The eClipse only creates one acitivity_main.xml file, but Android studio creates two xml layout files. The default layout for acitivity_main.xml is the CoordinatorLayout but for content_main.xml is RelativeLayout.
Why need two xmls ? The default is to refer activity_main as: setContentView(R.layout.activity_main), but I find setContentView(R.layout.content_main) also works.
What is the relationship between these two layouts ?
Is there any difference If I drop a button view to the content_main.xml or I drop a button view to activity_main.xml ?
Thanks
Why create 2 files :
These 2 files are created to make your work EASIER. As main file contain your stuff like FAB, toolbar in Coordinate layout. Now your content file is file in which you can make UI of view without interrupting the basic flow. I personally recommend this.
Why need two xmls ? The default is to refer activity_main as:
setContentView(R.layout.activity_main), but I find
setContentView(R.layout.content_main) also works.
These will work as after all these are layout files so can set as content view.
Is there any difference If I drop a button view to the content_main.xml or I drop a button view to activity_main.xml ?
No difference at all.
Related
I'm using android studio 4.1.1 and kotlin.
I'm trying to learn programming Android apps using Android Studio and Kotlin. I have a question that a couple of tutorials and searching threads have not answered for me. How does control pass from the MainActivity.kt class to another class, i.e: FirstFragment.kt?
I'm doing fine with other things I'm learning in tutorials, but I cannot figure this out.
Example:
I create a new Basic Activity app in Android Studio with Kotlin. In the java directory, I see these classes: FirstFragment.kt, MainActivity.kt and SecondFragment.kt.
In the res/layout/ directory, I see: activity_main.xml, content_main.xml, fragment_first.xml and fragment_second.xml.
Question 1) When the app loads in an emulator, I see the button and textView from the fragment_first.xml. How does this happen? I cannot see in the code where it says, "load fragment_first.xml".
MainActivity.kt has setContentView(R.layout.activity_main) which loads that layout. activity_main.xml has <include layout="#layout/content_main" />. But from there, I do not know where to find the code that loads the fragment_first.xml layout.
I believe that when fragment_first.xml loads, control passes from MainActivity.kt to FirstFragment.kt, yes? Question 2). Is this because of the onCreate function?
Thanks for helping me to understand this better.
There are multiple ways to load a fragment. Traditionally, you use the FragmentManager to create a Fragment transaction that tells the Activity to place a Fragment into the view hierarchy and start managing its lifecycle.
More recently, they have added the Navigation component, which can be used in place of directly using the FragmentManager.
In the current new project Basic Activity, the layout activity_main.xml includes the layout content_main. In content_main.xml, you'll see that it includes a fragment element that is set to the Fragment (using the name parameter) NavHostFragment, which is a special Fragment that the Navigation component uses to host children fragments that are specified in a navigation XML file. This fragment element also specifies the navigation xml file using the navGraph property. It specifies nav_graph.xml, which you'll find in the res/navigation directory.
If you open nav_graph.xml, you'll see that it has FirstFragment set as the home fragment, so that is what pulls it up as the first fragment that you see.
Basically, the control flow is:
Activity's onCreate() sets content view to activity_main, which includes content_main.
content_main includes a NavHostFragment that is automatically inserted in the view hierarchy so the Activity starts running it.
The NavHostFragment is set in the XML to use nav_graph, which tells it to load FirstFragment first.
Respected Android Programmer,
I am facing the one major problem is that nested scroll view not get disable. Here I am using RecylerView inside the Nested ScrollView.
Actually I am using the so many fragments in one Activity so when default recylerview loaded the listing user the Nested Scrolview now i have to click on floating button i have to hide the that fragment with with trance parent layout or frame layout. Its done but now problem is that when i use all function of recycler like
NestedScrollView mScrollView;
mScrollView.setNestedScrollingEnabled(false);
Not working may i know the reason.
Best
Romesh Chand
I have 4 activities in a single application. Each application can be launched individually. I would like to associate different icons for each activity. I have created the required icons for different resolutions and placed them in the drawable directory. In the AndroidManifest.xml, I have an icon defined for the application using Android:Icon as a default icon. In the activity group I entered the Android:Icon with a different icon. It does not seem to make a difference.
Please provide some guidance
If you want to show different icons in Actionbar, then you can add below given code in your activity's oncreate method..
getActionBar().setIcon(R.drawable.icon);
Per the question here,
What's "tools:context" in Android layout files?
The 'tools' namespace reference (xmlns:tools="http://schemas.android.com/tools") has begun to appear in my layouts recently, and I want to know more. The original post only described the 'tools:context' attribute, but I have also noticed usage of the "tools:listitem" attribute appearing when I have designated a preview layout item for a listview, i.e.
<ListView
android:id="#+id/lvCustomer"
tools:listitem="#layout/customer_list_item" >
</ListView>
Are there more elements?
What brought me to this 'tools' namespace is that I want to be able to have 'preview-only' text (i.e. in a TextView or EditText) when using the layout designer in eclipse.
Currently, I assign the 'text' or 'hint' property for previewing text when arranging my layouts... but then I always have to remember to clear the preview value from within the code.
Ideally, instead of
<string name="preview_customer_name">Billy Bob's Roadhouse Pub</string>
...
<TextView
android:id="#+id/tvCustomerName"
android:text="#string/preview_customer_name"
</TextView>
have a something like:
<TextView
android:id="#+id/tvCustomerName"
tools:previewText="#string/preview_customer_name"
</TextView>
Thanks-
We've just added support for designtime attributes like this in Android Studio 0.2.11. See http://tools.android.com/tips/layout-designtime-attributes for more.
Think of them as design time helpers only.They do not get processed in actual view rendering at run time.
For example you want to set background of some view in your layout design when working on android studio so that you can make clear distinction where that particular view is.So you would normally do that with
android:background="#color/<some-color>"
Now risk is that sometimes we forget to remove that color and it gets shipped in apk.
instead you can do as follows:
tools:background="#color/<some-color>"
These changes will be local to android studio and will never get transferred to apk.
And also check out http://tools.android.com/tech-docs/tools-attributes for more options.
You will find tool attribute when you set object in graphical layout.
Listview (in graphical mode) -> right Click -> Preview List Content -> Choose Layout...
produces:
tools:listitem="#layout/customer_list_item"
See in layout XML below. There are 2 namespace in use "xmlns:android" and "xmlns:tools".
Tools namespace is used when the developer wants to define placeholder content that is only used in preview or in design time. Tools namespace is removed when we compiled the app.
So in the code below, I want to show the placeholder image (image_empty) that will only be visible at design time, and image1 will the actual image that will be shown when the application launch
I'm new to android development and needs help here.I want to create a layout where buttons are added dynamically.In this the no of buttons to be added are decided on the fly.(at run time) i.e depending upon the number return by server i want to add buttons.below is the layout i want to create.Please suggest me suitable solution.I was trying creating this layout with table layout.Thank You
http://i.stack.imgur.com/tbrEq.jpg
Read in your array of buttons and initialize your empty layout (i.e. setContentView). Then, create your buttons using the ImageButton constructor and call .addView(btn) from the layout where you want to insert the button. Don't forget to set any layout parameters you need.