Android 我如何理解共享首选项文件是否存在

我编写了以下代码。但是当我按下按钮并重新启动程序时，我再次看到

没有file.xml文件的消息

File file = new File("/data/data/" + getPackageName() +  "/shared_prefs/" + getPackageName()+ "file.xml");
        if (file.exists())
            Toast.makeText(getApplicationContext(), "There is the file.xml file", Toast.LENGTH_SHORT).show();
        else
           Toast.makeText(getApplicationContext(),"There is no the file.xml file",Toast.LENGTH_SHORT).show();
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            SharedPreferences sharedpreferences;
            sharedpreferences = getApplicationContext().getSharedPreferences("file", MODE_PRIVATE);
            SharedPreferences.Editor editor = sharedpreferences.edit();
            editor.putString("file","I am a file");

            editor.commit();
        }
    });

当您存储首选项时，SharedReferences文件将自动创建，您直接访问它有什么原因吗？谢谢。上面代码的目的是，当我没有
file.xml
时，我看到
没有file.xml文件
消息，当我按下按钮时，我可以创建
file.xml
，当我启动代码时，我看到
有file.xml文件
消息。
if (file.exists())
            Toast.makeText(getApplicationContext(), "There is the file.xml file", Toast.LENGTH_SHORT).show();
        else
           Toast.makeText(getApplicationContext(),"There is no the file.xml file",Toast.LENGTH_SHORT).show();
you  can  test the  code in you project.
that  "There is no the file.xml file"  is a  message. you can  change it.

 if(file.exists()){
  Toast.makeText(getApplicationContext(), "There is not the file.xml file", Toast.LENGTH_SHORT).show();
}else{
Toast.makeText(getApplicationContext(), "There is the file.xml file", Toast.LENGTH_SHORT).show();
}