Develop Reference

Android with only one activity and multiple fragments

Sorry for my english,
I've read that between activity or fragment, we should use fragment as soon as we can. Because of that, I was developing my entire app with a lot of fragment and just one activity, switching from one to another with the beginTransaction().replace() method. But it seems that I have to implement all my event methods (like onClick) in the activity and not in the fragment. So if I develope everything in only one activity, I will have all my event method on just on class, wich will be unreadable...
I would like to know what is the best thing to do : one activity with a lot of fragment, or multiple activities... how ?
Thanks.

An entire app with only one activity and a lot of fragments might not be a very good idea.
If your app functionalities requires it, you can have multiple fragments managed by one activity : supporting tablets and handset / navigation drawer / ViewPager etc.
Anyway, using fragments doesn't force you to code all your event methods in the main activity. Your main activity handles the fragments creation/swaps but most of the actions that you do on a fragment's screen can be coded in the fragment class.
If you want to re-use a fragment in multiple activities it has to be this way.
As said in the google doc :
"You can think of a fragment as a modular section of an activity, which has its own lifecycle, receives its own input events, and which you can add or remove while the activity is running (sort of like a "sub activity" that you can reuse in different activities)".
The specific code you put in your main activity should be easily refactored in the fragments.
Did you look the official documentation ? There might be some good examples.
http://developer.android.com/guide/components/fragments.html
Coding actions in the fragment is very similar to coding them in the activity :
You can handle action bar actions in the fragment :
#Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
// Inflate your menu
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.option1:
// Handle option 1
return true;
case R.id.option2:
// Handle option 2
return true;
default:
return super.onOptionsItemSelected(item);
}
}
You can handle buttons actions in the fragment :
Button yourButton = (Button) view.findViewById(R.id.yourbutton);
btnUpload.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// Handle button click
}
});
You can code asynctask in the fragment.
If you have a list, you can code list context menu actions in the fragment :
#Override
public void onCreateContextMenu(ContextMenu menu, View v,
ContextMenuInfo menuInfo) {
super.onCreateContextMenu(menu, v, menuInfo);
// Inflate your context menu
}
#Override
public boolean onContextItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.option1:
// Handle option 1
return true;
case R.id.option2:
// Handle option 2
return true;
default:
return super.onContextItemSelected(item);
}
}
AlertDialog work in a fragment.
Etc. Etc.
Do you have a specific action that gives you trouble refactoring in a fragment ?

In Xamarin the OnOptionsItemSelected is not called

I read different articles here about OnOptionsItemSelected not been called in Android, because I have the same problem in Xamarin.Android.
I have an menu in my main activity, but I haven't used fragments at all. The menu is read from an XML file:
public override bool OnCreateOptionsMenu(IMenu menu)
{
MenuInflater.Inflate(Resource.Menu.main, menu);
return base.OnCreateOptionsMenu(menu);
}
And then I tried to catch the ItemSelected Events by using the following code:
public virtual bool OnOptionsItemSelected (IMenuItem item)
{
string test;
Console.WriteLine ("Test");
return true;
}
But it doesn't work and the event is not called.
I tried other events like:
public virtual bool OnMenuItemSelected (int featureId, IMenuItem item)
{
string test;
Console.WriteLine ("Test");
return true;
}
public void OnGroupItemClick( IMenuItem item) {
// One of the group items (using the onClick attribute) was clicked
// The item parameter passed here indicates which item it is
// All other menu item clicks are handled by onOptionsItemSelected()
int i = 0;
string test;
Console.WriteLine ("Test");
test = item.MenuInfo.ToString ();
}
But none of these events have been called. The menu is there, but I cannot catch the ClickedEvents.
How can I catch the ClickedEvents?

Your code seems to work in a clean application (just tried on Xamarin.Android Alpha channel, latest version, on VS2013).
A few things you might try:
Disable Fast Deployment in the project properties under Android Options
Delete the bin and obj folders from your project folder
Besides this, are you using any external library/component?

I have found the answer. The problem was that I was using virtual methods.
Instead of that I had to use override methods.

expanding an actionBar-ActionView in combination with showing a new Fragment

Several tries to ask this question in #android-dev (irc) and hours of searching, but I still don't have a solution to this problem.
I'm currently working on the search-function in my android music player. I'm using the amazing ActionBarSherlock to provide support for older android versions.
My Problem is the following:
When the user clicks the search menu/action button, the actionView of the clicked action should be expanded, and a new Fragment (the searchFragment) should be shown instead of the currently active one.
However when i'm attempting to do this, the actionView doesn't expand.
I've tried to expand the actionView, without adding the SearchFragment, and in that case the actionView DOES expand. However the combination seems impossible.
Here's my code:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item != null) {
if (item.getItemId() == R.id.collectionactivity_search_menu_button) {
item.expandActionView();
mTabsAdapter.replace(new SearchFragment(), false);
return true;
}
}
return false;
}
/**
* Replaces the view pager fragment at specified position.
*/
public void replace(int position, Fragment newFragment, boolean isBackAction) {
// Get currently active fragment.
ArrayList<Fragment> fragmentsStack = mFragments.get(position);
Fragment currentFragment = fragmentsStack.get(fragmentsStack.size() - 1);
if (currentFragment == null) {
return;
}
// Replace the fragment using a transaction.
this.startUpdate(mViewPager);
FragmentTransaction ft = mFragmentManager.beginTransaction();
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.attach(newFragment).remove(currentFragment).commit();
if (isBackAction == true)
fragmentsStack.remove(currentFragment);
else
fragmentsStack.add(newFragment);
this.notifyDataSetChanged();
this.finishUpdate(mViewPager);
}
The mTabsAdapter.replace(...) method replaces the currently shown Fragment with the one in the first parameter. In Addition the fragment is being added to a custom backStack.
Replacing the Fragment before or after expanding the View didn't make any difference.
Hopefully somebody is able to help me :)
thanks in advance!

Have you tried setting your actionviews android:showAsAction to collapseActionView? that way you don't have to manage the expand/close action.
If that does not work you can handle it in another way,you set an expand listener and replace your fragment once your action view starts expanding
item.setOnActionExpandListener(new OnActionExpandListener() {
#Override
public boolean onMenuItemActionCollapse(MenuItem item) {
// Do something when collapsed
return true; // Return true to collapse action view
}
#Override
public boolean onMenuItemActionExpand(MenuItem item) {
mTabsAdapter.replace(new SearchFragment(), false);
return true; // Return true to expand action view
}
});
remember to return true to let the actionview expand

I found out what the problem was caused by.
My mTabsAdapter.replace(..) method was calling notifyDataSetChanged();. So everytime I replaced the fragment, onPrepareOptionsMenu was being called, resulting in the search action button being removed and added again, thus resulting in the actionView being collapsed.
The solution to this is to fix my onPrepareOptionsMenu, so the actionView will be expanded again, whenever onPrepareOptionsMenu is called and the actionView was expanded before.

Re-using Options menu code

Is there a convenient way of showing the same Options menu options in multiple Activities?
Example: In my app, I display a TV Guide in one of three ways.
Seven day guide (TabActivity with 7 tabs)
All channels 'Now showing' (ListActivity)
All shows today by start time (Activity - could be changed easily to ListActivity)
For the Options menu in the TabActivity, the code is quite simple...
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
menu.clear();
inflater.inflate(R.menu.gv_options_menu, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.view:
...
...
}
}
...but at the moment it seems I need to copy/paste it to the other two Activities which I don't like doing. If I change the Options menu code for one I'll need to do it for the other two also.
The only alternative I can think of is I have a 'helper' class (POJO) to which I could add a method and pass the context into to allow use of the getMenuInflator() method and another method I could pass the result of item.getItemId() into to process with the switch-case.
What is the normal way of having multiple Activities with the same Options menu?

Create a simple separate class with these two methods:
public class MyMenuHandler {
private Activity mActivity;
public MyMenuHandler(Activity activity) {
mActivity = activity;
}
public boolean onPrepareOptionsMenu(Menu menu) {
MenuInflater inflater = mActivity.getMenuInflater();
menu.clear();
inflater.inflate(R.menu.gv_options_menu, menu);
return true;
}
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.view:
...
}
}
}
In your activities override those callback methods and redirect the call to an instance of your MyMenuHandler class:
public class MyActivity1 extends TabActivity {
private MyMenuHandler mMenuHandler;
#Override
public void onCreate(Bundle savedInstanceState) {
...
mMenuHandler = new MyMenuHandler(this);
}
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
// you may also add here some items which are specific
// for one activity, not for the others
...
return mMenuHandler.onPrepareOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// handle selection of your specific items here,
// if none of them has been selected call mMenuHandler method
...
return mMenuHandler.onOptionsItemSelected(item);
}
}
This will let you hold in one place the code which respond to selection of your basic menu items, so there will be no need to worry about copy-pasting it to all activities which are to have the same menu.

One approach is to use inheritance with your Activities. Create a base Activity that implements the options menu methods and then each child Activity will gain that functionality. This is the recommended approach on the Android developer site:
Tip: If your application contains multiple activities and some of them provide the same Options Menu, consider creating an activity that implements nothing except the onCreateOptionsMenu() and onOptionsItemSelected() methods. Then extend this class for each activity that should share the same Options Menu. This way, you have to manage only one set of code for handling menu actions and each descendant class inherits the menu behaviors.
Unfortunately this won't work for you as you are not inheriting from Activity itself but differing subclasses of it, but that is the 'normal' way to do it.

You can encapsulate your action menu in a fragment. In this way you only need to add the fragment in the onCreate menu of your activity.
You need to call setHasOptionsMenu once the fragment is created.
To add the add fragment use a tag instead of a layout id.

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()