androidx.recyclerview.widget.RecyclerView#findViewHolderForAdapterPosition ( )源码实例Demo

public void viewGame(int gid, boolean locked) {
    if (adapter == null) return;

    if (locked && adapter.doesFilterOutLockedLobbies()) {
        Prefs.putBoolean(PK.FILTER_LOCKED_LOBBIES, false);
        adapter.setFilterOutLockedLobbies(false);
    }

    int pos = Utils.indexOf(adapter.getVisibleGames(), gid);
    if (pos != -1) {
        RecyclerView list = rmv.list();
        list.scrollToPosition(pos);
        RecyclerView.ViewHolder holder = list.findViewHolderForAdapterPosition(pos);
        if (holder instanceof GamesAdapter.ViewHolder)
            ((GamesAdapter.ViewHolder) holder).expand.performClick();
    }
}
 

private void setAvatarAppearance(RecyclerView recyclerView) {
    User user = followingAdapter.getUser(avatarPosition);
    if (user == null) {
        return;
    }

    if (lastActor == null || !lastActor.username.equals(user.username)) {
        setAvatarImage(avatarPosition);
    }

    RecyclerView.ViewHolder lastHolder
            = recyclerView.findViewHolderForAdapterPosition(lastAvatarPosition);
    if (lastHolder instanceof TitleFeedHolder) {
        ((TitleFeedHolder) lastHolder).setAvatarVisibility(true);
    }

    RecyclerView.ViewHolder newHolder
            = recyclerView.findViewHolderForAdapterPosition(avatarPosition);
    if (newHolder instanceof TitleFeedHolder) {
        ((TitleFeedHolder) newHolder).setAvatarVisibility(false);
    }
}
 

public static Matcher<View> withOnlyMatchingDataItems(final Matcher<View> dataMatcher) {
    return new TypeSafeMatcher<View>() {
        @Override
        protected boolean matchesSafely(View view) {
            if (!(view instanceof RecyclerView))
                return false;

            RecyclerView recyclerView = (RecyclerView) view;
            for (int i = 0; i < recyclerView.getChildCount(); i++) {
                RecyclerView.ViewHolder viewHolder = recyclerView.findViewHolderForAdapterPosition(i);
                if (! dataMatcher.matches(viewHolder.itemView)) {
                    return false;
                }
            }
            return true;
        }

        @Override
        public void describeTo(Description description) {
            description.appendText("withOnlyMatchingDataItems: ");
            dataMatcher.describeTo(description);
        }
    };
}
 

@Override
void scrollToPosition(RecyclerView list, int pos) {
    if (list.getLayoutManager() instanceof LinearLayoutManager) {
        // Centering item in its parent
        final LinearLayoutManager manager = (LinearLayoutManager) list.getLayoutManager();
        final boolean isHorizontal = manager.getOrientation() == LinearLayoutManager.HORIZONTAL;

        int offset = isHorizontal
                ? (list.getWidth() - list.getPaddingLeft() - list.getPaddingRight()) / 2
                : (list.getHeight() - list.getPaddingTop() - list.getPaddingBottom()) / 2;

        final RecyclerView.ViewHolder holder = list.findViewHolderForAdapterPosition(pos);
        if (holder != null) {
            final View view = holder.itemView;
            offset -= isHorizontal ? view.getWidth() / 2 : view.getHeight() / 2;
        }

        manager.scrollToPositionWithOffset(pos, offset);
    } else {
        list.scrollToPosition(pos);
    }
}
 

@Nullable
private static RecyclerView.ViewHolder getFirstVisibleViewHolder(@NonNull RecyclerView list) {
    LinearLayoutManager llm = (LinearLayoutManager) list.getLayoutManager();
    if (llm == null) return null;

    int pos = llm.findFirstCompletelyVisibleItemPosition();
    if (pos == -1) return null;
    else return list.findViewHolderForAdapterPosition(pos);
}
 

public int getCurrentTemperatureTextHeight(RecyclerView recyclerView) {
    if (headerCurrentTemperatureTextHeight <= 0 && getItemCount() > 0) {
        AbstractMainViewHolder holder = (AbstractMainViewHolder) recyclerView.findViewHolderForAdapterPosition(0);
        if (holder instanceof HeaderViewHolder) {
            headerCurrentTemperatureTextHeight
                    = ((HeaderViewHolder) holder).getCurrentTemperatureHeight();
        }
    }
    return headerCurrentTemperatureTextHeight;
}
 

public void onScroll(RecyclerView recyclerView) {
    AbstractMainViewHolder holder;
    for (int i = 0; i < getItemCount(); i ++) {
        holder = (AbstractMainViewHolder) recyclerView.findViewHolderForAdapterPosition(i);
        if (holder != null && holder.getTop() < recyclerView.getMeasuredHeight()) {
            holder.enterScreen(pendingAnimatorList, listAnimationEnabled);
        }
    }
}
 

public void updateVisibleViewHolders() {
    RecyclerView recyclerView = boundRecyclerView;
    if (recyclerView == null) {
        Log.d(TAG, "Ignoring updateVisibleViewHolders() when no RecyclerView is bound");
        return;
    }

    RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
    if (layoutManager == null) {
        Log.d(TAG, "Ignoring updateVisibleViewHolders() when no LayoutManager is bound");
        return;
    }

    int startPosition = 0;
    if (layoutManager instanceof LinearLayoutManager) {
        startPosition = ((LinearLayoutManager)layoutManager).findFirstVisibleItemPosition();
    } else {
        Log.e(TAG, "updateVisibleViewHolders() currently only supports LinearLayoutManager and it's subclasses");
        return;
    }

    int i = startPosition;
    RecyclerView.ViewHolder holder = recyclerView.findViewHolderForAdapterPosition(startPosition);

    while (holder != null && i < getItemCount()) {
        holder = recyclerView.findViewHolderForAdapterPosition(i);
        if (holder != null && holder instanceof ActionableView) {
            ((ActionableView) holder).onActionModeChange(inActionMode);
        }
        i++;
    }
}
 

public void clearSelection(@NonNull RecyclerView recyclerView) {
    for (Integer i : getSelected()) {
        RecyclerView.ViewHolder viewHolder = recyclerView.findViewHolderForAdapterPosition(i);
        if (viewHolder != null) {
            viewHolder.itemView.setSelected(false);
        } else {
            Log.w(TAG, "Could not found viewholder to remove selection");
        }
    }
    selected.clear();
}
 

@Override
public void perform(UiController uiController, View view) {
  RecyclerView recyclerView = (RecyclerView) view;

  new ScrollToPositionViewAction(position).perform(uiController, view);
  uiController.loopMainThreadUntilIdle();

  @SuppressWarnings("unchecked")
  VH viewHolderForPosition = (VH) recyclerView.findViewHolderForAdapterPosition(position);
  if (null == viewHolderForPosition) {
    throw new PerformException.Builder()
        .withActionDescription(this.toString())
        .withViewDescription(HumanReadables.describe(view))
        .withCause(new IllegalStateException("No view holder at position: " + position))
        .build();
  }

  View viewAtPosition = viewHolderForPosition.itemView;
  if (null == viewAtPosition) {
    throw new PerformException.Builder()
        .withActionDescription(this.toString())
        .withViewDescription(HumanReadables.describe(viewAtPosition))
        .withCause(new IllegalStateException("No view at position: " + position))
        .build();
  }

  viewAction.perform(uiController, viewAtPosition);
}
 

@Override
public void onDetachedFromRecyclerView(RecyclerView recyclerView) {
    super.onDetachedFromRecyclerView(recyclerView);
    int childCount = recyclerView.getChildCount();
    //We need to stop the player to avoid a potential memory leak.
    for (int i = 0; i < childCount; i++) {
        ViewHolder holder = (ViewHolder) recyclerView.findViewHolderForAdapterPosition(i);
        if (holder != null && holder.videoView != null) {
            holder.videoView.stopPlayback();
        }
    }
}
 

public Matcher<View> atPositionOnView(final int position, final int targetViewId) {

        return new TypeSafeMatcher<View>() {
            Resources resources = null;
            View childView;

            public void describeTo(Description description) {
                String idDescription = Integer.toString(recyclerViewId);
                if (this.resources != null) {
                    try {
                        idDescription = this.resources.getResourceName(recyclerViewId);
                    } catch (Resources.NotFoundException var4) {
                        idDescription = String.format("%s (resource name not found)",
                                                      new Object[] { Integer.valueOf
                                                          (recyclerViewId) });
                    }
                }

                description.appendText("with id: " + idDescription);
            }

            public boolean matchesSafely(View view) {

                this.resources = view.getResources();

                if (childView == null) {
                    RecyclerView recyclerView =
                        (RecyclerView) view.getRootView().findViewById(recyclerViewId);
                    if (recyclerView != null && recyclerView.getId() == recyclerViewId) {
                        childView = recyclerView.findViewHolderForAdapterPosition(position).itemView;
                    }
                    else {
                        return false;
                    }
                }

                if (targetViewId == -1) {
                    return view == childView;
                } else {
                    View targetView = childView.findViewById(targetViewId);
                    return view == targetView;
                }

            }
        };
    }
 

/**
 * 绘制悬浮组
 *
 * @param c      Canvas
 * @param parent RecyclerView
 */
protected void onDrawOverGroup(Canvas c, RecyclerView parent) {
    int firstVisiblePosition = ((LinearLayoutManager) parent.getLayoutManager()).findFirstVisibleItemPosition();
    if (firstVisiblePosition == RecyclerView.NO_POSITION) {
        return;
    }
    Group group = getCroup(firstVisiblePosition);
    if (group == null)
        return;
    String groupTitle = group.toString();
    if (TextUtils.isEmpty(groupTitle)) {
        return;
    }
    boolean isRestore = false;
    Group nextGroup = getCroup(firstVisiblePosition + 1);
    if (nextGroup != null && !group.equals(nextGroup)) {
        //说明是当前组最后一个元素，但不一定碰撞了
        View child = parent.findViewHolderForAdapterPosition(firstVisiblePosition).itemView;
        if (child.getTop() + child.getMeasuredHeight() < mGroupHeight) {
            //进一步检测碰撞
            c.save();//保存画布当前的状态
            isRestore = true;
            c.translate(0, child.getTop() + child.getMeasuredHeight() - mGroupHeight);
        }
    }
    int left = parent.getPaddingLeft();
    int right = parent.getWidth() - parent.getPaddingRight();
    int top = parent.getPaddingTop();
    int bottom = top + mGroupHeight;
    c.drawRect(left, top, right, bottom, mBackgroundPaint);
    float x;
    float y = top + mTextBaseLine;
    if (isCenter) {
        x = parent.getMeasuredWidth() / 2 - getTextX(groupTitle);
    } else {
        x = mPaddingLeft;
    }
    c.drawText(groupTitle, x, y, mTextPaint);
    if (isRestore) {
        //还原画布为初始状态
        c.restore();
    }
}
 

private Matcher<View> atPositionOnView(final int position, final int targetViewId) {

    return new TypeSafeMatcher<View>() {
      Resources resources = null;
      View childView;

      public void describeTo(Description description) {
        String idDescription = Integer.toString(recyclerViewId);
        if (this.resources != null) {
          try {
            idDescription = this.resources.getResourceName(recyclerViewId);
          } catch (Resources.NotFoundException var4) {
            idDescription = String.format("%s (resource name not found)", recyclerViewId);
          }
        }

        description.appendText("with id: " + idDescription);
      }

      public boolean matchesSafely(View view) {

        this.resources = view.getResources();

        if (childView == null) {
          RecyclerView recyclerView = (RecyclerView) view.getRootView().findViewById(recyclerViewId);
          if (recyclerView != null && recyclerView.getId() == recyclerViewId) {
            childView = recyclerView.findViewHolderForAdapterPosition(position).itemView;
          } else {
            return false;
          }
        }

        if (targetViewId == -1) {
          return view == childView;
        } else {
          View targetView = childView.findViewById(targetViewId);
          return view == targetView;
        }
      }
    };
  }