登录成功后如何开始新的活动？

我想在登录成功后开始一项新活动。也就是说，当登录正确时，新的活动应该自动启动......我不知道在哪里提到启动活动。请帮我解决这个问题，我是 Android 新手。 这是我的代码...

    public class BackgroundTask extends AsyncTask<String,Void,String> {
    AlertDialog alertDialog;
    Context ctx;
    BackgroundTask(Context ctx)
    {
        this.ctx =ctx;
    }
    @Override
    protected void onPreExecute() {
        alertDialog = new AlertDialog.Builder(ctx).create();
        alertDialog.setTitle("Login Information....");
    }

    @Override
    protected String doInBackground(String... params) {
        String reg_url = "";
        String login_url = "";
        String method = params[0];
        if (method.equals("register")) {
            String name = params[1];
            String user_name = params[2];
            String user_pass = params[3];
            try {
                URL url = new URL(reg_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);

                //httpURLConnection.setDoInput(true);
                OutputStream OS = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(OS, "UTF-8"));
                String data = URLEncoder.encode("user", "UTF-8") + "=" + URLEncoder.encode(name, "UTF-8") + "&" +
                        URLEncoder.encode("user_name", "UTF-8") + "=" + URLEncoder.encode(user_name, "UTF-8") + "&" +
                        URLEncoder.encode("user_pass", "UTF-8") + "=" + URLEncoder.encode(user_pass, "UTF-8");
                bufferedWriter.write(data);
                bufferedWriter.flush();
                bufferedWriter.close();
                OS.close();
                InputStream IS = httpURLConnection.getInputStream();
                IS.close();
                //httpURLConnection.connect();
                httpURLConnection.disconnect();
                return "Registration Success...";
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        else if(method.equals("login"))
        {
            String login_name = params[1];
            String login_pass = params[2];
            try {
                URL url = new URL(login_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);
                OutputStream outputStream = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream,"UTF-8"));
                String data = URLEncoder.encode("login_name","UTF-8")+"="+URLEncoder.encode(login_name,"UTF-8")+"&"+
                        URLEncoder.encode("login_pass","UTF-8")+"="+URLEncoder.encode(login_pass,"UTF-8");
                bufferedWriter.write(data);
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();

                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,"iso-8859-1"));
                String response = "";
                String line  = "";
                while ((line = bufferedReader.readLine())!=null)
                {
                    response+= line;
                }
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();
                return response;


            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }


        }
        return null;
    }

    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
    }

    @Override
    protected void onPostExecute(String result) {
        if(result.equals("Registration Success..."))
        {
            Toast.makeText(ctx, result, Toast.LENGTH_LONG).show();
        }
        else
        {
            alertDialog.setMessage(result);
            alertDialog.show();
        }

    }
}

您可以将意图放入 onPostExecute 方法中，如下所示：

@Override
    protected void onPostExecute(String result) {
        if(result == null)
        {
            // do what you want to do
        }
        else if(result.equals("Registration Success..."))
        {
            Toast.makeText(ctx, result, Toast.LENGTH_LONG).show();
        }
        else if(result.contains("Login Success")) // msg you get from success like "Login Success"
        {
            Intent i = new Intent(ctx,NewActivity.class);
            ctx.startActivity(i);
            alertDialog.setMessage(result);
            alertDialog.show();
        }

    }

Edit :如果您想在登录成功后调用新活动，请将意图放在其他部分。