So I'm trying to decide whether it would be worth it to refactor out my current use of id's in all of my android layouts to an ids.xml file, or to just leave my view code the way it is (with multiple views sharing ids and both views using "#+id/id_name).
Is there a significant compile/runtime performance benefit to refactoring out the ids to the ids.xml file? How about if the application gets bigger?
Related resources:
http://developer.android.com/guide/topics/resources/more-resources.html#Id
Thank you for your time.
I used <item type="id"> resources in my app because I have TextEdit views that serve a similar purpose in more than one Activity.
ids.xml has the following advantage: all ids were declared, so compiler can recognize them. If something like this:
<TextView
android:id="#+id/text1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignBelow="#id/text2"
android:text="...."/>
<TextView
android:id="#+id/text2"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="...."/>
Can result in compiling error because text2 was refered before declared
Related
How do I reference a later XML element?
Here's a specific use case. Let's say I have a form with a root LinearLayout, containing LinearLayouts for multiple rows, each row having one or more text input areas.
Here's a visual of what I'm going for. First pic is from Venmo's app, second is a rendering of the following XML.
Such a layout could look like this:
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<LinearLayout
android:id="#+id/row_card_number"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<EditText
android:id="#+id/card_number"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:nextFocusDown="#id/month"/>
</LinearLayout>
<LinearLayout
android:id="#+id/row_date"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<EditText
android:id="#+id/month"
android:layout_height="wrap_content"
android:layout_width="100dp"
android:nextFocusDown="#id/year"/>
<EditText
android:id="#+id/year"
android:layout_height="wrap_content"
android:layout_width="match_parent"/>
</LinearLayout>
</LinearLayout>
In this use case, forward referencing is necassary in order to set the next focus element. That way, when you press the next button on the keyboard, it'll go to the correct view. In this sample xml, without the nextFocusDowns, pressing next would go from name to month, and never go to year.
However, if you try to compile this, you'll get an error:
Error:(18, 36) No resource found that matches the given name (at 'nextFocusDown' with value '#id/month').
This is because the id month hasn't yet been initialized when I'm trying to reference it, since that's later in the file. How can I reference an id in xml that appears later in the file?
The simplest solution is just to replace
android:nextFocusDown="#id/month"
with
android:nextFocusDown="#+id/month"
When the compiler is parsing your XML to add the id's to R.java, it just reads top to bottom. When you have #id/month, it searches through the existing id's, and fails to find it.
However, if you do #+id/month, it creates a new id, and links to that. When it gets to android:id=#+id/month in the actual month view, it links it to the same id that we already created.
This brings up the question: If you can replace #id/ with #+id/, and #+id/ will work regardless of the order of elements, why even bother to use #id/?
The reason for this is if the id doesn't exist, #id/ will throw a compiler error, while #+id/ will log a warning at runtime.
Consider this XML:
<EditText
android:id="#+id/month"
android:layout_height="wrap_content"
android:layout_width="100dp"
android:nextFocusDown="#+id/SOME_RANDOM_ID"/>
<EditText
android:id="#+id/year"
android:layout_height="wrap_content"
android:layout_width="match_parent"/>
When this is parsed, a new id element SOME_RANDOM_ID is created. However, when Android tries to apply it at runtime, it can't find an element with that id. If you look at Logcat, you'll see this:
W/View﹕ couldn't find view with id 2131689604
This log message is both hard to find and hard to debug. One small typo in a #+id/ and you'll have a bug that could be incredibly difficult to debug. However, if we had done:
android:nextFocusDown="#id/SOME_RANDOM_ID"
Then we'd get a compiler error, something like:
Error:(18, 36) No resource found that matches the given name (at 'nextFocusDown' with value '#id/SOME_RANDOM_ID').
This is much easier to find and debug.
tl;dr: You can use #+id/ instead of #id/ and you'll be able to forward reference, but note that that can make small typos incredibly difficult to debug.
You might be able to use a RelativeLayout to make all the Views exist in reverse order in the xml, but that seems like overkill to me.
I had the same issue recently and I used #+id/my_new_id the first time I referenced the element and later in the XML in the element definition, I assigned #id/my_new_id to the android:id attribute. It seems it works fine and it's not necessary write #+id with the same id more than one time avoiding possible warnings.
For example:
<LinearLayout
...
android:layout_toLeftOf="#+id/my_new_id"
... >
...
</LinearLayout>
<ImageButton
android:id="#id/my_new_id"
... />
I have many lists in my android app. I'm using strings as samples (android:text) for the layout preview.
Example:
<TextView
android:id="#+id/firstname"
android:layout_width="0dp"
style="#style/TextListStyle"
android:text="Peter"/>
Android studio is marking this as a warning but I don't want to put every sample string into the strings.xml file.
What is the best way to deal with this?
If you want it just for preview consider this:
tools:text="John Doe"
More Infos on Designtime Layout Attributes.
Add tools:ignore="HardcodedText" in your root layout, like:
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
tools:ignore="HardcodedText" >
However this is quite bad practice, for the reasons stated here:
Hardcoding text attributes directly in layout files is bad for several
reasons:
When creating configuration variations (for example for landscape or
portrait) you have to repeat the actual text (and keep it up to date when
making changes)
The application cannot be translated to other languages by just adding new
translations for existing string resources.
hi have problem when i view graphical.layout of this file
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical" >
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/hello_world" />
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="this is main text" />
</LinearLayout>
when i view graphical layout of this view this xml file then this warning show
[I18N] Hardcoded string "this is main text", should use #string resource
but i dont want to declare string valiable i want to show this "this is main text" without declaring string
The warning about 'should use #string resource' is just a reminder that locale-specific information should be placed in 'resource bundles' (eg /res/values/strings.xml) so that labels and other text can be provided in different languages without having to re-code and recompile the entire application for each language.
If you're just testing things out, you can safely ignore that warning, but it's a good idea to get in the habit of referencing strings as resources in external files rather than hardcoding them directly in the application itself.
It is not good practice to hard code strings into your layout files. You should add them to a string resource file and then reference them from your layout.
refer this answer and this one also.
You must declare your text using `#string` resource that
is a good programming format.You should prefer using
`string.xml` in value folder in res folder if you want
to use texts.
If you want to suppress the specific warning use
tools:ignore="HardcodedText"
more details
http://tools.android.com/recent/ignoringlintwarnings
I have a simple linear layout that I would like to change based on the screen size of the device. What I am trying to do is something like
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="#string/cover_orientation"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
I have created different dimen.xml files under values and values-xlarge so that the cover_orientation variable will take on a different value (either 'vertical' or 'horizontal') based on the screen size.
string name="cover_orientation">"vertical"
But this doesn't work. I have found a temporary work around that involves checking the screen size and changing the orientation manually:
if(getResources().getString(R.string.screen_size) == "xlarge"){
((LinearLayout)convertView).setOrientation(1);
}
but it seems like you should be able to do it the first way (much more elegant/less code).
I considered just having a different layout for each screen size, but the layout is actually quite big and this is the only change I need for the different screen sizes. So it didn't make much sense to me to duplicate the entire layout.
Thanks!
A nice way to do this is to add
android:orientation="#integer/cover_orientation"
on your LinearLayout and defining it like below.
in values/consts.xml:
<resources>
<integer name="orientation_horizontal">0</integer>
<integer name="orientation_vertical">1</integer>
</resources>
in values/something.xml:
<resources>
<integer name="cover_orientation">#integer/orientation_vertical</integer>
</resources>
in values-land/something.xml:
<resources>
<integer name="cover_orientation">#integer/orientation_horizontal</integer>
</resources>
This way you avoid hardcoding zeros and ones in your orientation variable definitions across the app.
I eventually found a solution to the problem by looking around the android docs. What I originally had was a LinearLayout, that contained an image an text inside of it (there was actually a lot more content inside of it but I'll keep it simple for this example), that looked something like this:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<ImageView android:id="#+id/cover"
android:layout_width="#dimen/cover_width"
android:layout_height="#dimen/cover_height"/>
<TextView android:id="#+id/title"
android:gravity="top"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#000000"
android:textSize="#dimen/title_font_size"
android:scrollHorizontally="true"
android:maxLines="1"
android:ellipsize="end" />
</LinearLayout>
What I wanted was to be able to dynamically change whether the text was beside the image or below the image, based on the device screen size. In other words i wanted to dynamically change the android:orientation dynamically. My first thought, which I posted in my question, was to have a string variable declared in the res/values/dimen.xml as
<string name="orientation">horizontal</string>
and another string variable declared in res/values-large/dimen.xml as
<string name="orientation">vertical</string>
Then when I was setting the orientation in the LinearLayout I thought I could use
android:orientation="#string/orientation"
But this didn't work. What I ended up doing was splitting the layout up. I originally had reservations about having two separate layouts because I thought I would have a lot of duplicated code for one simple change. That was before I learned about include and merge. First I created a common layout file that was the image and text in res/layout/content.xml that looked like:
<merge xmlns:android="http://schemas.android.com/apk/res/android" >
<ImageView android:id="#+id/cover"
android:layout_width="#dimen/cover_width"
android:layout_height="#dimen/cover_height"/>
<TextView android:id="#+id/title"
android:gravity="top"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#000000"
android:textSize="#dimen/title_font_size"
android:scrollHorizontally="true"
android:maxLines="1"
android:ellipsize="end" />
</merge>
(Sidenote: I was originally confused at what the merge tag did. It is not merging what is inside the merge tag (in this example the image and the text) it is basically saying whatever parent file includes this file, merge the contents in between the tags into the parent file)
Then I created two separate files for just the LinearLayout that included the image and description xml file. One in res/layout/container.xml:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/library_item_container"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<include layout="#layout/content"/>
</LinearLayout>
and one in res/layout-large/container.xml:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/library_item_container"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<include layout="#layout/library_item_contents"/>
</LinearLayout>
Notice the only difference between the two container.xml files is that the orientation has changed from vertical to horizontal. Now there is minimal code that is repeated and problem is solved!
#odiggity, thank you for posting this question. I was trying the same. Application crashed upon starting.
I would assume that it's a runtime typing issue. In other words, there are only two legal values for the orientation attribute, which is not reflected by the string "type". What the framework would probably have to do is introduce another specialized resource type, similar to dimen or boolean.
I feel there is an answer to your question which addresses more cases than your own answer above. One can use style inheritance to define all attributes except orientation in an orientation-independent parent style and then add only the orientation in a small orientation-dependent style definition with that as a parent.
This way, one can avoid duplication even in complex cases.
I suggest you do some reading: http://developer.android.com/guide/practices/screens_support.html
I'm working on a couple of apps at the moment while I try to learn my way around the Android SDK. I had a bit of trouble recently with my layouts where I was defining, for example, an EditText element as such...
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<EditText
android:id="#+id/price_per_pack"
android:layout_width="100dip"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toLeftOf="#id/price_per_pack"
android:layout_alignParentLeft="true"
android:textSize="12pt"
android:text="Price Per Pack"/>
</LinearLayout>
The application was compiling correctly, however when I attempted to start the activity which utilizes this layout nothing would happen. Through a process of elimination I identified the id attribute as the troublesome one and while playing about I discovered that changing
android:id="#+id/price_per_pack"
to
android:id="#+android:id/price_per_pack"
solved my problem and the application behaved as expected. My initial attempt at declaring the id attribute was based upon examples in the SDK documentation so I'm wondering if somebody could explain to me why I needed to make the above change to get it working?
I'm sure that it won't make any difference but I'm developing using the android-mode.el emacs plugin and have a completely up-to-date copy of the SDK.
Thanks in advance.
From Android Documentation:
With the android package namespace in place, we're now referencing an ID from the android.R resources class, rather than the local resources class.
It looks like you might have some syntax errors in your code posted.