Develop Reference

Programmatically set margins in a MotionLayout

I have some views that need some margins set programmatically (from an applyWindowInsets listener), but the views seem to be ignoring any margins I set with my code, even though I am not animating the margins.
I'm able to set padding just fine, but I cannot accomplish what I need using only padding.
The issue seems to be related to MotionLayout since it works fine if it is a ConstraintLayout.
I've been using this util method.
public static void addTopMargin(View v, int margin) {
((ViewGroup.MarginLayoutParams) v.getLayoutParams()).topMargin += margin;
}

The issue you're having is that MotionLayout derives its margins from the assigned ConstraintSets, so changing the base margin isn't actually doing anything. To get this to work, you need to target one or both of the ConstraintSets that define the MotionScene:
val motionLayout = findViewById(R.id.motionLayoutId)
motionLayout.getConstraintSet(R.id.startingConstraintSet)?
.setMargin(targetView.id, anchorId, value)
You could also do this for more than one view with a let:
val motionLayout = findViewById(R.id.motionLayoutId)
motionLayout.getConstraintSet(R.id.startingConstraintSet)?.let {
setMargin(firstView.id, anchorId, value)
setMargin(secondView.id, anchorId, value)
}
For the top margin, use ConstraintSet.TOP, etc.
Remember that if you're not wanting to animate that margin, you'll have to assign to both the start and end ConstraintSet.

Just adding a simple note to UnOrthodox solution that in case of you don't need to animate that margin you will need to keep the base margin with adding the ConstraintSets margin:
public static void addTopMargin(View v, int margin) {
((ViewGroup.MarginLayoutParams) v.getLayoutParams()).topMargin += margin;
MotionLayout root = findViewById(R.id.motion_layout);
root.getConstraintSet(R.id.start).setMargin(firstView.id, anchorId, margin);
root.getConstraintSet(R.id.end).setMargin(firstView.id, anchorId, margin);
}

Update layout_margin inside kotlin class for specific elements

So, this should be pretty basic, but I am new to Kotlin. So I basically have the following ImageView inside a RelativeLayout view.
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:srcCompat="#drawable/moon_0"
android:id="#+id/imagen_luna"
android:layout_marginStart="8dp"
android:layout_marginEnd="8dp"
android:layout_marginTop="8dp"
android:layout_marginBottom="8dp"
android:layout_alignParentStart="true"
android:layout_alignParentEnd="true"
android:layout_alignParentBottom="true"
android:layout_alignParentTop="true" />
The thing is that under certain condition this ImageView can collide visually with another element, so I have to modify the marginStart and the marginEnd properties. I saw in some tutorials that first I must obtain the current layout margins or something like that, but I am not sure why it's so complicated, in Swift I just modify the properties of each margin.
Is there an easy way to achieve this or in case there isn't what would be the easiest way to do this?
UPDATE - Added code in the Adapter
This is the code I have in my adapter for this specific ImageView:
override fun onBindViewHolder(holder: AnoViewHolder, position: Int) {
...
if(respec.nombre_icono_signo != "" && respec.imagen_luna != "") {
val layoutParamsLuna = holder.view?.imagen_luna.layoutParams as RelativeLayout.LayoutParams
layoutParamsLuna.setMargins(1, 8, 15, 8)
holder.view?.imagen_luna.layoutParams = layoutParamsLuna
}
...
}
The thing is that this does nothing and my theory is that the setMargins function accepts left and right margins, not start and end margins.

You can update margin in layoutParams of view
Ex:
val layoutParams= imagen_luna.layoutParams as RelativeLayout.LayoutParams
layoutParams.marginEnd=resources.getDimension(your_dimension).toInt()
layoutParams.marginStart=resources.getDimension(your_dimension).toInt()
layoutParams.bottomMargin=resources.getDimension(your_dimension).toInt()
layoutParams.topMargin=resources.getDimension(your_dimension).toInt()
//or
layoutParams.setMargins(start,top,end,bottom)
imagen_luna.layoutParams=layoutParams
You have to add value for margins in dimension file.because if you set setMargins(1, 8, 15, 8) like this,It's will margin in pixel not in dp.
So use margin values like below.
<dimen name="spacing_normal">16dp</dimen>
<dimen name="spacing_small">8dp</dimen>
<dimen name="spacing_tiny">4dp</dimen>
Update your dapter class like belo
override fun onBindViewHolder(holder: AnoViewHolder, position: Int) {
...
if(respec.nombre_icono_signo != "" && respec.imagen_luna != "") {
val layoutParamsLuna = holder.view?.imagen_luna.layoutParams as RelativeLayout.LayoutParams
layoutParamsLuna.setMargins(context.resources.getDimension(R.dimen.spacing_normal).toInt(),
context.resources.getDimension(R.dimen.spacing_normal).toInt(),
context.resources.getDimension(R.dimen.spacing_normal).toInt(),
context.resources.getDimension(R.dimen.spacing_normal).toInt())
holder.view?.imagen_luna.layoutParams = layoutParamsLuna
}else{
//reset margin for else case because recylerview reuse views so it's will keep previous states
}
...
}

Is there a way to make RecyclerView requiresFadingEdge unaffected by paddingTop and paddingBottom

Currently, I need to use paddingTop and paddingBottom of RecyclerView, as I want to avoid complex space calculation, in my first RecyclerView item and last item.
However, I notice that, requiresFadingEdge effect will be affected as well.
This is my XML
<androidx.recyclerview.widget.RecyclerView
android:requiresFadingEdge="vertical"
android:paddingTop="0dp"
android:paddingBottom="0dp"
android:overScrollMode="always"
android:background="?attr/recyclerViewBackground"
android:id="#+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false" />
When paddingTop and paddingBottom is 40dp
As you can see, the fading effect shift down by 40dp, which is not what I want.
When paddingTop and paddingBottom is 0dp
Fading effect looks fine. But, I need to have non-zero paddingTop and paddingBottom, for my RecyclerView.
Is there a way to make RecyclerView's requiresFadingEdge unaffected by paddingTop and paddingBottom?

I found the best and kind of official solution for this. Override this 3 methods of RecyclerView. Which play most important role for fading edge.
First create your recyclerView.
public class MyRecyclerView extends RecyclerView {
// ... required constructor
#Override
protected boolean isPaddingOffsetRequired() {
return true;
}
#Override
protected int getTopPaddingOffset() {
return -getPaddingTop();
}
#Override
protected int getBottomPaddingOffset() {
return getPaddingBottom();
}
}
That's it. Use this recyclerview and you will see fadding edge unaffected.
Following content is just for explanation. If you want to know behind the scene.
To understand how this edge effect is working I dig into the class where android:requiresFadingEdge is used, And I found that it's not handled by RecyclerView instead It's handled by View class which is parent for all view.
In onDraw method of View class I found the code for drawing fade edge by using help of this method isPaddingOffsetRequired. Which used only for handling the fade effect.
According to documentation this method should be overridden by child class If you want to change the behaviour of fading edge. Bydefault It return false. So By returning true we are asking view to apply some offset for edge at the time of view drawing.
Look following snippet of onDraw method of View class to understand the calculation.
final boolean offsetRequired = isPaddingOffsetRequired();
if (offsetRequired) {
paddingLeft += getLeftPaddingOffset();
}
int left = mScrollX + paddingLeft;
int right = left + mRight - mLeft - mPaddingRight - paddingLeft;
int top = mScrollY + getFadeTop(offsetRequired);
int bottom = top + getFadeHeight(offsetRequired);
if (offsetRequired) {
right += getRightPaddingOffset();
bottom += getBottomPaddingOffset();
}
As we can see top variable is initialize using getFadeTop(offsetRequired).
protected int getFadeTop(boolean offsetRequired) {
int top = mPaddingTop;
if (offsetRequired) top += getTopPaddingOffset();
return top;
}
In this method, top is calculated by adding value of topOffSet when offset is needed. So to reverse the effect we need to pass negative value of padding which you are passing. so we need to return -getPaddingTop().
Now for bottom we are not passing negative value because bottom is working on top + height. So passing negative value make fade more shorter from the bottom so we need to add bottom padding to make it proper visible.
You can override this 4 method to play with it. getLeftPaddingOffset(), getRightPaddingOffset(), getTopPaddingOffset(), getBottomPaddingOffset()

I suggest a few solutions
, I hope to be helpful
1- RecyclerView.ItemDecoration (keep requiresFadingEdge)
class ItemDecoration(private val spacing: Int) : RecyclerView.ItemDecoration(){
override fun getItemOffsets(outRect: Rect, view: View, parent:
RecyclerView, state: RecyclerView.State?) {
val position = parent.getChildAdapterPosition(view)
when(position)
0 -> { outRect.top = spacing /*40dp*/ }
parent.adapter.itemCount-1 -> { outRect.bottom = spacing /*40dp*/ }
}
2- Multiple ViewHolders (depending on the ViewHolder either keep or remove requiresFadingEdge)
https://stackoverflow.com/a/26245463/5255963
3- Gradient (remove requiresFadingEdge)
Make two gradients with drawables like this:
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<gradient
android:type="linear"
android:angle="90"
android:startColor="#000"
android:endColor="#FFF" />
</shape>
And set background to two views at the top and bottom of the Recyclerview.

There are many ways to achieve that but I preferred below solution that works for me.
You can use a third-party library called Android-FadingEdgeLayout checkout here
Here is a dependency.
implementation 'com.github.bosphere.android-fadingedgelayout:fadingedgelayout:1.0.0'
In yours.xml
<com.bosphere.fadingedgelayout.FadingEdgeLayout
android:id="#+id/fading_edge_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:fel_edge="top|left|bottom|right"
app:fel_size_top="40dp"
app:fel_size_bottom="40dp"
app:fel_size_left="0dp"
app:fel_size_right="0dp">
<androidx.recyclerview.widget.RecyclerView
android:paddingTop="0dp"
android:paddingBottom="0dp"
android:overScrollMode="always"
android:id="#+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false" />
</com.bosphere.fadingedgelayout.FadingEdgeLayout>
Change your ReacyclerView property according to your need. below is example image with all sided sades. I hope that will help you.
Credits Android-FadingEdgeLayout

how to MODIFY a constraint layout programmatically?

Ive got a view like below :
<org.rayanmehr.atlas.shared.customview.CustomTextView
android:id="#+id/tvDownVoteCount"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="6dp"
app:layout_constraintVertical_bias="0"
app:layout_constraintTop_toBottomOf="#+id/anchorHelper"
app:layout_constraintLeft_toRightOf="#+id/tvDownVoteIcon"
app:layout_constraintBottom_toBottomOf="#+id/imgComment"
/>
how can i modify the value of app:layout_constraintVertical_bias or any other constraint property programmatically without having top set the whole set of the properties again in my activity ?

Here is what I did (no need for ConstraintSet, we can work directly on the constraints themselves):
ConstraintLayout.LayoutParams params = (ConstraintLayout.LayoutParams) myView.getLayoutParams();
params.horizontalBias = 0.2f; // here is one modification for example. modify anything else you want :)
myView.setLayoutParams(params); // request the view to use the new modified params
it worked like a charm when I had a SeekBar and a TextView below it (aligned to it both left+right), and I wanted to update the TextView position to be under the SeekBar's cursor, so I had to update the horizontal bias params on the SeekBar's OnSeekBarChangeListener

If you are using Kotlin and you have androidx-core-ktx lib you can simply do:
someView.updateLayoutParams<ConstraintLayout.LayoutParams> { horizontalBias = 0.5f }

I just found the answer in here and you can use ConstraintSet to achieve this like below:
ConstraintSet constraintSet = new ConstraintSet();
constraintSet.clone(context, R.id.activity_constraint);
//for example lets change the vertical bias of tvDownVoteIcon
float biasedValue = 0.2f;
constraintSet.setVerticalBias(R.id.tvDownVoteIcon, biasedValue);
//or change the anchor
constraintSet.connect
(R.id.tvDownVoteIcon,ConstraintSet.RIGHT,R.id.txt,ConstraintSet.RIGHT,0);
//then apply
constraintSet.applyTo( (ConstraintLayout) findViewById(R.id.activity_constraint));

Disclaimer: I haven't used this specific functionality. This is just my interpretation on how I would try to do it.
I think that what you need is ConstraintSet. After obtaining it, you could modify it and apply it again. This is a relevant example from this article.
override fun onCreate(savedInstanceState: Bundle?) {
...
val constraintSet1 = ConstraintSet()
constraintSet1.clone(constraintLayout)
val constraintSet2 = ConstraintSet()
constraintSet2.clone(constraintLayout)
constraintSet2.centerVertically(R.id.image, 0)
var changed = false
findViewById(R.id.button).setOnClickListener {
TransitionManager.beginDelayedTransition(constraintLayout)
val constraint = if (changed) constraintSet1 else constraintSet2
constraint.applyTo(constraintLayout)
changed = !changed
}
}

Android get height of a wrap content view inflated as 0dp

I'm currently working on animation that will grow up the view if the user clicks it. Basically, its a card that, when clicked, it will reveal the bottom content. For that, I'm extending Animation like this:
Val collapseAnimation = object : Animation() {
override fun applyTransformation(interpolatedTime: Float, t: Transformation?) {
val interpolatedInverted = 1 - interpolatedTime
val headerLp = headerImage.layoutParams
headerLp.width = ...
headerImage.layoutParams = headerLp
}
}
The problem is that i need to get the height of a view (wrap_content) that is defined in XML as 0dp. Basically, I want to grow up a view from 0dp to wrap_content and for that i need to know what is the wrap_content size.
How can I accomplish that in the most efficient way, without hard coding the view size?

In order to measure a view with different layout params and get its height, we can do the following:
contentContainer.measure(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT)
val contentContainerFinalHeight = contentContainer.measuredHeight