我发现了一个更容易的解决方案来处理线程时，方向改变。你可以只保留一个静态引用到你的活动/片段，并在对ui进行操作之前验证它是否为空。我建议使用try catch:

 public class DashListFragment extends Fragment {
     private static DashListFragment ACTIVE_INSTANCE;

     @Override
     public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ACTIVE_INSTANCE = this;

        new Handler().postDelayed(new Runnable() {
            public void run() {
                try {
                        if (ACTIVE_INSTANCE != null) {
                            setAdapter(); // this method do something on ui or use context
                        }
                }
                catch (Exception e) {}


            }
        }, 1500l);

    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        ACTIVE_INSTANCE = null;
    }


}

我发现了一个更容易的解决方案来处理线程时，方向改变。你可以只保留一个静态引用到你的活动/片段，并在对ui进行操作之前验证它是否为空。我建议使用try catch:

 public class DashListFragment extends Fragment {
     private static DashListFragment ACTIVE_INSTANCE;

     @Override
     public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ACTIVE_INSTANCE = this;

        new Handler().postDelayed(new Runnable() {
            public void run() {
                try {
                        if (ACTIVE_INSTANCE != null) {
                            setAdapter(); // this method do something on ui or use context
                        }
                }
                catch (Exception e) {}


            }
        }, 1500l);

    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        ACTIVE_INSTANCE = null;
    }


}

我是这样做的:

    package com.palewar;
    import android.app.Activity;
    import android.app.ProgressDialog;
    import android.os.Bundle;
    import android.os.Handler;
    import android.os.Message;

    public class ThreadActivity extends Activity {


        static ProgressDialog dialog;
        private Thread downloadThread;
        final static Handler handler = new Handler() {

            @Override
            public void handleMessage(Message msg) {

                super.handleMessage(msg);

                dialog.dismiss();

            }

        };

        protected void onDestroy() {
    super.onDestroy();
            if (dialog != null && dialog.isShowing()) {
                dialog.dismiss();
                dialog = null;
            }

        }

        /** Called when the activity is first created. */
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);

            downloadThread = (Thread) getLastNonConfigurationInstance();
            if (downloadThread != null && downloadThread.isAlive()) {
                dialog = ProgressDialog.show(ThreadActivity.this, "",
                        "Signing in...", false);
            }

            dialog = ProgressDialog.show(ThreadActivity.this, "",
                    "Signing in ...", false);

            downloadThread = new MyThread();
            downloadThread.start();
            // processThread();
        }

        // Save the thread
        @Override
        public Object onRetainNonConfigurationInstance() {
            return downloadThread;
        }


        static public class MyThread extends Thread {
            @Override
            public void run() {

                try {
                    // Simulate a slow network
                    try {
                        new Thread().sleep(5000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    handler.sendEmptyMessage(0);

                } finally {

                }
            }
        }

    }

你也可以试着让我知道它对你是否有效

将长任务移动到单独的类中。将其实现为主题-观察者模式。每当创建活动时，注册并在关闭时注销任务类。任务类可以使用AsyncTask。

这是我面对这个问题时的解决方案: ProgressDialog不是一个Fragment子，所以我的自定义类“ProgressDialogFragment”可以扩展DialogFragment，以保持对话框显示的配置更改。

import androidx.annotation.NonNull;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.os.Bundle; 
import androidx.fragment.app.DialogFragment;
import androidx.fragment.app.FragmentManager;

 /**
 * Usage:
 * To display the dialog:
 *     >>> ProgressDialogFragment.showProgressDialogFragment(
 *              getSupportFragmentManager(), 
 *              "fragment_tag", 
 *              "my dialog title", 
 *              "my dialog message");
 *              
 * To hide the dialog
 *     >>> ProgressDialogFragment.hideProgressDialogFragment();
 */ 


public class ProgressDialogFragment extends DialogFragment {

    private static String sTitle, sMessage;
    private static ProgressDialogFragment sProgressDialogFragment;

    public ProgressDialogFragment() {
    }

    private ProgressDialogFragment(String title, String message) {
        sTitle = title;
        sMessage = message;
    }


    @NonNull
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        return ProgressDialog.show(getActivity(), sTitle, sMessage);
    }

    public static void showProgressDialogFragment(FragmentManager fragmentManager, String fragmentTag, String title, String message) {
        if (sProgressDialogFragment == null) {
            sProgressDialogFragment = new ProgressDialogFragment(title, message);
            sProgressDialogFragment.show(fragmentManager, fragmentTag);

        } else { // case of config change (device rotation)
            sProgressDialogFragment = (ProgressDialogFragment) fragmentManager.findFragmentByTag(fragmentTag); // sProgressDialogFragment will try to survive its state on configuration as much as it can, but when calling .dismiss() it returns NPE, so we have to reset it on each config change
            sTitle = title;
            sMessage = message;
        }

    }

    public static void hideProgressDialogFragment() {
        if (sProgressDialogFragment != null) {
            sProgressDialogFragment.dismiss();
        }
    }
}

我们面临的挑战是在屏幕上保留对话框标题和消息 当它们重置为默认空字符串时旋转，尽管对话框仍然显示

有两种方法可以解决这个问题:

第一种方法: 使利用对话框的活动在manifest文件中的配置更改期间保留状态:

android:configChanges="orientation|screenSize|keyboardHidden"

谷歌不喜欢此方法。

第二种方法: 在活动的onCreate()方法上，如果savedInstanceState不为空，你需要通过重新构建ProgressDialogFragment来保留你的对话片段。

@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_deal);

 if (savedInstanceState != null) {
      ProgressDialogFragment saveProgressDialog = (ProgressDialogFragment) getSupportFragmentManager()
              .findFragmentByTag("fragment_tag");
      if (saveProgressDialog != null) {
          showProgressDialogFragment(getSupportFragmentManager(), "fragment_tag", "my dialog title", "my dialog message");
      }
  }
}

我也遇到过同样的情况。我所做的就是在整个应用程序中只获取一个进度对话框的实例。

首先，我创建了一个DialogSingleton类来只获得一个实例(Singleton模式)

public class DialogSingleton
{
    private static Dialog dialog;

    private static final Object mLock = new Object();
    private static DialogSingleton instance;

    private DialogSingleton()
    {

    }

    public static DialogSingleton GetInstance()
    {
        synchronized (mLock)
        {
            if(instance == null)
            {
                instance = new DialogSingleton();
            }

            return instance;
        }
    }

    public void DialogShow(Context context, String title)
    {
        if(!((Activity)context).isFinishing())
        {
            dialog = new ProgressDialog(context, 2);

            dialog.setCanceledOnTouchOutside(false);

            dialog.setTitle(title);

            dialog.show();
        }
    }

    public void DialogDismiss(Context context)
    {
        if(!((Activity)context).isFinishing() && dialog.isShowing())
        {
            dialog.dismiss();
        }
    }
}

正如我在这个类中所展示的，我将进度对话框作为属性。每次我需要显示一个进度对话框时，我都会获得唯一的实例并创建一个新的ProgressDialog。

DialogSingleton.GetInstance().DialogShow(this, "My title here!");

当我完成后台任务时，我再次调用惟一实例并关闭它的对话框。

DialogSingleton.GetInstance().DialogDismiss(this);

我将后台任务状态保存在共享首选项中。当我旋转屏幕时，我问我是否有这个活动的任务运行:(onCreate)

if(Boolean.parseBoolean(preference.GetValue(IS_TASK_NAME_EXECUTED_KEY, "boolean").toString()))
{
    DialogSingleton.GetInstance().DialogShow(this, "Checking credentials!");
} // preference object gets the info from shared preferences (my own implementation to get and put data to shared preferences) and IS_TASK_NAME_EXECUTED_KEY is the key to save this flag (flag to know if this activity has a background task already running).

当我开始运行后台任务时:

preference.AddValue(IS_TASK_NAME_EXECUTED_KEY, true, "boolean");

DialogSingleton.GetInstance().DialogShow(this, "My title here!");

当我完成运行后台任务:

preference.AddValue(IS_TASK_NAME_EXECUTED_KEY, false, "boolean");

DialogSingleton.GetInstance().DialogDismiss(ActivityName.this);

我希望这能有所帮助。