android.support.v4.view.ViewCompat#getLayoutDirection ( )源码实例Demo

@Override
public void draw(Canvas canvas) {
    copyBounds(mTmpRect);
    canvas.save();

    // Layout direction must be obtained from the activity.
    final boolean isLayoutRTL = ViewCompat.getLayoutDirection(
            mActivity.getWindow().getDecorView()) == ViewCompat.LAYOUT_DIRECTION_RTL;
    final int flipRtl = isLayoutRTL ? -1 : 1;
    final int width = mTmpRect.width();
    canvas.translate(-mOffset * width * mPosition * flipRtl, 0);

    // Force auto-mirroring if it's not supported by the platform.
    if (isLayoutRTL && !mHasMirroring) {
        canvas.translate(width, 0);
        canvas.scale(-1, 1);
    }

    super.draw(canvas);
    canvas.restore();
}
 

@Override
public void draw(Canvas canvas) {
    copyBounds(mTmpRect);
    canvas.save();

    // Layout direction must be obtained from the activity.
    final boolean isLayoutRTL = ViewCompat.getLayoutDirection(
            mActivity.getWindow().getDecorView()) == ViewCompat.LAYOUT_DIRECTION_RTL;
    final int flipRtl = isLayoutRTL ? -1 : 1;
    final int width = mTmpRect.width();
    canvas.translate(-mOffset * width * mPosition * flipRtl, 0);

    // Force auto-mirroring if it's not supported by the platform.
    if (isLayoutRTL && !mHasMirroring) {
        canvas.translate(width, 0);
        canvas.scale(-1, 1);
    }

    super.draw(canvas);
    canvas.restore();
}
 

public void showHint(int color) {
  final int[] screenPos = new int[2];
  final Rect displayFrame = new Rect();
  getLocationOnScreen(screenPos);
  getWindowVisibleDisplayFrame(displayFrame);
  final Context context = getContext();
  final int width = getWidth();
  final int height = getHeight();
  final int midy = screenPos[1] + height / 2;
  int referenceX = screenPos[0] + width / 2;
  if (ViewCompat.getLayoutDirection(this) == ViewCompat.LAYOUT_DIRECTION_LTR) {
    final int screenWidth = context.getResources().getDisplayMetrics().widthPixels;
    referenceX = screenWidth - referenceX; // mirror
  }
  Toast cheatSheet = Toast
      .makeText(context, String.format("#%06X", 0xFFFFFF & color), Toast.LENGTH_SHORT);
  if (midy < displayFrame.height()) {
    // Show along the top; follow action buttons
    cheatSheet.setGravity(Gravity.TOP | GravityCompat.END, referenceX,
        screenPos[1] + height - displayFrame.top);
  } else {
    // Show along the bottom center
    cheatSheet.setGravity(Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL, 0, height);
  }
  cheatSheet.show();
}
 

private Drawable resolveLeftShadow() {
    int layoutDirection = ViewCompat.getLayoutDirection(this);
    // Prefer shadows defined with start/end gravity over left and right.
    if (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) {
        if (mShadowStart != null) {
            // Correct drawable layout direction, if needed.
            mirror(mShadowStart, layoutDirection);
            return mShadowStart;
        }
    } else {
        if (mShadowEnd != null) {
            // Correct drawable layout direction, if needed.
            mirror(mShadowEnd, layoutDirection);
            return mShadowEnd;
        }
    }
    return mShadowLeft;
}
 

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
    int position = parent.getChildAdapterPosition(view);
    Resources resources = context.getResources();
    int horizontalPadding = (int) resources.getDimension(R.dimen.whats_new__padding__app_card__horizontal);
    int verticalPadding = (int) resources.getDimension(R.dimen.whats_new__padding__app_card__vertical);

    int relativePositionInCycle = position % 5;
    if (position == 0) {
        outRect.set(horizontalPadding, verticalPadding, horizontalPadding, verticalPadding);
    } else if (relativePositionInCycle != 0) {
        // The item on the left will have both left and right padding. The item on the right
        // will only have padding on the right. This will allow the same amount of padding
        // on the left, centre, and right of the grid, rather than double the padding in the
        // middle (which would happen if both left and right padding was set for both items).
        boolean isLtr = ViewCompat.getLayoutDirection(parent) == ViewCompat.LAYOUT_DIRECTION_LTR;
        boolean isAtStart = relativePositionInCycle == 1 || relativePositionInCycle == 3;
        int paddingStart = isAtStart ? horizontalPadding : 0;
        int paddingLeft = isLtr ? paddingStart : horizontalPadding;
        int paddingRight = isLtr ? horizontalPadding : paddingStart;
        outRect.set(paddingLeft, 0, paddingRight, verticalPadding);
    } else {
        outRect.set(horizontalPadding, 0, horizontalPadding, verticalPadding);
    }
}
 

@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
    int layoutDirection = ViewCompat.getLayoutDirection(this);
    boolean isRtl;
    switch (mFlexDirection) {
        case FlexDirection.ROW:
            isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
            layoutHorizontal(isRtl, left, top, right, bottom);
            break;
        case FlexDirection.ROW_REVERSE:
            isRtl = layoutDirection != ViewCompat.LAYOUT_DIRECTION_RTL;
            layoutHorizontal(isRtl, left, top, right, bottom);
            break;
        case FlexDirection.COLUMN:
            isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
            if (mFlexWrap == FlexWrap.WRAP_REVERSE) {
                isRtl = !isRtl;
            }
            layoutVertical(isRtl, false, left, top, right, bottom);
            break;
        case FlexDirection.COLUMN_REVERSE:
            isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
            if (mFlexWrap == FlexWrap.WRAP_REVERSE) {
                isRtl = !isRtl;
            }
            layoutVertical(isRtl, true, left, top, right, bottom);
            break;
        default:
            throw new IllegalStateException("Invalid flex direction is set: " + mFlexDirection);
    }
}
 

private boolean calculateIsRtl(CharSequence text) {
    final boolean defaultIsRtl = ViewCompat.getLayoutDirection(mView)
            == ViewCompat.LAYOUT_DIRECTION_RTL;
    return (defaultIsRtl
            ? TextDirectionHeuristicsCompat.FIRSTSTRONG_RTL
            : TextDirectionHeuristicsCompat.FIRSTSTRONG_LTR).isRtl(text, 0, text.length());
}
 

private Drawable resolveLeftShadow() {
    int layoutDirection = ViewCompat.getLayoutDirection(this);
    if (layoutDirection == 0) {
        if (this.mShadowStart != null) {
            mirror(this.mShadowStart, layoutDirection);
            return this.mShadowStart;
        }
    } else if (this.mShadowEnd != null) {
        mirror(this.mShadowEnd, layoutDirection);
        return this.mShadowEnd;
    }
    return this.mShadowLeft;
}
 

@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
    final ImageButton leftButton;
    final ImageButton rightButton;
    if (ViewCompat.getLayoutDirection(this) == ViewCompat.LAYOUT_DIRECTION_RTL) {
        leftButton = nextButton;
        rightButton = prevButton;
    } else {
        leftButton = prevButton;
        rightButton = nextButton;
    }

    final int width = right - left;
    final int height = bottom - top;
    dayPickerView.layout(0, 0, width, height);

    final SimpleMonthView monthView = (SimpleMonthView) dayPickerView.getChildAt(0);
    final int monthHeight = monthView.getMonthHeight();
    final int cellWidth = monthView.getCellWidth();
    final int edgePadding = monthView.getEdgePadding();

    // Vertically center the previous/next buttons within the month
    // header, horizontally center within the day cell.
    final int leftDW = leftButton.getMeasuredWidth();
    final int leftDH = leftButton.getMeasuredHeight();
    final int leftIconTop = monthView.getPaddingTop() + (monthHeight - leftDH) / 2;
    final int leftIconLeft = edgePadding + (cellWidth - leftDW) / 2;
    leftButton.layout(leftIconLeft, leftIconTop, leftIconLeft + leftDW, leftIconTop + leftDH);

    final int rightDW = rightButton.getMeasuredWidth();
    final int rightDH = rightButton.getMeasuredHeight();
    final int rightIconTop = monthView.getPaddingTop() + (monthHeight - rightDH) / 2;
    final int rightIconRight = width - edgePadding - (cellWidth - rightDW) / 2 - 2;
    rightButton.layout(rightIconRight - rightDW, rightIconTop,
            rightIconRight, rightIconTop + rightDH);
}
 

@Override
    public boolean requestChildRectangleOnScreen(View child, Rect rect, boolean immediate) {
        final int parentLeft = getPaddingLeft();
        final int parentTop = getPaddingTop();
        final int parentRight = getWidth() - getPaddingRight();
        final int parentBottom = getHeight() - getPaddingBottom();

        final int childLeft = child.getLeft() + rect.left;
        final int childTop = child.getTop() + rect.top;

//        final int childLeft = child.getLeft() + rect.left - child.getScrollX();
//        final int childTop = child.getTop() + rect.top - child.getScrollY();

        final int childRight = childLeft + rect.width();
        final int childBottom = childTop + rect.height();

        final int offScreenLeft = Math.min(0, childLeft - parentLeft - mSelectedItemOffsetStart);
        final int offScreenTop = Math.min(0, childTop - parentTop - mSelectedItemOffsetStart);
        final int offScreenRight = Math.max(0, childRight - parentRight + mSelectedItemOffsetEnd);
        final int offScreenBottom = Math.max(0, childBottom - parentBottom + mSelectedItemOffsetEnd);

        final boolean canScrollHorizontal = getLayoutManager().canScrollHorizontally();
        final boolean canScrollVertical = getLayoutManager().canScrollVertically();

        // Favor the "start" layout direction over the end when bringing one side or the other
        // of a large rect into view. If we decide to bring in end because start is already
        // visible, limit the scroll such that start won't go out of bounds.
        final int dx;
        if (canScrollHorizontal) {
            if (ViewCompat.getLayoutDirection(this) == ViewCompat.LAYOUT_DIRECTION_RTL) {
                dx = offScreenRight != 0 ? offScreenRight
                        : Math.max(offScreenLeft, childRight - parentRight);
            } else {
                dx = offScreenLeft != 0 ? offScreenLeft
                        : Math.min(childLeft - parentLeft, offScreenRight);
            }
        } else {
            dx = 0;
        }

        // Favor bringing the top into view over the bottom. If top is already visible and
        // we should scroll to make bottom visible, make sure top does not go out of bounds.
        final int dy;
        if (canScrollVertical) {
            dy = offScreenTop != 0 ? offScreenTop : Math.min(childTop - parentTop, offScreenBottom);
        } else {
            dy = 0;
        }
        if (cannotScrollForwardOrBackward(isVertical() ? dy : dx)) {
            offset = -1;
        } else {
            offset = isVertical() ? dy : dx;
            if (dx != 0 || dy != 0) {
                if (immediate) {
                    scrollBy(dx, dy);
                } else {
                    smoothScrollBy(dx, dy);
                }
                return true;
            }

        }

        // 重绘是为了选中item置顶，具体请参考getChildDrawingOrder方法
        postInvalidate();

        return false;
    }
 

static boolean isLayoutRtl(View v) {
  return ViewCompat.getLayoutDirection(v) == ViewCompat.LAYOUT_DIRECTION_RTL;
}
 

@Override
protected void onDraw(Canvas canvas) {
    if (mDividerDrawableVertical == null && mDividerDrawableHorizontal == null) {
        return;
    }
    if (mShowDividerHorizontal == SHOW_DIVIDER_NONE
            && mShowDividerVertical == SHOW_DIVIDER_NONE) {
        return;
    }

    int layoutDirection = ViewCompat.getLayoutDirection(this);
    boolean isRtl;
    boolean fromBottomToTop = false;
    switch (mFlexDirection) {
        case FlexDirection.ROW:
            isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
            if (mFlexWrap == FlexWrap.WRAP_REVERSE) {
                fromBottomToTop = true;
            }
            drawDividersHorizontal(canvas, isRtl, fromBottomToTop);
            break;
        case FlexDirection.ROW_REVERSE:
            isRtl = layoutDirection != ViewCompat.LAYOUT_DIRECTION_RTL;
            if (mFlexWrap == FlexWrap.WRAP_REVERSE) {
                fromBottomToTop = true;
            }
            drawDividersHorizontal(canvas, isRtl, fromBottomToTop);
            break;
        case FlexDirection.COLUMN:
            isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
            if (mFlexWrap == FlexWrap.WRAP_REVERSE) {
                isRtl = !isRtl;
            }
            drawDividersVertical(canvas, isRtl, false);
            break;
        case FlexDirection.COLUMN_REVERSE:
            isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
            if (mFlexWrap == FlexWrap.WRAP_REVERSE) {
                isRtl = !isRtl;
            }
            drawDividersVertical(canvas, isRtl, true);
            break;
    }
}
 

@Override
boolean isLayoutRtl() {
    return ViewCompat.getLayoutDirection(mActivity.getWindow().getDecorView())
            == ViewCompat.LAYOUT_DIRECTION_RTL;
}
 

public boolean isLayoutRtl() {
    return ViewCompat.getLayoutDirection(this) == ViewCompat.LAYOUT_DIRECTION_RTL;
}
 

private boolean isLayoutRTL() {
    return ViewCompat.getLayoutDirection(mRecyclerView) == ViewCompat.LAYOUT_DIRECTION_RTL;
}
 

@Override
protected void onDraw(Canvas canvas) {
    if (mDividerDrawableVertical == null && mDividerDrawableHorizontal == null) {
        return;
    }
    if (mShowDividerHorizontal == SHOW_DIVIDER_NONE
            && mShowDividerVertical == SHOW_DIVIDER_NONE) {
        return;
    }

    int layoutDirection = ViewCompat.getLayoutDirection(this);
    boolean isRtl;
    boolean fromBottomToTop = false;
    switch (mFlexDirection) {
        case FLEX_DIRECTION_ROW:
            isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
            if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
                fromBottomToTop = true;
            }
            drawDividersHorizontal(canvas, isRtl, fromBottomToTop);
            break;
        case FLEX_DIRECTION_ROW_REVERSE:
            isRtl = layoutDirection != ViewCompat.LAYOUT_DIRECTION_RTL;
            if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
                fromBottomToTop = true;
            }
            drawDividersHorizontal(canvas, isRtl, fromBottomToTop);
            break;
        case FLEX_DIRECTION_COLUMN:
            isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
            if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
                isRtl = !isRtl;
            }
            fromBottomToTop = false;
            drawDividersVertical(canvas, isRtl, fromBottomToTop);
            break;
        case FLEX_DIRECTION_COLUMN_REVERSE:
            isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
            if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
                isRtl = !isRtl;
            }
            fromBottomToTop = true;
            drawDividersVertical(canvas, isRtl, fromBottomToTop);
            break;
    }
}
 

@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
    super.onLayout(changed, left, top, right, bottom);

    // Update the collapsed bounds by getting it's transformed bounds. This needs to be done
    // before the children are offset below
    if (mCollapsingTitleEnabled && mDummyView != null) {
        // We only draw the title if the dummy view is being displayed (Toolbar removes
        // views if there is no space)
        mDrawCollapsingTitle = ViewCompat.isAttachedToWindow(mDummyView) && mDummyView.getVisibility() == VISIBLE;

        if (mDrawCollapsingTitle) {
            final boolean isRtl = ViewCompat.getLayoutDirection(this) == ViewCompat.LAYOUT_DIRECTION_RTL;

            // Update the collapsed bounds
            int bottomOffset = 0;
            if (mToolbarDirectChild != null && mToolbarDirectChild != this) {
                final LayoutParams lp = (LayoutParams) mToolbarDirectChild.getLayoutParams();
                bottomOffset = lp.bottomMargin;
            }
            ViewGroupUtils.getDescendantRect(this, mDummyView, mTmpRect);
            mCollapsingTextHelper.setCollapsedBounds(
                    mTmpRect.left + (isRtl ? mToolbar.getTitleMarginEnd() : mToolbar.getTitleMarginStart()),
                    bottom + mToolbar.getTitleMarginTop() - mTmpRect.height() - bottomOffset,
                    mTmpRect.right + (isRtl ? mToolbar.getTitleMarginStart() : mToolbar.getTitleMarginEnd()),
                    bottom - bottomOffset - mToolbar.getTitleMarginBottom());

            // Update the expanded bounds
            mCollapsingTextHelper.setExpandedBounds(
                    isRtl ? mExpandedMarginEnd : mExpandedMarginStart,
                    mTmpRect.bottom + mExpandedMarginTop,
                    right - left - (isRtl ? mExpandedMarginStart : mExpandedMarginEnd),
                    bottom - top - mExpandedMarginBottom);
            // Now recalculate using the new bounds
            mCollapsingTextHelper.recalculate();
        }
    }

    // Update our child view offset helpers
    for (int i = 0, z = getChildCount(); i < z; i++) {
        final View child = getChildAt(i);

        if (mLastInsets != null && !ViewCompat.getFitsSystemWindows(child)) {
            final int insetTop = mLastInsets.getSystemWindowInsetTop();
            if (child.getTop() < insetTop) {
                // If the child isn't set to fit system windows but is drawing within the inset
                // offset it down
                ViewCompat.offsetTopAndBottom(child, insetTop);
            }
        }

        getViewOffsetHelper(child).onViewLayout();
    }

    // Finally, set our minimum height to enable proper AppBarLayout collapsing
    if (mToolbar != null) {
        if (mCollapsingTitleEnabled && TextUtils.isEmpty(mCollapsingTextHelper.getText())) {
            // If we do not currently have a title, try and grab it from the Toolbar
            mCollapsingTextHelper.setText(mToolbar.getTitle());
        }
        if (mToolbarDirectChild == null || mToolbarDirectChild == this) {
            setMinimumHeight(getHeightWithMargins(mToolbar));
        } else {
            setMinimumHeight(getHeightWithMargins(mToolbarDirectChild));
        }
    }
}
 

public int getDrawerLockMode(int edgeGravity) {
    int layoutDirection = ViewCompat.getLayoutDirection(this);
    switch (edgeGravity) {
        case 3:
            if (this.mLockModeLeft != 3) {
                return this.mLockModeLeft;
            }
            int leftLockMode = layoutDirection == 0 ? this.mLockModeStart : this.mLockModeEnd;
            if (leftLockMode != 3) {
                return leftLockMode;
            }
            break;
        case 5:
            if (this.mLockModeRight != 3) {
                return this.mLockModeRight;
            }
            int rightLockMode = layoutDirection == 0 ? this.mLockModeEnd : this.mLockModeStart;
            if (rightLockMode != 3) {
                return rightLockMode;
            }
            break;
        case GravityCompat.START /*8388611*/:
            if (this.mLockModeStart != 3) {
                return this.mLockModeStart;
            }
            int startLockMode = layoutDirection == 0 ? this.mLockModeLeft : this.mLockModeRight;
            if (startLockMode != 3) {
                return startLockMode;
            }
            break;
        case GravityCompat.END /*8388613*/:
            if (this.mLockModeEnd != 3) {
                return this.mLockModeEnd;
            }
            int endLockMode = layoutDirection == 0 ? this.mLockModeRight : this.mLockModeLeft;
            if (endLockMode != 3) {
                return endLockMode;
            }
            break;
    }
    return 0;
}
 

private boolean isLayoutRtlSupport() {
    return ViewCompat.getLayoutDirection(this) == ViewCompat.LAYOUT_DIRECTION_RTL;
}
 

public boolean isRtl() {
    return (ViewCompat.getLayoutDirection(this) == LAYOUT_DIRECTION_RTL) && mMirrorForRtl;
}