Develop Reference

Android - FrameLayout with a custom view requiring a constructor

What I am attempting to do is take a custom view (which is a constructor & onDraw method) and a set of controls in a RelativeLayout and display them together with-in a FrameLayout. My code currently gets to adding the overlay and crashes with a Null Pointer Execption but if I directly add the overlay and cut out the FrameLayout & custom view it works.
FrameLayout layout = new FrameLayout(this);
SampleView sv = new SampleView(this, objectA, objectB, ObjectC), RESULTS);
RelativeLayout overlay = (RelativeLayout) findViewById(R.layout.analysis_overlay);
layout.addView(sv);
layout.addView(overlay);
setContentView(layout);
I assume there is a better way to do this and I've seen examples of a FrameLayout existing in xml but I didn't see anyway of setting the constructor via that method... So is there a better way of doing this that still allows custom view to have a constructor or did I mess somthing up with my current code?

You are attempting to find an id of a layout resource. Instead, inflate your relative layout (the layout resource) and then add it.
FrameLayout layout = new FrameLayout(this);
SampleView sv = new SampleView(this, objectA, objectB, ObjectC), RESULTS);
RelativeLayout overlay = (RelativeLayout) LayoutInflater.from(this).inflate(R.layout.analysis_overlay, layout, false);
layout.addView(sv);
layout.addView(overlay);
setContentView(layout);

RelativeLayout overlay = (RelativeLayout) findViewById(R.layout.analysis_overlay);
You can never find anything with id from R.layout. Use R.id.
You can never find anything before setContentView() when using Activity findViewById().
Call findViewById() on a view hierarchy that actually contains the overlay you want to find.
If you just want to inflate an XML layout, use LayoutInflater.

drawing multiple layouts inside a view

I have a view/layout that I need to render multiple times on a canvas. Call it stats. So I create a stats.xml file and lay out my views in it. Then in the .java file, I inflate the layout and edit the appropriate child views of stats. At this point how do I add the view to my canvas at a specific location? Actually I already tried but my view is NOT showing. Here is the code:
LayoutInflater mInflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
RelativeLayout parentView = (RelativeLayout) mInflater.inflate(R.layout.stats, null, false);
addDateToTextView(date, (TextView) parentView.findViewById(R.id.timestamp));
parentView.setX(50);
parentView.setY(yOffset);
parentView.draw(canvas);
I am using the canvas from onDraw

So I find a crappy solution. I have to call layout and .draw(canvas) on every child view. I am convinced there must be a more sensible solution.

How to inflate another view from another view in Android

I know in my onCreate() I can inflate a view from XML by something like:
loadingScreen = (RelativeLayout) findViewById(R.id.loadingScreen);
But how could I do this from another view? Im trying to call up a loading screen by setting its visibility from GONE to VISIBLE but cant seem to figure out how to do this from my glSurfaceView

If you want to inflate a layout the code looks like this:
LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
LinearLayout myRoot = new LinearLayout(context);
View itemView = inflater.inflate(R.layout.layout_details, myRoot);
Here you first create a new LinearLayout an then inflate the layout with id R.layout.layout_details into it. The inflate method then returns the myRoot view.
Here is a tutorial about the LayoutInflater:
Layout resources in Android

Thats actually not inflating. Inflating is the process that parses a XML layout file and creates a structure of View and ViewGroup class instances out of it (setContentView() does this for you in the background for example).
What you do is getting a reference to a view in code that you have defined in your XML layout file. To change the visibility of your GLSurfaceView you have to reference it like you did above. But remember that the View (GLSurfaceView in this case) has to be defined in your layout file.
After referencing you have to call GLSurfaceView.setVisibility() to change it's visibility.
Here's an example:
GLSurfaceView glsurface = (GLSurfaceView) findViewById(R.id.myglsurfaceid);
glsurface.setVisibility(View.VISIBLE);
Of course you can use View.INVISIBLE or View.GONE either, depending on what you want to do.
If you reference a layout (such as a RelativeLayout), you may find children of this layout with the findViewById() of your RelativeLayout instance:
RelativeLayour rl = (RelativeLayout) findViewById(R.id.mylayout);
(Button) mybutton = (Button) rl.findViewById(R.id.mybutton);
But thats usually not neccessary (at least when you just started with Android) because the activities findViewById() finds all Views that are displayed, even in sublayouts. You only have to use it if you have duplicate ids in your ui structure (tbh I never had that case yet) and want to specifiy where to look for your particular View.

You can't get a reference to a View that's doesn't exists in your current Layout, or your current View, (your current Activity content) , but you can create a new View from another XML layout, using LayoutInflater from current Activity.
you can add to you current Activity content, a new View, that's what you mentioned as " loading screen ", even by showing it as a Dialog or by creating View and then add it to root layout in your Activity
I hope I helped you

If I correctly understood what you wanna do:
Supposing you have a glSurfaceView object and you wanna grab a view that's inside that one.
You'll do just the same thing you did for you normal view. Let's say a button:
Button button = (Button) glSurfaceView.findViewById(R.id.buttonid);
If you meant something different let me know in the comments.
EDIT: And then you can just set the button's visibility:
button.setVisibility(Button.GONE)

add layout as a view in Android

I have a pretty complex layout defined in xml file , now I want to add this layout as a view using addView or something else.
As layout is pretty much complex , its pretty cumbersome process to write the code for layout and then add it as a view. So is there anyway to load layout resource and add it as a view.
I want to add the layout into WebView

Use
LayoutInflater factory = LayoutInflater.from(this);
View myView = factory.inflate(R.layout.my_layout_id, null);
then use addView(myView)

You can also reduce this to one line of code;
View view = View.inflate(getActivity, R.layout.my_layout,null);
then add to your view.

If your view is a ViewGroup (layout)
You can use InflaterService.inflate(id, ViewGroup) and set the ViewGroup, it will set the current child(s) with the content of your xml.

How to Programmatically Add Views to Views

Let's say I have a LinearLayout, and I want to add a View to it, in my program from the Java code. What method is used for this? I'm not asking how it's done in XML, which I do know, but rather, how can I do something along the lines of this sample code?
(One View).add(Another View)
Like one can do in Swing.

Calling addView is the correct answer, but you need to do a little more than that to get it to work.
If you create a View via a constructor (e.g., Button myButton = new Button();), you'll need to call setLayoutParams on the newly constructed view, passing in an instance of the parent view's LayoutParams inner class, before you add your newly constructed child to the parent view.
For example, you might have the following code in your onCreate() function assuming your LinearLayout has id R.id.main:
LinearLayout myLayout = findViewById(R.id.main);
Button myButton = new Button(this);
myButton.setLayoutParams(new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.MATCH_PARENT));
myLayout.addView(myButton);
Making sure to set the LayoutParams is important. Every view needs at least a layout_width and a layout_height parameter. Also getting the right inner class is important. I struggled with getting Views added to a TableRow to display properly until I figured out that I wasn't passing an instance of TableRow.LayoutParams to the child view's setLayoutParams.

The best way I found is to use the inflate static method of View.
View inflatedView = View.inflate(context, yourViewXML, yourLinearLayout);
where yourViewXML is something like R.layout.myView
please notice that you need a ViewGroup in order to add a view (which is any layout you can think of)
so as an example lets say you have a fragment which it view already been inflated and you know that the root view is a layout, and you want to add a view to it:
View view = getView(); // returns base view of the fragment
if (view == null)
return;
if (!(view instanceof ViewGroup))
return;
ViewGroup viewGroup = (ViewGroup) view;
View popup = View.inflate(viewGroup.getContext(), R.layout.someView, viewGroup);
EDIT:
Kotlin code for the example above (view is the getView() of a fragment)
(view as? ViewGroup)?.let {
View.inflate(context, R.layout.add_credit_card, it)
}

To add the view programmatically, you can do:
LinearLayout rlmain = new LinearLayout(this);
LinearLayout.LayoutParams llp = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.FILL_PARENT,LinearLayout.LayoutParams.FILL_PARENT);
LinearLayout ll1 = new LinearLayout (this);
ImageView iv = new ImageView(this);
iv.setImageResource(R.drawable.logo);
LinearLayout .LayoutParams lp = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT);
iv.setLayoutParams(lp);
ll1.addView(iv);
rlmain.addView(ll1);
setContentView(rlmain, llp);
You can also add any number of views.

LinearLayout is a subclass of ViewGroup, which has a method called addView. The addView method should be what you are after.

The idea of programmatically setting constraints can be tiresome. This solution below will work for any layout whether constraint, linear, etc. Best way would be to set a placeholder i.e. a FrameLayout with proper constraints (or proper placing in other layout such as linear) at position where you would expect the programmatically created view to have.
All you need to do is inflate the view programmatically and it as a child to the FrameLayout by using addChild() method. Then during runtime your view would be inflated and placed in right position. Per Android recommendation, you should add only one childView to FrameLayout [link].
Here is what your code would look like, supposing you wish to create TextView programmatically at a particular position:
Step 1:
In your layout which would contain the view to be inflated, place a FrameLayout at the correct position and give it an id, say, "container".
Step 2
Create a layout with root element as the view you want to inflate during runtime, call the layout file as "textview.xml" :
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent">
</TextView>
BTW, set the layout-params of your frameLayout to wrap_content always else the frame layout will become as big as the parent i.e. the activity i.e the phone screen.
android:layout_width="wrap_content"
android:layout_height="wrap_content"
If not set, because a child view of the frame, by default, goes to left-top of the frame layout, hence your view will simply fly to left top of the screen.
Step 3
In your onCreate method, do this :
FrameLayout frameLayout = findViewById(R.id.container);
TextView textView = (TextView) View.inflate(this, R.layout.textview, null);
frameLayout.addView(textView);
(Note that setting last parameter of findViewById to null and adding view by calling addView() on container view (frameLayout) is same as simply attaching the inflated view by passing true in 3rd parameter of findViewById(). For more, see this.)

One more way to add view from Activity
ViewGroup rootLayout = findViewById(android.R.id.content);
rootLayout.addView(view);

You guys should also make sure that when you override onLayout you HAVE to call super.onLayout with all of the properties, or the view will not be inflated!