Using onClick attribute in layout xml causes a NoS

Question

I have created a custom dialog and a layout xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tap Me"
        android:onClick="dialogClicked" />
</LinearLayout>

In the dialog class I've implemented the method "dialogClicked(View v)":

public class TestDialog extends Dialog {

 public TestDialog(final Context context)
 {
  super(context);
 }

 @Override
 protected void onCreate(final Bundle savedInstanceState)
 {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.dialog);
 }

 public void dialogClicked(final View view)
 {
  System.out.println("clicked");
 }

}

When I tap the button I get a NoSuchMethodException 'dialogClicked'. Setting the onClick handler in layout xml works fine for activities, but not in dialogs. Any ideas? What I'm doing wrong?

Answer 1

Following on from Jett Hsieh's post, I've implemented my dialogs slightly differently using showDialog and dismissDialog, but the fundamentals of getting the android:onClick working have been the same, my example code is below for future reference.

public class ExampleActivity extends Activity { 
    static final int DIALOG_DISCLAIMER = 0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        showDialog(DIALOG_DISCLAIMER);
    }

    protected Dialog onCreateDialog(int id)
    {
        Dialog dialog;
        switch(id)
        {
            case DIALOG_DISCLAIMER:
                dialog = new Dialog(this);
                dialog.setContentView(R.layout.main_disclaimer);

                LinearLayout ll = (LinearLayout) LayoutInflater.from(this).inflate(R.layout.main_disclaimer, null);
                dialog.setContentView(ll);

                break;
            default:
                dialog = null;
        }       
        return dialog;
    }

    public void onClick(View v)
    {
        switch(v.getId())
        {
            case R.id.maindisclaimer_button_accept:
                dismissDialog(DIALOG_DISCLAIMER);
                break;
        }
    }
}

And the layout file:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent" 
              android:layout_height="fill_parent" 
              android:id="@+id/linearLayout1" 
              android:padding="10dp" 
              android:orientation="vertical"
              android:background="@drawable/roundedcorners">
    <Button
            android:id="@+id/maindisclaimer_button_accept"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:text="@string/string_accept"
            android:onClick="onClick" >
        </Button>
</LinearLayout>

Answer 2

I think the issue is one of scope. I'm not sure how'd you address this in xml, but essentially the dialogueClicked method in your layout xml doesn't know where to find the method you've defined in the dialog class.

The standard approach i've seen to bind buttons in custom layouts is as follows.

1. implement the OnClickListener class
2. Bind the buttons click event to the dialog class
3. Switch out the buttons in the onClick button based on id. You'd need to add an id to your button.

.

public class TestDialog extends Dialog implements android.view.View.OnClickListener
{
    protected void onCreate(final Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.dialog);
        ((Button)findViewById(R.id.dialog_btn_mybutton)).setOnClickListener(this);
    }



public void onClick(View view) 
{
    switch (view.getId())
    {
        case R.id.dialog_btn_mybutton:
            //do stuff
            // dismiss();
            // cancel etc.
        break;
    }
}

}

Hope that helps. Would still be interested in knowing if there was a solution to using xml onClick to bind to the method. Perhaps an additional argument in the setContentView? something r'other.

Answer 3

system looks for the method in the where the layout has been inflated from, or in the activity class to which the xml was set as content.

Answer 4

A dialog is always created and displayed as part of an Activity. According to Android References:

If you decide to create a dialog outside of the onCreateDialog() method, 
it will not be attached to an Activity. You can, however, 
attach it to an Activity with setOwnerActivity(Activity).

Also, are you passing the object returned by getApplicationContext(); to the constructor of TestDialog?

Answer 5

android:onClick="method" is pretty cool, but it doesn't work on Android 1.5 so I am avoiding for some time.

An easy workaround:

Make your Dialog an Activity and use android:theme="@android:style/Theme.Dialog" in you AndroidManifest.

Answer 6

I've found the following code in the View.java source:

public void onClick(View v) {
                            if (mHandler == null) {
                                try {
                                    mHandler = getContext().getClass().getMethod(handlerName,
                                            View.class);
    ...

-> The views uses its context to resolve the onclick handler method.

Noew the following code from Dialog.java source:

public Dialog(Context context, int theme) {
    mContext = new ContextThemeWrapper(context, theme == 0 ? com.android.internal.R.style.Theme_Dialog : theme);
    ...

In the constructor of the dialog an instance of ContextThemeWrapper gets created and set as context. This instance is neither the custom dialog class, nor the calling activity, which can be the place for implementing the handler method. Therefore views are not able to find the onclick handler method.

But I have to use the onclick XML attribut. Any workarounds available?