Question

What I have here is a custom view and then I want some widgets to go with it.

<com.zone.manager.Tab3
    android:id="@+id/tab3_display"
    android:layout_width="fill_parent"
    android:layout_height="620dp" >

<Button
    android:id="@+id/addZone"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Add Zone" />

</com.zone.manager.Tab3>

Now I want to have that button set to onclicklistener so I can do stuff with it in the View class so I did this…

addZone = (Button) findViewById(R.id.addZone);


  addZone.setOnClickListener(this);

I set that in the

public class Tab3 extends ViewGroup implements OnTouchListener, OnClickListener
    Public Tab3(Context context, AttributeSet attrs) 
    {
    super (context, attrs); 
    // here
    }

When I extended ViewGroup it made me implement this

@Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) 
    {
        // TODO Auto-generated method stub

    }

Is there something that I am suppsot to put in here in order to make this work?

But when I try to run the app it crashes, however if I // out the addZone.setOnClickListener(this); the app runs fine, any help for me?

tabs

        th.setup();
        TabSpec specs = th.newTabSpec("tag0");
        specs.setContent(R.id.connecttionTab);
        specs.setIndicator("Connection Tab");
        th.addTab(specs);
        specs = th.newTabSpec("tag1");
        specs.setContent(R.id.tab1);
        specs.setIndicator("Zone Manager");
        th.addTab(specs);
        specs = th.newTabSpec("tag2");
        specs.setContent(R.id.tab2);
        specs.setIndicator("",res.getDrawable(R.drawable.ic_tab_vaccontrol));
        th.addTab(specs);
        //this is the tab that has all this vvv
        specs = th.newTabSpec("tag3");
        specs.setContent(R.id.tab3);
        specs.setIndicator("Graphical Layout");
        th.addTab(specs);

Answer 1

In your xml, your custom view does not contain the button; it is a sibling view. The reason your app crashes is that findViewById(R.id.addZone) is returning null, so you are getting a NullPointerException when you call addZone.setOnClickListener(this). If you want your custom view to contain the button, the xml would have to look something like this:

<com.zone.manager.Tab3
    android:id="@+id/tab3_display"
    android:layout_width="fill_parent"
    android:layout_height="620dp" >

    <Button
        android:id="@+id/addZone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add Zone" />

</com.zone.manager.Tab3>

Also, your Tab3 class will have to extend ViewGroup, not View. This can get a bit complicated because you also need to write code to do the layout. The button will also be displayed inside the Tab3 view.

EDIT

Based on your comments of what you are trying to do, I do not recommend the above approach. Instead, you should just wrap your custom view and the Button in a LinearLayout. For example, the following layout will put the button at the bottom left of the screen and will have a Tab3 view fill the area above it:

res/layout.tab3.xml

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >

    <com.zone.manager.Tab3
        android:id="@+id/tab3_display"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

    <Button
        android:id="@+id/addZone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="onAddZone"
        android:text="Add Zone" />

</LinearLayout>

Then, move the click processing logic to a separate method in Tab3 that is visible to your Activity class. (Let’s assume that it is called addZone().) The Tab3 class should not implement OnClickListener and should extend View (not ViewGroup as above). By adding the android:onClick attribute to the button, you don’t need to add an OnClickListener to the button. Instead, you need to implement a click method of that name in the activity:

private Tab3 mTab3;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.tab3);
    mTab3 = (Tab3) findViewById(R.id.tab3_display);
    // . . .
}

@Override
/**
 * Called when a view with attribute android:onClick="onAddZone"
 * is clicked.
 *
 * @param view the view that was clicked.
 */
public void onAddZone(View view) {
    mTab3.addZone();
}

Although there is nothing in your code about the button, the framework will automatically wire everything up using reflection so that the onAddZone method of the activity will be called when the button is clicked.