mirror of
https://github.com/signalapp/Signal-Android.git
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Migrate ConversationList to paging library and apply abstractions to conversation.
This commit is contained in:
Alex Hart
committed by
Greyson Parrelli
Greyson Parrelli
parent
ce940235b0
commit
49f75d7036
@@ -0,0 +1,33 @@
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package org.thoughtcrime.securesms.util;
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import androidx.annotation.Nullable;
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public class Deferred {
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private Runnable deferred;
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private boolean isDeferred = true;
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public void defer(@Nullable Runnable deferred) {
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this.deferred = deferred;
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executeIfNecessary();
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}
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public void setDeferred(boolean isDeferred) {
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this.isDeferred = isDeferred;
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executeIfNecessary();
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}
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public boolean isDeferred() {
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return isDeferred;
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}
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private void executeIfNecessary() {
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if (deferred != null && !isDeferred) {
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Runnable local = deferred;
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deferred = null;
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local.run();
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}
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}
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}
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@@ -0,0 +1,182 @@
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package org.thoughtcrime.securesms.util;
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import androidx.annotation.CheckResult;
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import androidx.annotation.NonNull;
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import androidx.annotation.Nullable;
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import androidx.recyclerview.widget.LinearLayoutManager;
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import androidx.recyclerview.widget.RecyclerView;
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import java.util.Objects;
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/**
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* Helper class to scroll to the top of a RecyclerView when new data is inserted.
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* This works for both newly inserted data and moved data. It applies the following rules:
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*
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* <ul>
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* <li>If the user is currently scrolled to some position, then we will not snap.</li>
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* <li>If the user is currently dragging, then we will not snap.</li>
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* <li>If the user has requested a scroll position, then we will only snap to that position.</li>
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* </ul>
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*/
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public class SnapToTopDataObserver extends RecyclerView.AdapterDataObserver {
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private final RecyclerView recyclerView;
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private final LinearLayoutManager layoutManager;
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private final Deferred deferred;
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private final ScrollRequestValidator scrollRequestValidator;
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public SnapToTopDataObserver(@NonNull RecyclerView recyclerView,
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@Nullable ScrollRequestValidator scrollRequestValidator)
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{
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this.recyclerView = recyclerView;
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this.layoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
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this.deferred = new Deferred();
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this.scrollRequestValidator = scrollRequestValidator;
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}
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/**
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* Requests a scroll to a specific position. This call will defer until the position is loaded or
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* becomes invalid.
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*
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* @param position The position to scroll to.
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*/
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public void requestScrollPosition(int position) {
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buildScrollPosition(position).submit();
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}
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/**
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* Creates a ScrollRequestBuilder which can be used to customize a particular scroll request with
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* different callbacks. Don't forget to call `submit()`!
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*
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* @param position The position to scroll to.
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* @return A ScrollRequestBuilder that must be submitted once you are satisfied with it.
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*/
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@CheckResult(suggest = "#requestScrollPosition(int)")
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public ScrollRequestBuilder buildScrollPosition(int position) {
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return new ScrollRequestBuilder(position);
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}
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/**
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* Requests that instead of snapping to top, we should scroll to a specific position in the adapter.
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* It is up to the caller to ensure that the adapter will load the appropriate data, either by
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* invalidating and restarting the page load at the appropriate position or by utilizing
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* PagedList#loadAround(int).
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*
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* @param position The position to scroll to.
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* @param onPerformScroll Callback allowing the caller to perform the scroll themselves.
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* @param onScrollRequestComplete Notification that the scroll has completed successfully.
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* @param onInvalidPosition Notification that the requested position has become invalid.
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*/
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private void requestScrollPositionInternal(int position,
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@NonNull OnPerformScroll onPerformScroll,
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@NonNull Runnable onScrollRequestComplete,
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@NonNull Runnable onInvalidPosition)
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{
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Objects.requireNonNull(scrollRequestValidator, "Cannot request positions when SnapToTopObserver was initialized without a validator.");
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if (!scrollRequestValidator.isPositionStillValid(position)) {
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onInvalidPosition.run();
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} else if (scrollRequestValidator.isItemAtPositionLoaded(position)) {
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recyclerView.post(() -> {
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onPerformScroll.onPerformScroll(layoutManager, position);
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onScrollRequestComplete.run();
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});
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} else {
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deferred.setDeferred(true);
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deferred.defer(() -> requestScrollPositionInternal(position, onPerformScroll, onScrollRequestComplete, onInvalidPosition));
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}
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}
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@Override
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public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
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snapToTopIfNecessary(toPosition);
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}
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@Override
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public void onItemRangeInserted(int positionStart, int itemCount) {
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snapToTopIfNecessary(positionStart);
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}
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private void snapToTopIfNecessary(int newItemPosition) {
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if (deferred.isDeferred()) {
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deferred.setDeferred(false);
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return;
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}
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if (newItemPosition != 0 ||
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recyclerView.getScrollState() != RecyclerView.SCROLL_STATE_IDLE ||
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recyclerView.canScrollVertically(layoutManager.getReverseLayout() ? 1 : -1)) {
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return;
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}
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if (layoutManager.findFirstVisibleItemPosition() == 0) {
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layoutManager.scrollToPosition(0);
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}
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}
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public interface ScrollRequestValidator {
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/**
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* This method is responsible for determining whether a given position is still a valid jump target.
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* @param position The position to validate
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* @return Whether the position is valid
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*/
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boolean isPositionStillValid(int position);
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/**
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* This method is responsible for checking whether the desired position is available to be jumped to.
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* In the case of a PagedListAdapter, it is whether getItem returns a non-null value.
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* @param position The position to check for.
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* @return Whether or not the data for the given position is loaded.
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*/
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boolean isItemAtPositionLoaded(int position);
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}
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public interface OnPerformScroll {
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/**
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* This method is responsible for actually performing the requested scroll. It is always called
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* immediately before the onScrollRequestComplete callback, and is always run via recyclerView.post(...)
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* so you don't have to do this yourself.
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*
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* By default, SnapToTopDataObserver will utilize layoutManager.scrollToPosition. This lets you modify that
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* behavior, and also gives you a chance to perform actions just before scrolling occurs.
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*
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* @param layoutManager The layoutManager containing your items.
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* @param position The position to scroll to.
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*/
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void onPerformScroll(@NonNull LinearLayoutManager layoutManager, int position);
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}
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public final class ScrollRequestBuilder {
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private final int position;
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private OnPerformScroll onPerformScroll = LinearLayoutManager::scrollToPosition;
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private Runnable onScrollRequestComplete = () -> {};
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private Runnable onInvalidPosition = () -> {};
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public ScrollRequestBuilder(int position) {
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this.position = position;
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}
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@CheckResult
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public ScrollRequestBuilder withOnPerformScroll(@NonNull OnPerformScroll onPerformScroll) {
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this.onPerformScroll = onPerformScroll;
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return this;
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}
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@CheckResult
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public ScrollRequestBuilder withOnScrollRequestComplete(@NonNull Runnable onScrollRequestComplete) {
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this.onScrollRequestComplete = onScrollRequestComplete;
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return this;
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}
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@CheckResult
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public ScrollRequestBuilder withOnInvalidPosition(@NonNull Runnable onInvalidPosition) {
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this.onInvalidPosition = onInvalidPosition;
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return this;
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}
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public void submit() {
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requestScrollPositionInternal(position, onPerformScroll, onScrollRequestComplete, onInvalidPosition);
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}
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}
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}
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@@ -0,0 +1,17 @@
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package org.thoughtcrime.securesms.util.paging;
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import androidx.annotation.NonNull;
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public class Invalidator {
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private Runnable callback;
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public synchronized void invalidate() {
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if (callback != null) {
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callback.run();
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}
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}
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public synchronized void observe(@NonNull Runnable callback) {
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this.callback = callback;
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}
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}
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@@ -0,0 +1,48 @@
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package org.thoughtcrime.securesms.util.paging;
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import androidx.annotation.NonNull;
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import org.thoughtcrime.securesms.logging.Log;
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import java.util.List;
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public class SizeFixResult<T> {
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private static final String TAG = Log.tag(SizeFixResult.class);
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final List<T> items;
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final int total;
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private SizeFixResult(@NonNull List<T> items, int total) {
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this.items = items;
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this.total = total;
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}
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public List<T> getItems() {
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return items;
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}
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public int getTotal() {
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return total;
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}
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public static @NonNull <T> SizeFixResult<T> ensureMultipleOfPageSize(@NonNull List<T> records,
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int startPosition,
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int pageSize,
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int total)
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{
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if (records.size() + startPosition == total || (records.size() != 0 && records.size() % pageSize == 0)) {
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return new SizeFixResult<>(records, total);
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}
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if (records.size() < pageSize) {
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Log.w(TAG, "Hit a miscalculation where we don't have the full dataset, but it's smaller than a page size. records: " + records.size() + ", startPosition: " + startPosition + ", pageSize: " + pageSize + ", total: " + total);
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return new SizeFixResult<>(records, records.size() + startPosition);
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}
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Log.w(TAG, "Hit a miscalculation where our data size isn't a multiple of the page size. records: " + records.size() + ", startPosition: " + startPosition + ", pageSize: " + pageSize + ", total: " + total);
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int overflow = records.size() % pageSize;
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return new SizeFixResult<>(records.subList(0, records.size() - overflow), total);
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}
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}
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