转载
效果预览，真机上看到的效果会很清晰
View选择
上文中提到的效果是使用ListView实现的，我也尝试在它的基础上完善功能，但是各种奇葩的问题随之而来，焦点问题，快滑问题，还有辛苦添加的HeaderView居然无法动态更新数据和UI，最后想到了Google的新控件RecyclerView，本文的主角正是RecyclerView,可以选择是否添加headView与footView,可自由添加与删除.
效果实现关键点
只需关心界面上第一个可见的ItemView和界面上第一个完全可见的ItemView
//界面上第一个可见的ItemView
linearLayoutManager.findFirstVisibleItemPosition()
//界面上第一个完全可见的ItemView
linearLayoutManager.findFirstCompletelyVisibleItemPosition()
通过ViewHolder初始化所有ItemView，第一个ItemView高度最高，其余的都是普通高度
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
if (isFirst && position == 0) {
isFirst = false;
holder.itemView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, item_max_height));
} else {
holder.itemView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, item_normal_height));
}
holder.imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
Glide.with(holder.imageView.getContext()).load(walls.get(position)).into(holder.imageView);
}
图片高度固定为最高Item高度，图片放缩类型为scaleType，不然折叠效果出不来
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/image"
android:layout_width="match_parent"
android:layout_height="@dimen/item_max_height"
android:scaleType="centerCrop" />
</FrameLayout>
纵向滑动距离监听，RecyclerView提供了这样的接口回调
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// TODO: 2015/12/6 根据纵向滑动距离dy实现滑动折叠，阴影渐变，文字放缩效果
}
});
关于怎么样利用dy来实现炫酷的动画效果我就不细说了，我会稍后将代码传到github，
有两个adapter,一个是真正的，一个是实现加头部与尾部的adapter
真正的adapter
package com.yyydjk.miaojiedemo;
import android.content.Context;
import android.support.design.widget.Snackbar;
import android.support.v7.widget.RecyclerView;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import com.bumptech.glide.Glide;
import java.util.List;
/**
* Created by dongjunkun on 2015/12/1.
*/
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private boolean isFirst = true;
private List<Integer> walls;
private int item_normal_height;
private int item_max_height;
private float item_normal_alpha;
private float item_max_alpha;
private float item_normal_font_size;
private float item_max_font_size;
Context mContext;
static RecyclerView mrecyclerView;
public MyAdapter(Context context, List<Integer> walls,RecyclerView recyclerView) {
this.walls = walls;
item_max_height = (int) context.getResources().getDimension(R.dimen.item_max_height);
item_normal_height = (int) context.getResources().getDimension(R.dimen.item_normal_height);
item_normal_font_size = context.getResources().getDimension(R.dimen.item_normal_font_size);
item_max_font_size = context.getResources().getDimension(R.dimen.item_max_font_size);
item_normal_alpha = context.getResources().getFraction(R.fraction.item_normal_mask_alpha, 1, 1);
item_max_alpha = context.getResources().getFraction(R.fraction.item_max_mask_alpha, 1, 1);
mContext=context;
mrecyclerView=recyclerView;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_wall, null);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
if (isFirst && position == 0) {
isFirst = false;
holder.mark.setAlpha(item_max_alpha);
holder.text.setTextSize(TypedValue.COMPLEX_UNIT_PX, item_max_font_size);
holder.itemView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, item_max_height));
} else {
holder.mark.setAlpha(item_normal_alpha);
holder.text.setTextSize(TypedValue.COMPLEX_UNIT_PX, item_normal_font_size);
holder.itemView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, item_normal_height));
}
holder.text.setText(String.format("光谷天地%d", position));
holder.imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
Glide.with(holder.imageView.getContext()).load(walls.get(position)).into(holder.imageView);
}
@Override
public int getItemCount() {
return walls.size();
}
public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
public ImageView imageView;
public View mark;
public TextView text;
public ViewHolder(View itemView) {
super(itemView);
imageView = (ImageView) itemView.findViewById(R.id.image);
mark = itemView.findViewById(R.id.mark);
text = (TextView) itemView.findViewById(R.id.text);
itemView.setOnClickListener(this);
}
@Override
public void onClick(View view) {
String text1=text.getText().toString();
int positon=mrecyclerView.getChildAdapterPosition(view);
Snackbar.make(view, text1 + positon, Snackbar.LENGTH_SHORT).show();
}
}
}
将myadapter传到HeaderAndFooterRecyclerViewAdapter中，然后recyclerView设置其为adapter
HeaderAndFooterRecyclerViewAdapter headerAndFooterRecyclerViewAdapter = new HeaderAndFooterRecyclerViewAdapter(myAdapter);
recyclerView.setAdapter(headerAndFooterRecyclerViewAdapter);