"builder" is a local variable in scope of the onCreate method and is used in the anonymous inner class (new OnClickListener). Java keeps a copy of that local variable inside the listener object so Final ensures that the copy is consistent - you are not allowed to assign builder to some other value later in the method.
If "builder" were a instance field it would not have to be Final since inner classes can access fields in the containing object. On Jan 20, 12:20 pm, TreKing <[email protected]> wrote: > On Wed, Jan 20, 2010 at 11:35 AM, tim hansen < > > [email protected]> wrote: > > final Builder builder = new AlertDialog.Builder(this); > > > btnSave = (Button)findViewById(R.id.save_button); > > > btnSave.setOnClickListener(new OnClickListener() { > > @Override > > public void onClick(View v) { > > builder.show(); > > } > > }); > > I am no expert in Java, but I believe in this case you need the final > keyword to ensure that the "builder" variable that you're using in the > anonymous OnClickListener is still valid when it's onClick() function is > actually called. > > If it were not final, the variable "builder" would be invalidated as soon as > you exited the onCreate() function. Later, when you actually press the save > button and the onClick() function gets called, builder would be null (or > complete garbage). > > I'm sure someone will correct me if I'm mistaken. > > ------------------------------------------------------------------------------------------------- > TreKing - Chicago transit tracking app for Android-powered > deviceshttp://sites.google.com/site/rezmobileapps/treking
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