RecycleView在TV开发中滑动及分页加载焦点丢失的解决方法

问题描述：

在ipTv的开发中 因为不能触屏 所以当recycleView设置为GridLayoutManager之后 焦点移动到当前屏幕所能显示的最后一行时 recycleView并不会滑动  (LinearLayout可以)  然后按遥控器的向下按钮时 下一行的item还没有加载出来 这个时候 焦点就会丢失

解决方案：

首先 重写了RecyclerView 解决滑到下一屏时候 item没加载出来的问题

@Override
    public boolean dispatchKeyEvent(KeyEvent event) {
        if (mInterceptLister != null && mInterceptLister.onIntercept(event)) {
            return true;
        }
        boolean result = super.dispatchKeyEvent(event);
        View focusView = this.getFocusedChild();
        if (focusView == null) {
            return result;
        } else {
            int dy = 0;
            int dx = 0;
            if (getChildCount() > 0) {
                View firstView = this.getChildAt(0);
                dy = firstView.getHeight();
                dx = firstView.getWidth();
            }
            if (event.getAction() == KeyEvent.ACTION_UP) {
                return true;
            } else {
                switch (event.getKeyCode()) {
                    case KeyEvent.KEYCODE_DPAD_RIGHT:
                        View rightView = FocusFinder.getInstance().findNextFocus(this, focusView, View.FOCUS_RIGHT);
                        Log.i(TAG, "rightView is null:" + (rightView == null));
                        if (rightView != null) {
                            rightView.requestFocus();
                            return true;
                        } else {
                            this.smoothScrollBy(dx, 0);
                            return true;
                        }
                    case KeyEvent.KEYCODE_DPAD_LEFT:
                        View leftView = FocusFinder.getInstance().findNextFocus(this, focusView, View.FOCUS_LEFT);
                        Log.i(TAG, "leftView is null:" + (leftView == null));
                        if (leftView != null) {
                            leftView.requestFocus();
                            return true;
                        } else {
                            this.smoothScrollBy(-dx, 0);
                            return true;
                        }
                    case KeyEvent.KEYCODE_DPAD_DOWN:
                        View downView = FocusFinder.getInstance().findNextFocus(this, focusView, View.FOCUS_DOWN);
                        Log.i(TAG, " downView is null:" + (downView == null));
                        if (downView != null) {
                            downView.requestFocus();
                            return true;
                        } else {
                            this.smoothScrollBy(0, dy);
                            return true;
                        }
                    /*case KeyEvent.KEYCODE_DPAD_UP:
                        View upView = FocusFinder.getInstance().findNextFocus(this, focusView, View.FOCUS_UP);
                        Log.i(TAG, "upView is null:" + (upView == null));
                        if (event.getAction() == KeyEvent.ACTION_UP) {
                            return true;
                        } else {
                            if (upView != null) {
                                upView.requestFocus();
                                return true;
                            } else {
                                this.smoothScrollBy(0, -dy);
                                return true;
                            }
                        }*/
                }

            }
        }
        return result;
    }

然后写分页加载的方法

recycleView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                if (isLoad){
                    int lastPosition = -1;
                    //当前状态为停止滑动状态SCROLL_STATE_IDLE时
                    if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                        RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
                        if (layoutManager instanceof GridLayoutManager) {
                            //通过LayoutManager找到当前显示的最后的item的position
                            lastPosition = ((GridLayoutManager) layoutManager).findLastVisibleItemPosition();
                        } else if (layoutManager instanceof LinearLayoutManager) {
                            lastPosition = ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();
                        } else if (layoutManager instanceof StaggeredGridLayoutManager) {
                            //因为StaggeredGridLayoutManager的特殊性可能导致最后显示的item存在多个，所以这里取到的是一个数组
                            //得到这个数组后再取到数组中position值最大的那个就是最后显示的position值了
                            int[] lastPositions = new int[((StaggeredGridLayoutManager) layoutManager).getSpanCount()];
                            ((StaggeredGridLayoutManager) layoutManager).findLastVisibleItemPositions(lastPositions);
                            lastPosition = findMax(lastPositions);
                        }
                        //时判断界面显示的最后item的position是否等于itemCount总数-1也就是最后一个item的position
                        //如果相等则说明已经滑动到最后了
                        if (lastPosition == recyclerView.getLayoutManager().getItemCount() - 1) {
                            //   Toast.makeText(getContext(), "滑动到底了", Toast.LENGTH_SHORT).show();
                        }

                    }

                }
            }

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
            }
        });

    }

    private int findMax(int[] lastPositions) {
        int max = lastPositions[0];
        for (int value : lastPositions) {
            if (value > max) {
                max = value;
            }
        }
        return max;
    }

在设置Adapter时 调用adapter.setHasStableIds(true);  在调用notifyDataSetChanged方法时 已经加载的item将不会重新刷新 但

是这样写数据会重复所以需要在适配器中重写getItemId方法  用来记录位置

 @Override
    public long getItemId(int position) {
        return position;
    }

ps:自定义recycleView的下载链接 https://download.csdn.net/download/ayrascal/11182875

end