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In View pager Tab Layout, tab heading is not coming to center and tab indicator is not occupying whole layout

In View pager Tab Layout, when ever I have single tab, tab heading is not coming to center and tab indicator is not occupying whole layout, but when there is more than 1 tabs its dividing and occupying whole. I have used custom tab layout class.
My custom tab layout code is :-
public class OPTCustomTab extends TabLayout {
public OPTCustomTab(Context context) {
super(context);
}
public OPTCustomTab(Context context, AttributeSet attrs) {
super(context, attrs);
}
public OPTCustomTab(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
ViewGroup tabLayout = (ViewGroup) getChildAt(0);
int childCount = tabLayout.getChildCount();
if (childCount != 0) {
DisplayMetrics displayMetrics = getContext().getResources().getDisplayMetrics();
int tabMinWidth = displayMetrics.widthPixels / childCount;
for (int i = 0; i < childCount; ++i) {
tabLayout.getChildAt(i).setMinimumWidth(tabMinWidth);
}
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
I have tried giving this,
app:tabMaxWidth="0dp"
app:tabGravity="fill"

Error related to constructor calling. and passing of parameters

I have trying to make custom layout manager for my recyclerview in android. by the name CustomLinearLayoutManager. and trying to calling constructor and class of this into my home fragment. but failed. and getting some errors.
CustomLinearLayoutManager class
public class CustomLinearLayoutManager extends LinearLayoutManager {
public CustomLinearLayoutManager (Context context) {
super(context);
}
public CustomLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
}
public CustomLinearLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
#Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
final LinearSmoothScroller linearSmoothScroller =
new LinearSmoothScroller(recyclerView.getContext()) {
private static final float MILLISECONDS_PER_INCH = 200f;
#Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return CustomLinearLayoutManager.this
.computeScrollVectorForPosition(targetPosition);
}
#Override
protected float calculateSpeedPerPixel
(DisplayMetrics displayMetrics) {
return MILLISECONDS_PER_INCH / displayMetrics.densityDpi;
}
};
linearSmoothScroller.setTargetPosition(position);
startSmoothScroll(linearSmoothScroller);
}
}
Home Fragment
CustomLinearLayoutManager customLinearLayoutManager = new CustomLinearLayoutManager(getContext());
customLinearLayoutManager.smoothScrollToPosition();
recyclerViewHeaderSlider = view.findViewById(R.id.bannerSlider);
SnapHelper snapHelper = new PagerSnapHelper();
snapHelper.attachToRecyclerView(recyclerViewHeaderSlider);
recyclerViewHeaderSlider.setHasFixedSize(true);
recyclerViewHeaderSlider.setLayoutManager(new LinearLayoutManager(getActivity(), LinearLayoutManager.HORIZONTAL, false));
headerSliderAdapter.setOnClick(this);
recyclerViewHeaderSlider.setAdapter(headerSliderAdapter);
Errors which i am facing..
public CustomLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
}
Error: Constructor 'CustomLinearLayoutManager(android.content.Context, int, boolean)' is never used
public CustomLinearLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
Error: Constructor 'CustomLinearLayoutManager(android.content.Context, android.util.AttributeSet, int, int)' is never used
In Home Fragment:
customLinearLayoutManager.smoothScrollToPosition();
Error: smoothScrollToPosition() in CustomLinearLayoutManager cannot be
applied to:
Expected Parameters: Actual Arguments:
recyclerView: RecyclerView
state: State
position: int

Firs, if you defined those constructors and you are not using them then this:
Error: Constructor 'CustomLinearLayoutManager(android.content.Context, android.util.AttributeSet, int, int)' is never used
This is not an error in all. This is an warning since it is never used.
Second, if you call a method, please make sure that the parameters are added properly else then this message is displayed.
Error: smoothScrollToPosition() in CustomLinearLayoutManager cannot be applied to: Expected Parameters: Actual Arguments:
Then you should call this method smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) by adding:
First parameter : an object as RecyclerView
Second parameter: an enum as RecyclerView.State
Third parameter : a position as integer

Implement interface using custom ScrollView class - Android

I need to know when the user scroll up or down. I managed to achieve that but now I am stuck getting the result back to my main class where I need it. Specifically I don't know how to pass the results to an interface I created.
Here is the error I get:
Attempt to invoke interface method 'void
com.app.android.interfaces.ScrollDirection.Down(int)' on a
null object reference
And here is my custom ScrollView:
public class CustomScrollView extends ScrollView {
private ScrollDirection scrolldirection;
public CustomScrollView(Context context) {
super(context);
scrolldirection = (ScrollDirection) context;
}
public CustomScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CustomScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
#Override
protected void onScrollChanged(int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
super.onScrollChanged(scrollX, scrollY, oldScrollX, oldScrollY);
if(scrollY<oldScrollY){
scrolldirection.Down(1);
}else{
scrolldirection.Down(-1);
}
}
public interface ScrollDirection{
public void Down(int direction);
}
}

you need to add this line scrolldirection = (ScrollDirection) context; inside every constructor
public CustomScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
scrolldirection = (ScrollDirection) context;
}
public CustomScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
scrolldirection = (ScrollDirection) context;
}
To allow Android Studio to interact with your view, at a minimum you must provide a constructor that takes a Context and an AttributeSet object as parameters
Docs link
Update : The recent issue was the implementation of CustomScrollView inside Fragment but Fragment do not have their context. To implement this ,make parent Activity implements the ScrollDirection and make some function in Fragment and call them from Activity's Down function.

SeekBar.java has error

I have this SeekBar.java :
package android.widget;
import android.content.Context;
import android.util.AttributeSet;
public class SeekBar extends AbsSeekBar {
public interface OnSeekBarChangeListener {
void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser);
void onStartTrackingTouch(SeekBar seekBar);
void onStopTrackingTouch(SeekBar seekBar);
private OnSeekBarChangeListener mOnSeekBarChangeListener;
public SeekBar(Context context) {
this(context, null);
}
public SeekBar(Context context, AttributeSet attrs) {
this(context, attrs, com.android.internal.R.attr.seekBarStyle);
}
public SeekBar(Context context, AttributeSet attrs, int defStyleAttr) {
this(context, attrs, defStyleAttr, 0);
}
public SeekBar(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
#Override
void onProgressRefresh(float scale, boolean fromUser, int progress) {
super.onProgressRefresh(scale, fromUser, progress);
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onProgressChanged(this, progress, fromUser);
}
}
public void setOnSeekBarChangeListener(OnSeekBarChangeListener l) {
mOnSeekBarChangeListener = l;
}
#Override
void onStartTrackingTouch() {
super.onStartTrackingTouch();
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onStartTrackingTouch(this);
}
}
#Override
void onStopTrackingTouch() {
super.onStopTrackingTouch();
if (mOnSeekBarChangeListener != null) {
mOnSeekBarChangeListener.onStopTrackingTouch(this);
}
}
#Override
public CharSequence getAccessibilityClassName() {
return SeekBar.class.getName();
}
}
The Override lines in onProgressRefresh, onStartTrackingTouch, onStopTrackingTouch give this error :
Method does not override from its super class.
And this problem causes another error in my code, how can I fix this? Thanks.

SeekBar extends AbsSeekBar
AbsSeekBar doesn't have a method named onProgressRefresh yet you are using the override annotation.
The onProgressRefresh is in OnSeekBarChangeListener interface.
I am guessing you forgot to write implents.
SeekBar extends AbsSeekBar implements OnSeekBarChangeListener

That error means that its super class does not have those methods(onProgressRefresh, onStartTrackingTouch, onStopTrackingTouch). If you want to override those methods, you shall check the super class. Or you just remove #Override

Is this a good method to make ImageView square?

Parent layout has a specified width value (50dp), and height set to MATCH_PARENT. In that layout I am adding a few ImageView widgets using Java, and because parent layout has specified width, I can set width and height of each ImageView to MATCH_PARENT and using Java I can make that ImageView square by setting its height as width.
This is my code:
public class Icon extends ImageView {
public AppIcon(final Context context)
{
super(context);
}
public AppIcon(final Context context, final AttributeSet attrs)
{
super(context, attrs);
}
public AppIcon(final Context context, final AttributeSet attrs, final int defStyle)
{
super(context, attrs, defStyle);
}
#Override
protected void onMeasure(final int width, final int height)
{
setMeasuredDimension(width, width);
}
}
Is this a good method to make each ImageView square? I think it's too simple, like something is missing.
P.S.: My method works, but I need to be sure, that everything is fine.

Your code is working one but it can be enhanced. See my code:
Updated my code.
The image will be scaled based on the measured width and height and whichever is smaller.
public class Icon extends ImageView {
public Icon(final Context context) {
super(context);
}
public Icon(final Context context, final AttributeSet attrs) {
super(context, attrs);
}
public Icon(final Context context, final AttributeSet attrs,
final int defStyle) {
super(context, attrs, defStyle);
}
#Override
protected void onMeasure(int width, int height) {
super.onMeasure(width, height);
int measuredWidth = getMeasuredWidth();
int measuredHeight = getMeasuredHeight();
if (measuredWidth > measuredHeight) {
setMeasuredDimension(measuredHeight, measuredHeight);
} else {
setMeasuredDimension(measuredWidth, measuredWidth);
}
}
}