Button控制图片显示隐藏

点击Button，图片隐藏，再次点击，图片显示。
MainActivity.java

package com.example.hades.demo;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {
    ImageView img;
    Button bt;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        img = (ImageView)findViewById(R.id.imageView);
        bt = (Button)findViewById(R.id.button);
        bt.setOnClickListener(new click());
    }

    private class click implements View.OnClickListener {
        @Override
        public void onClick(View v) {
            if (img.isShown()) {
                img.setVisibility(View.INVISIBLE);
                bt.setText("show");
            } else {
                img.setVisibility(View.VISIBLE);
                bt.setText("fade");
            }
        }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.hades.demo.MainActivity">

    <LinearLayout
        android:layout_width="368dp"
        android:layout_height="495dp"
        android:orientation="vertical"
        tools:layout_editor_absoluteY="8dp"
        tools:layout_editor_absoluteX="8dp">

        <ImageView
            android:id="@+id/imageView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:srcCompat="@mipmap/header" />

        <Button
            android:id="@+id/button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Button" />
    </LinearLayout>
</android.support.constraint.ConstraintLayout>

运行