统一执行sqlite操作时，场景冻结了几秒钟

Question

In my application have a feature like 'Sync' data, In sync operation get the data from server and stored in local sqlite database and push local data to server. When user click on sync, scene freeze up to completed the push and pull operations. How can I get out of this problem. I have tried like using separate thread for doing database operations but I am getting exception like persistance database operations work on main thread only. How can I do sync operation without freeze the screen. Please suggest any idea, Thanks in advance.

Here is the sample code I have tried

 var thread = new System.Threading.Thread(() =>
 {
     //do sqlite operations
 });

 thread.start();

Answer 1

You should be doing expensive queries in another Thread. Once the query returns, you can use the result in the main Thread . I noticed you made attempt to use Thread but you're getting new error:

get_persistentDataPath can only be called from the main thread.

This is because you're using Application.persistentDataPath in another Thread . You cannot use most Unity API in another Thread and Application.persistentDataPath is one of them. This is a simple fix. There is no reason to use Application.persistentDataPath in another Thread. Get the value of Application.persistentDataPath and store in in a global string variable then use that global variable in the new Thread.

For example:

Don't do this ( this is what you're currently doing):

void Start()
{
    //This Start function is the main Thread (Unity's Thread)

    var thread = new System.Threading.Thread(() =>
    {
        //This is another Thread created by you

        //DO NOT DO THIS(Don't use Unity API in another Thread)
        string dbPath = Application.persistentDataPath;

        //do sqlite operations
    });
    thread.Start();
}

Do this instead (Get the variable of Application.persistentDataPath in the main thread before then use the stored value):

void Start()
{
    //This Start function is the main Thread (Unity's Thread)

    //Get path in the Main Thread
    string dbPath = Application.persistentDataPath;

    var thread = new System.Threading.Thread(() =>
    {
        //This is another Thread created by you

        //Use the path result here


        //do sqlite operations
    });
    thread.Start();
}

---

Finally, if you really need to use many other Unity API other than Application.persistentDataPath or for example, update the UI Text component with result from the database, you can use my UnityThread plugin which simplifies that.

public Text yourTextComponent;

void Start()
{
    UnityThread.initUnityThread();
    //This Start function is the main Thread (Unity's Thread)

    //Get path in the Main Thread
    string dbPath = Application.persistentDataPath;

    var thread = new System.Threading.Thread(() =>
    {
        //This is another Thread created by you

        //do sqlite operations

        //Show result on UI
        UnityThread.executeInUpdate(() =>
        {
            yourTextComponent.text = queryResult;
        });
    });
    thread.Start();
}