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 --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. 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