Android: Implementing a Back Button from a class

Question

Okay, so here is my problem. I'm working on an android app and learning android at the same time, so most of the times I get errors. Normaly I can fix them after researching a bit, but I'm getting stuck in this point.

I'm trying to make a back button for every Activity in my app, so I thought about making a "BackButton" class, so I can instanciate it every time I want to. Here is my BackButton code:

import android.content.Intent;
import android.view.View;
import android.widget.Button;
import android.app.Activity;

    public class BackButton extends Activity implements View.OnClickListener{

        public static Button BackButton;

        // Defining the button
        public BackButton() {

            BackButton = (Button) findViewById(R.id.bBack);

            BackButton.setOnClickListener(this);

        }

        //To get the Button
        public static Button getBackButton() {
            return BackButton;
        }


        // OnClickListener
        public void onClick(View v) {

                try {
                    Class MainActivityClass = Class.forName("eu.lafarga.treballderecerca.MainActivity");
                    Intent MainActivityIntent = new Intent(BackButton.this, MainActivityClass); 
                    startActivity(MainActivityIntent);
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                }finally {
                    // Save the things we've done. 
                }

        }

    }

So, how should I implement this in any activity? I'm doind something wrong? (Sure I'm lol)

Well dont override the back button, if you still need then instantiate an object of the class you have made inside on back pressed method. — Skynet, Sep 04 '13 at 13:05
if you merely want back button functionality then why don't you use action bar http://www.vogella.com/articles/AndroidActionBar/article.html — Mohit, Sep 04 '13 at 13:10
you don't need a back button you have a hardware back button when clicked takes you back to the previous activity. For navigation use actionbar and navigationbar — Raghunandan, Sep 04 '13 at 13:14

JavaDM · Answer 1 · 2013-09-04T13:23:03.727

4

There is a easier way to Listen to the backButton.

// Called when the activity has detected the user's press of the back key.
 onBackPressed()

And when you do not call the super-method, there shouldn't be any further steps. But it is not a good way to "disable" the back-button.

http://developer.android.com/reference/android/app/Activity.html

edited Sep 04 '13 at 13:23

answered Sep 04 '13 at 13:10

JavaDM

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score 2 · Accepted Answer · answered Sep 04 '13 at 13:14

Personally, I would suggest not doing this. I think overriding the back button in each Activity would be safer, more flexible, and just as easy, if not easier. Chances are, you aren't always going to want to return to the MainActivity as your app grows because its likely that this won't be the expected action for the users when they hit the back button. Override the back button in Activities that need it and run your code

    @Overrride
    public void onBackPressed(View v) {
     // save data first

      Intent MainActivityIntent = new Intent(CurrentActivityName.this, MainActivityClass); 
      startActivity(MainActivityIntent);
      super.onBackPressed();
}

You can also use flags such as FLAG_ACTIVITY_CLEAR_TOP if you want to remove all Activities between the current one and the target Activity(here MainActivity) by calling setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)

score 1 · Answer 3 · edited May 23 '17 at 10:30

1

There are multiple ways to block back button.

By overriding onKeyDown or onBackPressed of your Activity.

Please visit following question link for detailed description and its solution given in answer.

Link 1

Link 2

edited May 23 '17 at 10:30

Community

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answered Sep 04 '13 at 13:13

RPB

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Android: Implementing a Back Button from a class

3 Answers3