RecyclerView 实现瀑布流交错效果，并使最后一行子View高度占满RecyclerView

http://www.imooc.com/qadetail/91200 我在这个地址搜索到了，如何监听RecyclerView滑动到底的状态

而在实现完瀑布流后，觉得滑动到底部时，最后一行的高度，没有占满外部View，感觉不太好。（真正的瀑布流应该是条目数近乎无穷，可以一直加载更多）

既然是瀑布流，那么就选用StaggeredGridLayoutManager。

mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL)); //纵向3列

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

import java.util.Arrays;

/**
* 实现了滑动到底部的处理，暂未添加自定义监听器
* 实现了当LayoutManger是StaggeredGridLayoutManager时，滑到底部的那一行上的子view高度占满RecyclerView
*
* author : stone
* email  : aa86799@163.com
* time   : 16/5/6 14 23
*/
public class RichRecyclerView extends RecyclerView {

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

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

public RichRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}

@Override
protected void onMeasure(int widthSpec, int heightSpec) {
super.onMeasure(widthSpec, heightSpec);
}

@Override
public void onScrollStateChanged(int state) {
if (state == RecyclerView.SCROLL_STATE_IDLE) {
LayoutManager layoutManager = getLayoutManager();
if (layoutManager instanceof StaggeredGridLayoutManager) {
StaggeredGridLayoutManager lm = (StaggeredGridLayoutManager) layoutManager;
//                int columnCount = lm.getColumnCountForAccessibility(null,null);//列数
int columnCount = lm.getSpanCount();
//                System.out.println("----" +"columnCount" + columnCount);
int positions[] = new int[columnCount];
lm.findLastVisibleItemPositions(positions);//添加 可见的最后一行的 position 数据到数组 positions
System.out.println("----" +Arrays.toString(positions));
for (int i = 0; i < positions.length; i++) {
//                    System.out.println("当前视图上的最后可见列的位置" + positions[i]);
}
for (int i = 0; i < positions.length; i++) {
/**
* 判断lastItem的底边到recyclerView顶部的距离
* 是否小于recyclerView的高度
* 如果小于或等于 说明滚动到了底部
*/
if (positions[i] >= lm.getItemCount() - columnCount) {
//                        System.out.println("滑动到底了1");

//                        System.out.println("总adapter的条目数:" + lm.getItemCount()); //内部取的adapter的方法
//                        System.out.println("总的列数：" + columnCount);
//                        System.out.println("符号条件的最后可见列上的position" + positions[i]);

View child = lm.findViewByPosition(positions[i]);
ViewGroup.LayoutParams layoutParams = child.getLayoutParams();
layoutParams.height = getHeight() - child.getBottom() + child.getHeight();
child.setLayoutParams(layoutParams);
}
}
int[] into = new int[columnCount];
lm.findFirstCompletelyVisibleItemPositions(into);
for (int i = 0; i < into.length; i++) {
System.out.println("首次完全可见的view位置：" + into[i]);
}

lm.findFirstVisibleItemPositions(into);
for (int i = 0; i < into.length; i++) {
System.out.println("首次可见的view位置(即使部份可见)：" + into[i]);
}

} else if (layoutManager instanceof LinearLayoutManager){
LinearLayoutManager lm = (LinearLayoutManager) layoutManager;
int position = lm.findLastVisibleItemPosition();
if (position + 1 == lm.getItemCount()) {
System.out.println("滑动到底了2");

}
}
}
super.onScrollStateChanged(state);
}
}

相应的adapter：

/**
* author : stone
* email  : aa86799@163.com
* time   : 16/4/9 16 22
*/
public class StaggeredAdapter extends BaseRecyclerViewAdapter<String> {

private List<Integer> mWHs; //宽或高
private int mOrientation;

public StaggeredAdapter(Context context, int layoutID, List<String> datas, int orientation) {
super(context, layoutID, datas);
this.mWHs = new ArrayList<>();
this.mOrientation = orientation;

for (int i = 0, len = datas.size(); i < len; i++) {
if (mOrientation == StaggeredGridLayoutManager.VERTICAL) {
mWHs.add((int) (100 + Math.random() * 100));
} else {
mWHs.add((int) (80 + Math.random() * 100));
}
}

}

@Override
public void onBindViewHolderSetData(@NonNull BaseRecyclerViewHolder holder, int position) {

holder.itemView.setBackgroundColor(getColor());

String str = getItem(position);
holder.setText(R.id.tv_text, str);

ViewGroup.LayoutParams params = holder.itemView.getLayoutParams();
if (params == null) {
params = new ViewGroup.LayoutParams(-2, -2);
}
if (mOrientation == StaggeredGridLayoutManager.VERTICAL) {
//            holder.itemView.setMinimumHeight(mWHs.get(position));//该方法改变itemview高度，并requestLayout()，子view没有重新请求layout
params.height = mWHs.get(position);
} else {
//            holder.itemView.setMinimumWidth(mWHs.get(position));
params.width = mWHs.get(position);
}
holder.itemView.setLayoutParams(params);

}

/**
* 随机颜色
*
* @return
*/
@CheckResult
private int getColor() {
StringBuilder sb = new StringBuilder();
Random random = new Random();
String temp;
for (int i = 0; i < 3; i++) {
temp = Integer.toHexString(random.nextInt(0xFF));
if (temp.length() == 1) {
temp = "0" + temp;
}
sb.append(temp);
}
return Color.parseColor("#" + sb.toString());
}
}

item_adapter.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/sel_item_back">

<TextView
android:id="@+id/tv_text"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:focusable="true"
android:focusableInTouchMode="true"
android:gravity="center"/>
</RelativeLayout>