你还在为每个列表专门写一个 adapter 和 ViewHolder 吗？这里教大家用 databinding 打造通用列表适配器 , adapter * 1 + ViewHolder * 1 适配所有列表，支持 HeaderView、FooterView，以 RecyclerView 为例：
效果
a.gif
准备工作
- 想要支持 DataBinding， 需要在 module 的 buidle.gradle 的 android 中加上：
dataBinding {
enabled = true
}
引入 RecyclerView 包
compile 'com.android.support:recyclerview-v7:25.3.1'为方便使用，我们先对
RecyclerView.Adapter做简单封装，通过构造器传递列表数据和布局文件 id，并留出onBind(RecyclerHolder<B> holder, T t, int position)方法装载数据
/**
* RecyclerView 基类列表适配器
*
* @author gavin.xiong 2016/12/9
*/
public abstract class RecyclerAdapter<T, B extends ViewDataBinding> extends RecyclerView.Adapter<RecyclerHolder<B>> {
protected Context mContext;
protected List<T> mList;
private int layoutId;
public RecyclerAdapter(Context context, List<T> list, @LayoutRes int layoutId) {
this.mContext = context;
this.mList = list;
this.layoutId = layoutId;
}
@Override
public RecyclerHolder<B> onCreateViewHolder(ViewGroup parent, int viewType) {
B bing = DataBindingUtil.inflate(LayoutInflater.from(mContext), layoutId, parent, false);
return new RecyclerHolder<>(bing);
}
@Override
public void onBindViewHolder(RecyclerHolder<B> holder, int position) {
final T t = mList.get(position);
onBind(holder, t, position);
}
@Override
public int getItemCount() {
return mList == null ? 0 : mList.size();
}
protected abstract void onBind(RecyclerHolder<B> holder, T t, int position);
}
- 以及对应的
RecyclerHolder.java
/**
* RecyclerHolder
*
* @author gavin.xiong 2016/12/9
*/
public class RecyclerHolder<B extends ViewDataBinding> extends RecyclerView.ViewHolder {
public final B binding;
public RecyclerHolder(B binding) {
super(binding.getRoot());
this.binding = binding;
}
}
- 接下来就是主角
BindingAdapter.java了（这里除装载数据外只留了一个item点击事件监听器，如有需要可拓展）：
/**
* DataBinding 基类适配器
*
* @author gavin.xiong 2016/12/28
*/
public class BindingAdapter<T> extends RecyclerAdapter<T, ViewDataBinding> {
private IntConsumer onItemClickListener;
public BindingAdapter(Context context, List<T> list, @LayoutRes int layoutId) {
super(context, list, layoutId);
}
public void setOnItemClickListener(IntConsumer onItemClickListener) {
this.onItemClickListener = onItemClickListener;
}
@Override
protected void onBind(RecyclerHolder<ViewDataBinding> holder, T t, final int position) {
holder.binding.setVariable(BR.item, t);
holder.binding.executePendingBindings();
if (onItemClickListener != null) {
holder.itemView.findViewById(R.id.item).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
onItemClickListener.accept(position);
}
});
}
}
}
- item点击事件监听器：
@FunctionalInterface
public interface IntConsumer {
void accept(int i);
}
使用
Story.java
/**
* 测试数据
*
* @author gavin.xiong 2017/9/29
*/
public class Story {
private String title;
private String image;
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getImage() {
return image;
}
public void setImage(String image) {
this.image = image;
}
}
item_story.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<data>
<variable
name="item"
type="me.gavin.adapter.base.Story" />
</data>
<LinearLayout
android:id="@+id/item"
android:layout_width="match_parent"
android:layout_height="82dp"
android:clickable="true"
android:foreground="?attr/selectableItemBackground"
android:gravity="center_vertical"
android:paddingLeft="16dp"
android:paddingRight="16dp">
<ImageView
android:layout_width="50dp"
android:layout_height="50dp"
android:scaleType="centerCrop"
app:imageUrl="@{item.image}"
tools:ignore="contentDescription"
tools:src="@mipmap/ic_launcher" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="12dp"
android:layout_marginLeft="12dp"
android:lineSpacingMultiplier="1.2"
android:maxLines="2"
android:text="@{item.title}"
android:textColor="#99000000"
android:textSize="14sp"
tools:text="这就是理想主义，对彼此，对现实的妥协" />
</LinearLayout>
</layout>
- 特殊数据绑定如
加载图片等
/**
* 数据绑定适配器
*
* @author gavin.xiong 2017/8/15
*/
public class BindingHelper {
/**
* 使用DataBinding来加载图片
* 使用@BindingAdapter注解，注解值（这里的imageUrl）可任取，注解值将成为自定义属性
* 此自定义属性可在xml布局文件中使用，自定义属性的值就是这里定义String类型url
* 1. 方法名可与注解名一样，也可不一样
* 2. 第一个参数必须是View，就是自定义属性所在的View
* 3. 第二个参数就是自定义属性的值，与注解值对应。这是数组，可多个
* 这里需要INTERNET权限，别忘了
*
* @param imageView ImageView控件
* @param url 图片网络地址
*/
@BindingAdapter({"imageUrl"})
public static void loadImage(ImageView imageView, String url) {
Glide.with(imageView.getContext())
.load(url)
.into(imageView);
}
}
- 代码中使用 (只有一行代码，传入泛型数据列表和资源id，通用所有数据，做列表只需要写一个 item layout 就可以了)
recyclerView.setAdapter(new BindingAdapter<>(context, list, R.layout.item_test));
- Activity 完整代码
public class MainActivity extends AppCompatActivity {
ActivityMainBinding binding;
private String[] names = {
"处于 25-35 岁的你，开始买奢侈品了吗？",
"有些法律上的事，非要解释给你听，你才知道理解错了",
"要是早点知道这些，也不至于当初在校招季踩坑无数……",
"孩子眼中的爸爸，可不只是「走，我们出去玩儿」就够了",
"为什么胖这个字写成「月半」，不写成「月圆」或者「月全」？"
};
private String[] images = {
"https://pic2.zhimg.com/v2-f474e73c7aabf49a96cb39f68b81b6e1.jpg",
"https://pic2.zhimg.com/v2-f474e73c7aabf49a96cb39f68b81b6e1.jpg",
"https://pic1.zhimg.com/v2-d081c48015edde0e8065709f864ee474.jpg",
"https://pic3.zhimg.com/v2-4d8dcd6de27f81bc01435e0c6867b60e.jpg",
"https://pic2.zhimg.com/v2-006da90be72f74b5e7fc49f1658896a1.jpg",
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
Random random = new Random();
List<Story> userList = new ArrayList<>();
for (int i = 0; i < 15; i++) {
Story u = new Story();
int index = random.nextInt(names.length);
u.setTitle(i + " - " + names[index]);
u.setImage(images[index]);
userList.add(u);
}
binding.recycler.setLayoutManager(new LinearLayoutManager(this));
BindingAdapter adapter = new BindingAdapter<>(this, userList, R.layout.item_story);
adapter.setOnItemClickListener(new IntConsumer() {
@Override
public void accept(int i) {
Toast.makeText(MainActivity.this, i + " - 被点击了", Toast.LENGTH_SHORT).show();
}
});
binding.recycler.setAdapter(adapter);
}
}
补充
- 可以添加
HeaderView和FooterView的RecyclerHeaderFooterAdapter.java
/**
* Recycler 基类适配器
*
* @author gavin.xiong 2017/8/15
*/
public abstract class RecyclerHeaderFooterAdapter<T, B extends ViewDataBinding> extends RecyclerView.Adapter<RecyclerHolder> {
private static final int TYPE_NORMAL = 0;
private static final int TYPE_HEADER = 1;
private static final int TYPE_FOOTER = 2;
private ViewDataBinding mHeaderBinding;
private ViewDataBinding mFooterBinding;
protected Context mContext;
protected List<T> mList;
private int layoutId;
public RecyclerHeaderFooterAdapter(Context context, List<T> list, @LayoutRes int layoutId) {
this.mContext = context;
this.mList = list;
this.layoutId = layoutId;
}
public void setHeaderBinding(ViewDataBinding binding) {
this.mHeaderBinding = binding;
}
public void setFooterBinding(ViewDataBinding binding) {
this.mFooterBinding = binding;
}
@Override
public int getItemViewType(int position) {
if (mHeaderBinding != null && position == 0) return TYPE_HEADER;
if (mFooterBinding != null && position == (mList == null ? 0 : mList.size()) + (mHeaderBinding == null ? 0 : 1))
return TYPE_FOOTER;
return TYPE_NORMAL;
}
@Override
public RecyclerHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (mHeaderBinding != null && viewType == TYPE_HEADER) {
return new RecyclerHolder<>(mHeaderBinding);
} else if (mFooterBinding != null && viewType == TYPE_FOOTER) {
return new RecyclerHolder<>(mFooterBinding);
} else {
B bing = DataBindingUtil.inflate(LayoutInflater.from(mContext), layoutId, parent, false);
return new RecyclerHolder<>(bing);
}
}
@Override
public void onBindViewHolder(RecyclerHolder holder, int position) {
if (getItemViewType(position) == TYPE_NORMAL) {
final int pos = getRealPosition(holder);
final T data = mList.get(pos);
onBind(holder, pos, data);
}
}
@Override
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
super.onAttachedToRecyclerView(recyclerView);
RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
if (manager instanceof GridLayoutManager) {
final GridLayoutManager gridManager = ((GridLayoutManager) manager);
gridManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
@Override
public int getSpanSize(int position) {
return getItemViewType(position) == TYPE_NORMAL ? 1 : gridManager.getSpanCount();
}
});
}
}
@Override
public void onViewAttachedToWindow(RecyclerHolder holder) {
super.onViewAttachedToWindow(holder);
ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams();
if (lp == null) return;
if (lp.getClass() == RecyclerView.LayoutParams.class) {
lp.width = RecyclerView.LayoutParams.MATCH_PARENT; // 线性布局头尾全屏 (仅纵向有效，且所有 item 并非头尾有效)
}
if (mHeaderBinding != null && lp instanceof StaggeredGridLayoutManager.LayoutParams) {
StaggeredGridLayoutManager.LayoutParams p = (StaggeredGridLayoutManager.LayoutParams) lp;
p.setFullSpan(holder.getLayoutPosition() == 0 || p.isFullSpan());
}
if (mFooterBinding != null && lp instanceof StaggeredGridLayoutManager.LayoutParams) {
StaggeredGridLayoutManager.LayoutParams p = (StaggeredGridLayoutManager.LayoutParams) lp;
p.setFullSpan(holder.getLayoutPosition() == (mList == null ? 0 : mList.size()) + (mHeaderBinding == null ? 0 : 1) || p.isFullSpan());
}
}
private int getRealPosition(RecyclerHolder holder) {
int position = holder.getLayoutPosition();
return mHeaderBinding == null ? position : position - 1;
}
@Override
public int getItemCount() {
if (mHeaderBinding != null && mFooterBinding != null) {
return mList == null ? 2 : mList.size() + 2;
} else if (mHeaderBinding == null && mFooterBinding == null) {
return mList == null ? 0 : mList.size();
} else {
return mList == null ? 1 : mList.size() + 1;
}
}
protected abstract void onBind(RecyclerHolder<B> holder, int position, T t);
}
及对应的万能适配器
/**
* DataBinding 基类适配器
*
* @author gavin.xiong 2016/12/28
*/
public class BindingHeaderFooterAdapter<T> extends RecyclerHeaderFooterAdapter<T, ViewDataBinding> {
private IntConsumer onItemClickListener;
public BindingHeaderFooterAdapter(Context context, List<T> list, @LayoutRes int layoutId) {
super(context, list, layoutId);
}
public void setOnItemClickListener(IntConsumer listener) {
this.onItemClickListener = listener;
}
@Override
protected void onBind(RecyclerHolder<ViewDataBinding> holder, final int position, T t) {
holder.binding.setVariable(BR.item, t);
holder.binding.executePendingBindings();
if (onItemClickListener != null) {
holder.itemView.findViewById(R.id.item).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
onItemClickListener.accept(position);
}
});
}
}
}
完整代码已上传至github：https://github.com/gavinxxxxxx/BindingAdapter
