Android面试题 之 Kotlin DataBinding 图片加载和绑定RecyclerView

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定义BindingAdapter

public class MyBindingAdapter {

    //
    @BindingAdapter("image")
    public static void setImage(ImageView imageView, String url){

    }
}

布局里处理

//data里加上变量名字
<data>

    <variable
        name="networkImage"
        type="String" />
    <import type="com.example.databinding.IdolUtils"/>
</data>

//view上使用
<ImageView
    android:id="@+id/imageview"
    android:layout_width="300dp"
    android:layout_height="300dp"
    //这里的image就是BindingAdapter里@BindingAdapter注解后面的变量名
    //networkImage就是上面布局里定义的
    app:image="${networkImage}"
    app:layout_constraintBottom_toBottomOf="@+id/include"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/button" />

activity里传入图片的链接

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ActivityMainBinding activityMainBinding = DataBindingUtil.setContentView(this,R.layout.activity_main);
    //设置data标签里的变量的值
    //这个值会经布局，传给BindingAdapter处理
    activityMainBinding.setNetworkImage("网络图片地址");
}

BindingAdapter中同时定义多个参数

//requireAll = false表示2个值不需要都有值
@BindingAdapter(value = {"image", "localImage"},requireAll = false)
public static void setImage(ImageView imageView, String url, int resId){

}

绑定RecyclerView

主要是adapter

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder>{
    List<User> list;

    public MyAdapter(List<User> list) {
        this.list = list;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        ItemBinding itemBinding = DataBindingUtil.inflate(LayoutInflater.from(parent.getContext()),
                R.layout.item,
                parent,
                false);
        return new MyViewHolder(itemBinding);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        User user = list.get(position);
        holder.itemBinding.setUser(user);
    }

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

    static class MyViewHolder extends RecyclerView.ViewHolder{
        private ItemBinding itemBinding;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
        }

        public MyViewHolder(ItemBinding itemBinding) {
            super(itemBinding.getRoot());
            this.itemBinding = itemBinding;
        }
    }
}

布局绑定主要是在子布局中

//item.xml
<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="user"
            type="com.example.databinding3.User" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <ImageView
            android:id="@+id/imageView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            app:image="@{user.image}"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            tools:srcCompat="@tools:sample/avatars" />

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            tools:text="TextView"
            android:text="@{user.name}"
            android:textSize="20sp"
            app:layout_constraintBottom_toBottomOf="@+id/imageView"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.179"
            app:layout_constraintStart_toEndOf="@+id/imageView"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.512" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

图片的加载还是参考之前的用 @BindingAdapter

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