Develop Reference

Manage scroll position in scrollview during orientation change

I have a Bookshelf which is implemented as follows:
I have a ScrollView which contains a nested TableLayout which acts as a container for dynamically generated TableRows.
<com.test.bookshelf.CustomScrollView
android:id="#+id/scrollview"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="#id/newHeader"
android:overScrollMode="never"
android:fadingEdge="none" >
<TableLayout
android:id="#+id/tblLayout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="0dp" >
</TableLayout>
</com.test.bookshelf.CustomScrollView>
Custom ScrollView code:
public class CustomScrollView extends ScrollView {
private boolean enableScrolling = true;
private ScrollViewListener scrollViewListener = null;
public interface OnEndScrollListener {
public void onEndScroll();
}
private OnEndScrollListener mOnEndScrollListener;
public boolean isEnableScrolling() {
return enableScrolling;
}
public void setEnableScrolling(boolean enableScrolling) {
this.enableScrolling = enableScrolling;
}
public CustomScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public CustomScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CustomScrollView(Context context) {
super(context);
}
#Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if (isEnableScrolling()) {
return super.onInterceptTouchEvent(ev);
} else {
return false;
}
}
public void setScrollViewListener(ScrollViewListener scrollViewListener) {
this.scrollViewListener = scrollViewListener;
}
#Override
protected void onScrollChanged(int x, int y, int oldx, int oldy) {
super.onScrollChanged(x, y, oldx, oldy);
if(scrollViewListener != null) {
scrollViewListener.onScrollChanged(this, x, y, oldx, oldy);
}
}
public OnEndScrollListener getOnEndScrollListener() {
return mOnEndScrollListener;
}
public void setOnEndScrollListener(OnEndScrollListener mOnEndScrollListener) {
this.mOnEndScrollListener = mOnEndScrollListener;
}
}
Each table row consist of a fixed number of columns which is dynamically calculated based on the total number of books. On orientation change this entire layout is re created.
When the bookshelf is being generated I'm storing the total number of rows in a static variable.
When the user clicks on any of book it takes them to the details page.
I am storing the current scroll position during the click event:
public static currentScrollPosition = 0;
imageviewobj.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v)
{
currentScrollPosition = scrollviewObj.getScrollY();
....
When the user returns to this screen I restore the scroll position by using this value.
scrollviewObj.post(new Runnable() {
#Override
public void run() {
scrollviewObj.scrollTo(0, currentScrollPosition);
}
});
But how do I calculate the equivalent scroll position during orientation change?
The vertical offset (scroll position) of a Book in the portrait mode is different from landscape mode because the number of rows and columns differ.
Any thoughts on this?

You should simply keep the index of the row that is being seen (or clicked) in your case, and persist this information thanks to onSaveInstanceState/onCreate.
After that when the rotation will occur, inside your new instance onCreate, compute the vertical offset at which you will have to scroll.
For this, you will need to add a global tree layout observer to your list cells to get their height, if it is not fixed. And then you can ask to scroll.
This method allows you to be independent of your view by keeping track of the index in the list. It will then work in portrait to landscape but also landscape to portrait.

Detecting thumb position in SeekBar prior to API version 16

Basically, I need to detect when the progress changes in the SeekBar and draw a text view on top of the thumb indicating the progress value.
I do this by implementing a OnSeekBarChangeListener
and on the public void onProgressChanged(SeekBar seekBar, int progress, boolean b) method, I call Rect thumbRect = seekBar.getThumb().getBounds(); to determine where the thumb is positioned.
This works perfectly fine, but apparently getThumb() is only available in API level 16+ (Android 4.1), causing a NoSuchMethodError on earlier versions.
Any idea how to work around this issue?

I was able to use my own class to get the Thumb:
MySeekBar.java
package mobi.sherif.seekbarthumbposition;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.SeekBar;
public class MySeekBar extends SeekBar {
public MySeekBar(Context context) {
super(context);
}
public MySeekBar(Context context, AttributeSet attrs) {
super(context, attrs);
}
public MySeekBar(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
Drawable mThumb;
#Override
public void setThumb(Drawable thumb) {
super.setThumb(thumb);
mThumb = thumb;
}
public Drawable getSeekBarThumb() {
return mThumb;
}
}
In the activity this works perfectly:
package mobi.sherif.seekbarthumbposition;
import android.app.Activity;
import android.graphics.Rect;
import android.os.Bundle;
import android.util.Log;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
public class MainActivity extends Activity implements OnSeekBarChangeListener {
MySeekBar mSeekBar;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mSeekBar = (MySeekBar) findViewById(R.id.seekbar);
mSeekBar.setOnSeekBarChangeListener(this);
}
#Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
Rect thumbRect = mSeekBar.getSeekBarThumb().getBounds();
Log.v("sherif", "(" + thumbRect.left + ", " + thumbRect.top + ", " + thumbRect.right + ", " + thumbRect.bottom + ")");
}
#Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
#Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
}

Hopefully this can save some hours for someone else!
I created this method instead of a custom seekBar:
public int getSeekBarThumbPosX(SeekBar seekBar) {
int posX;
if (Build.VERSION.SDK_INT >= 16) {
posX = seekBar.getThumb().getBounds().centerX();
} else {
int left = seekBar.getLeft() + seekBar.getPaddingLeft();
int right = seekBar.getRight() - seekBar.getPaddingRight();
float width = (float) (seekBar.getProgress() * (right - left)) / seekBar.getMax();
posX = Math.round(width) + seekBar.getThumbOffset();
}
return posX;
}

A splendid solution! Thanks.
It's only nessesary to add that to use custom seekbar you need modify your xml
<com.example.MySeekBar
android:id="#+id/..."
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:layout_weight="1"
android:minHeight="3dp"
android:maxHeight="3dp"
android:progressDrawable="#drawable/seek_bar_2"
android:thumb="#drawable/thumbler_seekbart_circle"
android:thumbOffset="8dp" />
android:thumbOffset="8dp" - is a HALF of a thumb it's better to spesify, thus there will be no mismatching of the text center and the thumb
Positioning can look like this:
int possition = (int) (seekBar.getX() //the beginning of the seekbar
+ seekBar.getThumbOffset() / 2 //the half of our thumb - the text to be above it's centre
+ ((MySeekBar) seekBar).getSeekBarThumb().getBounds().exactCenterX()); //position of a thumb inside the seek bar

#Sherif elKhatib's answer is great but has the disadvantage of caching a copy of the thumb even on API>=16.
I've improved it so that it only caches the Thumb Drawable on API<=15 plus it overrides the method in SeekBar.java to avoid having two methods do the same on API>=16. Only downside: It needs target SDK to be >= 16 which should be the case in most apps nowadays.
public class ThumbSeekBar extends AppCompatSeekBar {
private Drawable thumb;
public ThumbSeekBar(Context context) {
super(context);
}
public ThumbSeekBar(Context context, AttributeSet attrs) {
super(context, attrs);
}
public ThumbSeekBar(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
#Override
public Drawable getThumb() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
return super.getThumb();
}
return thumb;
}
#Override
public void setThumb(Drawable thumb) {
super.setThumb(thumb);
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
this.thumb = thumb;
}
}
}

How do I draw a drawable with its exact size in my custom view?

SOLVED: Solution below as answer.
I have a custom view with a TransitionDrawable and when I draw it in the onDraw() method it scales automatically to fill the whole parent layout, even when it's set in the xml to wrap_content. The picture is in mdpi and hdpi and my testing device (samsung galaxy s) I think it's no more than hdpi.
package com.adyrsoft.pronunciationtrainer;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.TransitionDrawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
public class RecordButton extends View {
private static final String TAG = "RecordButton";
private TransitionDrawable mDrawable;
private boolean mActivated;
private OnClickListener mOnClickListenerInternal = new OnClickListener() {
#Override
public void onClick(View v) {
toggleState();
if(mOnClickListener != null) {
mOnClickListener.onClick(v);
}
}
};
private OnClickListener mOnClickListener = null;
public RecordButton(Context context) {
super(context);
init();
}
public RecordButton(Context context, AttributeSet attrib) {
super(context, attrib);
init();
}
public RecordButton(Context context, AttributeSet attrib, int defStyle) {
super(context, attrib, defStyle);
init();
}
public void setState(boolean activated) {
mActivated = activated;
if(mActivated){
mDrawable.startTransition(300);
}
else {
mDrawable.reverseTransition(300);
}
}
public void toggleState() {
if(mActivated) {
setState(false);
}
else {
setState(true);
}
}
#SuppressWarnings("deprecation")
private void init() {
mActivated = false;
mDrawable = (TransitionDrawable) getResources().getDrawable(R.drawable.btnrecord);
Log.d(TAG, "Drawable intrinsic width and height are: " +
Integer.toString(mDrawable.getIntrinsicWidth()) + " " +
Integer.toString(mDrawable.getIntrinsicHeight()));
mDrawable.setBounds(0,0,mDrawable.getIntrinsicWidth(), mDrawable.getIntrinsicHeight());
Log.d(TAG, "The bounds for the button are: "+mDrawable.getBounds().flattenToString());
super.setBackgroundDrawable(mDrawable);
setClickable(true);
super.setOnClickListener(mOnClickListenerInternal);
invalidate();
}
public void setOnClickListener(View.OnClickListener listener) {
mOnClickListener = listener;
}
protected void onDraw (Canvas canvas) {
super.onDraw(canvas);
}
}
What am I doing wrong?
Thanks.

After hours trying to understand how I should use the drawables in a custom view in order to be displayed in its original size, I've figured out how to do it.
First a few things that I didn't know but are a must is:
The background drawable should be left to the parent class to be
drawn when using View as the parent. If not, the TransitionDrawable can't be seen fading between pictures.
Only if I am going to draw on the background drawable I should override onDraw() and do the drawing there.
And the last but not less important is that I should override onMeasure() to specify the size of the view. If I don't do it, it will fill all the free space in the parent layout, as it was happening to me.
I've passed the TransitionDrawable to the parent class with setBackgroundDrawable() and since I wasn't drawing in the background drawable, I've removed the onDraw() method. Also I've implemented onMeasure() with a quick and dirty solution specifying the size of the picture I am drawing.
This is the final result:
public class RecordButton extends View {
private static final String TAG = "RecordButton";
private static final int DESIRED_WIDTH = 180;
private static final int DESIRED_HEIGHT = 66;
private TransitionDrawable mDrawable;
private Rect mViewRect;
private boolean mActivated;
private OnClickListener mOnClickListenerInternal = new OnClickListener() {
#Override
public void onClick(View v) {
toggleState();
if(mOnClickListener != null) {
mOnClickListener.onClick(v);
}
}
};
private OnClickListener mOnClickListener = null;
public RecordButton(Context context) {
this(context, null, 0);
}
public RecordButton(Context context, AttributeSet attrib) {
this(context, attrib, 0);
}
public RecordButton(Context context, AttributeSet attrib, int defStyle) {
super(context, attrib, defStyle);
init();
}
public void setState(boolean activated) {
mActivated = activated;
if(mActivated){
mDrawable.startTransition(300);
}
else {
mDrawable.reverseTransition(300);
}
}
public void toggleState() {
if(mActivated) {
setState(false);
}
else {
setState(true);
}
}
#SuppressWarnings("deprecation")
private void init() {
mActivated = false;
mDrawable = (TransitionDrawable) getResources().getDrawable(R.drawable.btnrecord);
setBackgroundDrawable(mDrawable);
setClickable(true);
super.setOnClickListener(mOnClickListenerInternal);
invalidate();
}
public void setOnClickListener(View.OnClickListener listener) {
mOnClickListener = listener;
}
#Override
protected void onMeasure(int m, int n) {
setMeasuredDimension(DESIRED_WIDTH, DESIRED_HEIGHT);
}
}

ScrollingTextView not working when clock is visible

I have a TextView in my application which shows the current time, i implemented it like this
private Handler handler = new Handler();
private Runnable runnable = new Runnable()
{
public void run()
{
batteryLevel();
if(clock_on == true) {
Handler clockUpdate = new Handler();
clockUpdate.postDelayed(new Runnable() {
public void run() {
executeClock();
}
}, 500);
}
handler.post(this);
}
public void executeClock() {
TextView timeTv = (TextView) findViewById(R.id.time);
long currentTime=System.currentTimeMillis();
Calendar cal=Calendar.getInstance();
cal.setTimeInMillis(currentTime);
String timeFormat24 = "%1$tH:%1$tM";
// String timeFormat12 = "%1$tI:%1$tM";
String showTime=String.format(timeFormat24,cal);
timeTv.setText(showTime);
}
In my app i have a ScrollingTextView aswell, ScrollingtextView.java
public class ScrollingTextView extends TextView {
public ScrollingTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public ScrollingTextView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public ScrollingTextView(Context context) {
super(context);
}
#Override
protected void onFocusChanged(boolean focused, int direction, Rect previouslyFocusedRect) {
if(focused)
super.onFocusChanged(focused, direction, previouslyFocusedRect);
}
#Override
public void onWindowFocusChanged(boolean focused) {
if(focused)
super.onWindowFocusChanged(focused);
}
#Override
public boolean isFocused() {
return true;
}
}
<com.doublep.example.ScrollingTextView
android:id="#+id/txt_lcd_message"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:ellipsize="marquee"
android:marqueeRepeatLimit="marquee_forever"
android:scrollHorizontally="true"
android:singleLine="true"
android:textColor="#f82424"
android:textSize="30dp" />
The ScrollingTextView doesn't work if the clock TextView is visible, when i make the visibility of the clock GONE then the ScrollingTextView works perfectly
Why is this happening?
How can i fix it?
EDIT: if i delay the clock the ScrollingTextView starts working, but as soon as the clock TextView gets set to the current time, the ScrollingTextView stops working
UPDATE: after a bit of testing i noticed that the ScrollingTextView is working, but every time the executeClock() method runs, the ScrollingTextView animation gets reset and starts once again

Do you have your clock textview and scrolltextview in the same viewgroup?? so for example are they all child views of the same linear or relative layout?? Try to separate them and make them child of different viewgroups. That worked for me once and may work for you too

Change ViewPager animation duration when sliding programmatically

I'm changing slide with the following code:
viewPager.setCurrentItem(index++, true);
But it changes too fast. Is there a way to set manually the animation speed?

I've wanted to do myself and have achieved a solution (using reflection, however). I haven't tested it yet but it should work or need minimal modification. Tested on Galaxy Nexus JB 4.2.1. You need to use a ViewPagerCustomDuration in your XML instead of ViewPager, and then you can do this:
ViewPagerCustomDuration vp = (ViewPagerCustomDuration) findViewById(R.id.myPager);
vp.setScrollDurationFactor(2); // make the animation twice as slow
ViewPagerCustomDuration.java:
import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.animation.Interpolator;
import java.lang.reflect.Field;
public class ViewPagerCustomDuration extends ViewPager {
public ViewPagerCustomDuration(Context context) {
super(context);
postInitViewPager();
}
public ViewPagerCustomDuration(Context context, AttributeSet attrs) {
super(context, attrs);
postInitViewPager();
}
private ScrollerCustomDuration mScroller = null;
/**
* Override the Scroller instance with our own class so we can change the
* duration
*/
private void postInitViewPager() {
try {
Field scroller = ViewPager.class.getDeclaredField("mScroller");
scroller.setAccessible(true);
Field interpolator = ViewPager.class.getDeclaredField("sInterpolator");
interpolator.setAccessible(true);
mScroller = new ScrollerCustomDuration(getContext(),
(Interpolator) interpolator.get(null));
scroller.set(this, mScroller);
} catch (Exception e) {
}
}
/**
* Set the factor by which the duration will change
*/
public void setScrollDurationFactor(double scrollFactor) {
mScroller.setScrollDurationFactor(scrollFactor);
}
}
ScrollerCustomDuration.java:
import android.annotation.SuppressLint;
import android.content.Context;
import android.view.animation.Interpolator;
import android.widget.Scroller;
public class ScrollerCustomDuration extends Scroller {
private double mScrollFactor = 1;
public ScrollerCustomDuration(Context context) {
super(context);
}
public ScrollerCustomDuration(Context context, Interpolator interpolator) {
super(context, interpolator);
}
#SuppressLint("NewApi")
public ScrollerCustomDuration(Context context, Interpolator interpolator, boolean flywheel) {
super(context, interpolator, flywheel);
}
/**
* Set the factor by which the duration will change
*/
public void setScrollDurationFactor(double scrollFactor) {
mScrollFactor = scrollFactor;
}
#Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, (int) (duration * mScrollFactor));
}
}

I have found better solution, based on #df778899's answer and the
Android ValueAnimator API. It works fine without reflection and is very flexible.
Also there is no need for making custom ViewPager and putting it into android.support.v4.view package.
Here is an example:
private void animatePagerTransition(final boolean forward) {
ValueAnimator animator = ValueAnimator.ofInt(0, viewPager.getWidth());
animator.addListener(new Animator.AnimatorListener() {
#Override
public void onAnimationStart(Animator animation) {
}
#Override
public void onAnimationEnd(Animator animation) {
viewPager.endFakeDrag();
}
#Override
public void onAnimationCancel(Animator animation) {
viewPager.endFakeDrag();
}
#Override
public void onAnimationRepeat(Animator animation) {
}
});
animator.setInterpolator(new AccelerateInterpolator());
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
private int oldDragPosition = 0;
#Override
public void onAnimationUpdate(ValueAnimator animation) {
int dragPosition = (Integer) animation.getAnimatedValue();
int dragOffset = dragPosition - oldDragPosition;
oldDragPosition = dragPosition;
viewPager.fakeDragBy(dragOffset * (forward ? -1 : 1));
}
});
animator.setDuration(AppConstants.PAGER_TRANSITION_DURATION_MS);
if (viewPager.beginFakeDrag()) {
animator.start();
}
}
UPDATE:
Just checked if this solution can be used to swipe several pages at once (for example if first page should be showed after the last one). This is slightly modified code to handle specified page count:
private int oldDragPosition = 0;
private void animatePagerTransition(final boolean forward, int pageCount) {
// if previous animation have not finished we can get exception
if (pagerAnimation != null) {
pagerAnimation.cancel();
}
pagerAnimation = getPagerTransitionAnimation(forward, pageCount);
if (viewPager.beginFakeDrag()) { // checking that started drag correctly
pagerAnimation.start();
}
}
private Animator getPagerTransitionAnimation(final boolean forward, int pageCount) {
ValueAnimator animator = ValueAnimator.ofInt(0, viewPager.getWidth() - 1);
animator.addListener(new Animator.AnimatorListener() {
#Override
public void onAnimationStart(Animator animation) {
}
#Override
public void onAnimationEnd(Animator animation) {
viewPager.endFakeDrag();
}
#Override
public void onAnimationCancel(Animator animation) {
viewPager.endFakeDrag();
}
#Override
public void onAnimationRepeat(Animator animation) {
viewPager.endFakeDrag();
oldDragPosition = 0;
viewPager.beginFakeDrag();
}
});
animator.setInterpolator(new AccelerateInterpolator());
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
#Override
public void onAnimationUpdate(ValueAnimator animation) {
int dragPosition = (Integer) animation.getAnimatedValue();
int dragOffset = dragPosition - oldDragPosition;
oldDragPosition = dragPosition;
viewPager.fakeDragBy(dragOffset * (forward ? -1 : 1));
}
});
animator.setDuration(AppConstants.PAGER_TRANSITION_DURATION_MS / pageCount); // remove divider if you want to make each transition have the same speed as single page transition
animator.setRepeatCount(pageCount);
return animator;
}

public class PresentationViewPager extends ViewPager {
public static final int DEFAULT_SCROLL_DURATION = 250;
public static final int PRESENTATION_MODE_SCROLL_DURATION = 1000;
public PresentationViewPager (Context context) {
super(context);
}
public PresentationViewPager (Context context, AttributeSet attrs) {
super(context, attrs);
}
public void setDurationScroll(int millis) {
try {
Class<?> viewpager = ViewPager.class;
Field scroller = viewpager.getDeclaredField("mScroller");
scroller.setAccessible(true);
scroller.set(this, new OwnScroller(getContext(), millis));
} catch (Exception e) {
e.printStackTrace();
}
}
public class OwnScroller extends Scroller {
private int durationScrollMillis = 1;
public OwnScroller(Context context, int durationScroll) {
super(context, new DecelerateInterpolator());
this.durationScrollMillis = durationScroll;
}
#Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, durationScrollMillis);
}
}
}

Better solution is to simply access the private fields by creating the class in the support package. EDIT This is bound to the MAX_SETTLE_DURATION of 600ms, set by the ViewPagerclass.
package android.support.v4.view;
import android.content.Context;
import android.util.AttributeSet;
public class SlowViewPager extends ViewPager {
// The speed of the scroll used by setCurrentItem()
private static final int VELOCITY = 200;
public SlowViewPager(Context context) {
super(context);
}
public SlowViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
void setCurrentItemInternal(int item, boolean smoothScroll, boolean always) {
setCurrentItemInternal(item, smoothScroll, always, VELOCITY);
}
}
You can, of course, then add a custom attribute so this can be set via XML.

Here is my code used in Librera Reader
public class MyViewPager extends ViewPager {
public MyViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
initMyScroller();
}
private void initMyScroller() {
try {
Class<?> viewpager = ViewPager.class;
Field scroller = viewpager.getDeclaredField("mScroller");
scroller.setAccessible(true);
scroller.set(this, new MyScroller(getContext())); // my liner scroller
Field mFlingDistance = viewpager.getDeclaredField("mFlingDistance");
mFlingDistance.setAccessible(true);
mFlingDistance.set(this, Dips.DP_10);//10 dip
Field mMinimumVelocity = viewpager.getDeclaredField("mMinimumVelocity");
mMinimumVelocity.setAccessible(true);
mMinimumVelocity.set(this, 0); //0 velocity
} catch (Exception e) {
LOG.e(e);
}
}
public class MyScroller extends Scroller {
public MyScroller(Context context) {
super(context, new LinearInterpolator()); // my LinearInterpolator
}
#Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, 175);//175 duration
}
}
}

I used Cicero Moura's version to make a Kotlin class that still works perfectly as of Android 10.
import android.content.Context
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.animation.DecelerateInterpolator
import android.widget.Scroller
import androidx.viewpager.widget.ViewPager
class CustomViewPager(context: Context, attrs: AttributeSet) :
ViewPager(context, attrs) {
private companion object {
const val DEFAULT_SPEED = 1000
}
init {
setScrollerSpeed(DEFAULT_SPEED)
}
var scrollDuration = DEFAULT_SPEED
set(millis) {
setScrollerSpeed(millis)
}
private fun setScrollerSpeed(millis: Int) {
try {
ViewPager::class.java.getDeclaredField("mScroller")
.apply {
isAccessible = true
set(this#CustomViewPager, OwnScroller(millis))
}
} catch (e: Exception) {
e.printStackTrace()
}
}
inner class OwnScroller(private val durationScrollMillis: Int) : Scroller(context, AccelerateDecelerateInterpolator()) {
override fun startScroll(startX: Int, startY: Int, dx: Int, dy: Int, duration: Int) {
super.startScroll(startX, startY, dx, dy, durationScrollMillis)
}
}
}
Initializing from the activity class:
viewPager.apply {
scrollDuration = 2000
adapter = pagerAdapter
}

After wasting my whole day I found a solution set offscreenPageLimit to total no. of the page.
In order to keep a constant length ViewPager scrolls smooth, setOffScreenLimit(page.length) will keep all the views in memory. However, this poses a problem for any animations that involves calling View.requestLayout function (e.g. any animation that involves making changes to the margin or bounds). It makes them really slow (as per Romain Guy) because the all of the views that's in memory will be invalidated as well. So I tried a few different ways to make things smooth but overriding requestLayout and other invalidate methods will cause many other problems.
A good compromise is to dynamically modify the off screen limit so that most of the scrolls between pages will be very smooth while making sure that all of the in page animations smooth by removing the views when the user. This works really well when you only have 1 or 2 views that will have to make other views off memory.
***Use this when no any solution works because by setting offeset limit u will load all the fragments at the same time