Android - Setonclicklistener VS Onclicklistener VS View.Onclicklistener

Android - setOnClickListener vs OnClickListener vs View.OnClickListener

The logic is simple. setOnClickListener belongs to step 2.

1. You create the button
2. You create an instance of OnClickListener* like it's done in that example and override the onClick-method.
3. You assign that OnClickListener to that button using btn.setOnClickListener(myOnClickListener); in your fragments/activities onCreate-method.
4. When the user clicks the button, the onClick function of the assigned OnClickListener is called.

*If you import android.view.View; you use View.OnClickListener. If you import android.view.View.*; or import android.view.View.OnClickListener; you use OnClickListener as far as I get it.

Another way is to let you activity/fragment inherit from OnClickListener. This way you assign your fragment/activity as the listener for your button and implement onClick as a member-function.

OnclickListener vs OnClick

Difference Between OnClickListener vs OnClick:

OnClickListener is the interface you need to implement and can be set to a view in java code.

OnClickListener is what waits for someone to actually click, onclick determines what happens when someone clicks.

Lately android added a xml attribute to views called android:onclick, that can be used to handle clicks directly in the view's activity without need to implement any interface.

Both function the same way, just that one gets set through java code and the other through xml code.

setOnClickListener Code Implementation:

Button button = (Button) findViewById(R.id.mybutton);

button.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        yourMethod(v);
    }
});
public void yourMethod(View v) {
    // does something very interesting
}

XML Implementation:

// method to be written in the class

public void yourMethod(View v) {
    // does something very interesting
}

//XML file
<?xml version="1.0" encoding="utf-8"?>
<!-- layout elements -->
<Button android:id="@+id/mybutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Click me!"
        android:onClick="yourMethod" />

Both are the same in performance. Xml is pre-parsed into binary code while compiling. so there is no over-head in Xml.

new OnClickListener() vs new View.OnClickListener()

Eclipse automatically imports View.OnClickListener so you don't have to use the View. prefix.

If you import android.view.View.OnClickListener; you can just use OnClickListener

but

if you import android.view.View; you have to use View.OnClickListener

Check how your imports list changes and it'll make more sense.

Difference between new View.OnClickListener and new OnClickListener

If you're imported View.OnClickListener, both will refer to the same class and will work identically.

View.OnClickListener is just often used to distinguish from DialogInterface.OnClickListener.

onClickListener vs onClick()

onClick in xml just calls through to setOnClickListener when the View is created. When you then call setOnClickListener in code, it overrides the existing OnClickListener that was set in xml.

Difference between specifying the view.onclicklistener and just having onclicklistener

There are 2 of setOnClickListener one for the View class and one refer to DialogInterface Class.

So to in order to manipulate the View like a Button or ImageView and add an action to it, you need to use View.OnClickListener while dealing with Dialog buttons you should use DialogIneterface.onClickListener both have different arguments.

Usually by adding onClickListener, the View Class will be imported by default or it will make you choose between both classes. so you don't need to add View.onClickListener. However, if the class DialogInterface have been imported already and you want to use the View onClickListener then you have to write View.onClickListener to differentiate both classes' onClickListener.

Hope it is clear now and this is what you are looking for.

Android onClick in XML vs. OnClickListener

Difference Between OnClickListener vs OnClick:

• OnClickListener is the interface you need to implement and can be set
  to a view in java code.
• OnClickListener is what waits for someone
  to actually click, onclick determines what happens when someone
  clicks.
• Lately android added a xml attribute to views called android:onclick,
  that can be used to handle clicks directly in the view's activity
  without need to implement any interface.
• You could easily swap one listener implementation with another if you need to.
• An OnClickListener enable you to separate the action/behavior of the click event from the View that triggers the event. While for simple cases this is not such a big deal, for complex event handling, this could mean better readability and maintainability of the code
• Since OnClickListener is an interface, the class that implements it has flexibilities in determining the instance variables and methods that it needs in order to handle the event. Again, this is not a big deal in simple cases, but for complex cases, we don't want to necessary mix up the variables/methods that related to event handling with the code of the View that triggers the event.
• The onClick with function binding in XML Layout is a binding between onClick and the function that it will call. The function have to have one argument (the View) in order for onClick to function.

Both function the same way, just that one gets set through java code and the other through xml code.

setOnClickListener Code Implementation:

Button btn = (Button) findViewById(R.id.mybutton);

btn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
    myFancyMethod(v);
    }
});

// some more code

public void myFancyMethod(View v) {
    // does something very interesting
}

XML Implementation:

<?xml version="1.0" encoding="utf-8"?>
<!-- layout elements -->
<Button android:id="@+id/mybutton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Click me!"
    android:onClick="myFancyMethod" />
<!-- even more layout elements -->

Performance:

Both are the same in performance. Xml is pre-parsed into binary code while compiling. so there is no over-head in Xml.

Limitation:

android:onClick is for API level 4 onwards, so if you're targeting < 1.6, then you can't use it.

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