AsyncOperation.allowSceneActivation

Description

Allow Scenes to be activated as soon as it is ready.

When used in combination with LoadLevelAsync & LoadLevelAdditiveAsync it allows you to delay the actual activation of the Scene. (And unloading of the previous Scene).

当 allowSceneActivation 设置为 false 时，进度将在 0.9 处停止。isDone 保持 false 状态。当 allowSceneActivation 设置为 true 时，isDone 可以完成。虽然 isDone 为 false，但 AsyncOperation 队列已停止。例如，如果 LoadSceneAsync.allowSceneActivation 设置为 false，并且另一个 AsyncOperation（例如 SceneManager.UnloadSceneAsync）已初始化，则在第一个 allowSceneActivation 设置为 true 之前不会调用最后一个操作。

//This script lets you load a Scene asynchronously. It uses an asyncOperation to calculate the progress and outputs the current progress to Text (could also be used to make progress bars).

//Attach this script to a GameObject
//Create a Button (Create>UI>Button) and a Text GameObject (Create>UI>Text) and attach them both to the Inspector of your GameObject
//In Play Mode, press your Button to load the Scene, and the Text changes depending on progress. Press the space key to activate the Scene.
//Note: The progress may look like it goes straight to 100% if your Scene doesn’t have a lot to load.

using System.Collections;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;

public class AsyncOperationProgressExample : MonoBehaviour
{
    public Text m_Text;
    public Button m_Button;

    void Start()
    {
        //Call the LoadButton() function when the user clicks this Button
        m_Button.onClick.AddListener(LoadButton);
    }

    void LoadButton()
    {
        //Start loading the Scene asynchronously and output the progress bar
        StartCoroutine(LoadScene());
    }

    IEnumerator LoadScene()
    {
        yield return null;

        //Begin to load the Scene you specify
        AsyncOperation asyncOperation = SceneManager.LoadSceneAsync("Scene3");
        //Don't let the Scene activate until you allow it to
        asyncOperation.allowSceneActivation = false;
        Debug.Log("Pro :" + asyncOperation.progress);
        //When the load is still in progress, output the Text and progress bar
        while (!asyncOperation.isDone)
        {
            //Output the current progress
            m_Text.text = "Loading progress: " + (asyncOperation.progress * 100) + "%";

            // Check if the load has finished
            if (asyncOperation.progress >= 0.9f)
            {
                //Change the Text to show the Scene is ready
                m_Text.text = "Press the space bar to continue";
                //Wait to you press the space key to activate the Scene
                if (Input.GetKeyDown(KeyCode.Space))
                    //Activate the Scene
                    asyncOperation.allowSceneActivation = true;
            }

            yield return null;
        }
    }
}