android - How to call a class extending Asynctask in the Main Activity from FIngerPrintHelper class

Question

I am implementing fingerprint authentication in my application. I have successfully authenticated fingerprint in the application. But the problem is, I want to call Asynctask class, which is inside the Main Activity, from a Finger Print Helper class.

Below is the code for FingerPrintHelper.java class:

public class FingerprintHandler extends FingerprintManager.AuthenticationCallback {


    private Context context;


    // Constructor
    public FingerprintHandler(Context mContext) {
        context = mContext;
    }


    public void startAuth(FingerprintManager manager, FingerprintManager.CryptoObject cryptoObject) {
        CancellationSignal cancellationSignal = new CancellationSignal();
        if (ActivityCompat.checkSelfPermission(context, Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED) {
            return;
        }
        manager.authenticate(cryptoObject, cancellationSignal, 0, this, null);
    }


    @Override
    public void onAuthenticationError(int errMsgId, CharSequence errString) {
        this.update("Fingerprint Authentication error\n" + errString, false);
    }


    @Override
    public void onAuthenticationHelp(int helpMsgId, CharSequence helpString) {
        this.update("Fingerprint Authentication help\n" + helpString, false);
    }


    @Override
    public void onAuthenticationFailed() {
        this.update("Fingerprint Authentication failed.", false);
        Vibrator v = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE);
        v.vibrate(1000);

        TextView lblFingerPrintError = (TextView) ((Activity)context).findViewById(R.id.lblFingerPrintError);
        lblFingerPrintError.setVisibility(View.VISIBLE);
        lblFingerPrintError.setText("Finger print did not match");
    }


    @Override
    public void onAuthenticationSucceeded(FingerprintManager.AuthenticationResult result) {
        this.update("Fingerprint Authentication succeeded.", true);


        context.startActivity(new Intent(context, HomePage.class));
    }


    public void update(String e, Boolean success){
        if(success){
            Log.i("WW", "Matched");
        }
    }
}

Inside the method, onAuthenticationSucceeded(), I want to call Asynctask Class which is the Main Activity.

Please respond if someone has the solution to this.

Thank You.

Answer 1

you can pass a callback to your calling activity to know about the authentication completion as follows.

callback interface

    public interface CallBackInterface  {
    void onAuthenticationSucceed();
}

when you call FingerprintHandler from the activity just pass the reference using method or constructor like this.

// Constructor
public FingerprintHandler(Context mContext,CallBackInterface callback) {
    context = mContext;
    this.callback = callback;
}

now you can use this reference to notify the calling activity about the completion of the authentication as follows.

 @Override
    public void onAuthenticationSucceeded(FingerprintManager.AuthenticationResult result) {
        this.update("Fingerprint Authentication succeeded.", true);
        //notify the caller about success
        callback.onAuthenticationSucceed();
    }

final code for FingerprintHandler as follows.

public class FingerprintHandler extends FingerprintManager.AuthenticationCallback {


private Context context;
private CallBackInterface callback;

// Constructor
public FingerprintHandler(Context mContext, CallBackInterface callback) {
    context = mContext;
    this.callback = callback;
}


public void startAuth(FingerprintManager manager, FingerprintManager.CryptoObject cryptoObject) {
    CancellationSignal cancellationSignal = new CancellationSignal();
    if (ActivityCompat.checkSelfPermission(context, Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED) {
        return;
    }
    manager.authenticate(cryptoObject, cancellationSignal, 0, this, null);
}


@Override
public void onAuthenticationError(int errMsgId, CharSequence errString) {
    this.update("Fingerprint Authentication error\n" + errString, false);
}


@Override
public void onAuthenticationHelp(int helpMsgId, CharSequence helpString) {
    this.update("Fingerprint Authentication help\n" + helpString, false);
}


@Override
public void onAuthenticationFailed() {
    this.update("Fingerprint Authentication failed.", false);
    Vibrator v = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE);
    v.vibrate(1000);

    TextView lblFingerPrintError = (TextView) ((Activity)context).findViewById(R.id.lblFingerPrintError);
    lblFingerPrintError.setVisibility(View.VISIBLE);
    lblFingerPrintError.setText("Finger print did not match");
}


@Override
public void onAuthenticationSucceeded(FingerprintManager.AuthenticationResult result) {
    this.update("Fingerprint Authentication succeeded.", true);
    //here notify the caller about the success
    callback.onAuthenticationSucceed();

   // context.startActivity(new Intent(context, HomePage.class));
}


public void update(String e, Boolean success){
    if(success){
        Log.i("WW", "Matched");
    }
}

}

and in your activity where you have passed the reference using constructor you must have to override the onAuthenticationSucceed() so now call your async task here

@Override
public void onAuthenticationSucceed(){
  //here start your async task.
}