) {
this.setHasOptionsMenu(true);
}
Setting this will actually make the Activity call onCreateOptionsMenu which allows you to add the menu items.
#Override
public boolean onCreateOptionsMenu(Menu menu){
super.onCreateOptionsMenu(menu);
// add items corresponding to this Fragment
menu.add(...);
return true;
}
The reason I recommend this is that it allows you to put more of the menu handling code into your Fragment instead of the Activity to figure out which Fragment to call, etc.
In this case, clicking the menu item will call onOptionsItemSelected inside of your Fragment which I suggest.
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.my_id1:
dothing1();
return true;
case R.id.my_id2:
dotghing2();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
More of a long winded answer, but this is the way to handle menu clicks inside your Fragment.
onMenuItemClickListener
In the case of onMenuItemClickListener, this is used when you DON'T want to use the pre-ready method above and implement your own.
What I mean by that is you implement OnMenuItemClickListener and generate the methods in the interface. You then assign the menu to call the Activity that implemented this where as the above option assumes what Activity to use based on the pre-ready implementation of the Activity to Fragment relationship.

If you are targeting API 14 or greater (ICS or above) you could implement an ActionProvider. If that's not an option then you could implement a base activity that will always populate the menu and handle any menu clicks using onOptionsItemSelected. This is a good approach to implement "About" or "Settings" menu items through all your activities.

Pressing the "go back" button closes the application

I'm currently moving slowly but steady forward in the making of a Android application and Im currently learning how to create a new window and switch to it. This is going all well but I have one small problem. When I pressing the "go back" button closes the application even if I have choosed to go back when just that button is pressed.
#Override
public void onBackPressed() {
finish();
return;
}
Have I missed something or what?
Thanks in advance.
EDIT
#Override
public boolean onCreateOptionsMenu(Menu menu)
{
MenuInflater menuInflater = getMenuInflater();
menuInflater.inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item)
{
// Handle item selection
switch (item.getItemId())
{
case R.id.menuItem1:
setContentView(R.layout.about);
return true;
case R.id.menuItem2:
System.exit(0);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
EDIT 2: About.java
package weather.right;
import weather.right.now.R;
import android.os.Bundle;
public interface About {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.about);
}
}

You need to use Intents to "switch windows". A "window" is called an Activity in Android and you set the visual content of an Activity using the setContentView() method in the onCreate() call of the Activity.
To launch another Activity from your current Activity, simply create an Intent with a few parameters and call startActivity() with that Intent. Here's an example:
Intent i = new Intent(this, TheNextActivity.class);
startActivity(i);
Don't forget to include your second Activity in the Android manifest file. All Activities in your application must be included in that file.
Other things to note is that you don't really use System.exit() in Android. Just call finish(). It's advised to let Android manage applications and its resources rather than doing it yourself, but if you want to make sure that your application really is shut down, feel free to use System.exit() anyway. There's also no need for overriding onBackPressed() if you're only calling finish(). That's standard behaviour in Android when you hit the back button.
Also, you don't call setContentView() more than once per Activity. You start a new Activity when you need to change the visuals (or use one of the specialized Widgets to switch between layouts.
This also explains why you're experiencing your "problem". You may have changed the layout of the Activity using setContentView(), but there's still only one Activity running - when you call finish(), that Activity gets closed. If you had started a second Activity with a different layout, like you're supposed to do, Android would have closed that second Activity and would have returned you to the first.

android setOnMenuItemClickListener not called

Inside of my onCreateOptionsMenu function I implemented this:
mymenuitem.setOnMenuItemClickListener(new OnMenuItemClickListener(){
public boolean onMenuItemClick(MenuItem item){
update_freq=1;
showChosen(); (some user defined function)
update_time();
return true;
}
});
However, the .setOnMenuItemClickListener only be called the first time I click my preference, later on when I went back to menu and click preference buttons, it never be called.
can anyone tell me what is the problem? My menu is written in xml file and inflated.

I think you need to override onOptionsItemSelected. The OnMenuItemClickListener is set on a single, specific MenuItem.