Reusing views on multiple activites in Android

Question

I have the following scenario: android up, compatible starting with android 1.6 and up. At the bottom of ALL activities I have a set of ToggleButtons that only start activities. Don't ask me why, that was the request :) Having these buttons do the same thing in all screens I thought like this:

1. Put the layout in a xml file and it in all my activities layout
2. Create a class that extends Activity and assign onClick methods for all my buttons
3. When a ToggleButton is checked, set all other buttons checked="false" and perform the button's operation.

I am stuck on my BaseActivity, when overriding onCreate(). How do I get a hold of my buttons and assign onClick listeners to them ?

public class BaseActivity extends Activity {
    private ToggleButton menuHome;

    @Override
    public void onCreate(Bundle savedInstanceState) {
             //this does not work as it cannot find R.id.menu_home)
        menuHome = (ToggleButton) findViewById(R.id.menu_home);
    }
}

Answer 1

In your other Activities that extend BaseActivity take a look at your OnCreate method. Does it look like this?

public class YourActivity extends BaseActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        base.Oncreate(saveInstanceState);     

        setContentView(R.layout.YourLayout);

        // Other code here...
    }
}

It has to do with the order... you haven't set the content view so your toggle button doesn't exist. Try this:

public class YourActivity extends BaseActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        setContentView(R.layout.YourLayout); // Set your content view first.

        base.Oncreate(saveInstanceState);     



        // Other code here...
    }
}

Answer 2

You need to initialize the GUI with a valid xml file or through runtime object initialization. Try using setContentView on your activity. Your code is not loading any xml, so there's no menu_home initialized.

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

I'm not sure if this is the right approach, I'd consider doing an external component to do the job: http://developer.android.com/guide/topics/ui/custom-components.html

Answer 3

You have to call setContentView(R.layout.your_layout) where your_layout is the layout containing the button R.id.menu_home. Right now you did not provide a layout to the activity so there is no hierarchy where to search for the button.