Android app crashes. Where can be an error?

Question

Android

Hello. Started learning how to develop for android and ran into a small problem.
I did a task in which, when you alternately press different buttons, pictures change. When you click on the second and third buttons, everything is fine, the picture above the buttons changes, but once you click on the first one, the application crashes. I can't figure out where I screwed up.
Rendering proceeds normally, without errors.

Here is the mainActivity code

package ru.paint_master.p0011;

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 {
    Button button1;
    Button button2;
    Button button3;

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

        imageView = (ImageView) findViewById(R.id.img1);
        button1=(Button) findViewById(R.id.button1);
        button2=(Button) findViewById(R.id.button2);
        button3=(Button) findViewById(R.id.button3);

        View.OnClickListener onClickListener = new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                switch (view.getId() ){
                    case R.id.button1:
                        imageView.setImageResource(R.drawable.mail);
                        break;
                    case R.id.button2:
                        imageView.setImageResource(R.drawable.zero);
                        break;
                    case R.id.button3:
                        imageView.setImageResource(R.drawable.logo);
                        break;
                }
            }
        };
        button1.setOnClickListener(onClickListener);
        button2.setOnClickListener(onClickListener);
        button3.setOnClickListener(onClickListener);
    }
}

Here is main.xml code

<?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"
    android:layout_margin="@dimen/hor_margin"
    android:layout_marginBottom="@dimen/vert_margin"
    tools:context="ru.paint_master.p0011.MainActivity">

    <LinearLayout
        android:layout_width="253dp"
        android:layout_height="386dp"
        android:orientation="vertical"
        tools:layout_editor_absoluteX="8dp"
        tools:layout_editor_absoluteY="8dp">

        <ImageView
            android:id="@+id/img1"
            android:layout_width="match_parent"
            android:layout_height="120dp"
            android:contentDescription="@string/andr"
            app:srcCompat="@mipmap/ic_launcher_round" />

        <Button
            android:id="@+id/button1"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="@string/bt1"
            android:textColor="#006600"/>

        <Button
            android:id="@+id/button2"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="@string/bt2"
            android:textColor="#006600"/>

        <Button
            android:id="@+id/button3"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="@string/bt3"
            android:textColor="#006600"/>
    </LinearLayout>

</android.support.constraint.ConstraintLayout>

Answer 1

Attach the full error stack and preferably in text, you can only guess from your picture that your picture is not decoded. See what the R.drawable.mail resource is and what's wrong with it.