点击图片a，跳转到相册。选择一张图片b，图片a切换成图片b。

package com.example.myapplication5;import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;public class PicActivity3 extends AppCompatActivity implements View.OnClickListener {private static final int REQUEST_SELECT_MEDIA = 1;private ImageView img_add;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_pic3);//添加图片按钮，点击跳转系统相册（使用intent）img_add = findViewById(R.id.img_add);img_add.setOnClickListener(this);}@Overridepublic void onClick(View view) {switch (view.getId()){case R.id.img_add:Intent intent = new Intent(Intent.ACTION_GET_CONTENT);intent.setType("image/*"); // 选择图片// intent.setType("video/*"); // 选择视频startActivityForResult(intent, REQUEST_SELECT_MEDIA);break;}}@Overrideprotected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {Toast.makeText(PicActivity3.this,"选择图片",Toast.LENGTH_LONG).show();super.onActivityResult(requestCode, resultCode, data);if (requestCode == REQUEST_SELECT_MEDIA && resultCode == RESULT_OK && data != null) {Uri selectedMediaUri = data.getData();// 处理选中的媒体文件img_add.setImageURI(selectedMediaUri);}}
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"><ImageViewandroid:id="@+id/img_add"android:layout_width="100dp"android:layout_height="100dp"android:src="@drawable/railway"/>
</LinearLayout>