I am using Turn layout manager to make my recyclerview circular everything is working fine, except I want the list to start from the first item in the center and end at the last item at the center, I tried giving margin and padding but did not work
/**
* An extension of {@link LinearLayoutManager}, where each list item can be offset along a circular
* trajectory.
*/
public class TurnLayoutManager extends LinearLayoutManager {
private static final int MIN_RADIUS = 0;
private static final int MIN_PEEK = 0;
/**
* Valid gravity settings for a {@link TurnLayoutManager}. This defines the direction of the center point
* around which items will rotate.
*/
@IntDef(value = {
Gravity.START,
Gravity.END
})
public @interface Gravity {
int START = android.view.Gravity.START;
int END = android.view.Gravity.END;
}
/**
* Orientation as defined in {@link RecyclerView}
*/
@IntDef(value = {
Orientation.VERTICAL,
Orientation.HORIZONTAL
})
public @interface Orientation {
int VERTICAL = RecyclerView.VERTICAL;
int HORIZONTAL = RecyclerView.HORIZONTAL;
}
@Gravity
private int gravity;
@Dimension
private int radius;
@Dimension
private int peekDistance;
private boolean rotate;
private Point center;
/**
* Define a new {@link TurnLayoutManager} with the given settings.<br>
* {@code gravity} and {@code orientation} combine to define the curvature of the turn:
* <br><br>
* {@link Gravity#START}<br>
* {@link Orientation#VERTICAL}
* <pre>
* ┏─────────┓
* ┃ x ┃
* ┃ x ┃
* ┃ x ┃
* ┃ x ┃
* ┃ x ┃
* ┃ x ┃
* ┃ x ┃
* ┗─────────┛
* </pre>
* <br>
* {@link Gravity#END}<br>
* {@link Orientation#VERTICAL}
* <pre>
* ┏─────────┓
* ┃ x ┃
* ┃ x ┃
* ┃ x ┃
* ┃ x ┃
* ┃ x ┃
* ┃ x ┃
* ┃ x ┃
* ┗─────────┛
* </pre>
* <p>
* <br>
* {@link Gravity#START}<br>
* {@link Orientation#HORIZONTAL}
* <pre>
* ┏─────────┓
* ┃x x┃
* ┃ x x ┃
* ┃ xxx ┃
* ┃ ┃
* ┃ ┃
* ┃ ┃
* ┃ ┃
* ┗─────────┛
* </pre>
* <p>
* <br>
* {@link Gravity#END}<br>
* {@link Orientation#HORIZONTAL}
* <pre>
* ┏─────────┓
* ┃ ┃
* ┃ ┃
* ┃ ┃
* ┃ ┃
* ┃ xxx ┃
* ┃ x x ┃
* ┃x x┃
* ┗─────────┛
* </pre>
*
* @param gravity The {@link Gravity} that will define where the anchor point is for this layout manager. The
* gravity point is the point around which items orbit.
* @param orientation The orientation as defined in {@link RecyclerView}, and enforced by {@link Orientation}
* @param radius The radius of the rotation angle, which helps define the curvature of the turn. This value
* will be clamped to {@code [0, MAX_INT]} inclusive.
* @param peekDistance The absolute extra distance from the {@link Gravity} edge after which this layout manager will start
* placing items. This value will be clamped to {@code [0, radius]} inclusive.
* @param rotate Should the items rotate as if on a turning surface, or should they maintain
* their angle with respect to the screen as they orbit the center point?
*/
public TurnLayoutManager(Context context,
@Gravity int gravity,
@Orientation int orientation,
@Dimension int radius,
@Dimension int peekDistance,
boolean rotate) {
super(context, orientation, false);
this.gravity = gravity;
this.radius = Math.max(radius, MIN_RADIUS);
this.peekDistance = Math.min(Math.max(peekDistance, MIN_PEEK), radius);
this.rotate = rotate;
this.center = new Point();
}
/**
* Create a {@link TurnLayoutManager} with default settings for gravity, orientation, and rotation.
*/
@SuppressWarnings("unused")
public TurnLayoutManager(Context context,
@Dimension int radius,
@Dimension int peekDistance) {
this(context, Gravity.START, Orientation.VERTICAL, radius, peekDistance, false);
}
public void setRadius(int radius) {
this.radius = Math.max(radius, MIN_RADIUS);
requestLayout();
}
public void setPeekDistance(int peekDistance) {
this.peekDistance = Math.min(Math.max(peekDistance, MIN_PEEK), radius);
requestLayout();
}
public void setGravity(@Gravity int gravity) {
this.gravity = gravity;
requestLayout();
}
public void setRotate(boolean rotate) {
this.rotate = rotate;
requestLayout();
}
@Override
public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
int by = super.scrollVerticallyBy(dy, recycler, state);
setChildOffsetsVertical(gravity, radius, center, peekDistance);
return by;
}
@Override
public int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state) {
int by = super.scrollHorizontallyBy(dx, recycler, state);
setChildOffsetsHorizontal(gravity, radius, center, peekDistance);
return by;
}
@SuppressWarnings("ConstantConditions")
@Override
public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
super.onLayoutChildren(recycler, state);
this.center = deriveCenter(gravity, getOrientation(), radius, peekDistance, center);
setChildOffsets(gravity, getOrientation(), radius, center, peekDistance);
}
/**
* Accounting for the settings of {@link Gravity} and {@link Orientation}, find the center point
* around which this layout manager should arrange list items. Place the resulting coordinates
* into {@code out}, to avoid reallocation.
*/
@SuppressWarnings("DuplicateExpressions")
private Point deriveCenter(@Gravity int gravity,
int orientation,
@Dimension int radius,
@Dimension int peekDistance,
Point out) {
final int gravitySign = gravity == Gravity.START ? -1 : 1;
final int distanceMultiplier = gravity == Gravity.START ? 0 : 1;
int x, y;
switch (orientation) {
case Orientation.HORIZONTAL:
y = (distanceMultiplier * getHeight()) + gravitySign * (Math.abs(radius - peekDistance));
x = getWidth() / 2;
break;
case Orientation.VERTICAL:
default:
y = getHeight() /2;
x = (distanceMultiplier * getWidth()) + gravitySign * (Math.abs(radius - peekDistance));
break;
}
out.set(x, y);
return out;
}
/**
* Find the absolute horizontal distance by which a view at {@code viewY} should offset
* to align with the circle {@code center} with {@code radius}, accounting for {@code peekDistance}.
*/
private double resolveOffsetX(double radius, double viewY, Point center, int peekDistance) {
final double opposite = Math.abs(center.y - viewY);
final double radiusSquared = radius * radius;
final double oppositeSquared = opposite * opposite;
final double adjacentSideLength = Math.sqrt(radiusSquared - oppositeSquared);
return adjacentSideLength - radius + peekDistance;
}
/**
* Find the absolute vertical distance by which a view at {@code viewX} should offset to
* align with the circle {@code center} with {@code radius}, account for {@code peekDistance}.
*/
private double resolveOffsetY(double radius, double viewX, Point center, int peekDistance) {
final double adjacent = Math.abs(center.x - viewX);
final double radiusSquared = radius * radius;
final double adjacentSquared = adjacent * adjacent;
final double oppositeSideLength = Math.sqrt(radiusSquared - adjacentSquared);
return oppositeSideLength - radius + peekDistance;
}
/**
* Traffic method to divert calls based on {@link Orientation}.
*
* @see #setChildOffsetsVertical(int, int, Point, int)
* @see #setChildOffsetsHorizontal(int, int, Point, int)
*/
private void setChildOffsets(@Gravity int gravity,
int orientation,
@Dimension int radius,
Point center,
int peekDistance) {
if (orientation == VERTICAL) {
setChildOffsetsVertical(gravity, radius, center, peekDistance);
} else if (orientation == HORIZONTAL) {
setChildOffsetsHorizontal(gravity, radius, center, peekDistance);
}
}
/**
* Set the bumper offsets on child views for {@link Orientation#VERTICAL}
*/
private void setChildOffsetsVertical(@Gravity int gravity,
@Dimension int radius,
Point center,
int peekDistance) {
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
if (child == null) continue;
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
final int xOffset = (int) resolveOffsetX(radius, child.getY() + child.getHeight() / 2.0f, center, peekDistance);
final int x = gravity == Gravity.START ? xOffset + getMarginStart(layoutParams)
: getWidth() - xOffset - child.getWidth() - getMarginStart(layoutParams);
child.layout(x, child.getTop(), child.getWidth() + x, child.getBottom());
setChildRotationVertical(gravity, child, radius, center);
}
}
/**
* Given that the is {@link Orientation#VERTICAL}, apply rotation if rotation is enabled.
*/
private void setChildRotationVertical(@Gravity int gravity, View child, int radius, Point center) {
if (!rotate) {
child.setRotation(0);
return;
}
boolean childPastCenter = (child.getY() + child.getHeight() / 2.0) > center.y;
float directionMult;
if (gravity == Gravity.END) {
directionMult = childPastCenter ? -1 : 1;
} else {
directionMult = childPastCenter ? 1 : -1;
}
final float opposite = Math.abs(child.getY() + child.getHeight() / 2.0f - center.y);
child.setRotation((float) (directionMult * Math.toDegrees(Math.asin(opposite / radius))));
}
/**
* Set bumper offsets on child views for {@link Orientation#HORIZONTAL}
*/
private void setChildOffsetsHorizontal(@Gravity int gravity,
@Dimension int radius,
Point center,
int peekDistance) {
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
if (child == null) continue;
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
final int yOffset = (int) resolveOffsetY(radius, child.getX() + child.getWidth() / 2.0f, center, peekDistance);
final int y = gravity == Gravity.START ? yOffset + getMarginStart(layoutParams)
: getHeight() - yOffset - child.getHeight() - getMarginStart(layoutParams);
child.layout(child.getLeft(), y, child.getRight(), child.getHeight() + y);
setChildRotationHorizontal(gravity, child, radius, center);
}
}
/**
* Given that the orientation is {@link Orientation#HORIZONTAL}, apply rotation if enabled.
*/
private void setChildRotationHorizontal(@Gravity int gravity, View child, int radius, Point center) {
if (!rotate) {
child.setRotation(0);
return;
}
boolean childPastCenter = (child.getX() + child.getWidth() / 2.0) > center.x;
float directionMult;
if (gravity == Gravity.END) {
directionMult = childPastCenter ? 1 : -1;
} else {
directionMult = childPastCenter ? -1 : 1;
}
final float opposite = Math.abs(child.getX() + child.getWidth() / 2.0f - center.x);
child.setRotation((float) (directionMult * Math.toDegrees(Math.asin(opposite / radius))));
}
/**
* @see android.view.ViewGroup.MarginLayoutParams#getMarginStart()
*/
private int getMarginStart(ViewGroup.MarginLayoutParams layoutParams) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
return layoutParams.getMarginStart();
}
return layoutParams.leftMargin;
}
}