DataBinding 绑定Recyclerview及点击事件

最近在学习DataBinding，在这里记录下学习的轨迹
收获：
1代码解耦。
2少些很多没有营养的代码，美观度高！
遇坑：
1官方文档 https://developer.android.com/topic/libraries/data-binding/index.html#listener_bindings 写的真是简单，
只提供码片段，需要结合博客和别的资料一齐看，才大概明白其中的奥妙。
2不容易定位错误。编译通过，无法安装。请看上篇文章 https://blog.csdn.net/qq_35599978/article/details/80028278 
3如果绑定数据的XML需要增加 <variable> 那么数据绑定的XXBinding无法调用.setVariable(),因为项目没有编译。后来发现就算
我手动build ，clean，sync project，或者删掉.build文件,再sync project，还是不管用，只能关掉studio，再打开，你发现
世界真美好。我的studio version 3.1

Activity主页布局代码

<?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="userbean"
            type="com.example.layoutmanager_sample.UserBean" />
    </data>

    <android.support.design.widget.CoordinatorLayout

        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true"
        tools:context="com.example.layoutmanager_sample.ScrollingActivity">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/app_bar"
            android:layout_width="match_parent"
            android:layout_height="160dp">

            <android.support.design.widget.CollapsingToolbarLayout
                android:id="@+id/toolbar_layout"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:fitsSystemWindows="true"
                app:layout_scrollFlags="scroll|exitUntilCollapsed">
 
                <android.support.v7.widget.Toolbar
                    android:id="@+id/toolbar"
                    android:layout_width="match_parent"
                    android:layout_height="30dp"
                    app:layout_collapseMode="pin">

                    <!--自定义带图片的立即播放按钮-->
                    <LinearLayout
                        android:id="@+id/playButton"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:layout_gravity="center_horizontal|start"
                        android:gravity="center"
                        android:orientation="horizontal">

                        <ImageView
                            android:layout_width="wrap_content"
                            android:layout_height="match_parent"
                            android:layout_gravity="center_horizontal"
                            android:src="@drawable/ic_subscriptions_black_24dp" />

                        <TextView
                            android:id="@+id/tv_play"
                            android:layout_width="0dp"
                            android:layout_height="wrap_content"
                            android:layout_gravity="center_vertical"
                            android:layout_weight="1"
                            android:text="@{userbean.name}"
                            android:textColor="#ffffff" />

                        <TextView
                            android:layout_width="wrap_content"
                            android:layout_height="wrap_content"
                            android:layout_gravity="center_vertical"
                            android:text="@{userbean.hobby}"
                            android:textColor="#ffffff" />

                        <ImageView
                            android:layout_width="wrap_content"
                            android:layout_height="match_parent"
                            android:layout_gravity="center_horizontal"
                            android:layout_margin="8dp"
                            android:src="@drawable/ic_subscriptions_black_24dp" />
                    </LinearLayout>

                </android.support.v7.widget.Toolbar>
            </android.support.design.widget.CollapsingToolbarLayout>

        </android.support.design.widget.AppBarLayout>

        <android.support.v7.widget.RecyclerView
            android:id="@+id/recycleVeiw"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior="@string/appbar_scrolling_view_behavior"></android.support.v7.widget.RecyclerView>

    </android.support.design.widget.CoordinatorLayout>
</layout>

RecyclerView Item 布局代码

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="user"
            type="com.example.bean.User" />
        <variable
            name="itemclidk"
            type="com.example.ItemClick" />
    </data>

    <android.support.constraint.ConstraintLayout xmlns:app="http://schemas.android.com/apk/res-auto"
        android:clickable="true"
        android:onClick="@{(view)->itemclidk.onClicked(view,user)}"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <ImageView
            android:id="@+id/iv_img"
            android:layout_width="60dp"
            android:layout_height="0dp"
            android:layout_marginTop="6dp"
            android:src="@{user.res}"
            app:layout_constraintBottom_toTopOf="@+id/tv_title"
            app:layout_constraintDimensionRatio="1:1"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/tv_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="6dp"
            android:gravity="center_horizontal"
            android:text="@{user.name}"
            android:textSize="16sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/iv_img" />

    </android.support.constraint.ConstraintLayout>
</layout>

点击事件的接口

public interface ItemClick {
    void onClicked(View veiw, User user);
}

Activitie 代码

public class ScrollingActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityScrolling2Binding binding = DataBindingUtil.setContentView(this, R.layout.activity_scrolling2);
        UserBean bean = new UserBean("andry","13years","swimming");
        binding.setUserbean(bean);
        bean.setName("new_name");
        binding.recycleVeiw.setAdapter(new UserAdapter(new ItemClick() {
            @Override
            public void onClicked(View veiw, User user) {
                                Snackbar.make(veiw, user.getName(), Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        }));
        binding.recycleVeiw.setLayoutManager(new LinearLayoutManager(this,
                LinearLayoutManager.VERTICAL,false));
    }
}

adapter 对应的bean 

public class User extends BaseObservable {

    public User(String name, @DrawableRes int res) {
        this.name = name;
        this.res = res;
    }

    String name;
   public  @Bindable int res;

    @Bindable
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
        notifyPropertyChanged(BR.name);
    }

    public void setRes(int res) {
        this.res = res;
    }

    public User getData() {
        return this;
    }
}

adapter对应的代码

public class UserAdapter extends RecyclerView.Adapter<UserAdapter.UserHolder> {
    ItemClick itemClick;
    @NonNull
    private List<User> mUsers;
    private static final int USER_COUNT = 10;
    public UserAdapter(ItemClick itemClick) {
        this.itemClick = itemClick;
        mUsers = new ArrayList<>(10);
        for (int i = 0; i < USER_COUNT; i ++) {
            User user = new User("name -- "+i, R.drawable.ic_launcher_background);
            mUsers.add(user);
        }
    }

    @Override
    public UserHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        ItemRecycleviewBinding binding = DataBindingUtil.
                inflate(LayoutInflater.from(parent.getContext())
                        ,R.layout.item_recycleview,
                        parent,
                        false);
        UserHolder userHolder = new UserHolder(binding.getRoot());
        userHolder.setBinding(binding);
        return userHolder;
    }

    @Override
    public void onBindViewHolder(UserHolder holder, int position) {
        holder.bind(mUsers.get(position),itemClick);

    }

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



    public static class UserHolder extends RecyclerView.ViewHolder {
        private ItemRecycleviewBinding mBinding;

        public UserHolder(View itemView) {
            super(itemView);

        }

        public void bind(@NonNull User user,ItemClick itemClick) {
            mBinding.setUser(user);
            mBinding.executePendingBindings();
            mBinding.setItemclidk(itemClick);
        }

        public void setBinding(ItemRecycleviewBinding binding) {
            this.mBinding = binding;
        }
    }
}

activity对应的viewmodel

public  class UserBean  {
    public String name,age,hobby;


    public String getName() {
        return name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public String getHobby() {
        return hobby;
    }

    public void setHobby(String hobby) {
        this.hobby = hobby;
    }

    public UserBean(String name, String age, String hobby) {
        this.name = name;
        this.age = age;
        this.hobby = hobby;
    }

    public void setName(String name) {
        this.name = name;
//        notifyPropertyChanged(BR.userbean);
    }
}