# AdapterDelegates

**Repository Path**: hihopeorg/AdapterDelegates

## Basic Information

- **Project Name**: AdapterDelegates
- **Description**: 使用组合模式构建列表适配器，方便组件重用
- **Primary Language**: Unknown
- **License**: Apache-2.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-09-02
- **Last Updated**: 2021-11-17

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# AdapterDelegates

**本项目是基于开源项目AdapterDelegates进行ohos化的移植和开发的，可以通过项目标签以及github地址( https://github.com/sockeqwe/AdapterDelegates )追踪到原项目版本**

#### 项目介绍

- 项目名称：AdapterDelegates
- 所属系列：ohos的第三方组件适配移植
- 功能：AdapterDelegates使用组合模式构建列表适配器，方便组件重用。
- 项目移植状态：完成
- 调用差异：无
- 项目作者和维护人：hihope
- 联系方式：hihope@hoperun.com
- 原项目Doc地址：https://github.com/sockeqwe/AdapterDelegates
- 原项目基线版本：v4.3.0, sha1:5092dbf64f35843b02fbf46ab3ac03a7c55496ea
- 编程语言：Java
- 外部库依赖：无

#### 安装教程

##### 方法一：

1. 下载har包adapterdelegates.har。
2. 启动 DevEco Studio，将下载的har/jar包，导入工程目录“entry->libs”下。
3. 在moudle级别下的build.gradle文件中添加依赖，在dependences标签中增加对libs目录下har/jar包的引用。

```
dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar', '*.har'])
}
```

4. 在导入的har包上点击右键，选择“Add as Library”对包进行引用，选择需要引用的模块，并点击“OK”即引用成功。

##### 方法二：

  1. 在工程的build.gradle的allprojects中，添加HAR所在的Maven仓地址:

```
 repositories {
     maven {
         url 'http://106.15.92.248:8081/repository/Releases/' 
     }
 }
```

  2. 在应用模块的build.gradle的dependencies闭包中，添加如下代码:

```
 dependencies {
     implementation 'com.hannesdorfmann.ohos:adapterdelegates4:1.0.0'
 }
```

#### 效果展示

![p1](picture/AdapterDelegates.gif)

#### 使用说明

该库使用主要思想是通过组合模式使用可重用的组件来构建列表适配器。

> Favor composition over inheritance

为每种组件类型定义一个`AdapterDelegate`。这个delegate负责创建ViewHolder并且负责对指定view类型进行bingding操作。
每个`AdapterDelegate`都需要添加到`AdapterDelegatesManager`中，以此来连接`RecyclerAdapter`。

举例如下:
```java
public class CatAdapterDelegate extends AdapterDelegate<List<DisplayableItem>> {

    private LayoutScatter scatter;

    public CatAdapterDelegate(Ability ability) {
        scatter = LayoutScatter.getInstance(ability);
    }

    @Override
    protected boolean isForViewType(List<DisplayableItem> items, int position) {
        return items.get(position) instanceof Cat;
    }

    @Override
    public RecyclerAdapter.ViewHolder onCreateViewHolder(ComponentContainer parent) {
        return new CatViewHolder(scatter.parse(ResourceTable.Layout_item_cat, parent, false));
    }

    @Override
    public void onBindViewHolder(List<DisplayableItem> items, int position,
                                 RecyclerAdapter.ViewHolder holder, List<Object> payloads) {
        CatViewHolder vh = (CatViewHolder) holder;
        Cat cat = (Cat) items.get(position);

        vh.name.setText(cat.getName());
    }

    static class CatViewHolder extends RecyclerAdapter.ViewHolder {

        public Text name;

        public CatViewHolder(Component itemView) {
            super(itemView);
            name = (Text) itemView.findComponentById(ResourceTable.Id_name);
        }
    }
}
```

对应的`AnimalAdapter`定义如下:

```java
public class AnimalAdapter extends RecyclerAdapter {

  private AdapterDelegatesManager<List<Animal>> delegatesManager;
  private List<Animal> items;

  public AnimalAdapter(Ability ability, List<Animal> items) {
    this.items = items;

    delegatesManager = new AdapterDelegatesManager<>();

    // AdapterDelegatesManager internally assigns view types integers
    delegatesManager.addDelegate(new CatAdapterDelegate(ability))
                    .addDelegate(new DogAdapterDelegate(ability))
                    .addDelegate(new GeckoAdapterDelegate(ability));

    // You can explicitly assign integer view type if you want to
    delegatesManager.addDelegate(23, new SnakeAdapterDelegate(ability));
  }

  @Override public int getItemViewType(int position) {
    return delegatesManager.getItemViewType(items, position);
  }

  @Override public RecyclerAdapter.ViewHolder onCreateViewHolder(ComponentContainer parent, int viewType) {
    return delegatesManager.onCreateViewHolder(parent, viewType);
  }

  @Override public void onBindViewHolder(RecyclerAdapter.ViewHolder holder, int position) {
    delegatesManager.onBindViewHolder(items, position, holder);
  }

  @Override public int getItemCount() {
    return items.size();
  }
}
```

##### 简化样板代码
如上面代码，为了将`AdapterDelegatesManager` 连接到 `Adapter`，需要不断编写类似的代码片段来实现。
如果适配器显示的数据源是 `java.util.List<?>` 或更一般的 `AbsDelegationAdapter`（不限于 `java.util.List`），则可以通过扩展`ListDelegationAdapter`来减少这种情况。

##### ListDelegationAdapter
如下代码可以通过扩展`ListDelegationAdapter`来简化`AnimalAdapter`的实现:

```java
public class AnimalAdapter extends ListDelegationAdapter<List<Animal>> {

  public AnimalAdapter(Ability ability, List<Animal> items) {

    // DelegatesManager is a protected Field in ListDelegationAdapter
    delegatesManager.addDelegate(new CatAdapterDelegate(ability))
                    .addDelegate(new DogAdapterDelegate(ability))
                    .addDelegate(new GeckoAdapterDelegate(ability))
                    .addDelegate(23, new SnakeAdapterDelegate(ability));

    // Set the items from super class.
    setItems(items);
  }
}
```

##### AbsListItemAdapterDelegate
另外，在使用list of items作为数据集源时，常常需要编写样板代码来转换items和ViewHolders。
此时可以使用`AbsListItemAdapterDelegate`来创建一个类似于`CatAdapterDelegate`的`CatListItemAdapterDelegate`，这样可以规避item元素的强制转换。

```java
public class CatListItemAdapterDelegate extends AbsListItemAdapterDelegate<Cat, Animal, CatViewHolder> {

  private LayoutScatter scatter;

  public CatAdapterDelegate(Ability ability) {
    scatter = LayoutScatter.getInstance(ability);
  }

  @Override public boolean isForViewType(Animal item, List<Animal> items, int position) {
    return item instanceof Cat;
  }

  @Override public CatViewHolder onCreateViewHolder(ComponentContainer parent) {
    return new CatViewHolder(scatter.parse(ResourceTable.Layout_item_cat, parent, false));
  }

  @Override public void onBindViewHolder(Cat item, CatViewHolder vh, List<Object> payloads) {
    vh.name.setText(item.getName());
  }

  static class CatViewHolder extends RecyclerAdapter.ViewHolder {

    public Text name;

    public CatViewHolder(Component itemView) {
      super(itemView);
      name = (Text) itemView.findComponentById(ResourceTable.Id_name);
    }
  }
}
```

##### DiffUtil & ListAdapter = AsyncListDifferDelegationAdapter
AsyncListDifferDelegationAdapter是一个通过DiffUtil支持来支持diff计算的ListAdapter.
使用如下：

```java
public class DiffAdapter extends AsyncListDifferDelegationAdapter<Animal> {
    public DiffAdapter() {
        super(DIFF_CALLBACK); // Your diff callback for diff utils
        delegatesManager
            .addDelegate(new DogAdapterDelegate())
            .addDelegate(new CatAdapterDelegate());
    }
}
```

##### Fallback AdapterDelegate
当adatper的数据源包含了一些特定的元素，这些特定元素并没有注册与之对应的`AdapterDelegate`时，可以定义一个fallback`AdapterDelegate`来统一处理。

```java
AdapterDelegate fallbackDelegate = ...;
adapterDelegateManager.setFallbackDelegate( fallbackDelegate );
```

#### 版本迭代

- v1.0.0

#### 版权和许可信息

```
Copyright 2015 Hannes Dorfmann

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

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
```