RecyclerView是如何不同于Listview?

一个区别是有一个LayoutManager类和RecyclerView，通过它你可以像-一样管理你的RecyclerView

水平或垂直滚动线性layoutmanager GridLayout by GridLayoutManager 交错网格布局由StaggeredGridLayoutManager

就像水平滚动的RecyclerView-

LinearLayoutManager llm = new LinearLayoutManager(context);
llm.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerView.setLayoutManager(llm);

这对我很管用。希望能有所帮助。最简单的方法。

内部视图Holder

class GeneralViewHolder extends RecyclerView.ViewHolder {
    View cachedView = null;

    public GeneralViewHolder(View itemView) {
        super(itemView);
        cachedView = itemView;
    }

内部OnBindViewHolder ()

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, final int position) {
            final GeneralViewHolder generalViewHolder = (GeneralViewHolder) holder;
            generalViewHolder.cachedView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(context, "item Clicked at "+position, Toast.LENGTH_SHORT).show();
                }
            });

如果你对这个解决方案有任何问题，请告诉我?

为什么RecyclerView没有onItemClickListener

RecyclerView是一个工具箱，与旧的ListView相比，它有更少的内置功能和更多的灵活性。onItemClickListener并不是ListView中唯一被删除的功能。但是它有很多听众和方法来扩展它到你的喜欢，它在正确的手中更强大;)

在我看来，RecyclerView中删除的最复杂的功能是快速滚动。大多数其他特性都可以很容易地重新实现。

如果你想知道RecyclerView还添加了什么很酷的功能，请阅读另一个问题的答案。

内存高效- dropin解决方案的onItemClickListener

这个解决方案是由Android GDE Hugo Visser在RecyclerView发布后提出的。他为您提供了一个免费的类，您只需输入代码并使用它。

它通过使用RecyclerView. onchildattachstatechangelistener展示了一些与RecyclerView引入的多功能性。

编辑2019:我的kotlin版本，java one，来自Hugo Visser，保存在下面

Kotlin / Java

创建一个values/ids.xml文件，并把它放在里面:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <item name="item_click_support" type="id" />
</resources>

然后将下面的代码添加到源代码中

科特林

用法:

recyclerView.onItemClick { recyclerView, position, v ->
    // do it
}

(它还支持长项目点击，看看下面我添加的另一个功能)。

实现(我对Hugo Visser Java代码的改编):

typealias OnRecyclerViewItemClickListener = (recyclerView: RecyclerView, position: Int, v: View) -> Unit
typealias OnRecyclerViewItemLongClickListener = (recyclerView: RecyclerView, position: Int, v: View) -> Boolean

class ItemClickSupport private constructor(private val recyclerView: RecyclerView) {

    private var onItemClickListener: OnRecyclerViewItemClickListener? = null
    private var onItemLongClickListener: OnRecyclerViewItemLongClickListener? = null

    private val attachListener: RecyclerView.OnChildAttachStateChangeListener = object : RecyclerView.OnChildAttachStateChangeListener {
        override fun onChildViewAttachedToWindow(view: View) {
            // every time a new child view is attached add click listeners to it
            val holder = this@ItemClickSupport.recyclerView.getChildViewHolder(view)
                    .takeIf { it is ItemClickSupportViewHolder } as? ItemClickSupportViewHolder

            if (onItemClickListener != null && holder?.isClickable != false) {
                view.setOnClickListener(onClickListener)
            }
            if (onItemLongClickListener != null && holder?.isLongClickable != false) {
                view.setOnLongClickListener(onLongClickListener)
            }
        }

        override fun onChildViewDetachedFromWindow(view: View) {

        }
    }

    init {
        // the ID must be declared in XML, used to avoid
        // replacing the ItemClickSupport without removing
        // the old one from the RecyclerView
        this.recyclerView.setTag(R.id.item_click_support, this)
        this.recyclerView.addOnChildAttachStateChangeListener(attachListener)
    }

    companion object {
        fun addTo(view: RecyclerView): ItemClickSupport {
            // if there's already an ItemClickSupport attached
            // to this RecyclerView do not replace it, use it
            var support: ItemClickSupport? = view.getTag(R.id.item_click_support) as? ItemClickSupport
            if (support == null) {
                support = ItemClickSupport(view)
            }
            return support
        }

        fun removeFrom(view: RecyclerView): ItemClickSupport? {
            val support = view.getTag(R.id.item_click_support) as? ItemClickSupport
            support?.detach(view)
            return support
        }
    }

    private val onClickListener = View.OnClickListener { v ->
        val listener = onItemClickListener ?: return@OnClickListener
        // ask the RecyclerView for the viewHolder of this view.
        // then use it to get the position for the adapter
        val holder = this.recyclerView.getChildViewHolder(v)
        listener.invoke(this.recyclerView, holder.adapterPosition, v)
    }

    private val onLongClickListener = View.OnLongClickListener { v ->
        val listener = onItemLongClickListener ?: return@OnLongClickListener false
        val holder = this.recyclerView.getChildViewHolder(v)
        return@OnLongClickListener listener.invoke(this.recyclerView, holder.adapterPosition, v)
    }

    private fun detach(view: RecyclerView) {
        view.removeOnChildAttachStateChangeListener(attachListener)
        view.setTag(R.id.item_click_support, null)
    }

    fun onItemClick(listener: OnRecyclerViewItemClickListener?): ItemClickSupport {
        onItemClickListener = listener
        return this
    }

    fun onItemLongClick(listener: OnRecyclerViewItemLongClickListener?): ItemClickSupport {
        onItemLongClickListener = listener
        return this
    }

}

/** Give click-ability and long-click-ability control to the ViewHolder */
interface ItemClickSupportViewHolder {
    val isClickable: Boolean get() = true
    val isLongClickable: Boolean get() = true
}

// Extension function
fun RecyclerView.addItemClickSupport(configuration: ItemClickSupport.() -> Unit = {}) = ItemClickSupport.addTo(this).apply(configuration)

fun RecyclerView.removeItemClickSupport() = ItemClickSupport.removeFrom(this)

fun RecyclerView.onItemClick(onClick: OnRecyclerViewItemClickListener) {
    addItemClickSupport { onItemClick(onClick) }
}
fun RecyclerView.onItemLongClick(onLongClick: OnRecyclerViewItemLongClickListener) {
    addItemClickSupport { onItemLongClick(onLongClick) }
}

(请记住，您还需要添加一个XML文件，参见上述部分)

Kotlin版本的额外功能

有时，您不希望RecyclerView的所有项都是可单击的。

为了处理这个问题，我引入了ItemClickSupportViewHolder接口，您可以在ViewHolder上使用该接口来控制可单击的项目。

例子:

class MyViewHolder(view): RecyclerView.ViewHolder(view), ItemClickSupportViewHolder {
    override val isClickable: Boolean get() = false
    override val isLongClickable: Boolean get() = false
}

Java

用法:

ItemClickSupport.addTo(mRecyclerView)
        .setOnItemClickListener(new ItemClickSupport.OnItemClickListener() {
    @Override
    public void onItemClicked(RecyclerView recyclerView, int position, View v) {
        // do it
    }
});

(也支持长项目点击)

实现(我添加的注释):

public class ItemClickSupport {
    private final RecyclerView mRecyclerView;
    private OnItemClickListener mOnItemClickListener;
    private OnItemLongClickListener mOnItemLongClickListener;
    private View.OnClickListener mOnClickListener = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (mOnItemClickListener != null) {
                // ask the RecyclerView for the viewHolder of this view.
                // then use it to get the position for the adapter
                RecyclerView.ViewHolder holder = mRecyclerView.getChildViewHolder(v);
                mOnItemClickListener.onItemClicked(mRecyclerView, holder.getAdapterPosition(), v);
            }
        }
    };
    private View.OnLongClickListener mOnLongClickListener = new View.OnLongClickListener() {
        @Override
        public boolean onLongClick(View v) {
            if (mOnItemLongClickListener != null) {
                RecyclerView.ViewHolder holder = mRecyclerView.getChildViewHolder(v);
                return mOnItemLongClickListener.onItemLongClicked(mRecyclerView, holder.getAdapterPosition(), v);
            }
            return false;
        }
    };
    private RecyclerView.OnChildAttachStateChangeListener mAttachListener
            = new RecyclerView.OnChildAttachStateChangeListener() {
        @Override
        public void onChildViewAttachedToWindow(View view) {
            // every time a new child view is attached add click listeners to it
            if (mOnItemClickListener != null) {
                view.setOnClickListener(mOnClickListener);
            }
            if (mOnItemLongClickListener != null) {
                view.setOnLongClickListener(mOnLongClickListener);
            }
        }

        @Override
        public void onChildViewDetachedFromWindow(View view) {

        }
    };

    private ItemClickSupport(RecyclerView recyclerView) {
        mRecyclerView = recyclerView;
        // the ID must be declared in XML, used to avoid
        // replacing the ItemClickSupport without removing
        // the old one from the RecyclerView
        mRecyclerView.setTag(R.id.item_click_support, this);
        mRecyclerView.addOnChildAttachStateChangeListener(mAttachListener);
    }

    public static ItemClickSupport addTo(RecyclerView view) {
        // if there's already an ItemClickSupport attached
        // to this RecyclerView do not replace it, use it
        ItemClickSupport support = (ItemClickSupport) view.getTag(R.id.item_click_support);
        if (support == null) {
            support = new ItemClickSupport(view);
        }
        return support;
    }

    public static ItemClickSupport removeFrom(RecyclerView view) {
        ItemClickSupport support = (ItemClickSupport) view.getTag(R.id.item_click_support);
        if (support != null) {
            support.detach(view);
        }
        return support;
    }

    public ItemClickSupport setOnItemClickListener(OnItemClickListener listener) {
        mOnItemClickListener = listener;
        return this;
    }

    public ItemClickSupport setOnItemLongClickListener(OnItemLongClickListener listener) {
        mOnItemLongClickListener = listener;
        return this;
    }

    private void detach(RecyclerView view) {
        view.removeOnChildAttachStateChangeListener(mAttachListener);
        view.setTag(R.id.item_click_support, null);
    }

    public interface OnItemClickListener {

        void onItemClicked(RecyclerView recyclerView, int position, View v);
    }

    public interface OnItemLongClickListener {

        boolean onItemLongClicked(RecyclerView recyclerView, int position, View v);
    }
}

它是如何工作的(为什么高效)

这个类通过附加一个RecyclerView来工作。OnChildAttachStateChangeListener到RecyclerView。每当一个子对象从RecyclerView附加或分离时，该侦听器都会被通知。这段代码使用它来附加一个点击/长点击监听器到视图。那个侦听器向RecyclerView请求RecyclerView。ViewHolder包含位置。

这比其他解决方案更有效，因为它避免了为每个视图创建多个侦听器，并在RecyclerView被滚动时不断销毁和创建侦听器。

如果需要更多，还可以调整代码，将holder本身还给您。

最后的评论

请记住，在适配器中通过在列表的每个视图上设置一个单击侦听器来处理它是完全没问题的，就像其他建议的答案一样。

这并不是最有效的方法(每次重用视图时都要创建一个新的侦听器)，但它是有效的，在大多数情况下这不是问题。

这也有点违背关注点分离，因为委托点击事件并不是适配器的真正工作。

RecyclerView是如何不同于Listview?

一个区别是有一个LayoutManager类和RecyclerView，通过它你可以像-一样管理你的RecyclerView

水平或垂直滚动线性layoutmanager GridLayout by GridLayoutManager 交错网格布局由StaggeredGridLayoutManager

就像水平滚动的RecyclerView-

LinearLayoutManager llm = new LinearLayoutManager(context);
llm.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerView.setLayoutManager(llm);

我喜欢这样，我正在用它

内部

public Adapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType)

Put

View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.view_image_and_text, parent, false);
v.setOnClickListener(new MyOnClickListener());

在任何你想要的地方创建这个类

class MyOnClickListener implements View.OnClickListener {
    @Override
    public void onClick(View v) {
       int itemPosition = recyclerView.indexOfChild(v);
       Log.e("Clicked and Position is ",String.valueOf(itemPosition));
    }
}

我以前读过有一个更好的方法，但我喜欢这个方法，简单，不复杂。

如果你想添加onClick()到项目的子视图，例如，项目中的按钮，我发现你可以很容易地在你自己的RecyclerView的onCreateViewHolder()中做到这一点。适配器就像这样:

        @Override
        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            View v = LayoutInflater
                    .from(parent.getContext())
                    .inflate(R.layout.cell, null);

            Button btn = (Button) v.findViewById(R.id.btn);
            btn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    //do it
                }
            });

            return new MyViewHolder(v);
        }

我不知道这是不是一个好方法，但它很有效。如果有人有更好的想法，很高兴告诉我并纠正我的答案!：）