RecyclerView 下拉刷新上拉加载（类似PullToRfresh）

自Android5.0出来，大家可能对RecyclerView不陌生了，可是在实际项目中却不敢用，因为不熟悉，

也不会像ListView那样有很多库支持，比如PullToRefreshListiew

现在我们就仿照来自定义PullToRefreshRecyclerView

我们不着急，先看看源代码的上下拉是怎么判断的吧

带着你们找找源码吧，去类库里找到上下拉的基类

PullToRefreshBase

下面重写的代码就是判断上下拉刷新的

isReadyForPullStart  控件是否到顶

isReadyForPullEnd  控件是否到底

@Overridepublic final boolean demo() {   if (mMode.showHeaderLoadingLayout() && isReadyForPullStart()) {      smoothScrollToAndBack(-getHeaderSize() * 2);      return true;   } else if (mMode.showFooterLoadingLayout() && isReadyForPullEnd()) {      smoothScrollToAndBack(getFooterSize() * 2);      return true;   }   return false;}

我们需要找到这两个方法是如何写的，去参照PullToRefreshListiew类吧

ctrl+f,找到这两个方法，没有找到，那我们就从继承的类里找

public class PullToRefreshListView extends PullToRefreshAdapterViewBase<ListView>进入到
PullToRefreshAdapterViewBase类中

ctrl+f
protected boolean isReadyForPullEnd() {   return isLastItemVisible();}
进入isLastItemVisible()方法如下
private boolean isLastItemVisible() {   final Adapter adapter = mRefreshableView.getAdapter();//获取adapter   if (null == adapter || adapter.isEmpty()) {      if (DEBUG) {         Log.d(LOG_TAG, "isLastItemVisible. Empty View.");      }      return true;   } else {      final int lastItemPosition = mRefreshableView.getCount() - 1;//找到最后一个元素对应的位置      final int lastVisiblePosition = mRefreshableView.getLastVisiblePosition();//最后一个可见元素对应的位置      if (lastVisiblePosition >= lastItemPosition - 1) {         final int childIndex = lastVisiblePosition - mRefreshableView.getFirstVisiblePosition();         final View lastVisibleChild = mRefreshableView.getChildAt(childIndex);         if (lastVisibleChild != null) {            return lastVisibleChild.getBottom() <= mRefreshableView.getBottom();//这是关键代码，//如果可见元素的y坐标小于等于整个空间的y坐标，就是到了最后一个元素了         }      }   }   return false;}

大家可能想，mRefreshableView这个变量哪里来的？不着急，我们后面会写到，同理另一个方法，我直接贴上，就不用解释了


private boolean isFirstItemVisible() {   final Adapter adapter = mRefreshableView.getAdapter();   if (null == adapter || adapter.isEmpty()) {      return true;   } else {      if (mRefreshableView.getFirstVisiblePosition() <= 1) {         final View firstVisibleChild = mRefreshableView.getChildAt(0);         if (firstVisibleChild != null) {            return firstVisibleChild.getTop() >= mRefreshableView.getTop();         }      }   }   return false;}好啦，方法看见了，我们直接自定义吧
package b2a.main.widget.RecycleRelating;import android.content.Context;import android.support.v7.widget.LinearLayoutManager;import android.support.v7.widget.RecyclerView;import android.util.AttributeSet;import android.util.Log;import android.view.View;import android.widget.Adapter;import com.handmark.pulltorefresh.library.PullToRefreshBase;import b2a.main.R;/** * Created by shf on 2015/7/23. */public class PullToRefreshRecyclerView extends PullToRefreshBase<RecyclerView> {    public PullToRefreshRecyclerView(Context context) {        super(context);    }    public PullToRefreshRecyclerView(Context context, AttributeSet attrs) {        super(context, attrs);    }    public PullToRefreshRecyclerView(Context context, Mode mode) {        super(context, mode);    }    public PullToRefreshRecyclerView(Context context, Mode mode, AnimationStyle animStyle) {        super(context, mode, animStyle);    }    /**     * 刷新的方向     *     * @return     */    @Override    public Orientation getPullToRefreshScrollDirection() {        return Orientation.VERTICAL;    }    /**     * 创建刷新内容     *     * @param context Context to create view with     * @param attrs   AttributeSet from wrapped class. Means that anything you     *                include in the XML layout declaration will be routed to the     *                created View     * @return     */    @Override    protected RecyclerView createRefreshableView(Context context, AttributeSet attrs) {        RecyclerView recycler = new RecyclerView(context, attrs);        recycler.setId(R.id.recyclerSHF);//在资源文件中配置ids        return recycler;    }    /**     * 控件是否到底     *     * @return     */    @Override    protected boolean isReadyForPullEnd() {        RecyclerView recycler = getRefreshableView();//获取刷新的view        final RecyclerView.Adapter adapter = recycler.getAdapter();        if (null == adapter || adapter.getItemCount() == 0) {            Log.i("SHF", "因为没有数据控件到底了-->001-->" + adapter.getItemCount());            return true;        } else {            final int lastItemPosition = adapter.getItemCount() - 1;            final int lastVisiblePosition = ((LinearLayoutManager) recycler.getLayoutManager()).                    findLastVisibleItemPosition();            Log.i("SHF", "lastItemPosition-->" + lastItemPosition + "lastVisiblePosition-->" + lastVisiblePosition);            if (lastVisiblePosition >= lastItemPosition - 1) {                final int childIndex = lastVisiblePosition -                        ((LinearLayoutManager) recycler.getLayoutManager()).findFirstVisibleItemPosition();                final View lastVisibleChild = recycler.getChildAt(childIndex);                if (lastVisibleChild != null) {                    Log.i("SHF", "因为数据控件到底了-->002");                    return lastVisibleChild.getBottom() <= recycler.getBottom();                }            }        }        Log.i("SHF", "因为数据控件没到底-->003");        return false;    }    @Override    protected boolean isReadyForPullStart() {        RecyclerView recycler = getRefreshableView();//获取刷新的view        final RecyclerView.Adapter adapter = recycler.getAdapter();        if (null == adapter || adapter.getItemCount() == 0) {            return true;        } else {            if (((LinearLayoutManager) recycler.getLayoutManager()).findFirstVisibleItemPosition() <= 1) {                final View firstVisibleChild = recycler.getChildAt(0);                if (firstVisibleChild != null) {                    return firstVisibleChild.getTop() >= recycler.getTop();                }            }        }        return false;    }}
参照listview我们也写好那两个判断方法即可，这里要提两个地方，
一个是RecyclerView recycler = getRefreshableView();//获取刷新的view
这就是获取控件，上面已经提到啦
另一个是recycler.setId(R.id.recyclerSHF);//在资源文件中配置ids
这里大家依照我写的配置一下就行了
res-->values-->ids.xml  没有的话新建一个
<?xml version="1.0" encoding="utf-8"?><resources>    <item type="id" name="gridview" />    <item type="id" name="webview" />    <item type="id" name="scrollview" /></resources>大功告成，放心大胆的用吧