敞开生长之旅!这是我参与「日新计划 12 月更文挑战」的第15天
界面编码规划完成中,咱们必定会用到列表展现控件,大家必定用过ListView。后来google推出了RecycleView,帮咱们去做了很多优化(内置viewholder增加复用率、能够支撑局部改写、布局能够经过外层指定layout等),正常的运用,如下:
MyRecycleViewAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_decorator);
Component component = new ConCreateComponent();
ComponentImplA impl1 = new ComponentImplA(component);
impl1.operation();
List<String> list = new ArrayList<>();
for (int i = 0; i < 100; i++) {
list.add("position " + i);
}
adapter = new MyRecycleViewAdapter(this);
adapter.setData(list);
}
/**
* 原始的yRecycleViewAdapter v1
*/
public void buttonv1(View view) {
findViewById(R.id.recycleview).setVisibility(View.VISIBLE);
findViewById(R.id.wrapperR).setVisibility(View.GONE);
RecyclerView recyclerView = findViewById(R.id.recycleview);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(adapter);
}
可是RecycleView大家发现有一个问题,咱们假如想要为这个RecycleView增加自界说的头部view、尾部view的话,官方这个显着做不到,那这时咱们能够考虑用装修者形式或许承继去扩展一下。
规划UML图
首要咱们经过UML图,来规划一下,规划之前想一下,咱们是想要扩展RecyclerView.Adapter和RecyclerView,从而能够完成addHeadView、addFootView的功能,那么需求以下几步骤。
1)首要,因为RecyclerView.Adapter已经是一个抽象类接口,咱们自己承继与它,然后进行包装界说为WrapperRecyclerAdapter类 2)WrapperRecyclerAdapter必定要持有RecyclerView.Adapter的引证,所以需求有一个构造办法,将RecyclerView.Adapter的引证传递进来 3)因为WrapperRecyclerAdapter承继与RecyclerView.Adapter,必定要去完成要害的办法,onCreateViewHolder(创立viewitem的holder)、onBindViewHolder(viewholder数据绑定)、getItemCount(获取列表item的数量) 4)要害的一步来了,便是运用RecyclerView.Adapter、footviews、headviews,这三者组合,重写上面的三个重要办法,给列表相应位置创立对应的item
代码完成1
WrapperRecyclerAdapter
package com.itbird.design.decorator.recycleview;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;
import java.util.List;
/**
* RecyclerView.Adapter包装类,扩展完成headView、footView的增加
* Created by itbird on 2022/6/10
*/
public class WrapperRecyclerAdapter extends RecyclerView.Adapter {
RecyclerView.Adapter adapter;
List<View> headViews = new ArrayList<>();
List<View> footViews = new ArrayList<>();
public WrapperRecyclerAdapter(RecyclerView.Adapter adapter) {
this.adapter = adapter;
adapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
@Override
public void onChanged() {
notifyDataSetChanged();
}
});
}
@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int position) {
//头部的,回来头部的viewholder
if (position < headViews.size()) {
return new WrapperViewHolder(headViews.get(position));
}
//adapter回来中心数据holder
if (position >= headViews.size() && position < headViews.size() + adapter.getItemCount()) {
return adapter.onCreateViewHolder(parent, adapter.getItemViewType(position - headViews.size()));
}
//尾部的,回来尾部的viewholder
return new WrapperViewHolder(footViews.get(position - headViews.size() - adapter.getItemCount()));
}
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
if (position < headViews.size() || position >= adapter.getItemCount() + headViews.size()) {
return;
}
//头部和底部不需求做处理,只需求实在的adapter需求处理
adapter.onBindViewHolder(holder, position - headViews.size());
}
@Override
public int getItemViewType(int position) {
return position;
}
@Override
public int getItemCount() {
return headViews.size() + footViews.size() + adapter.getItemCount();
}
public void addHeadView(View view) {
if (!headViews.contains(view)) {
headViews.add(view);
notifyDataSetChanged();
}
}
public void addFootView(View view) {
if (!footViews.contains(view)) {
footViews.add(view);
notifyDataSetChanged();
}
}
public void removeHeadView(View view) {
if (headViews.contains(view)) {
headViews.add(view);
notifyDataSetChanged();
}
}
public void removeFootView(View view) {
if (footViews.contains(view)) {
footViews.remove(view);
notifyDataSetChanged();
}
}
static class WrapperViewHolder extends RecyclerView.ViewHolder {
public WrapperViewHolder(@NonNull View itemView) {
super(itemView);
}
}
}
这时再去调用,发现就能够如下调用
/**
* 扩展的,能够增加头尾的recycleview v2
*/
public void buttonv2(View view) {
findViewById(R.id.recycleview).setVisibility(View.VISIBLE);
findViewById(R.id.wrapperR).setVisibility(View.GONE);
RecyclerView recyclerView = findViewById(R.id.recycleview);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
WrapperRecyclerAdapter wrapperRecyclerAdapter = new WrapperRecyclerAdapter(adapter);
//这儿head为什么不会全屏,因为LayoutInflater需求parent才会全屏
wrapperRecyclerAdapter.addHeadView(LayoutInflater.from(this).inflate(R.layout.layout_header_view, recyclerView, false));
wrapperRecyclerAdapter.addFootView(new Button(this));
recyclerView.setAdapter(wrapperRecyclerAdapter);
// 面向对象的六大基本准则,如同不符合最小知道准则,每次调用需求去new WrapperRecyclerAdapter这样的一个包装者,这必定是不对的,所以需求封装自己的recycleview
}
看一下运转效果
代码完成2
这儿咱们发现一个问题,这样岂不是让开发者,每每次去运用的时分,new原始的adapter,还需求去new WrapperRecyclerAdapter,然后才能给recyclerView去setAdapter,面向对象的六大基本准则,如同不符合最小知道准则,每次调用需求去new WrapperRecyclerAdapter这样的一个包装者,这必定是不对的,所以需求封装自己的recycleview。
所以咱们做如下优化,将WrapperRecyclerAdapter的new操作,咱们能够放入recyclerView中,这样外界开发者只需求去关心WrapperRecycleView和RecyclerView.Adapter就能够了,关于开发者来讲,只需关心RecyclerView自界说就能够了。
自界说WrapperRecycleView
,重写办法setAdapter,用于封装new WrapperRecyclerAdapter的操作
package com.itbird.design.decorator.recycleview;
import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.recyclerview.widget.RecyclerView;
/**
* 自界说WrapperRecycleView,重写办法setAdapter,用于封装new WrapperRecyclerAdapter的操作
* Created by itbird on 2022/6/10
*/
public class WrapperRecycleView extends RecyclerView {
WrapperRecyclerAdapter wrapperRecyclerAdapter;
public WrapperRecycleView(@NonNull Context context) {
super(context);
}
public WrapperRecycleView(@NonNull Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
public WrapperRecycleView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
public void setAdapter(@Nullable Adapter adapter) {
wrapperRecyclerAdapter = new WrapperRecyclerAdapter(adapter);
super.setAdapter(wrapperRecyclerAdapter);
}
@Nullable
@Override
public Adapter getAdapter() {
return wrapperRecyclerAdapter;
}
public void addHeadView(View view) {
wrapperRecyclerAdapter.addHeadView(view);
}
public void addFootView(View view) {
wrapperRecyclerAdapter.addFootView(view);
}
public void removeHeadView(View view) {
wrapperRecyclerAdapter.removeHeadView(view);
}
public void removeFootView(View view) {
wrapperRecyclerAdapter.removeFootView(view);
}
}
调用一下
/**
* 将wrapperadapter的new操作,内部完成 v3
* 封装的必要性,这样的话,只需求重视WrapperRecycleView,不再需求重视WrapperRecyclerAdapter
*/
public void buttonv3(View view) {
findViewById(R.id.wrapperR).setVisibility(View.VISIBLE);
findViewById(R.id.recycleview).setVisibility(View.GONE);
WrapperRecycleView wrapperRecycleView = findViewById(R.id.wrapperR);
wrapperRecycleView.setLayoutManager(new LinearLayoutManager(this));
wrapperRecycleView.setAdapter(adapter);
wrapperRecycleView.addHeadView(LayoutInflater.from(this).inflate(R.layout.layout_header_view, wrapperRecycleView, false));
wrapperRecycleView.addFootView(new Button(this));
//这时再去考虑一个事情,咱们经过装修者形式把adapter封装了一层,假如adpater有数据更新,导致变动,这时会有问题吗?
//这时会发现,并未更新,原因是装修类,并未做事情呼应
}
是不是简略了很多。