Add margins to divider in RecyclerView

问题:

i am building an android app which is using RecyclerView. I want to add dividers to RecyclerView, which I did using this code:

DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(recyclerView.getContext(), linearLayoutManager.getOrientation());
recyclerView.addItemDecoration(dividerItemDecoration);

So far everything works fine. However, the divider is taking the size of full screen and I want to add margins to it. Is there any way that I can add margins to the divider using a method that will add some space to the rectangle drawn and not by creating a custom drawable shape with margins and add it to the RecyclerView?

回答1:

Use this and customize according to your requirement.

public class DividerItemDecoration extends RecyclerView.ItemDecoration {

private static final int[] ATTRS = new int[]{android.R.attr.listDivider};

private Drawable divider;

/**
 * Default divider will be used
 */
public DividerItemDecoration(Context context) {
    final TypedArray styledAttributes = context.obtainStyledAttributes(ATTRS);
    divider = styledAttributes.getDrawable(0);
    styledAttributes.recycle();
}

/**
 * Custom divider will be used
 */
public DividerItemDecoration(Context context, int resId) {
    divider = ContextCompat.getDrawable(context, resId);
}

@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
    int left = parent.getPaddingLeft();
    int right = parent.getWidth() - parent.getPaddingRight();

    int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        View child = parent.getChildAt(i);

        RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();

        int top = child.getBottom() + params.bottomMargin;
        int bottom = top + divider.getIntrinsicHeight();

        divider.setBounds(left, top, right, bottom);
        divider.draw(c);
    }
}

}

回答2:

I think the most straightforward solution is to use the setDrawable method on the Decoration object and pass it an inset drawable with the inset values you want for the margins. Like so:

int[] ATTRS = new int[]{android.R.attr.listDivider};

TypedArray a = context.obtainStyledAttributes(ATTRS);
Drawable divider = a.getDrawable(0);
int inset = getResources().getDimensionPixelSize(R.dimen.your_margin_value);
InsetDrawable insetDivider = new InsetDrawable(divider, inset, 0, inset, 0);
a.recycle();

DividerItemDecoration itemDecoration = new DividerItemDecoration(context, DividerItemDecoration.VERTICAL);
itemDecoration.setDrawable(insetDivider);
recyclerView.addItemDecoration(itemDecoration);

回答3:

You can create your own item decoration for recycler view. Here is code for the same.

public class SimpleItemDecorator extends RecyclerView.ItemDecoration {

    int space;
    boolean isHorizontalLayout;
    public SimpleItemDecorator(int space) {
        this.space = space;
    }

    public SimpleItemDecorator(int space, boolean isHorizontalLayout) {
        this.space = space;
        this.isHorizontalLayout = isHorizontalLayout;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        if(isHorizontalLayout)
        {
            outRect.bottom=space;
            outRect.right=space;
            outRect.left=space;
            outRect.top=space;

        } else {
            outRect.bottom = space;
            if (parent.getChildAdapterPosition(view) == 0)
                outRect.top = space;
            else
                outRect.top = 0;

        }


    }
}

And to use it with your recyclerview you can do like this:

 recyclerView.addItemDecoration(new SimpleItemDecorator(5));

回答4:

Same like @Vivek answer but in Kotlin and different params

class SimpleItemDecorator : RecyclerView.ItemDecoration {

    private var top_bottom: Int = 0
    private var left_right: Int = 0

    /**
     * @param top_bottom for top and bottom margin
     * @param left_right for left and right margin
     */
    constructor(top_bottom: Int, left_right: Int = 0) {
        this.top_bottom = top_bottom
        this.left_right = left_right
    }

    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
        super.getItemOffsets(outRect, view, parent, state)
        outRect.bottom = top_bottom
        outRect.top = top_bottom
        outRect.right = left_right
        outRect.left = left_right
    }
}