Android中的服务器端验证：if语句中调用的异步方法

Question

I was using the Parse API and was trying to implement a change password feature when came across this issue.

I was trying to validate that the user's current password matches their attempted current password (what the user entered into the EditText).

Since the Parse API, doesn't allow access to the user's encrypted password , I'm validating that the user's input matches the current password by trying to log in with the attempted current password and username. If the log in was successful, then the attempted current password is correct.

When the change password button is clicked, I check if the attempted current password matches the actual current password:

if (mCurrentPassword != null && passwordsMatch(mCurrentPassword)) {
    mCurrentPasswordEditText.setError(getString(R.string.error_incorrect_password));
}

I created a passwordsMatch(String mAttemptedCurrentPassword) method here:

private boolean passwordsMatch(String mCurrentPassword) {
    HashMap<String, Object> params = new HashMap<String, Object>();
    params.put("username", mUser.getUsername());
    params.put( "attemptedCurrentPassword", mCurrentPassword);

    ParseCloud.callFunctionInBackground("validateMatchingPasswords", params, new FunctionCallback<Object>() {
       public void done(Object o, ParseException e) {
           if (e == null) {
             // password match (success)
           } else {
             // password do not match (failure)
           }
       }
    });

}

The above code is incomplete. I have a cloud code function, which tries log the user in and responds with a success or error. I am having trouble finding a workaround because I don't understand threading that well.

How can I make the if (passwordsMatch) statement wait for the passwordsMatch method to get a result?

Edit:

For those unfamiliar to Parse, here is what the ParseCloud.callFunctionInBackground function is doing:

It is essentially an AsyncTask. It has a callback FunctionCallback , which implements the done method. The done method is called when ParseCloud.callFunctionInBackground returns a result. It's analogous to the onPostExecute method.

The problem is that I have to return a boolean after the asynchronous task is finished.

Answer 1

What you need to do is make a server request (GET/POST) with a pair of username and password. You can use the following code

new AsyncTask<String, String, String>(){

@Override
protected String doInBackground(String... params) {
// TODO Auto-generated method stub
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://www.urloflink.com");

try {
    // Add your data
    List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>;
    nameValuePairs.add(new BasicNameValuePair("username", "user"));
    nameValuePairs.add(new BasicNameValuePair("password", "pass"));
    httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

    // Execute HTTP Post Request
    HttpResponse response = httpclient.execute(httppost);

    } catch (ClientProtocolException e) {
    // TODO Auto-generated catch block
    } catch (IOException e) {
    // TODO Auto-generated catch block
 }
}

 @Override
 protected void onPostExecute(String result) {
     result = response.getresult(); // a hypothetical function according to your server response format
   // Extract response string from response and check the result
   if(result == "success"){
    // DO something
   }
   else if(result == "failure"){
    // Do something
   }
 }.execute();

This is an asynctask which runs in a separate thread. Hence during this process you can show processing ring or some animation. The content in doInBackground() runs in background and to make any changes to the UI you can use onPostExecute() block.

You can use the above code in your password match function as:

private boolean passwordsMatch(String mCurrentPassword) {

   new AsyncTask<String,....
    ....
   }.execute();
 }

Make sure that you replace the function response.getResult() with an actual function or some code segment that gives you the result.

Answer 2

Usually you don't do it this way. You may create a Loader while it's still connecting or parsing and onec it's done you process your stuff in onPostExecute. There you can disable the loaders view and execute or run your new activity/fragment.