How to get the dirty(changed) properties(any controls subclasses of view) amongst a number of properties on a layout. Does android has a dirty flag to mark if the layout has any field that has a changed content??
Actually, i have a layout that has a few edittexts,spinners,datewidgets.Now doing a save should make request to the server only if the user has modified anything .I wanted to know that how can i check if the user has changed anything in that layout or not.Does android has any flag or something that sets itself when the user modifies any input control?
Hmm..Blckberry Does have isDirty(){boolean net.rim.device.api.ui.Manager.isDirty()}method.
The activity is not tightly coupled to the elements in your layout, so you'll have to do this yourself. You could maintain a Map where the key is the id of the layout element, and the value is a boolean that signals if the element has been modified by the user. You would probably need to set up listeners on each element (such as OnKeyListener for your EditTexts) and additionally capture their initial values.
Does android has a dirty flag to mark
if the layout has any field that has a
changed content??
No, sorry.
Bit late with my answer, but the way I do it is to store the form (activity) fields in a container object (for validation, etc). This container object implements the
java.lang.Comparable interface, where T is the same class as the container.
The compareTo(T) method then returns
0 if both objects are equal (thereby form contents haven't changed).
-1 indicates that something has changed and therefore the data is dirty
You can always return other numeric values to indicate what exactly has changed if required.
Related
I want to give ids to multiple views created programmatically and each id to be a specific integer based on my own logic. Consider the following example:
I have M colors defined in a sequential way, e.g. using enum, or using an array to put M color values. (Which implementation/structure to use is part of the puzzle and suggestions need to be provided for this as well, in order to achieve the final goal described below.)
Create N instances of a custom Class and store them in a sequential way too (e.g. an array of N elements). This custom Class will just have a member mColor where a color for the specific instance will be stored.
Create (programmatically always) N RadioGroups with M RadioButtons for each RadioGroup.
The goal is when user clicks the j-th RadioButton of the i-th RadioGroup, then the i-th instance will use as background color the j-th color.
So, I would like to do something like this when OnCheckedChanged event occurs for a RadioGroup:
public void onCheckedChanged(RadioGroup group, int checkedId) {
int i = group.getId();
/*j variable is not actually needed here, but is used for concistency
with the description above.*/
int j = checkedId;
/*assume for simplicity that an array of N elements is used to store
the N CustomCLass instances and an array of M elements is used for
colors*/
customClassArray[i].setmColor(colorsArray[j]);
}
From the above, I think it is necessary that specific ids for the programmatically created RadioGroups and RadioButtons need to be set. If there is a way for this to be done, then code will be clear, optimized and no switch statements will be needed for N RadioGroups and M RadioButtons (for which, in any case, I have no clue about how it could be implemented too).
Which is the best way to achieve this, firstly with efficiency in mind and secondly, with clear code in mind?
Thank you in advance for any suggestions.
Edit: For clarification, I have read about setting my own ids by using View.setId(), but there are many resources on the web which are against this hardcoded approach (and I also vote against this if there is another way) and many of them suggest using xml resource to put your ids. However, as I said earlier, I think this is not what I want in order to achieve my goal.
Example links suggesting this approach: https://code.google.com/p/android/issues/detail?id=75081 or also How to set Id of dynamic created layout?.
Also, this approach is the suggested one in the android developer documentation: http://developer.android.com/guide/topics/resources/more-resources.html#Id
Lastly, I have also read this: What is the main purpose of setTag() getTag() methods of View? which explains the purpose of Tags and the use of setTag()/getTag() methods. This may be the best approach I've found so far for what I need. However, it surely introduces more complicated, unsupportable code. In any case, the right way, I think, has to be connected with ids, whose purpose is to uniquely identify views, rather than tags.
As you are creating RadioGroups and RadioButtons from java, I suggest to create a map and use radiobutton reference as key and instance-color combination as value. assign a single checkChangedListener to all your radioButtons and process the event as follows
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
colorInstanceCombo = map.get(buttonView);
//use colorInstanceCombo to do your work
}
assigning ids dynamically can cause problems as id is an integer and your assigned ids may cause conflict with system assigned ids to other components.
I is there way to set input type on a View object? Note it is not TextView or any derived class like EditText, Button etc.
I is there way to set input type on a View object?
No.
In my case, I have constraints that require me to extend View and not TextView, yet I need to show the soft keyboard of differing types based on focus changes to objects that accept text (the objects accepting text are part of a custom, cross-platform framework and are therefore not EditText objects, etc.). Obviously, this is fighting the framework, but that's the situation.
In this case, you would have already needed to override onCreateInputConnection, which gives you an opportunity to set up the input type. It's kind of a hack, but you can get onCreateInputConnection called again by doing the following:
InputMethodManager mgr = (InputMethodManager)context.
getSystemService(Context.INPUT_METHOD_SERVICE);
mgr.restartInput(this); // 'this' is the View
I would receive a notification from my custom objects that the keyboard needed to be opened with a certain intent, cached that intent, then performed the above couple lines. That would in turn result in a call to onCreateInputConnection, which allows you to set the input type to the cached value.
I have a view which I get from the parent ViewGroup:
mActiveCard = getChildAt(LAST_OBJECT_IN_STACK);
I later what to check if mActiveCard equals to another view:
anotherCard = getChildAt(x);
A naive approach would have been to check if x== LAST_OBJECT_IN_STACK however there might be many changes in the ViewGroup e.g. removed objects. So the positions are relative.
Also I can save the object for later but that will consume some more memory, like:
mActiveCard.equals( getChildAt(LAST_OBJECT_IN_STACK) )
One idea is to setId() of the view or setTag(). So if I have a unique String/int then I could later get the id or the tag. So saving just the id/tag would require less memory, right?
First of all is my theory correct? Also, does Android SDK offer a way to identify tags and what can be an good id/tag to generate and set on that view?
If you are truly holding onto a reference to a View (mActiveCard) that you know is also in the child list, you can simply compare their references.
if (mActiveCard == getChildAt(x))
{
// ...
}
On subclasses of View there is a getTag() method, which returns the android:tag attribute's value from .xml.
I would like the same for a MenuItem... is it okay to just cast it to a View?
Because item elements also allow a tag attribute in .xml...
Update: My goal with this is setting a tag in .xml, i.e. "notranslate", and querying it at runtime (we localize by hand at runtime, don't ask...)
It is always alright to cast, however, casting any Interface cannot be checked at compile time, only runtime. This is normally the reason many do not recommend casting an Interface that you have no control over. Having the proper error checking code is the best way to insure that such a cast does not break your code.
For the casting, it doesn't really matter whether the MenuItem is an Interface or a View, but the object it references must be one of View's subclasses, if not a View itself. If you are going to cast it, try the cast and catch a ClassCastException just in case as this is the error that will be thrown in runtime.
Another option is that since the MenuItem is simply an interface, you can easily just create a View subclass that utilizes MenuItem allowing you to do the cast. If you are doing a custom ContextMenu as many launchers do, then chances are your answer is nearly complete.
Hope this helps,
FuzzicalLogic
MenuItem is an interface. Any class can implement this interface and so it will not always be safe to cast the MenuItem to a View. You can use the "instanceOf" operator to test to see if the object that implements the MenuItem interface is indeed a View or not.
I understand that you want to define a flag in the XML definition of the menu and then at run time interrogate that flag to make a programmatic decision.
The Menu Resource Documentation records what attributes can be set in the XML. You can consider using (abusing) one of those settings such as the "android:alphabeticShortcut" to encode the flag and use the MenuItem::getAlphabeticShortcut() method to get the value. This does not require casting - it just uses the existing fields in the MenuItem XML construct/class for your own purposes.
Perhaps a less hacky way to do this is to keep a simple table in a separate assets file that lists the menu item identifiers and the special behavior associated with that identifier such as to translate or not to translate.
Alternatively create a simple class that has a table with this configuration information hard coded using the logical "#[+][package:]id/resource_name" resource identifier as the keys to the table. While this doesn't keep it all in one place (in the XML) it does it in a manner that is not encoding information in unused attributes, or relying on the ids not changing. The "table" could be implemented as a static method with an embedded switch statement allowing code such as "if (TranslationTable.shouldTranslate(menuItem.getItemId())) { do translation }"
I had a similar problem in that I wanted to associate some arbitrary data with each menu item so that I could handle menu items in a generic way without having to use hardcoded checks for individual item ids in code.
What I did was for a particular menu item (e.g. #+id/foo) There was an a TypedArray that was defined using the same name as the menu item ID. You could do this with other types of resources as well.
So to do the association, you get the resouce entry name (foo in my example) and then use that to look up the id of the other resource of a different type (#array/foo in my example).
In my handler for menu I had code like this:
Resources resources = getResources();
String name = resources.getResourceEntryName(item.getItemId());
int id = resources.getIdentifier(name, "array", "com.example");
if(id != 0)
{
TypedArray data = resources.obtainTypedArray(id);
// Use the typed array to get associated data
}
EDIT:
Actually it is even easier than that. There is nothing special about the ids on menu items other than you don't want multiple menu items with the same id. The id does not have to be of the form #+id/foo. It can actually also refer to other resources. So in my example above, instead of having the menu have an id of #+id/foo and using the resource manager to use that to find #array/foo, I changed to actually have the menu item have the id of #array/foo.
Now in my onOptionsItemSelected I have this:
Resources resources = getResources();
if("array".equals(resources.getResourceTypeName(item.getItemId())))
{
TypedArray data = resources.obtainTypedArray(item.getItemId());
// Use the typed array
}
I'm writing an application and need some help with consistently storing and loading preferences related to certain resources. Let me give an example.
Suppose I have 10 spinners. They all have the same functionality but different meaning. Because they have the same functionality, I can bind them to the same onItemSelectedListener, which will then deal with the selected value.
Well, what if I also want to store the preferences for each spinner? For example, when a spinner value is selected, I'd store a key "spinner SOMETHING" = SOME_DATA.
The problem is - what should this SOMETHING be? The listener has the following signature:
public void onItemSelected(AdapterView parent, View v, int position, long id)
The position and id are not helpful here as they're set relative to each spinner.
However, the parent, which in this case is the spinner itself, should have all the information I need. I tried using parent.getId() to get a resource ID of each spinner and store the preference using a key "spinner ID" but apparently these resource IDs change when you add more resources into your app, so my settings would get reset because the keys change.
What should I do here? I can't seem to find a simple parent.getName() function of some sort that would return me a consistent name of each spinner.
Thank you.
The getId is the only thing I know of that has a unique reference to the View, but as you say, a view might not have the same Id in the next build of your app.
The best human-readable identifier available out of the box would be getPrompt, which would simply show you whatever you have set as the spinners prompt. It should be an OK identifier, but it is of course also prone to breakage if you manually change your prompt texts.
The most break-proof way, then, is to specify an identifier in the general container - tag - that every View contains.
String myIdentifier = (String) parent.getTag();
If you're already using the tag for something else, the 1.6+ APIs include the ability to specify several tags, and access them via index. If you need to support older API versions, you could always set the tag to a wrapper object that contains both the identifier, and your original tag.