RecyclerView的焦點記憶封裝

上一篇中介紹了TV開發(fā)中的列表焦點實現(xiàn)
android tv列表焦點記憶實現(xiàn)术瓮，是用外部代碼控制的方式實現(xiàn)的，比較繁瑣翎猛，現(xiàn)在介紹用自定義RecyclerView的方式來實現(xiàn)嗓节，并增加了其他的功能：限制縱向和橫向移出焦點，移入移出焦點的事件監(jiān)聽等帕膜。

代碼實現(xiàn)如下：


import android.content.Context;
import android.support.annotation.Nullable;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.KeyEvent;
import android.view.View;
import android.view.ViewGroup;


import java.util.ArrayList;



public class FocusKeepRecyclerView extends RecyclerView {

    private static final String TAG = FocusKeepRecyclerView.class.getSimpleName();
    //是否可以縱向移出
    private boolean mCanFocusOutVertical = true;
    //是否可以橫向移出
    private boolean mCanFocusOutHorizontal = true;
    //焦點移出recyclerview的事件監(jiān)聽
    private FocusLostListener mFocusLostListener;
    //焦點移入recyclerview的事件監(jiān)聽
    private FocusGainListener mFocusGainListener;
    //默認第一次選中第一個位置
    private int mCurrentFocusPosition = 0;

    public FocusKeepRecyclerView(Context context) {
        this(context, null);
    }

    public FocusKeepRecyclerView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public FocusKeepRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
        setChildrenDrawingOrderEnabled(true);
        setItemAnimator(null);
        this.setFocusable(true);
    }


    public boolean isCanFocusOutVertical() {
        return mCanFocusOutVertical;
    }

    public void setCanFocusOutVertical(boolean canFocusOutVertical) {
        mCanFocusOutVertical = canFocusOutVertical;
    }

    public boolean isCanFocusOutHorizontal() {
        return mCanFocusOutHorizontal;
    }

    public void setCanFocusOutHorizontal(boolean canFocusOutHorizontal) {
        mCanFocusOutHorizontal = canFocusOutHorizontal;
    }

    @Override
    public View focusSearch(int direction) {
        return super.focusSearch(direction);
    }

   //覆寫focusSearch尋焦策略
    @Override
    public View focusSearch(View focused, int direction) {
        Log.i(TAG, "focusSearch " + focused + ",direction= " + direction);
        View view = super.focusSearch(focused, direction);
        if (focused == null) {
            return view;
        }

        if (view != null) {
    //該方法返回焦點view所在的父view,如果是在recyclerview之外枣氧，就會是null.所以根據(jù)是否是null,來判斷是否是移出了recyclerview
            View nextFocusItemView = findContainingItemView(view);
            if (nextFocusItemView == null) {
                if (!mCanFocusOutVertical && (direction == View.FOCUS_DOWN || direction == View.FOCUS_UP)) {
                    //屏蔽焦點縱向移出recyclerview
                    return focused;
                }
                if (!mCanFocusOutHorizontal && (direction == View.FOCUS_LEFT || direction == View.FOCUS_RIGHT)) {
                    //屏蔽焦點橫向移出recyclerview
                    return focused;
                }
              //調(diào)用移出的監(jiān)聽
                if (mFocusLostListener != null) {
                    mFocusLostListener.onFocusLost(focused, direction);
                }
                return view;
            }
        }
        return view;
    }

    public void setFocusLostListener(FocusLostListener focusLostListener) {
        this.mFocusLostListener = focusLostListener;
    }

    public interface FocusLostListener {
        void onFocusLost(View lastFocusChild, int direction);
    }

    public void setGainFocusListener(FocusGainListener focusListener) {
        this.mFocusGainListener = focusListener;
    }


    public interface FocusGainListener {
        void onFocusGain(View child, View focued);
    }

    @Override
    public void requestChildFocus(View child, View focused) {
        Log.i(TAG, "nextchild= " + child + ",focused = " + focused);
        if (!hasFocus()) {
            //recyclerview 子view 重新獲取焦點，調(diào)用移入焦點的事件監(jiān)聽
            if (mFocusGainListener != null) {
                mFocusGainListener.onFocusGain(child, focused);
            }
        }
        super.requestChildFocus(child, focused);//執(zhí)行過super.requestChildFocus之后hasFocus會變成true
        mCurrentFocusPosition = getChildViewHolder(child).getAdapterPosition();
        Log.i(TAG,"focusPos = "+mCurrentFocusPosition);
    }

 //實現(xiàn)焦點記憶的關(guān)鍵代碼
    @Override
    public void addFocusables(ArrayList<View> views, int direction, int focusableMode) {
        View view = null;
        if (this.hasFocus() || mCurrentFocusPosition < 0 || (view = getLayoutManager().findViewByPosition(mCurrentFocusPosition)) == null) {
            super.addFocusables(views,direction,focusableMode);
        }else if(view.isFocusable()){
//將當(dāng)前的view放到Focusable views列表中垮刹，再次移入焦點時會取到該view,實現(xiàn)焦點記憶功能
            views.add(view);
        }else{
            super.addFocusables(views,direction,focusableMode);
        }
    }

   
    /**
     * 控制當(dāng)前焦點最后繪制达吞，防止焦點放大后被遮擋
     * 原順序123456789，當(dāng)4是focus時荒典，繪制順序變?yōu)?23567894
     * @param childCount
     * @param i
     * @return
     */
    @Override
    protected int getChildDrawingOrder(int childCount, int i) {
        View focusedChild = getFocusedChild();
        Log.i(TAG,"focusedChild ="+focusedChild);
        if(focusedChild== null){
            return super.getChildDrawingOrder(childCount, i);
        }else{
            int index = indexOfChild(focusedChild);
            Log.i(TAG, " index = " + index + ",i=" + i + ",count=" + childCount);
            if(i == childCount-1){
                return index;
            }
            if(i<index){
                return i;
            }
            return i+1;
        }
    }

}

代碼實現(xiàn)和注釋說明如上酪劫。
可以直接作為一個recyclerview使用，已經(jīng)具有了焦點記憶的功能了寺董，不需要在外層增加額外的代碼覆糟；要增加限制縱向和橫向移出焦點，移入移出焦點的事件監(jiān)聽的功能遮咖，可以再調(diào)用上面的setXXXListener等方法搪桂。