从线程启动android活动

Question

What i am trying to do over here is that I want to call a webservice and based on its response i might invoke another webservice or start an activity.I am already writing the web service in a separate thread but the issue is that i am calling the activity in a worker thread, To make myself more clear i have put my pseudo code .

if (User ID and Password present in the shared preference) THEN 
                 Utils.checkauthorisation(API)   //Web Service Call
                 if(respsonse is Paswordexpired)
                    erase password from DB
                    Goto (LOGIN SCREEN)
                 else if( download of images hasn't happened today) ) THEN
                        UTILS.DownloadImages//Web service call
                        if(response==connectivityorOtherError)
                            Toast respective Message
                            GOTO (GALLERY SCREEN)
                        else if (response==confilicted Data)
                            Goto (CHANGES SCREEN)
                        endif
                endif
endif

I was planning to show a progress bar and do all these events in a thread like this

  progressDialog = ProgressDialog.show(this, "Loading",
                "Authenticating Please wait.");

     new Thread() {
        public void run() {

        ///execute the pseudo code

        Message msg = Message.obtain();
        msg.what = 1;
        messagHandler.sendMessage(msg);
        }

    }.start();



            private static Handler messagHandler = new Handler() {
    public void handleMessage(Message message) {
        super.handleMessage(message);
        switch (message.what) {
        case 1:
            progressDialog.dismiss();
            break;
        default:
            break;
        }
    }

};

But something that disturbs me is that I have to start an activity in a worker thread here. Is this good practice? I initially thought that we could only start an activity from the UI thread. What is the process happening in the back end here(in the thread sense)? If this is not a good practice what are the other alternatives to implement my pseudocode ?

Thanks

Answer 1

Launch the intent with a message to the Handler not on your worker Thread. Handlers are run on the UI thread. If they were not, you would not be able to update UI elements in a Handler.