android eventhandling
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ANDROID EVENT
HANDLING
L. Grewe
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Widget : Views that have
events For a ist o! the widgets "rovided #$ Android%see the android.widget "a&'age.
(o)e E*a)"es
+,tton -he&'+o* Datei&'er EditTe*t I)ageView (ear&hView ("inner
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Event Handing
De&ide what Widgets who/s events to "ro&ess Defne an event listener and register it
with the View.
View.On-i&'Listener 0!or handing 1&i&'s1 on aView2% View.OnTo,&hListener 0!or handing to,&hs&reen events in a View2% andView.On3e$Listener 0!or handing devi&e 'e$"resses within a View2
http://developer.android.com/guide/topics/ui/ui-events.html details more
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4sing E&i"se 55ets re&a o,r e*a)"e!ro) o,r starting e&t,re
6Heo Word ro7e&t8 Lets add a #,tton
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Lets add a +,tton to a
"rogra)5#ased inter!a&e (te" 9: Add #,tton (te" : Register Event Hander
TWO OTION( se"arate &ass to hande
event0s2% OR have the A&tivit$ &ontaining the#,tton do the event handing
(te" ;: I)"e)ent Event Hander
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Event handing done #$
A&tivit$ itse! Here &ode to hande is inside A&tivit$ itse! ",#i& &ass E*a)"eA&tivit$ e*tends A&tivit$ i)"e)ents On-i&'Listener=
"rote&ted void on-reate0+,nde savedVa,es2 =
...
+,tton #,tton ? 0+,tton2@ndView+$Id0R.id.&or'$2 //STEP 1 #,tton.setOn-i&'Listener0this2 //STEP - registration B
CC I)"e)ent the On-i&'Listener &a#a&' //STEP ! "event handler ",#i& void on-i&'0View v2 =
CC do so)ething when the #,tton is &i&'ed B ...B
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Event Handing 5 here have
a (EARATE &assEVE#T $%#D&'#( )*DE in separate o+,ect m)or&istner CC -reate an anon$)o,s i)"e)entation o! On-i&'Listener STEP !
"rivate On-i&'Listener )-or'$Listener ? new On-i&'Listener02 = ",#i& void on-i&'0View v2 = CC do so)ething when the #,tton is &i&'ed
BB
CCNow inside $o,r A&tivit$ &ass"rote&ted void on-reate0+,nde savedVa,es2 = ...
// STEP 1: -a"t,re o,r #,tton !ro) a$o,t +,tton #,tton ? 0+,tton2@ndView+$Id0R.id.&or'$2 // STEP : Register the on-i&' istener with the i)"e)entation a#ove #,tton.setOn-i&'Listener0)-or'$Listener2 ...B
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De"ends on IDE
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(TE9: -reate a +,tton
-reate #,tton,sing L G4Iinter!a&e in E&i"se
(et "ro"ert$ soa#e on #,tton is6Hit e8
Aso% added te*tview withinstr,&tions teing,ser to hit #,tton
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(TE: Register the )ainA""i&ation A&tivit$ as
EventHander !or #,tton Gra# #,tton asso&iated with its id% store ino&a varia#e #.
-a seton-i&'Listener0this2pu+lic class %ndroidEample0Event$adling%ctivit etends %ctivit implements *n)lic&istener
int hits 234
C -aed when the a&tivit$ is @rst &reated. C
Override
pu+lic void on)reate56undle saved'nstanceState7
super.on)reate5saved'nstanceState74
set-ontentView0R.a$o,t.main);
+,tton # ? 0+,tton2@ndView+$Id0R.id.button1);
#.setOn-i&'Listener0this74
B
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(TE: Register the )ainA""i&ation A&tivit$ as
EventHander !or #,tton Have the )ain &ass 6AndroidE*a)"eeventHandingA&tivit$8i)"e)ent On-i&'Listener !or #,tton
In )ethod on-i&' in&re)ent hits and ,se in dis"a$ string.pu+lic class %ndroidEample0Event$adling%ctivit etends %ctivit implements *n)lic&istener
int hits 234
C -aed when the a&tivit$ is @rst &reated. C
Override
pu+lic void on)reate56undle saved'nstanceState7
//see previous slide88..
B
CC I)"e)ent the On-i&'Listener &a#a&'
CC(TE ; event hander
pu+lic void on)lic5View v7
CC do so)ething when the #,tton is &i&'ed
this.hits994
Te*tView te*t ? 0Te*tView2@ndView+$Id0R.id.textView1);
(tring s ? 1Jo, hit )e 1 K this.hits4
te*t.setTe*t0s2
B
B
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Lets r,n the "revio,s &ode.
R,n $o,r &ode
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A!ter r,nning it#e!ore hit
#,tton
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A!ter hitting #,tton a !ew
ti)es
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Re)e)#er
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