UnityWebRequest class analysis

First of all, you need to know what this class does. It mainly loads the AB package from the server or locally. The official explanation is:

The UnityWebRequest object is used to communicate with the web server.
The unitywebre task handles the HTTP communication flow with the web server. Other objects—notably DownloadHandler and UploadHandler—manage download and upload data, respectively.
For convenience, a set of static functions are provided; these return UnityWebRequest objects configured correctly for many common use cases. See: Get, Post, Put, GetTexture.
Note: When UnityWebRequest starts communicating with a remote server by calling the Send method, most properties on the UnityWebRequest object cannot be changed.

1. Static variables:

kHttpVerbCREATE	The string "CREATE", usually used as the verb of the HTTP CREATE request.
kHttpVerbDELETE	The string "DELETE", usually used as the verb for HTTP DELETErequest.
kHttpVerbGET	The string "GET", typically used as the verb for HTTP GETrequest.
kHttpVerbHEAD	The string "HEAD", typically used as the verb for HTTP HEADrequest.
kHttpVerbPOST	The string "POST", usually used as the verb for HTTP POSTrequest.
kHttpVerbPUT	The string "PUT", typically used as the verb for HTTP PUTrequest.

I don't understand what it is used for, but I haven't used it here, if I use it, I will add it

2. Properties

certificateHandler	Holds a reference to the certificate handler object responsible for managing certificate validation for UnityWebRequest.
chunkedTransfer	Indicates whether the UnityWebRequest system should use the HTTP/1.1 transfer encoding method.
disposeCertificateHandlerOnDispose	If true, then any certificate handler connected to the UnityWebRequest will have a certificate handler. Automatically invoked when UnityWebRequest is processed.
disposeDownloadHandlerOnDispose	If true, then any download handler connected to this UnityWebRequest will have a DownloadHandler. Called automatically when UnityWebRequest. deal with.
disposeUploadHandlerOnDispose	If true, any UploadHandler attached to this UnityWebRequest will have the UploadHandler. Automatically invoked when UnityWebRequest is processed.
downloadedBytes	Returns the number of bytes of body data that the system downloaded from the remote server. (read only)
downloadHandler	Holds a reference to a DownloadHandler object that manages the body data received by this UnityWebRequest from the remote server.
downloadProgress	Returns a floating point value between 0.0 and 1.0 indicating the progress of downloading data from the server. (read only)
error	A human-readable string describing any system errors that the UnityWebRequest object encountered while processing an HTTP request or response. (read only)
isDone	Returns true after UnityWebRequest has finished communicating with the remote server. (read only)
isHttpError	Returns true after this UnityWebRequest receives an HTTP response code indicating an error. (read only)
isModifiable	Returns true when the configuration property of UnityWebRequest can be changed. (read only)
isNetworkError	Returns true after this UnityWebRequest encounters a system error. (read only)
method	Define the HTTP verb (that is, the above static property) used by this UnityWebRequest, such as GET or POST.
redirectLimit	Indicates the number of redirects that UnityWebRequest will follow before stopping with the "Redirect Limit Exceeded" system error.
responseCode	The numeric HTTP response code returned by the server, such as 200, 404 or 500. (read only)
timeout	Sets UnityWebRequest to attempt to abort after a timeout in seconds.
uploadedBytes	Returns the number of bytes of body data uploaded by the system to the remote server. (read only)
uploadHandler	Holds a reference to an UploadHandler object that manages the body data to be uploaded to the remote server.
uploadProgress	Returns a floating point value between 0.0 and 1.0 indicating the progress of uploading data to the server.
uri	Defines the target URI that UnityWebRequest communicates with.
url	Defines the target URL that UnityWebRequest communicates with.
useHttpContinue	Determines whether this UnityWebRequest includes Expect: 100-Continue in its outgoing request headers. (default: true).

The main commonly used attributes are:

downloadProgress/isDone/timeout/uri/uploadProgress

3. Static method

Abort	If there is progress, stop the UnityWebRequest as soon as possible.
Dispose	This is a signal that this UnityWebRequest is no longer in use and any resources it uses should be cleaned up.
GetRequestHeader	Retrieves the value of a custom request header.
GetResponseHeader	Retrieves the value of the response header from the latest HTTP response received.
GetResponseHeaders	Retrieve a dictionary containing all response headers received by this UnityWebRequest in the latest HTTP response.
SendWebRequest	Start communicating with the remote server. After calling this method, UnityWebRequest will perform DNS resolution (if necessary), send an HTTP request to the remote server at the target URL and process the server's response. This method should only be called once on any given UnityWebRequest object. Once this method is called, you cannot change any properties of UnityWebRequest. This method returns a WebRequestAsyncOperation object. Spawning a WebRequestAsyncOperation within a coroutine will cause the coroutine to pause until UnityWebRequest encounters a system error or completes communication.
SetRequestHeader	Set an HTTP request header to a custom value.

4. Public methods

Abort	If there is progress, stop the UnityWebRequest as soon as possible.
Dispose	This is a signal that this UnityWebRequest is no longer in use and any resources it uses should be cleaned up.
GetRequestHeader	Retrieves the value of a custom request header.
GetResponseHeader	Retrieves the value of the response header from the latest HTTP response received.
GetResponseHeaders	Retrieve a dictionary containing all response headers received by this UnityWebRequest in the latest HTTP response.
SendWebRequest	Start communicating with the remote server. After calling this method, UnityWebRequest will perform DNS resolution (if necessary), send an HTTP request to the remote server at the target URL and process the server's response. This method should only be called once on any given UnityWebRequest object. Once this method is called, you cannot change any properties of UnityWebRequest. This method returns a WebRequestAsyncOperation object. Spawning a WebRequestAsyncOperation within a coroutine will cause the coroutine to pause until UnityWebRequest encounters a system error or completes communication.
SetRequestHeader	Set an HTTP request header to a custom value.

Get method:

private IEnumerator SendUrl(string url)
{
    using (UnityWebRequest www = UnityWebRequest.Get(url))
    {
        yield return www.Send();
        if (www.error != null)
        {
            Debug.Log(www.error);
        }
        else
        {
            if (www.responseCode == 200)//200表示接受成功
            {
               Debug.Log(www.downloadHandler.text);
            }
        }
    }
}

Post method:

public IEnumerator PostUrl(string url, string postData)
{
    using (UnityWebRequest www = new UnityWebRequest(url,"POST"))
    {
        byte[] postBytes = System.Text.Encoding.UTF8.GetBytes(postData);
        www.uploadHandler = (UploadHandler)new UploadHandlerRaw(postBytes);
        www.downloadHandler = (DownloadHandler)new DownloadHandlerBuffer();
        www.SetRequestHeader("Content-Type", "application/json");
        yield return www.Send();
        if (www.isError)
        {
            Debug.Log(www.error);
        }
        else
        {
            // Show results as text  
            if (www.responseCode == 200)
            {
                Debug.Log(www.downloadHandler.text);
            }
        }
    }
}

UnityWebRequest class analysis

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