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

@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 + mDivider.getIntrinsicHeight();

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

@SuppressLint("NewApi")
private void drawVertical(Canvas canvas, RecyclerView parent) {
    canvas.save();
    final int left;
    final int right;
    if (parent.getClipToPadding()) {
        left = parent.getPaddingLeft();
        right = parent.getWidth() - parent.getPaddingRight();
        canvas.clipRect(left, parent.getPaddingTop(), right,
                parent.getHeight() - parent.getPaddingBottom());
    } else {
        left = 0;
        right = parent.getWidth();
    }

    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        parent.getDecoratedBoundsWithMargins(child, mBounds);
        final int bottom = mBounds.bottom + Math.round(ViewCompat.getTranslationY(child));
        final int top = bottom - mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(canvas);
    }
    canvas.restore();
}
 

@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
    super.onDraw(c, parent, state);

    final int left = parent.getPaddingLeft();
    final int right = parent.getWidth() - parent.getPaddingRight();
    final int childCount = parent.getChildCount();

    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
        int position = params.getViewLayoutPosition();

        if (position != RecyclerView.NO_POSITION) {

            String currentTag = mDatas.get(position).getTag();
            if (!currentTag.equals(mTopTag) && (position == 0 || !currentTag.equals(mDatas.get(position - 1).getTag()))) {
                //不为空 且跟前一个tag不一样了，说明是新的分类，也要title
                drawTitleArea(c, left, right, child, params, position);
            }
        }
    }
}
 

@Override
public void onDrawOver(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 + mDivider.getIntrinsicHeight();

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

private void drawHorizontal(Canvas canvas, RecyclerView parent) {
    int left = parent.getPaddingLeft();
    int right = parent.getMeasuredWidth() - parent.getPaddingRight();
    final int childSize = parent.getChildCount();
    for (int i = 0; i < childSize; i++) {
        final View child = parent.getChildAt(i);
        RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
        int top = child.getBottom() + layoutParams.bottomMargin;
        int bottom = top + space;
        if (mDivider != null) {
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        if (mPaint != null) {
            canvas.drawRect(left, top, right, bottom, mPaint);
        }

    }
}
 

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

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

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

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

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

private boolean isStickyHeaderBeingPushedOffscreen(@NonNull RecyclerView recyclerView, @NonNull View stickyHeader) {
    View viewAfterHeader = getFirstViewUnobscuredByHeader(recyclerView, stickyHeader);
    int firstViewUnderHeaderPosition = recyclerView.getChildAdapterPosition(viewAfterHeader);
    if (firstViewUnderHeaderPosition == RecyclerView.NO_POSITION) {
        return false;
    }

    boolean isReverseLayout = mOrientationProvider.isReverseLayout(recyclerView);
    if (firstViewUnderHeaderPosition > 0 && hasNewHeader(firstViewUnderHeaderPosition, isReverseLayout)) {
        View nextHeader = mHeaderProvider.getHeader(recyclerView, firstViewUnderHeaderPosition);
        mDimensionCalculator.initMargins(mTempRect1, nextHeader);
        mDimensionCalculator.initMargins(mTempRect2, stickyHeader);

        if (mOrientationProvider.getOrientation(recyclerView) == LinearLayoutManager.VERTICAL) {
            int topOfNextHeader = viewAfterHeader.getTop() - mTempRect1.bottom - nextHeader.getHeight() - mTempRect1.top;
            int bottomOfThisHeader = recyclerView.getPaddingTop() + stickyHeader.getBottom() + mTempRect2.top + mTempRect2.bottom;
            if (topOfNextHeader < bottomOfThisHeader) {
                return true;
            }
        } else {
            int leftOfNextHeader = viewAfterHeader.getLeft() - mTempRect1.right - nextHeader.getWidth() - mTempRect1.left;
            int rightOfThisHeader = recyclerView.getPaddingLeft() + stickyHeader.getRight() + mTempRect2.left + mTempRect2.right;
            if (leftOfNextHeader < rightOfThisHeader) {
                return true;
            }
        }
    }

    return false;
}
 

public void drawVertical(Canvas c, RecyclerView parent) {

        final int left = parent.getPaddingLeft();
        final int right = parent.getWidth() - parent.getPaddingRight();

        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int top = child.getBottom() + params.bottomMargin;
            final int bottom = top + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }
 

/**
 * Called when {@link #onMove(RecyclerView, RecyclerView.ViewHolder, RecyclerView.ViewHolder)} returns true.
 * <p>
 * WeSwipeHelper does not create an extra Bitmap or View while dragging, instead, it
 * modifies the existing View. Because of this reason, it is important that the View is
 * still part of the layout after it is moved. This may not work as intended when swapped
 * Views are close to RecyclerView bounds or there are gaps between them (e.g. other Views
 * which were not eligible for dropping over).
 * <p>
 * This method is responsible to give necessary hint to the LayoutManager so that it will
 * keep the View in visible area. For example, for LinearLayoutManager, this is as simple
 * as calling {@link LinearLayoutManager#scrollToPositionWithOffset(int, int)}.
 * <p>
 * Default implementation calls {@link RecyclerView#scrollToPosition(int)} if the View's
 * new position is likely to be out of bounds.
 * <p>
 * It is important to ensure the ViewHolder will stay visible as otherwise, it might be
 * removed by the LayoutManager if the move causes the View to go out of bounds. In that
 * case, drag will end prematurely.
 *
 * @param recyclerView The RecyclerView controlled by the WeSwipeHelper.
 * @param viewHolder   The ViewHolder under user's control.
 * @param fromPos      The previous adapter position of the dragged item (before it was
 *                     moved).
 * @param target       The ViewHolder on which the currently active item has been dropped.
 * @param toPos        The new adapter position of the dragged item.
 * @param x            The updated left value of the dragged View after drag translations
 *                     are applied. This value does not include margins added by
 *                     {@link RecyclerView.ItemDecoration}s.
 * @param y            The updated top value of the dragged View after drag translations
 *                     are applied. This value does not include margins added by
 *                     {@link RecyclerView.ItemDecoration}s.
 */
public void onMoved(final RecyclerView recyclerView,
                    final RecyclerView.ViewHolder viewHolder, int fromPos, final RecyclerView.ViewHolder target, int toPos, int x,
                    int y) {
    final RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
    if (layoutManager instanceof WeSwipeHelper.ViewDropHandler) {
        ((WeSwipeHelper.ViewDropHandler) layoutManager).prepareForDrop(viewHolder.itemView,
                target.itemView, x, y);
        return;
    }

    // if layout manager cannot handle it, do some guesswork
    if (layoutManager.canScrollHorizontally()) {
        final int minLeft = layoutManager.getDecoratedLeft(target.itemView);
        if (minLeft <= recyclerView.getPaddingLeft()) {
            recyclerView.scrollToPosition(toPos);
        }
        final int maxRight = layoutManager.getDecoratedRight(target.itemView);
        if (maxRight >= recyclerView.getWidth() - recyclerView.getPaddingRight()) {
            recyclerView.scrollToPosition(toPos);
        }
    }

    if (layoutManager.canScrollVertically()) {
        final int minTop = layoutManager.getDecoratedTop(target.itemView);
        if (minTop <= recyclerView.getPaddingTop()) {
            recyclerView.scrollToPosition(toPos);
        }
        final int maxBottom = layoutManager.getDecoratedBottom(target.itemView);
        if (maxBottom >= recyclerView.getHeight() - recyclerView.getPaddingBottom()) {
            recyclerView.scrollToPosition(toPos);
        }
    }
}
 

private void drawVertical(Canvas canvas, RecyclerView parent) {
    canvas.save();
    final int left;
    final int right;
    //noinspection AndroidLintNewApi - NewApi lint fails to handle overrides.
    if (parent.getClipToPadding()) {
        left = parent.getPaddingLeft();
        right = parent.getWidth() - parent.getPaddingRight();
        canvas.clipRect(left, parent.getPaddingTop(), right,
                parent.getHeight() - parent.getPaddingBottom());
    } else {
        left = 0;
        right = parent.getWidth();
    }

    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        parent.getDecoratedBoundsWithMargins(child, mBounds);
        final int bottom = mBounds.bottom + Math.round(child.getTranslationY());
        final int top = bottom - mDividerSize;
        mDividerPaint.setColor(mDividerColor);
        mDividerPaint.setStyle(Paint.Style.FILL);
        canvas.drawRect(left + mMarginStart, top + mMarginTop, right - mMarginEnd, bottom - mMarginBottom, mDividerPaint);
    }
    canvas.restore();
}
 

private void drawVertical(Canvas canvas, RecyclerView parent) {
    canvas.save();

    int left;
    int right;
    if (parent.getClipToPadding()) {
        left = parent.getPaddingLeft();
        right = parent.getWidth() - parent.getPaddingRight();
        canvas.clipRect(left, parent.getPaddingTop(), right, parent.getHeight() - parent.getPaddingBottom());
    } else {
        left = 0;
        right = parent.getWidth();
    }

    int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        if (isDecorated(i)) {
            View child = parent.getChildAt(i);
            parent.getDecoratedBoundsWithMargins(child, mBounds);
            int bottom = mBounds.bottom + Math.round(child.getTranslationY());
            int top = bottom - mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
    }

    canvas.restore();
}
 

/**
 * @param c
 * @param parent
 * @param state
 */
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
    if (dividerDrawable == null) {
        return;
    }

    int childCount = parent.getChildCount();
    int rightV = parent.getWidth();
    for (int i = 0; i < childCount; i++) {
        View child = parent.getChildAt(i);
        RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();

        int leftV = parent.getPaddingLeft() + child.getPaddingLeft();
        int bottomV = child.getTop() - params.topMargin;
        int topV = bottomV - dividerDrawable.getIntrinsicHeight();

        int topH = child.getTop() + params.topMargin;
        int bottomH = child.getBottom() + params.bottomMargin;
        int rightH = child.getLeft() - params.leftMargin;
        int leftH = rightH - dividerDrawable.getIntrinsicWidth();
        dividerDrawable.setBounds(leftH, topH, rightH, bottomH);
        dividerDrawable.draw(c);
        dividerDrawable.setBounds(leftV, topV, rightV, bottomV);
        dividerDrawable.draw(c);
    }
}
 

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {

  if (parent.getPaddingLeft() != halfSpace) {
    parent.setPadding(halfSpace, halfSpace, halfSpace, halfSpace);
    parent.setClipToPadding(false);
  }

  outRect.top = halfSpace;
  outRect.bottom = halfSpace;
  outRect.left = halfSpace;
  outRect.right = halfSpace;
}
 

private void drawVertical(Canvas canvas, RecyclerView parent) {
    canvas.save();
    final int left;
    final int right;
    //noinspection AndroidLintNewApi - NewApi lint fails to handle overrides.
    if (parent.getClipToPadding()) {
        left = parent.getPaddingLeft();
        right = parent.getWidth() - parent.getPaddingRight();
        canvas.clipRect(left, parent.getPaddingTop(), right,
                parent.getHeight() - parent.getPaddingBottom());
    } else {
        left = 0;
        right = parent.getWidth();
    }

    final int childCount = parent.getChildCount();
    RecyclerView.Adapter adapter = parent.getAdapter();
    final int itemCount = adapter == null ? -1 : adapter.getItemCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        int adapterPosition = parent.getChildAdapterPosition(child);
        if (adapterPosition == 0 || adapterPosition == itemCount - 1)
            continue;

        parent.getDecoratedBoundsWithMargins(child, mBounds);
        final int bottom = mBounds.bottom + Math.round(child.getTranslationY());
        final int top = bottom - mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(canvas);
    }
    canvas.restore();
}
 

public void drawVertical(Canvas c, RecyclerView parent) {
    final int left = parent.getPaddingLeft();
    final int right = parent.getWidth() - parent.getPaddingRight();

    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                .getLayoutParams();
        final int top = child.getBottom() + params.bottomMargin;
        final int bottom = top + mDrawable.getIntrinsicHeight();
        mDrawable.setBounds(left, top, right, bottom);
        mDrawable.draw(c);
    }
}
 

public void drawVertical(Canvas c, RecyclerView parent) {
    final int left = parent.getPaddingLeft();
    final int right = parent.getWidth() - parent.getPaddingRight();

    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                .getLayoutParams();
        final int top = child.getBottom() + params.bottomMargin;
        final int bottom = top + mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}
 

@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
    if (parent.getLayoutManager() == null) {
        return;
    }

    c.save();
    final int left;
    final int right;
    if (parent.getClipToPadding()) {
        left = parent.getPaddingLeft();
        right = parent.getWidth() - parent.getPaddingRight();
        c.clipRect(left, parent.getPaddingTop(), right, parent.getHeight() - parent.getPaddingBottom());
    } else {
        left = 0;
        right = parent.getWidth();
    }

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

        int position = parent.getChildAdapterPosition(child);
        if (parent.getAdapter().getItemViewType(position) == EventListAdapter.ITEM_TYPE_HEADER ||
            parent.getAdapter().getItemViewType(position + 1) == EventListAdapter.ITEM_TYPE_HEADER ||
            position == state.getItemCount() - 1) {
            continue;
        }

        final int bottom = bounds.bottom + Math.round(ViewCompat.getTranslationY(child));
        final int top = bottom - divider.getIntrinsicHeight();
        divider.setBounds(left, top, right, bottom);
        divider.draw(c);
    }
    c.restore();
}
 

@Override
public void onDraw(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
    canvas.save();
    final int left;
    final int right;
    if (parent.getClipToPadding()) {
        left = parent.getPaddingLeft();
        right = parent.getWidth() - parent.getPaddingRight();
        canvas.clipRect(left, parent.getPaddingTop(), right,
                parent.getHeight() - parent.getPaddingBottom());
    } else {
        left = 0;
        right = parent.getWidth();
    }
    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        if (!hasDivider(parent, child))
            continue;
        parent.getDecoratedBoundsWithMargins(child, mBounds);
        final int bottom = mBounds.bottom + Math.round(ViewCompat.getTranslationY(child));
        final int top = bottom - mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.setAlpha((int) (child.getAlpha() * 255));
        mDivider.draw(canvas);
    }
    canvas.restore();
}
 

/**
 * Calculates and adds the amount of spacing that needs to be between each
 * column, row, and the edges of the RecyclerView.  This pays attention to
 * the value from {@link #setSpacingMethod(SpacingMethod)}
 *
 * @param recyclerView The RecyclerView to use for determining the amount of space that needs to be added
 * @param gridItemWidth The requested width for the items
 * @param columnCount The number of columns to display
 */
protected void updateSpacing(@NonNull RecyclerView recyclerView, int gridItemWidth, int columnCount) {
    //Sets the decoration for the calculated spacing
    if (spacerDecoration == null) {
        spacerDecoration = new SpacerDecoration();
        spacerDecoration.setAllowedEdgeSpacing(SpacerDecoration.EDGE_SPACING_LEFT | SpacerDecoration.EDGE_SPACING_RIGHT);
        recyclerView.addItemDecoration(spacerDecoration);
    }

    edgeSpacing = minColumnSpacingEdge;
    int separatorSpacing = minColumnSpacingSeparator / 2;


    //Calculates the edge spacing requirements
    int padding = recyclerView.getPaddingLeft() + recyclerView.getPaddingRight();
    int usableWidth = recyclerView.getWidth() - padding;

    int separatorCount = columnCount -1;
    int spacerCount = 2 * columnCount;

    int freeSpace = usableWidth - (gridItemWidth * columnCount);
    int extraSpace = freeSpace - (2 * minColumnSpacingEdge) - (separatorCount * minColumnSpacingSeparator);

    //If we can add spacing, then we need to calculate how much and where to add it
    if (extraSpace >= spacerCount) {
        if (spacingMethod == SpacingMethod.ALL) {
            int totalMinEdges = minColumnSpacingEdge * 2;
            int totalMinSeparators = separatorCount * minColumnSpacingSeparator;

            //If the totalMinSpace is 0, then the percentage is edge count / separators + edges
            int totalMinSpace = totalMinEdges + totalMinSeparators;
            double edgeSpacePercentage = totalMinSpace == 0 ? (2 / (2 + separatorCount)) : (double)totalMinEdges / (double)totalMinSpace;
            int totalSeparatorSpace = (int)((1d - edgeSpacePercentage) * freeSpace);

            separatorSpacing = spacerCount == 0 ? 0 : totalSeparatorSpace / spacerCount;
            edgeSpacing = ((freeSpace - totalSeparatorSpace) / 2) + separatorSpacing;
        } else if (spacingMethod == SpacingMethod.EDGES) {
            edgeSpacing = (freeSpace - (separatorSpacing * spacerCount)) / 2;
        } else { //SEPARATOR
            separatorSpacing = spacerCount == 0 ? 0 : freeSpace / spacerCount;
        }

        edgeSpacing -= separatorSpacing;
    }

    //Updates the spacing using the decoration and padding
    recyclerView.setPadding(
            recyclerView.getPaddingLeft() + edgeSpacing,
            recyclerView.getPaddingTop(),
            recyclerView.getPaddingRight() + edgeSpacing,
            recyclerView.getPaddingBottom()
    );

    spacerDecoration.update(separatorSpacing, matchSpacing ? separatorSpacing : rowSpacing / 2);
}
 

/**
 * 绘制悬浮组
 *
 * @param c      Canvas
 * @param parent RecyclerView
 */
protected void onDrawOverGroup(Canvas c, RecyclerView parent) {
    int firstVisiblePosition = ((LinearLayoutManager) parent.getLayoutManager()).findFirstVisibleItemPosition();
    if (firstVisiblePosition == RecyclerView.NO_POSITION) {
        return;
    }
    Group group = getCroup(firstVisiblePosition);
    if (group == null)
        return;
    String groupTitle = group.toString();
    if (TextUtils.isEmpty(groupTitle)) {
        return;
    }
    boolean isRestore = false;
    Group nextGroup = getCroup(firstVisiblePosition + 1);
    if (nextGroup != null && !group.equals(nextGroup)) {
        //说明是当前组最后一个元素，但不一定碰撞了
        View child = parent.findViewHolderForAdapterPosition(firstVisiblePosition).itemView;
        if (child.getTop() + child.getMeasuredHeight() < mGroupHeight) {
            //进一步检测碰撞
            c.save();//保存画布当前的状态
            isRestore = true;
            c.translate(0, child.getTop() + child.getMeasuredHeight() - mGroupHeight);
        }
    }
    int left = parent.getPaddingLeft();
    int right = parent.getWidth() - parent.getPaddingRight();
    int top = parent.getPaddingTop();
    int bottom = top + mGroupHeight;
    c.drawRect(left, top, right, bottom, mBackgroundPaint);
    float x;
    float y = top + mTextBaseLine;
    if (isCenter) {
        x = parent.getMeasuredWidth() / 2 - getTextX(groupTitle);
    } else {
        x = mPaddingLeft;
    }
    c.drawText(groupTitle, x, y, mTextPaint);
    if (isRestore) {
        //还原画布为初始状态
        c.restore();
    }
}