Reusing layout XML and the code behind

Question

I am trying to turn a couple buttons into a reusable component in Android. I have successfully gotten the XML / UI portion working, but I can\'t figure out how to make code

Answer 1

By using in XML layout, you're making only the layout reusable, not any Java code that uses it.

You must create a subclass of View, if you want to reuse Java logic as well. The tutorial from your link has a sample that fits your need very well:

public class OkCancelBar extends LinearLayout {
...

Answer 2

What I do is make an actual component that contains all of the common code and use it directly. Here is a dumbed down version of the component class:

public class NavigationBar extends LinearLayout {
    public NavigationBar(Context context) {
        super(context);
        setupView(context);
        hookupButtons(context);
    }
    public NavigationBar(Context context, AttributeSet attrs) {
        super(context, attrs);
        setupView(context);
        hookupButtons(context);
    }
    private void setupView(Context context) {
        LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        // inflate whatever layout xml has your common xml
        inflater.inflate(R.layout.navigation_bar, this);
    }
}

In my class hookupButtons does exactly what you think it would do. :-)

Then my in all my layout xmls look similar to this:

<?xml version="1.0" encoding="UTF-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <com.dragonglobal.dragonplayer.ui.widgets.NavigationBar
        android:id="@+id/nav_bar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <ListView
        android:id="@+id/list_of_playlists"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />
</LinearLayout>

In the onCreate of each activity I also have this (that you can adapt to whatever you need):

NavigationBar navbar = (NavigationBar) findViewById(R.id.nav_bar);
navbar.setText("Playlists");

Of course you will need to add whatever imports you need.

EDIT

Just a clarification: My navigation_bar.xml looks very similar to yours except I don't have the merge lines in mine.

EDIT 2

Here is what hookupButtons looks like. I'm only showing one button but you should get the idea.

private void hookupButtons(final Context context) {
    ImageButton playlistsBtn = (ImageButton)findViewById(R.id.nav_playlists_btn);
    if (context instanceof PlaylistsActivity) {
        playlistsBtn.setBackgroundDrawable(getResources().getDrawable(R.drawable.nav_playlists_active));
    } else {
        playlistsBtn.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent(context, PlaylistsActivity.class);
                i.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
                context.startActivity(i);
            }
        });
    }
}