与构造函数调用相关的错误。 和参数传递

Question

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

Answer 1

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