Possible Duplicate:
Difference between OnClick() event and OnClickListener?
I'm semi-new to Android development and when I first started I tried to avoid using the xml layout by any means necessary so some of my earlier projects involve buttons that explicitly create an OnClickListener and implement it as an anonymous inner class. Such as -
final Button button = new Button(this);
button.setText("Click to change second line of text");
OnClickListener buttonListener = new View.OnClickListener() {
boolean clicked = false;
int numClicks = 0;
@Override
public void onClick(View v) {
if(numClicks > 5) {
button.setText("STOP IT");
}
numClicks++;
if(clicked == false){
clicked = true;
tv2.setText("Text Changed on Button Click");
}
else
{
clicked = false;
tv2.setText("Click again");
}
}
};
button.setOnClickListener(buttonListener);
But as I got more familiar with android, I began to understand the value of the xml layouts and implemented buttons like this
<Button
android:id="@+id/button1"
android:layout_height = "wrap_content"
android:layout_width ="wrap_content"
android:text = "lets do this"
android:onClick = "DoIt"
/>
In the layout xml, where DoIt was defined in the java.
My question is, are these 2 methods functionally the same thing? Is there an OnClickListener being defined by the compiler somewhere behind the scenes? Are there any features you trade off by using one way or the other?
These are exactly the same. android:onClick
was added in API level 4 to make it easier, more Javascript-web-like, and drive everything from the XML. What it does internally is add an OnClickListener
on the Button, which calls your DoIt
method.
Here is what using a android:onClick="DoIt"
does internally:
Button button= (Button) findViewById(R.id.buttonId);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
DoIt(v);
}
});
The only thing you trade off by using android:onClick
, as usual with XML configuration, is that it becomes a bit more difficult to add dynamic content (programatically, you could decide to add one listener or another depending on your variables). But this is easily defeated by adding your test within the DoIt
method.