虽然RecyclerView面世有一段时间了,但由于它的学习成本相对较高,很多码友只是粗略的认识了一下而没有细致的品味RecyclerView的真谛。
那么从现在开始我将带你装逼带你飞,一起领略Google工程师们赋予RecyclerView独特的魅力。
首先我们看一下官方文档是怎么介绍RecyclerView的简介:
A flexible view for providing a limited window into a large data set.
Google的工程师写文档还真够精辟的,写的什么鬼?这不等于没写吗?OK,别激动,我们慢慢来。先看看怎么样把RecyclerView跑起来?
接下来简单写一个使用RecyclerView加载网络图片的demo。
布局文件如下:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.zqlite.android.recyclerviewadvance.MainActivity">
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v7.widget.RecyclerView>
</RelativeLayout>
Activity文件如下:
package com.zqlite.android.recyclerviewadvance;
import android.media.Image;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.CardView;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import com.squareup.picasso.Picasso;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
public class MainActivity extends AppCompatActivity {
private RecyclerView recyclerView;
private Handler handler = new Handler();
public static final int ADD_DATA_DURATION = 2000;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}
private void initView(){
recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
final RecyclerView.LayoutManager layoutManager = new GridLayoutManager(this,3);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setHasFixedSize(true);
RecyclerView.ItemAnimator itemAnimator = new DefaultItemAnimator();
recyclerView.setItemAnimator(itemAnimator);
final MyAdapter adapter = new MyAdapter();
recyclerView.setAdapter(adapter);
handler.postDelayed(new Runnable() {
@Override
public void run() {
adapter.addData();
handler.postDelayed(this, ADD_DATA_DURATION);
layoutManager.scrollToPosition(adapter.getSize());
}
},ADD_DATA_DURATION);
}
private class MyAdapter extends RecyclerView.Adapter{
private final String[] imageUrlArray = {
"http://o6p4e1uhv.bkt.clouddn.com/tu24967_22.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/cce4b48f8c5494ee7008eb9528f5e0fe98257eca.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/tu25422_4.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/ad7fd688d43f879424026deed01b0ef41ad53a2e.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/tu25422_6.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/refsdg.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/ggfnvbn.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/sghgfsh.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/asfasdf.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/fsbgbsfg.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/gsfdtrysrtsfdg.jpg",
"http://o6p4e1uhv.bkt.clouddn.com/sdfgsrters.jpg"};
private List<String> datas = new ArrayList<>();
public MyAdapter(){
}
public void addData(){
Random random = new Random();
datas.add(imageUrlArray[random.nextInt(imageUrlArray.length)]);
notifyItemInserted(datas.size());
}
public int getSize(){
return datas.size();
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
RecyclerView.LayoutParams reLP = new RecyclerView.LayoutParams(RecyclerView.LayoutParams.MATCH_PARENT,RecyclerView.LayoutParams.WRAP_CONTENT);
reLP.setMargins(20, 20, 20, 20);
CardView cardView = new CardView(parent.getContext());
cardView.setLayoutParams(reLP);
CardView.LayoutParams cLP = new CardView.LayoutParams(parent.getMeasuredWidth()/3,(int)(parent.getMeasuredWidth()/3*1.3));
ImageView imageView = new ImageView(parent.getContext());
imageView.setLayoutParams(cLP);
imageView.setScaleType(ImageView.ScaleType.FIT_XY);
cardView.addView(imageView);
MyHolder holder = new MyHolder(cardView);
return holder;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
MyHolder myHolder = (MyHolder)holder;
ImageView imageView = myHolder.imageView;
Picasso.with(imageView.getContext()).load(datas.get(position)).into(imageView);
}
@Override
public int getItemCount() {
return datas.size();
}
private class MyHolder extends RecyclerView.ViewHolder{
public ImageView imageView ;
public MyHolder(View itemView) {
super(itemView);
imageView = (ImageView) ((CardView)itemView).getChildAt(0);
}
}
}
}
使用RecyclerView以下几个东西是必备的:
- RecyclerView.LayoutManager
- RecyclerView.Adapter
其中LayoutManager负责布局,Adapter负责数据集。
该demo运行结果如下:
后面我们对RecyclerView的研究就给予这个demo,demo完整源码地址:
https://github.com/ZhangQinglian/RecyclerViewAdvance