使用DataBinding从drawable文件夹加载图像

Question

我正在尝试从drawable文件夹加载图像，而我正在使用数据绑定。图片未加载。

此文件的XML文件是

 <?xml version="1.0" encoding="utf-8"?>
    <layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="viewModel"
            type="com.example.user.finaldatabinder.ProfileViewModel"/>
        <variable
            name="user"
            type="com.example.user.finaldatabinder.User"/>
    </data>
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#E0E0E0">
    <android.support.v7.widget.CardView
        xmlns:card_view="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="150dp"
        card_view:cardCornerRadius="6dp"
        android:layout_margin="4dp"
        android:elevation="4dp"
        android:background="#ffffff">


    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        >


            <View
                android:layout_width="20dp"
                android:layout_height="20dp"
                android:layout_alignParentRight="true"
                android:id="@+id/dot"
                android:background="@{user.isOnline ? @drawable/is_online :    @drawable/is_offline }"/>
            <ImageView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentStart="true"

                android:layout_alignParentLeft="true"
                android:id="@+id/image"
                android:src="@{viewModel.imageUrl}"/>
                />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@{user.name+' '+user.surname}"
                android:id="@+id/username"
                android:layout_toRightOf="@+id/image"
                android:textSize="30dp"/>
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@{user.status}"
                android:layout_toRightOf="@+id/image"
                android:layout_below="@+id/username"
                android:id="@+id/status"
                android:textSize="20dp"
                android:layout_marginBottom="10dp"/>
        <Button
            android:layout_width="150dp"
            android:layout_height="wrap_content"
            android:id="@+id/button1"
            android:layout_below="@+id/status"
            android:layout_marginLeft="30dp"
            android:layout_marginRight="10dp"
            android:background="#F57C00"
            android:textColor="#ffffff"
            android:gravity="center_horizontal"/>
        <Button
            android:layout_width="150dp"
            android:layout_height="wrap_content"
            android:layout_below="@+id/status"
            android:textColor="#ffffff"
            android:background="#F57C00"
            android:layout_toRightOf="@+id/button1"/>
        <Button
            android:layout_width="150dp"
            android:layout_height="wrap_content"
            android:layout_below="@+id/status"
            android:textColor="#ffffff"
            android:background="#F57C00"
            android:layout_toRightOf="@+id/button1"/>




    </RelativeLayout>

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            >

        </RelativeLayout>
    </android.support.v7.widget.CardView>
    </RelativeLayout>

    </layout>

我正在使用BindingAdapter的ProfileViewModel类是

   package com.example.user.finaldatabinder;

    import android.databinding.BindingAdapter;
    import android.widget.ImageView;
    import com.squareup.picasso.Picasso;



    public class ProfileViewModel {

        public String getImageUrl() {
            // The URL will usually come from a model (i.e Profile)
            return "drawable//mark";
        }

        @BindingAdapter({"bind:imageUrl"})
        public static void loadImage(ImageView view, String imageUrl) {
            Picasso.with(view.getContext())
                    .load(imageUrl)

                    .into(view);
        }
    }

和我正在执行DataBinding的MainActivity类是

 package com.example.user.finaldatabinder;

    import android.databinding.DataBindingUtil;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;

    import com.example.user.finaldatabinder.databinding.ActivityMainBinding;

    public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityMainBinding binding= DataBindingUtil.setContentView(this, R.layout.activity_main);
        User user=new User("Mark","Zuckerberg","CEO of Facebook", false, false);
        binding.setUser(user);

        binding.setViewModel(new ProfileViewModel());

    }
    }

但是当我写作时

android: src="@drawable/mark"

图像加载完美。