在片段而不是主要部分中执行按钮操作

Question

I have an Android app where i'm using tabs (with ActionBarSherlock). So my main activity creates the tabs for me and from there i load in the fragment layouts.

In my MainActivity.java i create a tab (this is just a snippet):

mTabsAdapter = new TabsAdapter(this, mViewPager);

mTabsAdapter.addTab(
    bar.newTab().setText("Fragment 1"),
    MainMenuFragment.class, null);

My MainMenu.java looks like this:

public class MainMenuFragment extends SherlockFragment
{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState)
    {
        View view = inflater.inflate(R.layout.mainmenu_fragment, container, false);

        return view;
    }

    public void showMainMenu(View view)
    {
        Log.e("app", "olol: button!"); // never called!!
    }
}

---

And this is mainmenu_fragment

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000" >

    <Button
        android:id="@+id/btnMenu"
        android:layout_width="170dp"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="41dp"
        android:text="@string/mainmenu"
        android:onClick="showMainMenu" />
</RelativeLayout>

Now all i have to do is place the method showMainMenu(View view) somewhere. I thought this would go in the corresponding java file (MainMenuFragment.java in my case). But it only works when i put the method in the MainAvtivity.java file.

That means that all my button actions from all kinds of fragment layouts will go in one (the main) java file. Why can't i simply place it inside the java file that calls the Fragment layout..??

Answer 1

Now all I have to do is place the method showMainMenu() somewhere - this is wrong. Please, refer to the documentation of android:onClick :

For instance, if you specify android:onClick="sayHello", you must declare a public void sayHello(View v) method of your context (typically, your Activity).

Seems You cannot place your callback somewhere , because framework won't be able to find that callback. If You're defining it inside Activity (which is actually, a Context), it's possible for View to find it back. Actually, View.java contains the following code:

case R.styleable.View_onClick:
    if (context.isRestricted()) {
        throw new IllegalStateException("The android:onClick attribute cannot " + "be used within a restricted context");
    }

    final String handlerName = a.getString(attr);
    mHandler = getContext().getClass().getMethod(handlerName, View.class);
    ...
    mHandler.invoke(getContext(), View.this);

Seems it's the only possible way to call callback defined in layout file with current android:onClick attribute specification.

Answer 2

The short answers is (like already pointed out), you can't.

The only way to do this is by creating an onClick even listener. In the MainMenuFragment.java in the onCreate method, do something like this:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState)
{
    View view = inflater.inflate(R.layout.scan_fragment, container, false);

    Button menuButton = (Button)view.findViewById(R.id.btnMenu);
    menuButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            Log.e("app", "onclick listener");
        }
    });

    return view;
}

You can remove the onClick attribute from the layout xml.

Answer 3

I solved this using the following:

Fragment xml contains

android:onClick="myFunction"

Activity Contains

public void myFunction(View v)
{ getSupportFragmentManager().findViewById/Tag(...).myFunction(v); }

Fragment Code can then implement as below to have access to local data

public void myFunction(View v) {...}

Hope this helps.