要进行 Android Scoped Storage 测试，可以按照以下步骤进行：

1. 在 AndroidManifest.xml 文件中添加以下权限：

2. 在 MainActivity.java 文件中添加以下代码示例：

   import android.Manifest;
   import android.content.pm.PackageManager;
   import android.os.Build;
   import android.os.Bundle;
   import android.os.Environment;
   import android.view.View;
   import android.widget.Button;
   import android.widget.Toast;
   
   import androidx.annotation.NonNull;
   import androidx.appcompat.app.AppCompatActivity;
   
   import java.io.File;
   import java.io.FileOutputStream;
   import java.io.IOException;
   
   public class MainActivity extends AppCompatActivity {
       private static final int REQUEST_CODE_PERMISSION = 101;
       private Button btnWriteFile;
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
           btnWriteFile = findViewById(R.id.btn_write_file);
           btnWriteFile.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View v) {
                   checkPermissionsAndSaveFile();
               }
           });
       }
   
       private void checkPermissionsAndSaveFile() {
           if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
               if (checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                   requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CODE_PERMISSION);
                   return;
               }
           }
           saveFile();
       }
   
       @Override
       public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
           super.onRequestPermissionsResult(requestCode, permissions, grantResults);
           if (requestCode == REQUEST_CODE_PERMISSION) {
               if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                   saveFile();
               } else {
                   Toast.makeText(MainActivity.this, "Permission Denied", Toast.LENGTH_SHORT).show();
               }
           }
       }
   
       private void saveFile() {
           File directory = getExternalFilesDir(Environment.DIRECTORY_DOCUMENTS);
           File file = new File(directory, "test.txt");
           try {
               FileOutputStream fos = new FileOutputStream(file);
               fos.write("Hello, Scoped Storage!".getBytes());
               fos.close();
               Toast.makeText(MainActivity.this, "File saved successfully", Toast.LENGTH_SHORT).show();
           } catch (IOException e) {
               e.printStackTrace();
               Toast.makeText(MainActivity.this, "Error saving file", Toast.LENGTH_SHORT).show();
           }
       }
   }
   

3. 在 activity_main.xml 文件中添加一个按钮：

这样，当用户点击 "Write File" 按钮时，会检查是否有写入外部存储的权限。如果没有权限，则会请求权限。如果有权限，则会保存文件到外部存储的 Documents 目录下，并显示保存成功的 Toast 消息。