Xamarin.Android Custom Component Click event binding using xaml - xamarin.android

Question

I am creating a custom button component which involves an label and button. I can set the displaytext and other properties using XAML after defining them in the attrs.xml (like
<UButton displayText="Hello" ... />
). but i need to allow the Click event of this control to be handled by the user by defining it in the XAML like
mclick="button_click"
. but i am not able to find a documentation for handling this. Can you please guide me.

Answer 1

Let's look Button's source code.
In this link (Android attrs.xml source code), search onClick, you will find:
<!-- Name of the method in this View's context to invoke when the view is
clicked. This name must correspond to a public method that takes
exactly one parameter of type View. For instance, if you specify
<code>android:onClick="sayHello"</code>, you must declare a
<code>public void sayHello(View v)</code> method of your context
(typically, your Activity). -->
<attr name="onClick" format="string" />
That why when you use :
<Button
android:layout_width="match_parent"
android:layout_height="match_parent"
android:onClick="onClick"/>
it will find the onClick method.
Here, you will see how Android handle the android:onClick="onClick", in it's View(Context context, AttributeSet attrs, int defStyleAttr) method, android:onClick="onClick" is correspond to R.styleable.View_onClick:
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);
if (handlerName != null) {
setOnClickListener(new OnClickListener() {
private Method mHandler;
public void onClick(View v) {
if (mHandler == null) {
try {
mHandler = getContext().getClass().getMethod(handlerName,
View.class);
} catch (NoSuchMethodException e) {
int id = getId();
String idText = id == NO_ID ? "" : " with id '"
+ getContext().getResources().getResourceEntryName(
id) + "'";
throw new IllegalStateException("Could not find a method " +
handlerName + "(View) in the activity "
+ getContext().getClass() + " for onClick handler"
+ " on view " + View.this.getClass() + idText, e);
}
}
try {
mHandler.invoke(getContext(), View.this);
} catch (IllegalAccessException e) {
throw new IllegalStateException("Could not execute non "
+ "public method of the activity", e);
} catch (InvocationTargetException e) {
throw new IllegalStateException("Could not execute "
+ "method of the activity", e);
}
}
});
}
break;
You will find, it find the method by reflection.
So, I guess you have forgot to handle the mclick="button_click". As usually, we don't use this to add click listener, it is a little complex. We use View's setOnClickListener.