file로 이미지 표시하는 방법

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <WebView
        android:id="@+id/upperview"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>
    <WebView
        android:id="@+id/lowerview"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>
</LinearLayout>

package com.example.urano_joji.test1;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.webkit.WebView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        WebView upperView = (WebView)findViewById(R.id.upperview);
        upperView.loadUrl("file:///android_asset/android.jpg");
    }
}

android {
    sourceSets{
        main{
            assets.srcDirs = ['htmlSource']
        }
    }
}