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

@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 canvas, 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++) {
        final View view = parent.getChildAt(i);
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) view.getLayoutParams();

        if (params == null) continue;

        final LocalAdapterItem adapterItem = recyclerAdapter.getLocalAdapterItem(params.getViewAdapterPosition());

        if (adapterItem == null) continue;

        if (!isRegistered(adapterItem)) {
            continue;
        }

        final int top = view.getBottom() + params.bottomMargin;
        final int bottom = top + (dividerHeight / 2);

        canvas.drawLine(left, bottom, right, bottom, dividerPaint);
    }
}
 

@Override
public void onDraw(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
    canvas.save();
    final int right;
    //noinspection AndroidLintNewApi - NewApi lint fails to handle overrides.
    if (parent.getClipToPadding()) {
        right = parent.getWidth() - parent.getPaddingRight();
        canvas.clipRect(leftPadding, parent.getPaddingTop(), right,
                parent.getHeight() - parent.getPaddingBottom());
    } else {
        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);
        final int bottom = bounds.bottom + Math.round(child.getTranslationY());
        final int top = bottom - 1;
        divider.setBounds(leftPadding, top, right, bottom);
        divider.draw(canvas);
    }
    canvas.restore();
}
 

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

    int childCount = parent.getAdapter().getItemCount();
    for (int i = 0; i < childCount; i++) {

        if (i == (childCount - 1)) {
            continue;
        }

        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 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() - (doNotDrawForLastItem ? 1 : 0);
    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 - mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(canvas);
    }
    canvas.restore();
}
 

@Override
public void onDraw(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
    int dividerLeft = parent.getPaddingLeft();
    int dividerRight = parent.getWidth() - parent.getPaddingRight();

    int childCount = parent.getChildCount();
    for (int i = 0; i <= childCount - 2; i++) {
        View child = parent.getChildAt(i);

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

        int dividerTop = child.getBottom() + params.bottomMargin;
        int dividerBottom = dividerTop + mDivider.getIntrinsicHeight();

        mDivider.setBounds(dividerLeft, dividerTop, dividerRight, dividerBottom);
        mDivider.draw(canvas);
    }
}
 

/**
 * Performs the actual calculation for determining the number of possible
 * columns by using the {@link #maxColumnCount}, {@link #minColumnSpacingEdge}, and
 * {@link #minColumnSpacingSeparator} in conjunction with the requested width
 * for the items
 *
 * @param recyclerView The RecyclerView to use when determining the possible number of columns
 * @param gridItemWidth The requested width for items to be
 * @return The calculated number of possible columns
 */
protected int getColumnCount(@NonNull RecyclerView recyclerView, int gridItemWidth) {
    int padding = recyclerView.getPaddingLeft() + recyclerView.getPaddingRight();
    int usableWidth = recyclerView.getWidth() - padding;

    int columnCount = Math.min(usableWidth / gridItemWidth, maxColumnCount);
    int usedColumnWidth, minRequiredSpacing;

    //Decreases the columnCount until the specified min spacing can be achieved.
    do {
        usedColumnWidth = columnCount * gridItemWidth;
        minRequiredSpacing = (2 * minColumnSpacingEdge) + ((columnCount -1) * minColumnSpacingSeparator);

        //If the specified min spacing is reached, return the number of columns
        if (usableWidth - usedColumnWidth - minRequiredSpacing >= 0) {
            return columnCount;
        }

        columnCount--;
    } while(columnCount > 1);

    return columnCount;
}
 

@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);
    }
}
 

@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
    if (divider != null) {
        int count = parent.getChildCount();
        int left = parent.getPaddingLeft();
        int right = parent.getWidth() - parent.getPaddingRight();
        View child = null;
        for (int i = 0; i < count; i++) {
            if (count == 1) {
                break;
            }
            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);
        }
    }
}
 

/**
 * Update the visibility item according the current layout.
 *
 * @param view        the current {@link com.airbnb.epoxy.EpoxyViewHolder}'s itemView
 * @param parent      the {@link androidx.recyclerview.widget.RecyclerView}
 * @return true if the view has been measured
 */
boolean update(@NonNull View view, @NonNull RecyclerView parent, boolean detachEvent) {
  // Clear the rect before calling getLocalVisibleRect
  localVisibleRect.setEmpty();
  boolean viewDrawn = view.getLocalVisibleRect(localVisibleRect) && !detachEvent;
  height = view.getHeight();
  width = view.getWidth();
  viewportHeight = parent.getHeight();
  viewportWidth = parent.getWidth();
  visibleHeight = viewDrawn ? localVisibleRect.height() : 0;
  visibleWidth = viewDrawn ? localVisibleRect.width() : 0;
  return height > 0 && width > 0;
}
 

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();
}
 

/**
 * Called when {@link #onMove(RecyclerView, ViewHolder, ViewHolder)} returns true.
 * <p>
 * ItemTouchHelper 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
 * <p>
 * <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 ItemTouchHelper.
 * @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 ViewHolder viewHolder, int fromPos, final ViewHolder target, int toPos, int x,
                    int y) {
    final RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
    if (layoutManager instanceof ViewDropHandler) {
        ((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);
        }
    }
}
 

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);
    }
}
 

/**
 * @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);
    }
}
 

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

private void drawVertical(Canvas canvas, RecyclerView parent) {
    canvas.save();
    int left;
    int right;
    if (mDividerPadding != 0) {
        left = mDividerPadding;
        right = parent.getWidth() - mDividerPadding;
        canvas.clipRect(left, parent.getPaddingTop(), right, parent.getHeight() - parent.getPaddingBottom());
    } else 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) {
        View child = parent.getChildAt(i);
        parent.getDecoratedBoundsWithMargins(child, this.mBounds);
        int bottom = this.mBounds.bottom + Math.round(child.getTranslationY());
        int top = bottom - this.mDivider.getIntrinsicHeight();
        this.mDivider.setBounds(left, top, right, bottom);
        this.mDivider.draw(canvas);
    }

    canvas.restore();
}
 

private void drawVertical(Canvas c, RecyclerView parent) {
    int firstDataItemPosition = 0;
    int lastDataItemPosition = 0;
    RecyclerView.Adapter adapter = recyclerView.getAdapter();
    AssemblyRecyclerAdapter recyclerAdapter = null;
    if (adapter instanceof AssemblyRecyclerAdapter) {
        recyclerAdapter = (AssemblyRecyclerAdapter) adapter;
        firstDataItemPosition = recyclerAdapter.getHeaderCount();
        lastDataItemPosition = firstDataItemPosition + (recyclerAdapter.getDataCount() - 1);
    }

    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);
        int itemPosition = ((RecyclerView.LayoutParams) child.getLayoutParams()).getViewLayoutPosition();
        int bottomMargin = ((RecyclerView.LayoutParams) child.getLayoutParams()).bottomMargin;

        if (recyclerAdapter == null || (itemPosition >= firstDataItemPosition && itemPosition <= lastDataItemPosition)) {
            final int top = child.getBottom() + bottomMargin;
            final int bottom = top + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }
}
 

@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();
}
 

/**
 * 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();
    }
}
 

/**
 * Call from the owning {@link Component}'s onUnmount. This is where the adapter is removed from
 * the {@link RecyclerView}.
 *
 * @param view the {@link RecyclerView} being unmounted.
 */
@UiThread
@Override
public void unmount(RecyclerView view) {
  ThreadUtils.assertMainThread();
  if (mIsSubAdapter) {
    throw new RuntimeException("Can't unmount a RecyclerView in sub adapter mode");
  }

  final LayoutManager layoutManager = mLayoutInfo.getLayoutManager();
  final View firstView = layoutManager.findViewByPosition(mCurrentFirstVisiblePosition);

  if (firstView != null) {
    final boolean reverseLayout = getReverseLayout();

    if (mLayoutInfo.getScrollDirection() == HORIZONTAL) {
      mCurrentOffset =
          reverseLayout
              ? view.getWidth()
                  - layoutManager.getPaddingRight()
                  - layoutManager.getDecoratedRight(firstView)
              : layoutManager.getDecoratedLeft(firstView) - layoutManager.getPaddingLeft();
    } else {
      mCurrentOffset =
          reverseLayout
              ? view.getHeight()
                  - layoutManager.getPaddingBottom()
                  - layoutManager.getDecoratedBottom(firstView)
              : layoutManager.getDecoratedTop(firstView) - layoutManager.getPaddingTop();
    }
  } else {
    mCurrentOffset = 0;
  }

  view.removeOnScrollListener(mViewportManager.getScrollListener());

  unregisterDrawListener(view);
  maybeDispatchDataRendered();

  view.setAdapter(null);
  view.setLayoutManager(null);

  mViewportManager.removeViewportChangedListener(mViewportChangedListener);

  // We might have already unmounted this view when calling mount with a different view. In this
  // case we can just return here.
  if (mMountedView != view) {
    return;
  }

  mMountedView = null;
  if (mStickyHeaderController != null) {
    mStickyHeaderController.reset();
  }

  mLayoutInfo.setRenderInfoCollection(null);
}