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Adding a view to a constraint layout through code

so my screen has an image view which I dragged down the screen with animation using this code:
float bottomOfScreen = context.getResources().getDisplayMetrics()
.heightPixels - (myImageView.getHeight() * 2);
myImageView.animate()
.translationY(bottomOfScreen)
.setDuration(durationOfFalling);
so basically, I had an image and it was dragged down and out of the screen and now my image has disappeared but I need it to come back to the same place that it was before I dragged it down (at the top of the screen) so I can drag it down again whenever I want. Do you have any solutions as to how I can make the image appear again at the top of the screen so I can re-use it?
I also tried adding it through ConstraintLayout and then constraintLayout.addView(myImageView) like that (and probably did it wrong):
ConstraintLayout ly = findViewById(R.id.ly);
noteiv1.setLayoutParams(new ConstraintLayout.LayoutParams(ConstraintLayout.LayoutParams.WRAP_CONTENT, ConstraintLayout.LayoutParams.WRAP_CONTENT));
noteiv1.setId(View.generateViewId());
ly.addView(noteiv1);
ConstraintSet set = new ConstraintSet();
set.clone(ly);
set.connect(noteiv1.getId(), ConstraintSet.LEFT, ly.getId(), ConstraintSet.LEFT);
set.connect(noteiv1.getId(), ConstraintSet.RIGHT, ly.getId(), ConstraintSet.RIGHT);
set.connect(noteiv1.getId(), ConstraintSet.TOP, ly.getId(), ConstraintSet.TOP);
set.connect(noteiv1.getId(), ConstraintSet.BOTTOM, ly.getId(), ConstraintSet.BOTTOM);
set.applyTo(ly);
*noteiv1 is the image view I need to re-use
I'd be glad for some help :)

This has already been asked and answered.
Here's an answer from there.
I think you should clone the layout after adding your ImageView.
ConstraintLayout parentLayout = (ConstraintLayout)findViewById(R.id.mainConstraint);
ConstraintSet set = new ConstraintSet();
ImageView childView = new ImageView(this);
// set view id, else getId() returns -1
childView.setId(View.generateViewId());
layout.addView(childView, 0);
set.clone(parentLayout);
// connect start and end point of views, in this case top of child to top of parent.
set.connect(childView.getId(), ConstraintSet.TOP, parentLayout.getId(), ConstraintSet.TOP, 60);
// ... similarly add other constraints
set.applyTo(parentLayout);

LayoutParams won't properly put ImageViews next to each other

Currently, I'm trying to make an infinitely long chain of ImageViews that are all next to each other.
I attempt to do this by using addRule and LayoutParam so that every new ImageView has to be set to the right of the ImageView before it.
However, I encounter an odd problem. When I do run my code, this is the result :
Not only are my two ImageViews not even next to each other, it doesn't work for any number past two! If I just create two blocks, it gives the result below.
If I make any more blocks than 2, they'll just stack on top of block #2. Which is what happens in the image above.
Also, I have to set every ImageView with its own ID because if I don't, they'll all have an ID of -1.
I've been stuck on this for like 5 hours in a row, and it's really starting to get annoying. (Please do not suggest that I use a LinearLayout. I already know, and I can't use it.)
public class TerrainFactory {
int count = 0;
int idCount = 1;
Terrain terrain;
public Terrain createNewTerrain(Activity activity, RelativeLayout relativeLayout,
final ArrayList<Terrain> terrainArrayList){
//TODO: Add the rectangle bounds into this.
terrain = new Terrain();
terrain.is = activity.getResources().openRawResource(+R.drawable.game_tile);
terrain.tile = BitmapFactory.decodeStream(terrain.is);
terrain.tileDrawable = new BitmapDrawable(activity.getResources(), terrain.tile);
terrain.terrainImage = new ImageView(activity);
terrain.terrainImage.setImageDrawable(terrain.tileDrawable);
//noinspection ResourceType
terrain.terrainImage.setId(idCount);
idCount++;
if(count >= 1) {
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);;
layoutParams.addRule(RelativeLayout.RIGHT_OF, terrainArrayList.get(count - 1).terrainImage.getId());
relativeLayout.addView(terrain.terrainImage, layoutParams);
terrain.terrainImage.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
public void onGlobalLayout() {
//TODO: Set rectangle bounds in here
++count;
terrain.terrainImage.getViewTreeObserver().removeOnGlobalLayoutListener(this);
}
});
}else{
++count;
relativeLayout.addView(terrain.terrainImage);
terrain.terrainImage.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
public void onGlobalLayout() {
//TODO: Set rectangle bounds in here
terrain.terrainImage.getViewTreeObserver().removeOnGlobalLayoutListener(this);
}
});
}
return terrain;
}
public int getCount() { return count; }
}
Here is my PlayActivity class, where all the block creating happens :
public class PlayActivity extends Activity {
RelativeLayout relativeLayout;
TerrainFactory terrainFactory;
ArrayList<Terrain> terrainArrayList = new ArrayList<Terrain>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_play);
relativeLayout = (RelativeLayout) findViewById(R.id.relativeLayout);
terrainFactory = new TerrainFactory();
for(int i = 0; i < 7; i++){
terrainArrayList.add(terrainFactory.createNewTerrain(PlayActivity.this, relativeLayout, terrainArrayList));
}
}
}
And here is the Terrain class
public class Terrain {
public Bitmap tile;
public InputStream is;
public ObjectAnimator moveLeft;
public Drawable tileDrawable;
public Rect bounds;
public ImageView terrainImage;
}
Here's the XML for the RelativeLayout. The RelativeLayout I'm using is the one nested inside the RelativeLayout that fills the entire screen.
<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="com.hooray.project.fun.activity.PlayActivity">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="100dp"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="false"
android:id="#+id/relativeLayout"></RelativeLayout>
</RelativeLayout>

Basically I jsut would tackle this in another way....using not Views for buildiung terrains but using surfaceview and draw bitmaps on it...
But well lets do it your way:
Place your views into a FrameLayout. Then when you create your views give them their dimension in code and also set the x and y positions in code.
For example this is how I give a View the needed Dimension and the position in my Code. Its a Textview and I jsut set the x and y position which I have stuffed iinto variables so I can chnage them how i want:
tView.setLayoutParams(new FrameLayout.LayoutParams(hintListWidth,hintListHeight));
tView.setX(hintListPosX);
tView.setY(hintListPosY);
maybe for your example do it like this:
float startPosX=???;
float startPosY=???;
float i=0;
for(Terrian t:terrainArrayList)
{
tView.setLayoutParams(new FrameLayout.LayoutParams(width,height));
tView.setX(startPosX+width*i);
tView.setY(startPosY);
i++;
}
If you have the width and height ready and know where to start placing the first view every view will be placed side by side from left to right...

As suggested in the other answer(s) to your question, the problem is that counter on the if-true branch is never incremented before views are drawn (aka tree observer callback being called). You are calling addView but I think this goes on and adds the view asynchronously, while you go on and add views. So you finish adding the views and only after that they are drawn. I suggest taking the counter out of the callback and place it at the end of the if-true block.
Note: if you are targeting SDK17+ you can use View.generateViewId() instead of manually keeping track / incrementing it yourself. Not that it matters in this particular scenario, but it will not allow the generated id to conflict with aapt-generated ids and it will roll it over once the top limit is reached.

How to draw a view on top of everything?

I want to make an app that can create notification on the screen on top of anything that is currently being displayed. Something like the Go SMS message popup or something like the ChatHead in the following picture:
It would be even better if it is possible to draw it dynamically including touch events.What is the conventional or standard way to do this?
Example:
Like an Icon that can be clicked or dragged no matter whether you are on home screen or app drawer or other apps.Pay attention to the circular icons near the edges of the screen in the picture posted. You can drag them anywhere in any app.

What you are looking for is System Alert Window.
There's a library called StandOut! which will assist you in creating such apps.

Here is how things like Toast and dialog windows work:
In the case where just adding or bringing to front does not work, say when you are having a service add its own view to another client activity or application (FaceUnlock does this), or you cannot depend on hierarchies, you need to use the window manager and a window token to do the trick. You can then create layouts and take advantage of animations and hardware acceleration as before.
WindowManager windowManager = (WindowManager) getBaseContext().getSystemService(Context.WINDOW_SERVICE);
WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(WindowManager.LayoutParams.FIRST_SUB_WINDOW);
layoutParams.width = 300;
layoutParams.height = 300;
layoutParams.format = PixelFormat.RGBA_8888;
layoutParams.flags =
WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN
| WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED;
layoutParams.token = getWindow().getDecorView().getRootView().getWindowToken();
//Feel free to inflate here
mTestView = new View(this);
mTestView.setBackgroundColor(Color.RED);
//Must wire up back button, otherwise it's not sent to our activity
mTestView.setOnKeyListener(new View.OnKeyListener() {
#Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
onBackPressed();
}
return true;
}
});
windowManager.addView(mTestView, layoutParams);
Then be sure to remove the view onDestroy (or onPause) or you will crash
if (mTestView != null) {
WindowManager windowManager = (WindowManager) getBaseContext().getSystemService(Context.WINDOW_SERVICE);
if (mTestView.isShown()) {
windowManager.removeViewImmediate(mTestView);
}
}

You don't need a new activity to do this. All you need to do is to add another view into your existing activity and bring it to the front, and draw/write the things that you want into that view.
If you want to do special things with this extra view, you could create your own view class
class DrawOnTop extends View {
public DrawOnTop(Context activity) {
super(activity);
}
#Override
protected void onDraw(Canvas canvas) {
// put your drawing commands here
}
}
and then you do something like
DrawOnTop mDraw = new DrawOnTop(this);
addContentView(mDraw, new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
mDraw.bringToFront();
Then to force it to draw, you need to use mDraw.invalidate();

You could have the parent of your whole layout as RelativeLayout. The first child being the "root" of your main layout. Anything after that can be considered an overlay which is placeable to your whims.
Example:
<RelativeLayout>
<LinearLayout>
... Main Layout here ...
</LinearLayout>
<TextView left="20dip" top="20dip" text="Overlay" alpha="0.7" />
</RelativeLayout>

The best way is to start a service with your application.
Create an ImageView.
Set the LayoutParams of the Image View.
Add the view along with the params to the window manager when the service is created.
ALL SET
Your Image sticks to your window (At any screen over all apps), till you application is closed.
You can even add onclicklisteners and ontouchlisteners to the imageview.
Eg. OnClick listeners to perform some actions and Ontouchlisteners move the image along the screen.

Android: HorizontalScrollView inside ScrollView

I have multiple HorizontalScrollViews inside a ScrollView. Horizontal scroll isn't smooth at all. I have to scroll almost perfectly horizontally for scrolling to work. Is there a simple fix to tweak this ??? Thanks!

You can use Recycler view with Staggered layout manager
StaggeredGridLayoutManager staggeredGridLayoutManager = new StaggeredGridLayoutManager(4, StaggeredGridLayoutManager.HORIZONTAL);
RecyclerViewAdapter recyclerViewAdapter = newRecyclerViewAdapter(this);
recyclerView.setAdapter(recyclerViewAdapter); //Don't miss to initialize your adapter

This class creates a ScrollView containing a HorizontalScrollView combined into one class. You can put stuff inside it using the AddChild() method. The dispatchTouchEvent overide keeps the scrolling smooth so you can pan around with a single slide of the finger.
(I recently used this to wrap a programmatically created TextView)
class MultiScrollView extends ScrollView
{
public HorizontalScrollView hscroll;
public MultiScrollView ( Context context )
{
super( context );
}
public void AddChild( View child )
{
hscroll.addView( child );
}
#Override
public boolean dispatchTouchEvent( MotionEvent event )
{
hscroll.dispatchTouchEvent(event);
onTouchEvent(event);
return true;
}
}

If you are using the horizontal scroll view solution from (http://www.dev-smart.com/archives/34) the solution for the cross focus problem between the scroll view and the list view is blocking the focus to the scroll view once you have focus on the list view.
From a technical point of view you should add the following line to the onScroll function inside the HorizontalListView class.
getParent().requestDisallowInterceptTouchEvent(true);
Hope this helps.

I've found the solution and still can't believe that this is what you have to do to make this work normal! Just added blank onClickListener to the each item in the HorizontalScrollView:
item.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
}
});
After this slide is really smooth, both upwards and downwards.

In general, you shouldn't be using nested ScrollViews in Android at all, the behaviour of scrolling in this way is unnatural too.
You may want to rethink your layout design, is it anything that couldn't be achieved with an expandable list?

While David's answer works, it has a downside. It passes ScrollView's MotionEvent object directly to HorizontalScrollView.onTouchEvent(), so if HorizontalScrollView or its children try to get the event coordinates, they will get the wrong coordinates which based on ScrollView.
My solution:
public class CustomScrollView extends ScrollView{
/*************skip initialization*************/
#Override
public boolean onInterceptTouchEvent(MotionEvent e){
//returning false means ScrollView is not interested at any events,
//so ScrollView's onTouchEvent() won't be called,
//and all of the events will be passed to ScrollView's child
return false;
}
#Override
public boolean dispatchTouchEvent(MotionEvent ev) {
//manually call ScrollView's onTouchEvent(),
//the vertical scrolling happens there.
onTouchEvent(ev);
//dispatch the event,
//ScrollView's child will have every event.
return super.dispatchTouchEvent(ev);
}
}
Just wrap this CustomScrollView around the HorizontalScrollView in your layout file.

Why does LinearLayout child getWidth method return 0?

I have a LinearLayout, and this LinearLayout will hold dynamically placed views. I need to find out what the width of the children of LinearLayout, however this has to be done in onCreate method. From researching I've found out that you can't use getWidth from this method. So instead I'm using onWindowFocusChanged, which works for the parent LinearLayout (returning me the actual size), but it doesn't work with its children.
Another thing I noticed is that when the screen is fading away and the screen is locked, I can see at the logs the actual width of the children being returned (I think the activity is being paused).
I'm really stuck and this is needed because I need to dynamically place those views depending on the children width.

You might be able to get with the below. But as others pointed out, this probably isn't a great idea.
LinearLayout.measure(MeasureSpec.UNSPECIFIED, MeasureSpec.UNSPECIFIED);
LinearLayout.getMeasuredWidth();

inside the onCreate , views still can't know the state of the nearby views and the children ,etc... so only after all is prepared and the layout process is done , you can get the size of views .
here's a quick code for getting the size of the view just before it's being drawn:
private static void runJustBeforeBeingDrawn(final View view, final Runnable runnable)
{
final ViewTreeObserver vto = view.getViewTreeObserver();
final OnPreDrawListener preDrawListener = new OnPreDrawListener()
{
#Override
public boolean onPreDraw()
{
Log.d(App.APPLICATION_TAG, CLASS_TAG + "onpredraw");
runnable.run();
final ViewTreeObserver vto = view.getViewTreeObserver();
vto.removeOnPreDrawListener(this);
return true;
}
};
vto.addOnPreDrawListener(preDrawListener);
}
alternatively , you can use addOnGlobalLayoutListener instead of addOnPreDrawListener if you wish.
example of usage :
runJustBeforeBeingDrawn(view,new Runnable()
{
#Override
public void run()
{
int width=view.getWidth();
int height=view.getHeight();
}
});
another approach is to use onWindowFocusChanged (and check that hasFocus==true) , but that's not always the best way ( only use for simple views-creation, not for dynamic creations)
EDIT: Alternative to runJustBeforeBeingDrawn: https://stackoverflow.com/a/28136027/878126

https://stackoverflow.com/a/3594216/1397218
So you should somehow change your logic.