Issue
I am trying to make an app view that, when presented with a subtraction problem, will show an animation of a growing rectangle (or fat line) that crawls up the number line to that integer.
I already have things set up so that I click "show me!" and bars are drawn along the number line showing the minuend, the subtrahend and the difference, but I'd like to be able to have a positive number's rectangle crawl up in a positive direction, negative from zero in the negative direction.
In looking through the documentation there seem to be several different ways to go about this. I am hoping somebody can suggest a way that's reasonably simple for this novice to implement. Here are the different approaches I've found:
This seems very much like this person's desire to have a bar graph where the bars "pop up," but it doesn't have an answer. Android Animated Bar Chart (invalidate())
I've perused http://developer.android.com/guide/topics/resources/drawable-resource.html -- but I don't have a "drawable" because it's being drawn in the View. I'm thinking of making the rest of the number line a background bitmap per Android View.getDrawingCache returns null, only null but I want three rectangles (for the minuend, subtrahend and difference).
I have thought of making a series of rectangle drawables and showing them frame-by-frame to show the growth.
I have looked at Animation at a specified rate using canvas / Ondraw but cannot discern just what code to wrap in that "if" statement, if in fact my problem is re-drawing...
I looked at using Paths -- and put the following code together. If direction matters, then it seems I should be able to slow things down and watch the path going in that direction, but it's instantaneous. I found I saw an example at http://www.curious-creature.org/2013/12/21/android-recipe-4-path-tracing/
if (minuendLength > 0) // start at 0 and go to the minuend length
{
path.addRect(interpX(0), yPosition(40), interpX(minuendLength), yPosition(43) , Path.Direction.CW);
// interpX lets me say what number on the number line it should align with;
//yPosition is percent of the way down the screen.
canvas.drawPath(path,minuendPaint);
// Seems same as drawRect -- instantaneous.
}
(The number line in the 'background' code is as follows, with different options for different sized integers entered:
if ( (minuendLength <10 && subtrahendLength <10 ) && (minuendLength >-10 && subtrahendLength >-10 ) )
{
this.setLineDimension(10); // default
super.onDraw(canvas);
canvas.drawLine(interpX(-this.getLineDimension()), yPosition(52 ),
interpX(this.getLineDimension()), yPosition(52), axisPaint);
int step = this.getLineDimension()/5; // so you're not writing *all* the numbers
// when they enter numbers and you make your own number line.
// paints the little hatch marks
for (int x = -this.getLineDimension(); x <= this.getLineDimension(); x+=step/2)
canvas.drawLine(interpX(x), yPosition(52), interpX(x), yPosition(53) , littleAxisPaint);
// draw the numbers on the hatch marks
textPaint.setTextAlign(Paint.Align.CENTER);
for (int x = -this.getLineDimension() + step; x < this.getLineDimension(); x += step)
{
canvas.drawText(Integer.toString(x), interpX(x), yPosition(56), textPaint);
}
}
Solution
I ended up doing this using Runnables.
animate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if ( ((addend1 > 0) && (addend2 < 0)) )
{
tempNum1 =addend1 ;
tempNum2 = addend2;
h.post(shrink1bigger);
}
else if (addend1 < 0 && addend2 > 0)
{
tempNum1 =addend1 ;
tempNum2 = addend2;
h.post(shrink2bigger);
}
}
});
private Runnable shrink2bigger = new Runnable(){
@Override
public void run() {
tempNum1+=1;
tempNum2-=1;
shrinkDraw();
Log.i("WatchAnimActivity", "tempNum1 is " + tempNum1);
h.postDelayed(shrink2bigger, 500);
checkTemp(shrink2bigger);
}};
private void shrinkDraw()
{
numLine.setFirstNum(tempNum1);
numLine.setNextNum(tempNum2);
numLine.invalidate();
}
public void checkTemp(Runnable shrink)
{
Log.i("WatchAnimActivity", "tempNum1 in CHeckTemp is " + tempNum1);
if (tempNum1 ==0 || tempNum2==0)
h.removeCallbacks(shrink);
}
Answered By - geonz
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