Develop Reference

Why don't I get an error when I reference a id that hasn't been flagged with "#+id"?

I'm referencing #id/action_profile before assigning #+id/action_profile. Why doesn't this give me an error? Is it because the ids are assigned in R.java and the attributes are assigned at runtime?
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:id="#+id/search"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toLeftOf="#id/action_profile"/>
<LinearLayout
android:id="#+id/action_profile"
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true">
<ImageView android:id="#+id/profile_icon"
android:layout_height="25dp"
android:layout_width="25dp"/>
<TextView android:id="#+id/profile_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>
</RelativeLayout>

In order to talk about this topic, we need to have a solid foundation of understanding about what the android:id and android:layout_toLeftOf attributes (and any other attribute that expects an id resource) actually "do".
They only set int fields on their View (or their View's LayoutParams object).
These int fields can then later be used to specify behavior, but as far as the <TextView> tag is concerned, all that android:layout_toLeftOf="#id/action_profile" means is "store R.id.action_profile as the id of the view I should position myself to the left of". There is no top-down parsing of the text file to look for whether or not a view tag with that id was already previously declared. The TextView is just saving an int for later.
In fact, taking it to an extreme, the following is perfectly legal:
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#id/some_other_id"
android:text="hello world"/>
</RelativeLayout>
There's nothing in this layout with the id some_other_id, so how could my TextView be below it? Well, if you run this app, it just positions itself at the top-left, because it couldn't find the view I was referring to.
The reason this compiles is that I have a different layout file in my project:
<TextView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/some_other_id"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="I'm hiding!"/>
This layout file isn't used in my activity. It has nothing to do with the first example at all. But all that matters is that it has #+id/some_other_id in it. This causes R.id.some_other_id to be created, and then my first layout is quite happy to use it.

New resource id declaration without the plus sign

This documentation always puzzles me:
For the ID value, you should usually use this syntax form:
"#+id/name". The plus symbol, +, indicates that this is a new resource
ID and the aapt tool will create a new resource integer in the R.java
class, if it doesn't already exist. For example:
<TextView android:id="#+id/nameTextbox"/>
I've been programming for quite a while now. However, I've never encountered any case wherein I have to use the ID declaration without the plus sign. It is also counter-intuitive. IDs are supposed to be unique!
Any good use-case for this? Why would one want to re-use the same resource id name?

#+id/name When you create a new id
"#id/" When you link to existing id
Use-case example 1:
Let's say you created your own resource in XML:
<resources>
<item name="plusIcon" type="id"/>
</resources>
Now you can use this resource at multiple places without creating a new resource using #+id. Say layout_one.xml:
<TextView android:id="#id/plusIcon"/>
Same resource in layout_two.xml:
<TextView android:id="#id/plusIcon"/>
Use-case example 2:
There are a number of other ID resources that are offered by the Android framework. If you want to referencing an Android resource ID in that case you can use #android you don't need to create your own new resource ID

It means if you have declared a view in a layout_one.xml like
<TextView
android:text="Sample Text"
android:id="#+id/text_view_sample"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
And if you have similar textView into layout_two.xml like
<TextView
android:text="Sample Text2"
android:id="#+id/text_view_sample"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
In both cases there will be only one id created into R.java and it will be reused into another xml (whichever will be called after).
SO here you can live with (in layout_two.xml)
<TextView
android:text="Sample Text2"
android:id="#id/text_view_sample"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
here Android will reuse id as it was created before from layout_one.xml.
You should also read Difference between "#id/" and "#+id/" in Android and What is the difference between #id and #+id?

Firstly
we use + when we're referencing a id for the first time(in top to down order) in a particular xml file, not when we create some id for the first time.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="#+id/another_button"
android:layout_alignParentTop="true"
android:text="#string/button" />
<Button
android:id="#id/another_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:text="#string/another_button" />
</RelativeLayout>
Secondly
when someone is working with RelativeLayout or ConstraintLayout i.e. some relative parent view they need to use same id multiple times in order to define the activity or some view in the activity etc.
Thirdly
The plus-symbol (+) means that this is a new resource name that must be created and added to our resources (in the R.java file).
So every time we use #+id/some_id, it triggers the creation of a new resource reference to the same view, i.e., redundant.
Example(for the second use case)
<RelativeLayout
android:id="#+id/final_order_activity_order_rl"
android:layout_margin="5dp"
android:background="#drawable/gradient_for_btns"
android:paddingBottom="8dp"
android:paddingTop="8dp"
android:paddingStart="4dp"
android:paddingEnd="4dp"
android:layout_alignParentBottom="true"
android:gravity="center"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:layout_centerInParent="true"
android:layout_marginStart="8dp"
android:textStyle="bold"
android:textSize="18dp"
android:text="$2000"
android:textColor="#android:color/white"
android:maxLines="1"
android:layout_toLeftOf="#+id/final_order_activity_place_order_btn"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/final_order_activity_total_tv" />
<Button
android:paddingStart="6dp"
android:paddingEnd="6dp"
android:layout_marginEnd="8dp"
android:text="Place Order"
android:background="#drawable/ripple_effect"
android:textColor="#color/baseColorBright"
android:layout_alignParentEnd="true"
android:layout_width="wrap_content"
android:layout_height="28dp"
android:id="#id/final_order_activity_place_order_btn"/>
</RelativeLayout>

Defining the constraints within a RelativeLayout might be a good example.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:text="Top"/>
<TextView
android:id="#+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:text="Bottom"/>
<TextView
android:id="#+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#id/textView3"
android:layout_below="#id/textView1"
android:text="Center"/>
</RelativeLayout>
On the last TextView android:layout_above and android:layout_below don't require the plus symbol because textView1 and textView2 are already defined IDs.

Layout XML View IDs and R problems

I am creating a layout in XML, and I have noticed this very strange occurrence. It has never happened before, but lately it's been getting on my nerves. I kind of want to abandon Eclipse and find a better IDE because of it.
Here is my layout:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<EditText
android:id="#+id/action_search_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10"
android:hint="kkm" >
</EditText>
<ListView
android:id="#+id/actions_list"
android:layout_width="90dp"
android:layout_height="match_parent"
android:layout_above="#id/cancel_action_selection"
android:layout_below="#id/action_search_bar" >
</ListView>
<TextView
android:id="#+id/action_preview_pane"
android:layout_width="230dp"
android:layout_height="match_parent"
android:layout_alignBottom="#id/actions_list"
android:layout_alignTop="#id/actions_list"
android:layout_toRightOf="#id/actions_list"
android:gravity="center_vertical|center_horizontal"
android:text="kk" />
<Button
android:id="#+id/cancel_action_selection"
android:layout_width="wrap_content"
android:layout_height="48dp"
android:layout_alignParentBottom="true"
android:text="Cancel" />
<Button
android:id="#+id/define_new_action"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_toRightOf="#id/cancel_action_selection"
android:text="NEW" />
<Button
android:id="#+id/select_action"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_toRightOf="#id/define_new_action"
android:text="OK" />
</RelativeLayout>
Here is what I'm trying to achieve:
The problem is, if I try to set the ListView to be above the cancel button (via android:layout_above), it will say that it can't find the id for the cancel button.
Now, what I have noticed is that if I try and specify any ids for layouts BEFORE they are created with #+id, then I will get that strange error. What I mean by this is the following:
In the XML, apparently IDs have to be declared in order. Strange, no?
I would have to declare the cancel button's id first with #+id way before I define the ListView and set its layout_above attribute.
If I try to do what I have done here, it will say that it cannot find the id for the cancel button.
I have tried cleaning the project, ending adb.exe, refreshing, etc. and all it does is corrupt my project even more. R is not even generated afterwards. I don't want to have to go in a loop problem after problem because Eclipse can't handle things like this properly.
Does anyone have a solution for this? Or a better IDE?

http://developer.android.com/guide/topics/ui/layout/relative.html
RelativeLayout lets child views specify their position relative to the parent view or to each other (specified by ID). So you can align two elements by right border, or make one below another, centered in the screen, centered left, and so on.
So you are placing listview relative to the button cancel. So you need to define button with a id. Position the listview relative to the button.
http://developer.android.com/guide/topics/ui/layout/linear.html
There is an example in the links posted both for linearlayout and relative layout have a look at it.
Edit:
If you have errors in your resource files R.java will not be generated. So make sure you do not have errors in your resource files and then clean and build the project.
To clarify the confusion. Note android:layout_above="#+id/button1"
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".OtherScreenActivity1" >
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="24dp"
android:text="Button" />
<ListView
android:id="#+id/listView1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="#+id/button1"
>
</ListView>
</RelativeLayout>
Same as above
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".OtherScreenActivity1" >
<ListView
android:id="#+id/listView1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="#+id/button1"
android:layout_alignParentTop="true" >
</ListView>
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="24dp"
android:text="Button" />
</RelativeLayout>
You have this
android:layout_above="#id/cancel_action_selection"
Use
android:layout_above="#+id/cancel_action_selection"
http://developer.android.com/guide/topics/ui/declaring-layout.html.
Look at the attribute id in the above link

TextView overlap in ListView implementation android with 2 textviews

I am implementing listview with 2 textviews , and for reference used Basic Layout and Formatting
Instead of stock names which are short i am using long text, so when i use a long text, it overlaps with the second .
So how to get it right, so that the 2 textviews don't overlap each other.

You can used following code to solve your problem:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:weightSum="1">
<TextView
android:layout_width="0dp"
android:layout_height="fill_parent"
android:id="#+id/ticker_symbol"
android:text="sdasd sadas"
android:layout_weight=".5"/>
<TextView
android:layout_width="0dp"
android:layout_height="fill_parent"
android:id="#+id/ticker_price"
android:text="dfsd"
android:layout_weight=".5"
android:gravity="right" />
</LinearLayout>
Output:

To avoid overlapping, you could set the second textview to align to right (android:layout_toRightOf).
For example:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:id="#+id/ticker_symbol"
android:layout_alignParentLeft="true" />
<TextView
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:id="#+id/ticker_price"
android:layout_toRightOf="#id/ticker_symbol"
android:layout_alignParentRight="true" />
</RelativeLayout>

I guess you mean due to long length of text it goes to next line or on next TextView
So i suggest you to use textView property android:ellipsized="end" and also use android:single_line="true" instead this you can directly specify the maxline=1
I'm not sure with names spelled correctly so check while typing
<TextView
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:id="#+id/ticker_symbol"
android:ellipsezed="end"
android:singe_line="true"
android:layout_alignParentLeft="true" />
Hope this explanation woks for you let me know..

RelativeLayout textviews overlapping

I have a rather simple ListView row:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:id="#+id/tournament_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:textSize="25dp" />
<TextView
android:id="#+id/tournament_winner"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:textSize="25dp" />
</RelativeLayout>
When the text of "#+id/tournament_name"is long - it overlaps with the one from "#+id/tournament_winner" and I don't understand why.
I tried using android:singleLine="false"to no avail. I also tried using android:inputType="textMultiLine"as the docu says android:singleLine="false" is deprecated but then I get the warning: Attribute android:inputType should not be used with <TextView>: Change element type to
<EditText> ? so no good here as well.
I also tried using android:ellipsize="end" but this doesn't work. I assume it is because the text in the left TextView ("#+id/tournament_name") is NOT long enough to fill up the full width of the ListView (which code is not sowing here).
I was sure that if I use android:layout_width="wrap_content"the two TextView fields shouldn't overlap.
Here is an example (see the second line):
Any further ideas how this could be fixed?

android:layout_toLeftOf="#id/tournament_winner" in First TextView.
Also set android:maxLines="1" and Fix width for tournament winner because when it gets long tournament name cant see...
row.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:id="#+id/tournament_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_toLeftOf="#id/tournament_winner"
android:maxLines="1"
android:text="NAMEEEEEEEEEEEEEEEEEEEEEEEEEEE"
android:textSize="25dp" />
<TextView
android:id="#+id/tournament_winner"
android:layout_width="wrap_content" android:layout_marginLeft="10dp"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:text="WINER"
android:textSize="25dp" />
</RelativeLayout>

Thank you very much for your answer - sorry it took me some time to respond. I ended up using your android:layout_toLeftOf="#+id/tournament_winner" but left the single line and the margin to the left unused, as the result seemed perfect to me (hope this is also the case for other devices).
One thing though - in the first text view (tournament_name) I had to use android:layout_toLeftOf="#+id/tournament_winner"and not android:layout_toLeftOf="#id/tournament_winner" - pay attention to the added +. For some reason I get an error using android:layout_toLeftOf="#id/tournament_winner": Error: No resource found that matches the given name... so it seems that it is possible and NEEDED to define the resource in the time of calling it because the system doesn't know it before it was defined.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:id="#+id/tournament_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toLeftOf="#+id/tournament_winner"
android:layout_alignParentLeft="true"
android:textSize="25dp" />
<TextView
android:id="#+id/tournament_winner"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:textSize="25dp" />
</RelativeLayout>

You can use single text view in place of two and simply display both strings in one text view !!