<?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=".MainActivity">

    <LinearLayout

        android:layout_width="match_parent"

        android:layout_height="60dp"

        android:gravity="center"

        android:orientation="horizontal">

        <Button

            android:id="@+id/button1"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="放大" />

        <Button

            android:id="@+id/button2"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="缩小" />

    </LinearLayout>

    <ImageView

        android:id="@+id/imageView"

        android:layout_width="150dp"

        android:layout_height="150dp"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toTopOf="parent"

        app:srcCompat="@drawable/img01" />

</android.support.constraint.ConstraintLayout>

package com.example.chenrui.app1;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.view.ViewGroup;

import android.widget.Button;

import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        final ImageView image = findViewById(R.id.imageView);

        Button button1 = findViewById(R.id.button1);

        button1.setOnClickListener(new View.OnClickListener(){

            @Override

            public void onClick(View v) {

                ViewGroup.LayoutParams params = image.getLayoutParams();

                params.width = params.width + 50;

                params.height = params.height + 50;

                image.setLayoutParams(params);

            }

        });

        Button button2 = findViewById(R.id.button2);

        button2.setOnClickListener(new View.OnClickListener(){

            @Override

            public void onClick(View v) {

                ViewGroup.LayoutParams params = image.getLayoutParams();

                params.width = params.width - 50;

                params.height = params.height - 50;

                image.setLayoutParams(params);

            }

        });

    }

}