You should call setBackgroundResource() but NOT from onDraw(). Just call this method from setIlluminated() for instance.
On Sun, Aug 30, 2009 at 1:06 PM, Nick_Zaillian<[email protected]> wrote: > > Mark and Romain, > Thanks. That was a much prompter response than I either expected or > deserved. > Romain, I am not sure that I totally understand what you've said. How > am I to set the background in accordance with the state of isChecked > and isIlluminated from within onDraw if not by calling > setBackgroundResource()? I guess this post probably belongs in the > Android Beginner's group. > Thanks, > Nick Zaillian > > On Aug 30, 2:59 pm, Romain Guy <[email protected]> wrote: >> Do not call setBacgroundResource() in onDraw()! You are loading and >> setting an image every time your view is drawn. You are actually >> creating a infinite "loop"; >> >> onDraw() -> setBacgroundResource() -> invalidate() -> onDraw() -> >> setBacgroundResource() -> etc. >> >> >> >> On Sun, Aug 30, 2009 at 11:47 AM, Nick_Zaillian<[email protected]> wrote: >> >> > Hey all, >> > I am writing an app that emulates a drum machine with a step >> > sequencer. For those unfamiliar with step sequencers, a step >> > sequencer is basically a set of switches where the state of each >> > switch indicates whether or not a sound is to be played at a >> > particular point in a pattern. I've already got audio playback >> > working using SoundPool and can play patterns (represented as objects >> > containing boolean arrays mapped to audio resources) by stepping >> > through these patterns using a timer. What I am trying and struggling >> > to do at present is to write my UI. I have subclassed ToggleSwitch >> > and made a custom switch called SeqSwitch which, in addition to >> > ToggleSwitch's isChecked field, also holds an isIlluminated field. >> > I've written another class called SwitchController that takes an array >> > of these switches and has a method (which I've called runSwitches) >> > that, with each call, advances one switch, illuminates the current >> > switch, and unilluminates the previous switch (the idea is that, when >> > the user plays his pattern, the button representing the current step >> > will illuminate, letting him know the current position of playback in >> > the sequence). The SeqSwitches seem to render and behave fine in >> > response to clicks. My SwitchController.runSwitches method also works >> > so long as I place it in a click handler of a button in my main >> > Activity. When, however, I pass it into the runnable (called >> > PatternPlayTask) that I give to my Timer (which then calls >> > SwitchController.runSwitches every 300 milliseconds as it steps >> > through the pattern), it stops working. I have used the debugger to >> > make sure that the object I am passing into the runnable is the same >> > as the one for which the call to SwitchController.runSwitches was >> > working in the main activity and have found that definitely it is. >> > Does anybody have any idea what's going on here. Hopefully I am just >> > doing something totally stupid, here. I've pasted the code for my >> > ToggleButton subclass below, if that helps: >> >> > package com.drummachine; >> > import android.widget.*; >> > import android.view.*; >> > import android.content.Context; >> > import com.drummachine.Instrument; >> > import android.util.*; >> > import android.content.res.TypedArray; >> > import android.graphics.Canvas; >> > import android.graphics.Paint; >> > import android.graphics.drawable.*; >> > import android.util.AttributeSet; >> > import android.view.View; >> >> > public class SeqSwitch extends ToggleButton { >> >> > //SeqSwitch holds an isIlluminated state. >> > //if isIlluminated is true, onDraw will render an illuminated >> > //button image as the SeqSwitch's drawable (currently the same image >> > used for >> > //a ToggleButton whose isChecked == true) >> > public boolean isIlluminated; >> >> > public SeqSwitch(Context context) >> > { >> > super(context); >> > isIlluminated = false; >> >> > } >> >> > //constructor called when params are taken from XML layout >> > public SeqSwitch(Context context, AttributeSet attributes) { >> > super(context, attributes); >> >> > TypedArray a = context.obtainStyledAttributes(attributes, >> > R.styleable.SeqSwitch); >> >> > isIlluminated = false; >> > super.setBackgroundResource >> > (R.drawable.seqswitchbackgroundsoneoff); >> >> > a.recycle(); >> > } >> >> > public void setIlluminated(boolean state) >> > { >> > isIlluminated = state; >> > this.invalidate(); >> >> > } >> >> > //yes, I know having illumniate() and unIlluminate() methods is >> > redundant >> > //when I have a setIlluminated(boolean) method, but I am presently >> > too lazy >> > //to rearrange code elsewhere that presently relies on these two >> > methods. >> > public void unIlluminate() >> > { >> > isIlluminated = false; >> > this.invalidate(); >> > } >> >> > public void illuminate() >> > { >> > isIlluminated = true; >> > this.invalidate(); >> > } >> >> > public boolean switchIsIlluminated() >> > { >> > return isIlluminated; >> > } >> >> > /** >> > * renders a image of a switch with an illuminated LED if either >> > the SeqSwitch's isChecked or >> > * isIllumniated == true. Otherwise it renders a drawable of a >> > button with an unIlluminated LED >> > */ >> > public void onDraw(Canvas canvas) >> > { >> > if(super.isChecked() == true || this.isIlluminated == true) >> > { >> > super.setBackgroundResource >> > (R.drawable.seqswitchbackgroundsoneonon); >> > } >> > else >> > { >> > super.setBackgroundResource >> > (R.drawable.seqswitchbackgroundsoneoff); >> > } >> >> > } >> > } >> >> > Thanks, >> > Nick Zaillian >> >> -- >> Romain Guy >> Android framework engineer >> [email protected] >> >> Note: please don't send private questions to me, as I don't have time >> to provide private support. All such questions should be posted on >> public forums, where I and others can see and answer them > > > -- Romain Guy Android framework engineer [email protected] Note: please don't send private questions to me, as I don't have time to provide private support. 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