这篇文章主要介绍Android RecyclerView中焦点记忆封装的示例分析，文中介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们一定要看完！
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android tv列表焦点记忆实现 ，是用外部代码控制的方式实现的，比较繁琐，现在介绍用自定义RecyclerView的方式来实现，并增加了其他的功能：限制纵向和横向移出焦点，移入移出焦点的事件监听等。
代码实现如下：
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();
//是否可以纵向移出
private boolean mCanFocusOutVertical = true;
//是否可以横向移出
private boolean mCanFocusOutHorizontal = true;
//焦点移出recyclerview的事件监听
private FocusLostListener mFocusLostListener;
//焦点移入recyclerview的事件监听
private FocusGainListener mFocusGainListener;
//默认第一次选中第一个位置
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);
}
//覆写focusSearch寻焦策略
@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) {
//该方法返回焦点view所在的父view,如果是在recyclerview之外，就会是null.所以根据是否是null,来判断是否是移出了recyclerview
View nextFocusItemView = findContainingItemView(view);
if (nextFocusItemView == null) {
if (!mCanFocusOutVertical && (direction == View.FOCUS_DOWN || direction == View.FOCUS_UP)) {
//屏蔽焦点纵向移出recyclerview
return focused;
}
if (!mCanFocusOutHorizontal && (direction == View.FOCUS_LEFT || direction == View.FOCUS_RIGHT)) {
//屏蔽焦点横向移出recyclerview
return focused;
}
//调用移出的监听
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 重新获取焦点，调用移入焦点的事件监听
if (mFocusGainListener != null) {
mFocusGainListener.onFocusGain(child, focused);
}
}
super.requestChildFocus(child, focused);//执行过super.requestChildFocus之后hasFocus会变成true
mCurrentFocusPosition = getChildViewHolder(child).getAdapterPosition();
Log.i(TAG,"focusPos = "+mCurrentFocusPosition);
}
//实现焦点记忆的关键代码
@Override
public void addFocusables(ArrayList 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()){
//将当前的view放到Focusable views列表中，再次移入焦点时会取到该view,实现焦点记忆功能
views.add(view);
}else{
super.addFocusables(views,direction,focusableMode);
}
}
/**
* 控制当前焦点最后绘制，防止焦点放大后被遮挡
* 原顺序123456789，当4是focus时，绘制顺序变为123567894
* @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代码实现和注释说明如上。
可以直接作为一个recyclerview使用，已经具有了焦点记忆的功能了，不需要在外层增加额外的代码；要增加限制纵向和横向移出焦点，移入移出焦点的事件监听的功能，可以再调用上面的setXXXListener等方法。
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文章题目：AndroidRecyclerView中焦点记忆封装的示例分析
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