Android RecyclerView+CardView 实现瀑布流并保存瀑布流状态

步骤分解
第一步：导入recyclerview与cardview的包
compile 'com.android.support:appcompat-v7:24.+'
compile 'com.android.support.constraint:constraint-layout:1.0.2'
compile'com.android.support:recyclerview-v7:24.2.0'
compile'com.android.support:cardview-v7:24.2.0'首先导入v7包然后导入recyclerview与cardview注意后面的版本与v7统一，加号的意思是不确定哪个版本
第二步： 在布局文件中引用recyclerview
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler"
android:layout_width="match_parent"
android:layout_height="match_parent">

</android.support.v7.widget.RecyclerView>第三步： 在代码中操作
（1） 首先初始化recyclerview
（2） 初始化manager三种 1线性 list 2 格子grid 3瀑布流
（3）  自定义adapter自定义viewholder
（4） 调用
第四步：上代码
package com.test.testcard;

import android.app.Activity;
import android.graphics.Rect;
import android.graphics.drawable.GradientDrawable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;

public class MainActivity extends Activity {
private RecyclerView recyclerView;
private StaggeredGridLayoutManager manager;
private MyAdapter adapter;
private List<String> list = new ArrayList<>();
private Map<String,Integer> map=new HashMap<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
for (int i = 0; i < 40; i++) {
list.add(i + "pop");
}
recyclerView = (RecyclerView) findViewById(R.id.recycler);
manager = new StaggeredGridLayoutManager(4, StaggeredGridLayoutManager.VERTICAL);
adapter = new MyAdapter();
manager.setGapStrategy(StaggeredGridLayoutManager.GAP_HANDLING_NONE);
recyclerView.setLayoutManager(manager);
recyclerView.addItemDecoration(new MyItemDection(20));
recyclerView.setAdapter(adapter);
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
manager.invalidateSpanAssignments();
}
});
}

/**
* 自定义分割线
*
*/
public class MyItemDection extends RecyclerView.ItemDecoration {
int space;

public MyItemDection(int space) {
this.space = space;
}

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
outRect.top = space;
outRect.bottom = space;
outRect.left = space;
outRect.right = space;
}
}

/**
* 自定义 适配器
* 这里的MyViewHolder是你自己定义的
*/
public class MyAdapter extends RecyclerView.Adapter<MyViewHolder> {

@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = getLayoutInflater().inflate(R.layout.cardlayout, null);
return new MyViewHolder(view);
}

@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
ViewGroup.LayoutParams de = holder.textView.getLayoutParams();
int height=(int)( Math.random() * 500)+200;
//随机产生宽高map是记住每个item的大小防止重新刷新
if (map.containsKey(position+"")){
//如果存在则
de.height = map.get(position+"");
holder.textView.setLayoutParams(de);

}else{
//如果不在
map.put(""+position,height);
de.height = height;
holder.textView.setLayoutParams(de);

}
holder.textView.setText(list.get(position));

}

@Override
public int getItemCount() {
return list.size(
b1dd
);
}
}

/**
*防止多次查id
*/
public class MyViewHolder extends RecyclerView.ViewHolder {
public TextView textView;

public MyViewHolder(View itemView) {
super(itemView);
textView = itemView.findViewById(R.id.cad);
}
}
}