Java tutorial
package io.github.prashantsolanki3.snaplibrary.snap.layoutmanagers; import android.content.Context; import android.graphics.Rect; import android.support.v4.view.ViewCompat; import android.support.v7.widget.RecyclerView; import android.util.Log; import android.view.View; import java.lang.reflect.Field; import io.github.prashantsolanki3.snaplibrary.BuildConfig; /* * Copyright 2014 serso aka se.solovyev 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. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Contact details Email: se.solovyev@gmail.com Site: http://se.solovyev.org * */ /** * Not Usable Right Now! * Do not use #SnapNestedGridLayoutManager * */ class SnapNestedGridLayoutManager extends android.support.v7.widget.GridLayoutManager { private static boolean canMakeInsetsDirty = true; private static Field insetsDirtyField = null; private static final int CHILD_WIDTH = 0; private static final int CHILD_HEIGHT = 1; private static final int DEFAULT_CHILD_SIZE = 100; private final int[] childDimensions = new int[2]; private final RecyclerView view; private int childSize = DEFAULT_CHILD_SIZE; private boolean hasChildSize; private int overScrollMode = ViewCompat.OVER_SCROLL_ALWAYS; private final Rect tmpRect = new Rect(); /* @SuppressWarnings("UnusedDeclaration") public SnapNestedLinearLayoutManger(Context context) { super(context); this.view = null; }*/ public SnapNestedGridLayoutManager(RecyclerView view, Context context, int spanCount) { super(context, spanCount); view.setNestedScrollingEnabled(false); this.view = null; } @SuppressWarnings("UnusedDeclaration") public SnapNestedGridLayoutManager(RecyclerView view, Context context, int spanCount, int orientation, boolean reverseLayout) { super(context, spanCount, orientation, reverseLayout); view.setNestedScrollingEnabled(false); this.view = null; } /* @SuppressWarnings("UnusedDeclaration") public SnapNestedLinearLayoutManger(RecyclerView view) { super(view.getContext()); this.view = view; this.overScrollMode = ViewCompat.getOverScrollMode(view); } @SuppressWarnings("UnusedDeclaration") public SnapNestedLinearLayoutManger(RecyclerView view, int orientation, boolean reverseLayout) { super(view.getContext(), orientation, reverseLayout); this.view = view; this.overScrollMode = ViewCompat.getOverScrollMode(view); }*/ public void setOverScrollMode(int overScrollMode) { if (overScrollMode < ViewCompat.OVER_SCROLL_ALWAYS || overScrollMode > ViewCompat.OVER_SCROLL_NEVER) throw new IllegalArgumentException("Unknown overscroll mode: " + overScrollMode); if (this.view == null) throw new IllegalStateException("view == null"); this.overScrollMode = overScrollMode; ViewCompat.setOverScrollMode(view, overScrollMode); } public static int makeUnspecifiedSpec() { return View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED); } @Override public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec) { final int widthMode = View.MeasureSpec.getMode(widthSpec); final int heightMode = View.MeasureSpec.getMode(heightSpec); final int widthSize = View.MeasureSpec.getSize(widthSpec); final int heightSize = View.MeasureSpec.getSize(heightSpec); final boolean hasWidthSize = widthMode != View.MeasureSpec.UNSPECIFIED; final boolean hasHeightSize = heightMode != View.MeasureSpec.UNSPECIFIED; final boolean exactWidth = widthMode == View.MeasureSpec.EXACTLY; final boolean exactHeight = heightMode == View.MeasureSpec.EXACTLY; final int unspecified = makeUnspecifiedSpec(); if (exactWidth && exactHeight) { // in case of exact calculations for both dimensions let's use default "onMeasure" implementation super.onMeasure(recycler, state, widthSpec, heightSpec); return; } final boolean vertical = getOrientation() == VERTICAL; initChildDimensions(widthSize, heightSize, vertical); int width = 0; int height = 0; // it's possible to get scrap views in recycler which are bound to old (invalid) adapter entities. This // happens because their invalidation happens after "onMeasure" method. As a workaround let's clear the // recycler now (it should not cause any performance issues while scrolling as "onMeasure" is never // called whiles scrolling) recycler.clear(); final int stateItemCount = state.getItemCount(); final int adapterItemCount = getItemCount(); // adapter always contains actual data while state might contain old data (f.e. data before the animation is // done). As we want to measure the view with actual data we must use data from the adapter and not from the // state for (int i = 0; i < adapterItemCount; i++) { if (vertical) { if (!hasChildSize) { if (i < stateItemCount) { // we should not exceed state count, otherwise we'll get IndexOutOfBoundsException. For such items // we will use previously calculated dimensions measureChild(recycler, i, widthSize, unspecified, childDimensions); } else { logMeasureWarning(i); } } height += childDimensions[CHILD_HEIGHT]; if (i == 0) { width = childDimensions[CHILD_WIDTH]; } if (hasHeightSize && height >= heightSize) { break; } } else { if (!hasChildSize) { if (i < stateItemCount) { // we should not exceed state count, otherwise we'll get IndexOutOfBoundsException. For such items // we will use previously calculated dimensions measureChild(recycler, i, unspecified, heightSize, childDimensions); } else { logMeasureWarning(i); } } width += childDimensions[CHILD_WIDTH]; if (i == 0) { height = childDimensions[CHILD_HEIGHT]; } if (hasWidthSize && width >= widthSize) { break; } } } if (exactWidth) { width = widthSize; } else { width += getPaddingLeft() + getPaddingRight(); if (hasWidthSize) { width = Math.min(width, widthSize); } } if (exactHeight) { height = heightSize; } else { height += getPaddingTop() + getPaddingBottom(); if (hasHeightSize) { height = Math.min(height, heightSize); } } if (vertical) setMeasuredDimension(width, height / getSpanCount()); else setMeasuredDimension(width / getSpanCount(), height); if (view != null && overScrollMode == ViewCompat.OVER_SCROLL_IF_CONTENT_SCROLLS) { final boolean fit = (vertical && (!hasHeightSize || height < heightSize)) || (!vertical && (!hasWidthSize || width < widthSize)); ViewCompat.setOverScrollMode(view, fit ? ViewCompat.OVER_SCROLL_NEVER : ViewCompat.OVER_SCROLL_ALWAYS); } } private void logMeasureWarning(int child) { if (BuildConfig.DEBUG) { Log.w("SnapGridLayoutManger", "Can't measure child #" + child + ", previously used dimensions will be reused." + "To remove this message either use #setChildSize() method or don't run RecyclerView animations"); } } private void initChildDimensions(int width, int height, boolean vertical) { if (childDimensions[CHILD_WIDTH] != 0 || childDimensions[CHILD_HEIGHT] != 0) { // already initialized, skipping return; } if (vertical) { childDimensions[CHILD_WIDTH] = width; childDimensions[CHILD_HEIGHT] = childSize; } else { childDimensions[CHILD_WIDTH] = childSize; childDimensions[CHILD_HEIGHT] = height; } } @Override public void setOrientation(int orientation) { // might be called before the constructor of this class is called //noinspection ConstantConditions if (childDimensions != null) { if (getOrientation() != orientation) { childDimensions[CHILD_WIDTH] = 0; childDimensions[CHILD_HEIGHT] = 0; } } super.setOrientation(orientation); } public void clearChildSize() { hasChildSize = false; setChildSize(DEFAULT_CHILD_SIZE); } public void setChildSize(int childSize) { hasChildSize = true; if (this.childSize != childSize) { this.childSize = childSize; requestLayout(); } } private void measureChild(RecyclerView.Recycler recycler, int position, int widthSize, int heightSize, int[] dimensions) { final View child; try { child = recycler.getViewForPosition(position); } catch (IndexOutOfBoundsException e) { if (BuildConfig.DEBUG) { Log.w("SnapGridLayoutManger", "SnapNestedLinearLayoutManger doesn't work well with animations. Consider switching them off", e); } return; } final RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) child.getLayoutParams(); final int hPadding = getPaddingLeft() + getPaddingRight(); final int vPadding = getPaddingTop() + getPaddingBottom(); final int hMargin = p.leftMargin + p.rightMargin; final int vMargin = p.topMargin + p.bottomMargin; // we must make insets dirty in order calculateItemDecorationsForChild to work makeInsetsDirty(p); // this method should be called before any getXxxDecorationXxx() methods calculateItemDecorationsForChild(child, tmpRect); final int hDecoration = getRightDecorationWidth(child) + getLeftDecorationWidth(child); final int vDecoration = getTopDecorationHeight(child) + getBottomDecorationHeight(child); final int childWidthSpec = getChildMeasureSpec(widthSize, hPadding + hMargin + hDecoration, p.width, canScrollHorizontally()); final int childHeightSpec = getChildMeasureSpec(heightSize, vPadding + vMargin + vDecoration, p.height, canScrollVertically()); child.measure(childWidthSpec, childHeightSpec); dimensions[CHILD_WIDTH] = getDecoratedMeasuredWidth(child) + p.leftMargin + p.rightMargin; dimensions[CHILD_HEIGHT] = getDecoratedMeasuredHeight(child) + p.bottomMargin + p.topMargin; // as view is recycled let's not keep old measured values makeInsetsDirty(p); recycler.recycleView(child); } private static void makeInsetsDirty(RecyclerView.LayoutParams p) { if (!canMakeInsetsDirty) { return; } try { if (insetsDirtyField == null) { insetsDirtyField = RecyclerView.LayoutParams.class.getDeclaredField("mInsetsDirty"); insetsDirtyField.setAccessible(true); } insetsDirtyField.set(p, true); } catch (NoSuchFieldException e) { onMakeInsertDirtyFailed(); } catch (IllegalAccessException e) { onMakeInsertDirtyFailed(); } } private static void onMakeInsertDirtyFailed() { canMakeInsetsDirty = false; if (BuildConfig.DEBUG) { Log.w("SnapGridLayoutManger", "Can't make LayoutParams insets dirty, decorations measurements might be incorrect"); } } }