java - 在Android 11中弃用了Android AsyncTask API，使用了Executor作为替代

Question

我正在使用下面的代码在后台和后执行中运行，但是我的问题是，我如何像以前在AsyncTask中那样执行onPrexecute，例如能够设置可见的进度条运行:
我到目前为止使用的代码，但是UI出现错误:

    ExecutorService executor = Executors.newSingleThreadExecutor();
    Handler handler = new Handler(Looper.getMainLooper());

    executor.execute(new Runnable() {
        @Override
        public void run() {

            //Background work here
        progressBar_main_activity.setVisibility(View.VISIBLE);
        runbackground();    
        
            handler.post(new Runnable() {
                @Override
                public void run() {
                    //UI Thread work here
          update_UI();
                }
            });
        }
    });

错误在这里“progressBar_main_activity.setVisibility(View.VISIBLE);”
错误如下:

android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.         at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:8205)         at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:1426)

Answer 1

ExecutorService executor = Executors.newSingleThreadExecutor();
    Handler handler = new Handler(Looper.getMainLooper());

//onPreExecute() before to get into executor, as below
progressBar_main_activity.setVisibility(View.VISIBLE);


    executor.execute(new Runnable() {
        @Override
        public void run() {

            //Background work here
        runbackground();    
        
            handler.post(new Runnable() {
                @Override
                public void run() {
                    //UI Thread work here
          update_UI();
                }
            });
        }
    });