封面
1.在RecyclerView中使用DataBinding
Adapter的定義方式和普通方式相同，都是繼承了RecyclerView.Adapter<ViewHolder>，然后實現(xiàn)其中的方法，但是具體的實現(xiàn)方式還是有所差別的：
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.BindingHolder> {
private List<RecyclerViewItem> list;
public RecyclerViewAdapter(List<RecyclerViewItem> list) {
this.list = list;
}
@Override
public RecyclerViewAdapter.BindingHolder onCreateViewHolder(ViewGroup parent, int viewType) {
AdapterRecyclerViewBinding binding = DataBindingUtil.inflate(
LayoutInflater.from(parent.getContext()), R.layout.adapter_recycler_view, parent, false);
BindingHolder holder = new BindingHolder(binding.getRoot());
holder.setBinding(binding);
return holder;
}
@Override
public void onBindViewHolder(RecyclerViewAdapter.BindingHolder holder, int position) {
holder.getBinding().setVariable(BR.item, list.get(position));
holder.getBinding().executePendingBindings();
}
@Override
public int getItemCount() {
return list.size();
}
public class BindingHolder extends RecyclerView.ViewHolder {
private AdapterRecyclerViewBinding binding;
public BindingHolder(View itemView) {
super(itemView);
}
public AdapterRecyclerViewBinding getBinding() {
return binding;
}
public void setBinding(AdapterRecyclerViewBinding binding) {
this.binding = binding;
}
}
}
首先看下BindingHolder，由于使用了DataBinding機制，不需要在Holder中初始化控件了，只需要提供Binding的get和set方法就可以了：
public class BindingHolder extends RecyclerView.ViewHolder {
private AdapterRecyclerViewBinding binding;
public BindingHolder(View itemView) {
super(itemView);
}
public AdapterRecyclerViewBinding getBinding() {
return binding;
}
public void setBinding(AdapterRecyclerViewBinding binding) {
this.binding = binding;
}
}
在onCreateViewHolder中綁定UI，獲取到Binding對象，然后將Binding對象set到Holder中：
@Override
public RecyclerViewAdapter.BindingHolder onCreateViewHolder(ViewGroup parent, int viewType) {
AdapterRecyclerViewBinding binding = DataBindingUtil.inflate(
LayoutInflater.from(parent.getContext()), R.layout.adapter_recycler_view, parent, false);
BindingHolder holder = new BindingHolder(binding.getRoot());
holder.setBinding(binding);
return holder;
}
在onBindViewHolder方法中，調(diào)用Binding的setVariable方法設(shè)置UI顯示的數(shù)據(jù)，其中item是RecyclerView內(nèi)置的變量，如果RecyclerView只使用了一種布局，還可以使用holder.getBinding().setItem(list.get(position));來設(shè)置數(shù)據(jù)。由于數(shù)據(jù)改變后，DataBinding會在下一幀刷新UI，這樣會導(dǎo)致屏幕閃一下，所以還需要調(diào)用Binding的executePendingBindings方法立即刷新UI：
@Override
public void onBindViewHolder(RecyclerViewAdapter.BindingHolder holder, int position) {
holder.getBinding().setVariable(BR.item, list.get(position));
holder.getBinding().executePendingBindings();
}
adapter_recycler_view布局文件：
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable
name="item"
type="com.yl.databindingdemo.bean.RecyclerViewItem" />
</data>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:padding="10dp"
android:text="@{item.content}"
android:textColor="@color/colorAccent"
android:textSize="18sp" />
</RelativeLayout>
</layout>
在Activity中使用：
public class RecyclerViewActivity extends AppCompatActivity {
private List<RecyclerViewItem> list;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initData();
ActivityRecyclerViewBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_recycler_view);
binding.recyclerView.setLayoutManager(new LinearLayoutManager(this));
RecyclerViewAdapter recyclerViewAdapter = new RecyclerViewAdapter(list);
binding.recyclerView.setAdapter(recyclerViewAdapter);
// 更新
updateData();
recyclerViewAdapter.notifyDataSetChanged();
}
private void initData() {
list = new ArrayList<>();
for (int i = 0; i < 10; i++) {
list.add(new RecyclerViewItem(String.valueOf(i)));
}
}
private void updateData() {
for (int i = 10; i < 20; i++) {
list.add(new RecyclerViewItem(String.valueOf(i)));
}
}
}
activity_recycler_view布局文件：
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
</data>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
</layout>
2.在多布局RecyclerView中使用DataBinding
和普通的多布局Adapter類似，重寫getItemViewType方法，然后在onCreateViewHolder方法中根據(jù)viewType加載相應(yīng)的布局，onBindViewHolder方法中不需要再判斷Holder類型，直接設(shè)置數(shù)據(jù)然后立即刷新UI即可：
public class MultiRecyclerViewAdapter extends RecyclerView.Adapter<MultiRecyclerViewAdapter.BindingHolder> {
private List<RecyclerViewItem> list;
public MultiRecyclerViewAdapter(List<RecyclerViewItem> list) {
this.list = list;
}
@Override
public int getItemViewType(int position) {
if (position < 5) {
return 0;
} else {
return 1;
}
}
@Override
public MultiRecyclerViewAdapter.BindingHolder onCreateViewHolder(ViewGroup parent, int viewType) {
ViewDataBinding binding;
if (viewType == 0) {
binding = DataBindingUtil.inflate(
LayoutInflater.from(parent.getContext()), R.layout.adapter_recycler_view_other, parent, false);
} else {
binding = DataBindingUtil.inflate(
LayoutInflater.from(parent.getContext()), R.layout.adapter_recycler_view, parent, false);
}
BindingHolder holder = new BindingHolder(binding.getRoot());
holder.setBinding(binding);
return holder;
}
@Override
public void onBindViewHolder(MultiRecyclerViewAdapter.BindingHolder holder, int position) {
holder.getBinding().setVariable(BR.item, list.get(position));
holder.getBinding().executePendingBindings();
}
@Override
public int getItemCount() {
return list.size();
}
public class BindingHolder extends RecyclerView.ViewHolder {
private ViewDataBinding binding;
public BindingHolder(View itemView) {
super(itemView);
}
public ViewDataBinding getBinding() {
return binding;
}
public void setBinding(ViewDataBinding binding) {
this.binding = binding;
}
}
}
除此之外，還可以通過定義多個Holder的方式來實現(xiàn)。
3.自定義屬性
舉個栗子，如果你的項目中用到了Glide，或者是其他的圖片加載框架，由于這些框架都是通過url給ImageView設(shè)置圖片的，但是ImageView中并沒有設(shè)置url的屬性，那么該如何使用DataBinding綁定UI呢？這時DataBinding強大的自定義屬性功能就派上用場了，一起來看看：
public class ImageUtils {
/**
* 加載圖片
* 無需手動調(diào)用此方法
*
* @param view ImageView
* @param url 圖片地址
*/
@BindingAdapter({"imageUrl"})
public static void loadImage(ImageView view, String url) {
Glide.with(view.getContext()).load(url).into(view);
}
}
使用@BindingAdapter注解設(shè)置自定義屬性的名稱，如上所示，imageUrl就是屬性的名稱，當(dāng)ImageView中使用imageUrl屬性時，會自動調(diào)用loadImage方法，參數(shù)view為當(dāng)前使用imageUrl屬性的View，參數(shù)url為圖片地址。
布局文件：
<?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">
<data>
<variable
name="url"
type="String" />
</data>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- 當(dāng)imageUrl存在時，會自動調(diào)用ImageUtils的loadImage方法 -->
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
app:imageUrl="@{url}" />
</RelativeLayout>
</layout>
Activity中使用：
public class CustomAttributeActivity extends AppCompatActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ActivityCustomAttributeBinding binding = DataBindingUtil.setContentView(this,
R.layout.activity_custom_attribute);
binding.setUrl(null);
}
}
4.ViewStub
在Android開發(fā)中，為了提高布局性能，經(jīng)常使用ViewStub來動態(tài)顯示UI，在DataBinding中也是支持使用ViewStub的，一起來學(xué)習(xí)下：
首先在布局文件中定義ViewStub，和普通方式相同：
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable
name="clickListener"
type="android.view.View.OnClickListener" />
</data>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="10dp"
android:orientation="vertical">
<ViewStub
android:id="@+id/view_stub"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout="@layout/layout_include" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
android:onClick="@{clickListener}"
android:text="顯示ViewStub"
android:textAllCaps="false" />
</LinearLayout>
</layout>
在Activity中顯示ViewStub：
public class ViewStubActivity extends AppCompatActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final ActivityViewStubBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_view_stub);
binding.viewStub.setOnInflateListener(new ViewStub.OnInflateListener() {
@Override
public void onInflate(ViewStub stub, View inflated) {
LayoutIncludeBinding viewStubBinding = DataBindingUtil.bind(inflated);
User user = new User("容華", "謝后");
viewStubBinding.setUser(user);
}
});
binding.setClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (!binding.viewStub.isInflated()) {
binding.viewStub.getViewStub().inflate();
}
}
});
}
}
布局中的ViewStub控件在Binding中會被轉(zhuǎn)換成代理類ViewStubProxy，所以需要調(diào)用代理類的getViewStub方法獲取到ViewStub控件，然后再調(diào)用ViewStub控件的inflate方法顯示布局，同時還需要監(jiān)聽ViewStub的OnInflateListener，當(dāng)布局顯示成功后調(diào)用DataBindingUtil的bind方法綁定數(shù)據(jù)。
看下效果：
ViewStub
OK，到這里DataBinding的大部分用法就講完了，更多用法可以查看官方文檔。
5.寫在最后
源碼已托管到GitHub上，歡迎Fork，覺得還不錯就Start一下吧！
歡迎同學(xué)們吐槽評論，如果你覺得本篇博客對你有用，那么就留個言或者點下喜歡吧(＾－＾)
