/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.support.v7.widget;
import android.view.View;
import android.widget.LinearLayout;
/**
* Helper class for LayoutManagers to abstract measurements depending on the View's orientation.
* <p>
* It is developed to easily support vertical and horizontal orientations in a LayoutManager but
* can also be used to abstract calls around view bounds and child measurements with margins and
* decorations.
*
* @see #createHorizontalHelper(RecyclerView.LayoutManager)
* @see #createVerticalHelper(RecyclerView.LayoutManager)
*/
public abstract class OrientationHelper {
private static final int INVALID_SIZE = Integer.MIN_VALUE;
protected final RecyclerView.LayoutManager mLayoutManager;
public static final int HORIZONTAL = LinearLayout.HORIZONTAL;
public static final int VERTICAL = LinearLayout.VERTICAL;
private int mLastTotalSpace = INVALID_SIZE;
private OrientationHelper(RecyclerView.LayoutManager layoutManager) {
mLayoutManager = layoutManager;
}
/**
* Call this method after onLayout method is complete if state is NOT pre-layout.
* This method records information like layout bounds that might be useful in the next layout
* calculations.
*/
public void onLayoutComplete() {
mLastTotalSpace = getTotalSpace();
}
/**
* Returns the layout space change between the previous layout pass and current layout pass.
* <p>
* Make sure you call {@link #onLayoutComplete()} at the end of your LayoutManager's
* {@link RecyclerView.LayoutManager#onLayoutChildren(RecyclerView.Recycler,
* RecyclerView.State)} method.
*
* @return The difference between the current total space and previous layout's total space.
* @see #onLayoutComplete()
*/
public int getTotalSpaceChange() {
return INVALID_SIZE == mLastTotalSpace ? 0 : getTotalSpace() - mLastTotalSpace;
}
/**
* Returns the start of the view including its decoration and margin.
* <p>
* For example, for the horizontal helper, if a View's left is at pixel 20, has 2px left
* decoration and 3px left margin, returned value will be 15px.
*
* @param view The view element to check
* @return The first pixel of the element
* @see #getDecoratedEnd(android.view.View)
*/
public abstract int getDecoratedStart(View view);
/**
* Returns the end of the view including its decoration and margin.
* <p>
* For example, for the horizontal helper, if a View's right is at pixel 200, has 2px right
* decoration and 3px right margin, returned value will be 205.
*
* @param view The view element to check
* @return The last pixel of the element
* @see #getDecoratedStart(android.view.View)
*/
public abstract int getDecoratedEnd(View view);
/**
* Returns the space occupied by this View in the current orientation including decorations and
* margins.
*
* @param view The view element to check
* @return Total space occupied by this view
* @see #getDecoratedMeasurementInOther(View)
*/
public abstract int getDecoratedMeasurement(View view);
/**
* Returns the space occupied by this View in the perpendicular orientation including
* decorations and margins.
*
* @param view The view element to check
* @return Total space occupied by this view in the perpendicular orientation to current one
* @see #getDecoratedMeasurement(View)
*/
public abstract int getDecoratedMeasurementInOther(View view);
/**
* Returns the start position of the layout after the start padding is added.
*
* @return The very first pixel we can draw.
*/
public abstract int getStartAfterPadding();
/**
* Returns the end position of the layout after the end padding is removed.
*
* @return The end boundary for this layout.
*/
public abstract int getEndAfterPadding();
/**
* Returns the end position of the layout without taking padding into account.
*
* @return The end boundary for this layout without considering padding.
*/
public abstract int getEnd();
/**
* Offsets all children's positions by the given amount.
*
* @param amount Value to add to each child's layout parameters
*/
public abstract void offsetChildren(int amount);
/**
* Returns the total space to layout. This number is the difference between
* {@link #getEndAfterPadding()} and {@link #getStartAfterPadding()}.
*
* @return Total space to layout children
*/
public abstract int getTotalSpace();
/**
* Offsets the child in this orientation.
*
* @param view View to offset
* @param offset offset amount
*/
public abstract void offsetChild(View view, int offset);
/**
* Returns the padding at the end of the layout. For horizontal helper, this is the right
* padding and for vertical helper, this is the bottom padding. This method does not check
* whether the layout is RTL or not.
*
* @return The padding at the end of the layout.
*/
public abstract int getEndPadding();
/**
* Creates an OrientationHelper for the given LayoutManager and orientation.
*
* @param layoutManager LayoutManager to attach to
* @param orientation Desired orientation. Should be {@link #HORIZONTAL} or {@link #VERTICAL}
* @return A new OrientationHelper
*/
public static OrientationHelper createOrientationHelper(
RecyclerView.LayoutManager layoutManager, int orientation) {
switch (orientation) {
case HORIZONTAL:
return createHorizontalHelper(layoutManager);
case VERTICAL:
return createVerticalHelper(layoutManager);
}
throw new IllegalArgumentException("invalid orientation");
}
/**
* Creates a horizontal OrientationHelper for the given LayoutManager.
*
* @param layoutManager The LayoutManager to attach to.
* @return A new OrientationHelper
*/
public static OrientationHelper createHorizontalHelper(
RecyclerView.LayoutManager layoutManager) {
return new OrientationHelper(layoutManager) {
@Override
public int getEndAfterPadding() {
return mLayoutManager.getWidth() - mLayoutManager.getPaddingRight();
}
@Override
public int getEnd() {
return mLayoutManager.getWidth();
}
@Override
public void offsetChildren(int amount) {
mLayoutManager.offsetChildrenHorizontal(amount);
}
@Override
public int getStartAfterPadding() {
return mLayoutManager.getPaddingLeft();
}
@Override
public int getDecoratedMeasurement(View view) {
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
view.getLayoutParams();
return mLayoutManager.getDecoratedMeasuredWidth(view) + params.leftMargin
+ params.rightMargin;
}
@Override
public int getDecoratedMeasurementInOther(View view) {
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
view.getLayoutParams();
return mLayoutManager.getDecoratedMeasuredHeight(view) + params.topMargin
+ params.bottomMargin;
}
@Override
public int getDecoratedEnd(View view) {
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
view.getLayoutParams();
return mLayoutManager.getDecoratedRight(view) + params.rightMargin;
}
@Override
public int getDecoratedStart(View view) {
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
view.getLayoutParams();
return mLayoutManager.getDecoratedLeft(view) - params.leftMargin;
}
@Override
public int getTotalSpace() {
return mLayoutManager.getWidth() - mLayoutManager.getPaddingLeft()
- mLayoutManager.getPaddingRight();
}
@Override
public void offsetChild(View view, int offset) {
view.offsetLeftAndRight(offset);
}
@Override
public int getEndPadding() {
return mLayoutManager.getPaddingRight();
}
};
}
/**
* Creates a vertical OrientationHelper for the given LayoutManager.
*
* @param layoutManager The LayoutManager to attach to.
* @return A new OrientationHelper
*/
public static OrientationHelper createVerticalHelper(RecyclerView.LayoutManager layoutManager) {
return new OrientationHelper(layoutManager) {
@Override
public int getEndAfterPadding() {
return mLayoutManager.getHeight() - mLayoutManager.getPaddingBottom();
}
@Override
public int getEnd() {
return mLayoutManager.getHeight();
}
@Override
public void offsetChildren(int amount) {
mLayoutManager.offsetChildrenVertical(amount);
}
@Override
public int getStartAfterPadding() {
return mLayoutManager.getPaddingTop();
}
@Override
public int getDecoratedMeasurement(View view) {
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
view.getLayoutParams();
return mLayoutManager.getDecoratedMeasuredHeight(view) + params.topMargin
+ params.bottomMargin;
}
@Override
public int getDecoratedMeasurementInOther(View view) {
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
view.getLayoutParams();
return mLayoutManager.getDecoratedMeasuredWidth(view) + params.leftMargin
+ params.rightMargin;
}
@Override
public int getDecoratedEnd(View view) {
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
view.getLayoutParams();
return mLayoutManager.getDecoratedBottom(view) + params.bottomMargin;
}
@Override
public int getDecoratedStart(View view) {
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
view.getLayoutParams();
return mLayoutManager.getDecoratedTop(view) - params.topMargin;
}
@Override
public int getTotalSpace() {
return mLayoutManager.getHeight() - mLayoutManager.getPaddingTop()
- mLayoutManager.getPaddingBottom();
}
@Override
public void offsetChild(View view, int offset) {
view.offsetTopAndBottom(offset);
}
@Override
public int getEndPadding() {
return mLayoutManager.getPaddingBottom();
}
};
}
}