androidx.recyclerview.widget.RecyclerView#ItemDecoration ( )源码实例Demo

@NonNull
@Override
public VH createViewHolder(final ViewGroup parent) {
	final RendererRecyclerViewAdapter adapter = createAdapter();
	for (final ViewRenderer renderer : mRenderers) {
		adapter.registerRenderer(renderer);
	}

	final VH viewHolder = createCompositeViewHolder(parent);
	viewHolder.setAdapter(adapter);

	if (viewHolder.getRecyclerView() != null) {
		viewHolder.getRecyclerView().setLayoutManager(createLayoutManager());
		viewHolder.getRecyclerView().setAdapter(adapter);
		viewHolder.getRecyclerView().setRecycledViewPool(mRecycledViewPool);
		for (final RecyclerView.ItemDecoration itemDecoration : createItemDecorations()) {
			viewHolder.getRecyclerView().addItemDecoration(itemDecoration);
		}
	}

	return viewHolder;
}
 

public void setDividerAlpha(float dividerAlpha) {
    if (0 > dividerAlpha || dividerAlpha > 1) return;

    if (mDividerItemDecoration != null) {
        mDividerItemDecoration.setDividerAlpha(dividerAlpha);
    }

    boolean hasDividerDecoration = false;
    for (int i = 0; i < getItemDecorationCount(); i++) {
        RecyclerView.ItemDecoration itemDecoration = getItemDecorationAt(i);
        if (itemDecoration instanceof DividerItemDecoration) {
            hasDividerDecoration = true;
            invalidateItemDecorations();
            break;
        }
    }

    if (!hasDividerDecoration && mDividerItemDecoration != null) {
        addItemDecoration(mDividerItemDecoration);
    }
}
 

@BindingAdapter({"item_touch"})
public static void setItemTouchHelper(final RecyclerView view, final ItemTouchHelper helper) {
	for (int i = 0;; i ++) try {
		final RecyclerView.ItemDecoration decoration = view.getItemDecorationAt(i);
		if (decoration == null) break;								// Null is returned on RecyclerView library 27+
		if (decoration == helper) return;
	} catch (final IndexOutOfBoundsException ignored) { break; }	// IndexOutOfBoundsException is thrown on RecyclerView library prior to 27.
	helper.attachToRecyclerView(view);
}
 

@Bindable
public RecyclerView.ItemDecoration[] getItemDecorations() {
    return new RecyclerView.ItemDecoration[] {
            new BackgroundDecoration(),
            new DividerDecoration(getContext())
    };
}
 

/**
 * Please use a constructor without Context
 */
@Deprecated
public CompositeViewBinder(final int layoutID,
                           @IdRes final int recyclerViewID,
                           @NonNull final Class<M> type,
                           @NonNull final Context context,
                           @NonNull final List<? extends RecyclerView.ItemDecoration> decorations) {
	this(layoutID, recyclerViewID, type, context);
	mDecorations.addAll(decorations);
}
 

@CallSuper @Override public void setupViews() {
  super.setupViews();
  RecyclerView.ItemDecoration itemDecoration = getItemDecoration();
  if (itemDecoration != null) {
    getRecyclerView().addItemDecoration(itemDecoration);
  }
}
 

public CompositeViewBinder(final int layoutID,
                           @IdRes final int recyclerViewID,
                           @NonNull final Class<M> type,
                           @NonNull final List<? extends RecyclerView.ItemDecoration> decorations) {
	this(layoutID, recyclerViewID, type);
	mDecorations.addAll(decorations);
}
 

@Override
protected RecyclerView.ItemDecoration createItemDecoration() {
    return new RecyclerView.ItemDecoration() {
        @Override
        public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent,
            @NonNull RecyclerView.State state) {
            outRect.set(20, 20, 20, 20);
        }
    };
}
 

public void addDecoration(@NonNull RecyclerView.ItemDecoration decor) {
    list.addItemDecoration(decor);
}
 

public static RecyclerViewHeader fromXml(Context context, @LayoutRes int layoutRes, RecyclerView.ItemDecoration decoration) {
    RecyclerViewHeader header = new RecyclerViewHeader(context);
    View.inflate(context, layoutRes, header);
    header.setDecor(decoration);
    return header;
}
 

protected RecyclerView.ItemDecoration getItemDecoration()
{
    //We must draw dividers ourselves if we want them in a list
    return new DividerDecoration(getActivity());
}
 

public void removeItemDecoration(RecyclerView.ItemDecoration decoration) {
    mRecyclerView.removeItemDecoration(decoration);
}
 

@NonNull
@Override
protected List<? extends RecyclerView.ItemDecoration> createItemDecorations() {
	return Collections.singletonList(new BetweenSpacesItemDecoration(0, 10));
}
 

@NonNull
protected List<? extends RecyclerView.ItemDecoration> createItemDecorations() {
	return new ArrayList<>();
}
 

private void setDecor(RecyclerView.ItemDecoration decor) {
    mDecoration = decor;
}
 

@Override
protected RecyclerView.ItemDecoration getItemDecoration()
{
    //We must draw dividers ourselves if we want them in a list
    return new DividerDecoration(getActivity());
}
 

@Override
public void onAttach(Context context) {
    super.onAttach(context);

    adapter = new ScannedDevicesAdapter(new DeviceInfoViewHolder.Generator(R.layout.device_item) {
        @Override
        public DeviceInfoViewHolder generate(View itemView) {
            final ViewHolder holder = new ViewHolder(itemView);
            holder.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    int adapterPos = holder.getAdapterPosition();
                    if (adapterPos != RecyclerView.NO_POSITION) {
                        BluetoothDeviceInfo devInfo = (BluetoothDeviceInfo) adapter.getDevicesInfo().get(adapterPos);
                        connect(devInfo);
                    }
                }
            });
            return holder;
        }

    }, context);

    discovery = new Discovery(adapter, this);

    adapter.setThermometerMode();

    discovery.connect(context);

    layout = new GridLayoutManager(context, context.getResources().getInteger(R.integer.device_selection_columns), LinearLayoutManager.VERTICAL, false);
    itemDecoration = new RecyclerView.ItemDecoration() {
        final int horizontalMargin = getResources().getDimensionPixelSize(R.dimen.item_margin);

        @Override
        public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
            final int columns = layout.getSpanCount();
            if (columns == 1) {
                outRect.set(0, 0, 0, 0);
            } else {
                int itemPos = parent.getChildAdapterPosition(view);
                if (itemPos % columns == columns - 1) {
                    outRect.set(0, 0, 0, 0);
                } else {
                    outRect.set(0, 0, horizontalMargin, 0);
                }
            }
        }
    };
}
 

/**
 * Remove an {@link RecyclerView.ItemDecoration} from wrapped RecyclerView.
 * <p>
 * <p>The given decoration will no longer impact the measurement and drawing of
 * item views.</p>
 *
 * @param decor Decoration to remove
 * @see #addItemDecoration(RecyclerView.ItemDecoration)
 */
@SuppressWarnings("unused")
public final void removeItemDecoration(RecyclerView.ItemDecoration decor) {
    getRvCategories().removeItemDecoration(decor);
}
 

/**
 * Add an {@link RecyclerView.ItemDecoration} to this RecyclerView. Item decorations can affect both measurement and drawing of individual item views.
 * <p>Item decorations are ordered. Decorations placed earlier in the list will be run/queried/drawn first for their effects on item views. Padding added to views will be nested; a padding added by an earlier decoration will mean further item decorations in the list will be asked to draw/pad within the previous decoration's given area.</p>
 *
 * @param itemDecoration Decoration to add
 * @param index          Position in the decoration chain to insert this decoration at. If this value is negative the decoration will be added at the end.
 */
public void addItemDecoration(RecyclerView.ItemDecoration itemDecoration, int index) {
    mRecyclerView.addItemDecoration(itemDecoration, index);
}
 

/**
 * Add an {@link RecyclerView.ItemDecoration} to wrapped RecyclerView. Item decorations can
 * affect both measurement and drawing of individual item views.
 * <p>
 * <p>Item decorations are ordered. Decorations placed earlier in the list will
 * be run/queried/drawn first for their effects on item views. Padding added to views
 * will be nested; a padding added by an earlier decoration will mean further
 * item decorations in the list will be asked to draw/pad within the previous decoration's
 * given area.</p>
 *
 * @param decor Decoration to add
 */
@SuppressWarnings("unused")
public final void addItemDecoration(RecyclerView.ItemDecoration decor) {
    getRvCategories().addItemDecoration(decor);
}