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A ItemDecoration to center the contents of a RecyclerView. This comes in handy when you want to build a responsive UI.
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| /* | |
| * Copyright 2015 Johannes Homeier | |
| * | |
| * 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 de.twoid.ui.decoration; | |
| import android.support.v7.widget.GridLayoutManager; | |
| /** | |
| * A {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper} backed by a {@link android.support.v7.widget.GridLayoutManager} | |
| */ | |
| public class GridSpanSizeLookupHelper extends InsetItemDecoration.SpanSizeLookupHelper<GridLayoutManager> { | |
| private GridLayoutManager.SpanSizeLookup spanSizeLookup; | |
| public GridSpanSizeLookupHelper(GridLayoutManager layoutManager) { | |
| super(layoutManager); | |
| spanSizeLookup = layoutManager.getSpanSizeLookup(); | |
| spanSizeLookup.setSpanIndexCacheEnabled(true); | |
| } | |
| @Override | |
| public int getSpanCount() { | |
| return layoutManager.getSpanCount(); | |
| } | |
| @Override | |
| public int getSpanIndex(int position){ | |
| return spanSizeLookup.getSpanIndex(position, getSpanCount()); | |
| } | |
| @Override | |
| public int getSpanSize(int position) { | |
| return spanSizeLookup.getSpanSize(position); | |
| } | |
| @Override | |
| public int getOrientation() { | |
| return layoutManager.getOrientation(); | |
| } | |
| } |
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| /* | |
| * Copyright 2015 Johannes Homeier | |
| * | |
| * 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 de.twoid.ui.decoration; | |
| import android.graphics.Rect; | |
| import android.support.v7.widget.GridLayoutManager; | |
| import android.support.v7.widget.LinearLayoutManager; | |
| import android.support.v7.widget.OrientationHelper; | |
| import android.support.v7.widget.RecyclerView; | |
| import android.support.v7.widget.StaggeredGridLayoutManager; | |
| import android.view.View; | |
| import android.widget.ImageView; | |
| /** | |
| * An ItemDecoration to center the content of a RecyclerView. | |
| * This class comes in handy when you want to build a responsive UI while still receiving touch- and scroll-events on the "borders" of the {@link android.support.v7.widget.RecyclerView} | |
| */ | |
| public class InsetItemDecoration extends RecyclerView.ItemDecoration { | |
| protected SpanSizeLookupHelper spanSizeLookupHelper; | |
| private float maxContentSize; | |
| private float parentSize; | |
| private boolean setup = false; | |
| /** | |
| * Create a new InsetItemDecoration without specifying a LayoutManager; | |
| * The needed {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper} will be generated during the first call of {@link #getItemOffsets(android.graphics.Rect, android.view.View, android.support.v7.widget.RecyclerView, android.support.v7.widget.RecyclerView.State)} | |
| * @param maxContentSize the desired max-dimension of the content in pixel | |
| */ | |
| public InsetItemDecoration(float maxContentSize) { | |
| this.maxContentSize = maxContentSize; | |
| } | |
| /** | |
| * Create a new InsetItemDecoration by creating a new {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper} with the passed {@link android.support.v7.widget.GridLayoutManager} | |
| * @param layoutManager the associated GridLayoutManager | |
| * @param maxContentSize the desired max-dimension of the content in pixel | |
| */ | |
| public InsetItemDecoration(GridLayoutManager layoutManager, float maxContentSize) { | |
| this(new GridSpanSizeLookupHelper(layoutManager), maxContentSize); | |
| } | |
| /** | |
| * Create a new InsetItemDecoration by creating a new {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper} with the passed {@link android.support.v7.widget.LinearLayoutManager} | |
| * @param layoutManager the associated LinearLayoutManager | |
| * @param maxContentSize the desired max-dimension of the content in pixel | |
| */ | |
| public InsetItemDecoration(LinearLayoutManager layoutManager, float maxContentSize) { | |
| this(new LinearSpanSizeLookupHelper(layoutManager), maxContentSize); | |
| } | |
| /** | |
| * Create a new InsetItemDecoration by creating a new {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper} with the passed {@link android.support.v7.widget.StaggeredGridLayoutManager} | |
| * @param layoutManager the associated StaggeredGridLayoutManager | |
| * @param maxContentSize the desired max-dimension of the content in pixel | |
| */ | |
| public InsetItemDecoration(StaggeredGridLayoutManager layoutManager, float maxContentSize) { | |
| this(new StaggeredGridSpanSizeLookupHelper(layoutManager), maxContentSize); | |
| } | |
| /** | |
| * Create a new InsetItemDecoration with the passed {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper} | |
| * @param spanSizeLookupHelper the SpanSizeLookupHelper to work with | |
| * @param maxContentSize the desired max-dimension of the content in pixel | |
| */ | |
| public InsetItemDecoration(SpanSizeLookupHelper spanSizeLookupHelper, float maxContentSize) { | |
| this.spanSizeLookupHelper = spanSizeLookupHelper; | |
| this.maxContentSize = maxContentSize; | |
| setup = true; | |
| } | |
| /** | |
| * {@inheritDoc} | |
| */ | |
| @Override | |
| public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) { | |
| if(!setup){ | |
| setup = generateSpanSizeLookupHelper(parent.getLayoutManager()); | |
| if(!setup){ | |
| return; | |
| } | |
| } | |
| int position = spanSizeLookupHelper.getPosition(view); | |
| int spanSize = spanSizeLookupHelper.getSpanSize(position); | |
| int spanIndex = spanSizeLookupHelper.getSpanIndex(position); | |
| if(spanSizeLookupHelper.getOrientation() == OrientationHelper.VERTICAL){ | |
| parentSize = parent.getWidth(); | |
| }else{ | |
| parentSize = parent.getHeight(); | |
| } | |
| if(parentSize <= maxContentSize){ | |
| super.getItemOffsets(outRect, view, parent, state); | |
| return; | |
| } | |
| inset(outRect, spanIndex, spanSize); | |
| } | |
| /** | |
| * Generates a new {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper} if the passed {@link android.support.v7.widget.RecyclerView.LayoutManager} | |
| * is either a {@link android.support.v7.widget.LinearLayoutManager}, a {@link android.support.v7.widget.GridLayoutManager}, or a {@link android.support.v7.widget.StaggeredGridLayoutManager} | |
| * @param layoutManager | |
| * @return allways true; | |
| */ | |
| protected boolean generateSpanSizeLookupHelper(RecyclerView.LayoutManager layoutManager){ | |
| if(layoutManager instanceof LinearLayoutManager){ | |
| spanSizeLookupHelper = new LinearSpanSizeLookupHelper((LinearLayoutManager) layoutManager); | |
| }else if(layoutManager instanceof GridLayoutManager){ | |
| spanSizeLookupHelper = new GridSpanSizeLookupHelper((GridLayoutManager) layoutManager); | |
| }else if(layoutManager instanceof StaggeredGridLayoutManager){ | |
| spanSizeLookupHelper = new StaggeredGridSpanSizeLookupHelper((StaggeredGridLayoutManager) layoutManager); | |
| }else{ | |
| throw new UnsupportedLayoutManagerException(); | |
| } | |
| return true; | |
| } | |
| /** | |
| * Applies a inset to the passed Rect depending on the spanIndex and spanSize; | |
| * @param outRect the {@link android.graphics.Rect} to modify | |
| * @param spanIndex the span-index of a view | |
| * @param spanSize the span-size of a view | |
| */ | |
| protected void inset(Rect outRect, int spanIndex, int spanSize) { | |
| final float totalSizeDifference = getTotalSizeDifference(); | |
| final int baseInset = (int) (totalSizeDifference / 2f); | |
| if(spanSizeLookupHelper.getOrientation() == OrientationHelper.VERTICAL){ | |
| outRect.set( | |
| (int) (baseInset - spanSizeLookupHelper.getSpanPositionDifference(spanIndex, totalSizeDifference)) | |
| , 0 | |
| , (int) -(baseInset - spanSizeLookupHelper.getSpanPositionDifference(spanIndex + spanSize, totalSizeDifference)) | |
| , 0); | |
| }else{ | |
| outRect.set( | |
| 0 | |
| , (int) (baseInset - spanSizeLookupHelper.getSpanPositionDifference(spanIndex, totalSizeDifference)) | |
| , 0 | |
| , (int) (baseInset - spanSizeLookupHelper.getSpanPositionDifference(spanIndex + spanSize, totalSizeDifference))); | |
| } | |
| } | |
| /** | |
| * Returns the sizeDifference between the size of the parent {@link android.support.v7.widget.RecyclerView} and the passed maxContentSize | |
| * @return 0 if maxContentSize is bigger than the size of the RecyclerView, else the difference of both sizes | |
| */ | |
| protected float getTotalSizeDifference(){ | |
| return Math.max(0, parentSize - maxContentSize); | |
| } | |
| /** | |
| * @return the max size of the RecyclerViews content in pixels | |
| */ | |
| protected float getMaxContentSize() { | |
| return maxContentSize; | |
| } | |
| /** | |
| * @return the size of the RecyclerView | |
| */ | |
| protected float getParentSize() { | |
| return parentSize; | |
| } | |
| /** | |
| * Indicates whether the {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper} has been created or not | |
| * @return true if the SpanSizeLookupHelper got created | |
| */ | |
| protected boolean isSetup(){ | |
| return setup; | |
| } | |
| /** | |
| * Invalidate the current {@link android.support.v7.widget.RecyclerView.LayoutManager} (and with that the {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper}) | |
| * and look far a new one in the next call of {@link #getItemOffsets(android.graphics.Rect, android.view.View, android.support.v7.widget.RecyclerView, android.support.v7.widget.RecyclerView.State)} | |
| * This has to be called when you set a new {@link android.support.v7.widget.RecyclerView.LayoutManager} to the {@link android.support.v7.widget.RecyclerView} | |
| */ | |
| public void invalidateLayoutManager(){ | |
| setup = false; | |
| } | |
| public void swapSpanSizeLookupHeler(SpanSizeLookupHelper spanSizeLookupHelper){ | |
| if(spanSizeLookupHelper == null){ | |
| setup = false; | |
| } | |
| this.spanSizeLookupHelper = spanSizeLookupHelper; | |
| } | |
| /** | |
| * A helper-class to provide span-information to the {@link de.twoid.ui.decoration.InsetItemDecoration} | |
| * @param <E> | |
| */ | |
| public static abstract class SpanSizeLookupHelper<E extends RecyclerView.LayoutManager>{ | |
| protected E layoutManager; | |
| protected int spanCount; | |
| protected SpanSizeLookupHelper(E layoutManager, int spanCount) { | |
| this.layoutManager = layoutManager; | |
| this.spanCount = spanCount; | |
| } | |
| /** | |
| * @param view | |
| * @return the position of the view in the {@link android.support.v7.widget.RecyclerView.LayoutManager} | |
| */ | |
| public int getPosition(View view){ | |
| return layoutManager.getPosition(view); | |
| } | |
| /** | |
| * @return the span-count of the {@link android.support.v7.widget.RecyclerView.LayoutManager} | |
| */ | |
| public abstract int getSpanCount(); | |
| /** | |
| * @param position | |
| * @return the span-index for a view at the passed position | |
| */ | |
| public abstract int getSpanIndex(int position); | |
| /** | |
| * @param position | |
| * @return the span-size for a view at the passed position | |
| */ | |
| public abstract int getSpanSize(int position); | |
| /** | |
| * Generates a offset for a span-index; | |
| * This offset is used to inset and shrink a view according to its span-index and span-size | |
| * @param spanIndex | |
| * @param sizeDifference | |
| * @return the offset for the passed spanIndex in pixels | |
| */ | |
| public float getSpanPositionDifference(int spanIndex, float sizeDifference){ | |
| if(sizeDifference <= 0){ | |
| return 0; | |
| }else{ | |
| return spanIndex * sizeDifference / ((float) getSpanCount()); | |
| } | |
| } | |
| /** | |
| * @return the orientation of the {@link android.support.v7.widget.RecyclerView.LayoutManager} | |
| */ | |
| public abstract int getOrientation(); | |
| } | |
| public static class UnsupportedLayoutManagerException extends ClassCastException{ | |
| private static final String ADDITIONAL_MESSAGE = | |
| InsetItemDecoration.class.getName()+" only supports " | |
| + LinearLayoutManager.class.getName() | |
| + ", " + GridLayoutManager.class.getName() | |
| + " and " + StaggeredGridLayoutManager.class.getName() | |
| + ". If you want to use a custom LayoutManager, you should create a new SpanSizeLookupHelper and pass it in the constructor"; | |
| public UnsupportedLayoutManagerException() { | |
| super(ADDITIONAL_MESSAGE); | |
| } | |
| } | |
| } |
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| /* | |
| * Copyright 2015 Johannes Homeier | |
| * | |
| * 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 de.twoid.ui.decoration; | |
| import android.support.v7.widget.LinearLayoutManager; | |
| /** | |
| * A {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper} backed by a {@link android.support.v7.widget.LinearLayoutManager} | |
| */ | |
| public class LinearSpanSizeLookupHelper extends InsetItemDecoration.SpanSizeLookupHelper<LinearLayoutManager> { | |
| public LinearSpanSizeLookupHelper(LinearLayoutManager layoutManager) { | |
| super(layoutManager); | |
| } | |
| @Override | |
| public int getSpanCount() { | |
| return 1; | |
| } | |
| /** | |
| * As the {@link android.support.v7.widget.LinearLayoutManager} only has one column, this method always returns 0; | |
| * | |
| * {@inheritDoc} | |
| */ | |
| @Override | |
| public int getSpanIndex(int position) { | |
| return 0; | |
| } | |
| /** | |
| * As the {@link android.support.v7.widget.LinearLayoutManager} only has one column, this method always returns 1; | |
| * | |
| * {@inheritDoc} | |
| */ | |
| @Override | |
| public int getSpanSize(int position) { | |
| return 1; | |
| } | |
| @Override | |
| public int getOrientation() { | |
| return layoutManager.getOrientation(); | |
| } | |
| } |
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| /* | |
| * Copyright 2015 Johannes Homeier | |
| * | |
| * 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 de.twoid.ui.decoration; | |
| import android.support.v7.widget.StaggeredGridLayoutManager; | |
| import android.view.View; | |
| /** | |
| * A {@link de.twoid.ui.decoration.InsetItemDecoration.SpanSizeLookupHelper} backed by a {@link android.support.v7.widget.StaggeredGridLayoutManager} | |
| */ | |
| public class StaggeredGridSpanSizeLookupHelper extends InsetItemDecoration.SpanSizeLookupHelper<StaggeredGridLayoutManager> { | |
| protected StaggeredGridSpanSizeLookupHelper(StaggeredGridLayoutManager layoutManager) { | |
| super(layoutManager); | |
| } | |
| @Override | |
| public int getSpanCount() { | |
| return layoutManager.getSpanCount(); | |
| } | |
| @Override | |
| public int getSpanIndex(int position) { | |
| StaggeredGridLayoutManager.LayoutParams params = getLayoutParams(position); | |
| return params.getSpanIndex(); | |
| } | |
| @Override | |
| public int getSpanSize(int position) { | |
| StaggeredGridLayoutManager.LayoutParams params = getLayoutParams(position); | |
| return params.isFullSpan() ? getSpanCount() : 1; | |
| } | |
| @Override | |
| public int getOrientation() { | |
| return layoutManager.getOrientation(); | |
| } | |
| private StaggeredGridLayoutManager.LayoutParams getLayoutParams(int position){ | |
| View view = layoutManager.getChildAt(position); | |
| return (StaggeredGridLayoutManager.LayoutParams) view.getLayoutParams(); | |
| } | |
| } |
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