An Android library to retrofit multiple item view types
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Previously, when we need to develop a complex RecyclerView/ListView, it is a boring and troublesome work.
We should override the getItemViewType
of RecyclerView.Adapter
and add some types,
then we create some ViewHolder
to relate the type, all of the process it is a very bad experience.
And once we need to add a new type, we have to go to the original Adapter and modify some old codes, so sad.
Today, I create a new graceful way to easily develop the complex RecyclerView/ListView, with my MultiType library, no matter how complex and how frequently changing list, we could insert a new type without changing the old codes.
In your build.gradle
:
dependencies {
compile 'me.drakeet.multitype:multitype:1.2-beta1'
}
public class TextItemContent implements ItemContent, Savable {
@NonNull public String text;
public TextItemContent(@NonNull String text) {
this.text = text;
}
public TextItemContent(@NonNull byte[] data) {
init(data);
}
@Override public void init(@NonNull byte[] data) {
String json = new String(data);
this.text = new Gson().fromJson(json, TextItemContent.class).text;
}
@NonNull @Override public byte[] toBytes() {
return new Gson().toJson(this).getBytes();
}
}
Step 2. Create a class extends ItemViewProvider<C extends ItemContent, V extends ViewHolder>
, for example:
public class TextItemViewProvider
extends ItemViewProvider<TextItemContent, TextItemViewProvider.TextHolder> {
static class TextHolder extends RecyclerView.ViewHolder {
@NonNull final TextView text;
TextHolder(@NonNull View itemView) {
super(itemView);
this.text = (TextView) itemView.findViewById(R.id.text);
}
}
@NonNull @Override
protected TextHolder onCreateViewHolder(
@NonNull LayoutInflater inflater, @NonNull ViewGroup parent) {
View root = inflater.inflate(R.layout.item_text, parent, false);
TextHolder holder = new TextHolder(root);
return holder;
}
@Override
protected void onBindViewHolder(
@NonNull TextHolder holder, @NonNull TextItemContent content, @NonNull TypeItem typeItem) {
holder.text.setText("hello: " + content.text);
}
}
Step 3. You do not need to create another new class. Just add a RecyclerView
and List<TypeItem>
to your Activity
, for example:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = (RecyclerView) findViewById(R.id.list);
itemFactory = new TypeItemFactory.Builder().build();
TypeItem textItem = itemFactory.newItem(new TextItemContent("world"));
TypeItem imageItem = itemFactory.newItem(new ImageItemContent(R.mipmap.ic_launcher));
TypeItem richItem = itemFactory.newItem(new RichItemContent("小艾大人赛高", R.mipmap.avatar));
List<TypeItem> typeItems = new ArrayList<>(80);
for (int i = 0; i < 20; i++) {
typeItems.add(textItem);
typeItems.add(imageItem);
typeItems.add(richItem);
}
/* register the types before setAdapter, that's all right */
ItemTypePool.register(TextItemContent.class, new TextItemViewProvider());
ItemTypePool.register(ImageItemContent.class, new ImageItemViewProvider());
ItemTypePool.register(RichItemContent.class, new RichItemViewProvider());
recyclerView.setAdapter(new MultiTypeAdapter(typeItems));
}
You're good to go!
You could check the sample
module for more details and after running it will look like:
Q: 为什么使用静态或者全局类型池?(Why we need static and single TypePool?)
A: 我不反对局部或临时类型池的设计,你可以 fork 这个项目自行实现,它们对于内存更加友好(但也只是微小优势而已),但在我看来,全局类型池在多方面更好:
- 它能够显式连接 Type 和它的 Item View,能够在同一地方统一 register,这将避免分散,带来很好的直观性和可管理性;
- 一个应用不会有超级大量的类型定义,类型 class 和 provider 对象都是非常轻薄的对象,直接静态存于内存,并不会导致内存泄漏和大的内存占用问题,几乎可以忽略;
- 至于要不要支持 optional 的局部类型池参数,我也是不喜欢支持的,前面说了,这是没必要的,而且若是可选(optional)也会使用户疑惑:“到底要还是不要?”
因此我喜欢和坚持使用全局静态类型池,它不会带来什么问题,而且好处诸多,有人给我提交了使用反射的方法来自动获取类型连接,为了避免性能话题,我不喜欢反射,而且将类型连接变得复杂和不可见性未必是好事。我一直坚持的原则是:写简单的代码,写可读的代码,实现复杂的需求(你们看我的代码是不是感觉很自然而然而且可读性十分好?)
Copyright 2016 drakeet.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
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