Develop Reference

changing ImageView properties several times

Does anybody knows how to change imageView properties within the same function?
I´ve got this piece of code:
double angle = MyTrigonometry.angleTwoVectors(sP, eP);
imgViewSelected.setPivotX(0);
imgViewSelected.setPivotY(0);
imgViewSelected.setRotation((int) angle);
switch (sCombination) {
case "C1":
if (mMeasure.getmDescription() == "VPI") {
if (mMeasure.getmCoordenate().x > mPartner.getmCoordenate().x) {
pX = imgViewSelected.getLayoutParams().width / 2;
pY = imgViewSelected.getLayoutParams().height / 2;
angle = 180;
doRotation(imgViewSelected, pX, pY, angle);
}
} else {
if (mMeasure.getmCoordenate().x > mPartner.getmCoordenate().x) {
} else {
pX = imgViewSelected.getLayoutParams().width / 2;
pY = imgViewSelected.getLayoutParams().height / 2;
angle += 180;
doRotation(imgViewSelected, pX, pY, angle);
}
}
break;
}
is it only listening to the last rotation instruction. how can I change thee properties so it listens to all the instructions within the same function?

It is not possible to set different pivot points during an Adapter getView() call, View will not refresh the view before the adapter is done with its child, therefore only after view is updated setPivot() will set its new properties.
Found a way around by just positioning to a desired point of the screen and rotating the ImageView only once per call.

Drawing stripes in a flag math formula

I have a rectangle with known size and position. (flag)
I have to fill this rectangle with 4 other rectangles. (stripes)
Each stripe must have 1/4 of the total width of the flag and his position is near the previous.
I have to draw this stripes with a random angle that goes from 0° to 90°.
0° = Vertical stripes (stripe width = flag width / 4)
90° = Horizontal stripes (stripe width = flag height / 4)
How can I calculate the width of each stripe for other angles?
int stripes = 4;
RectF rect = new RectF(0, 0, 100f, 75f);
float angle = new Random.nextInt(90);
float stripeSize;
if (angle == 0) {
stripeSize = rect.width() / stripes;
} else if (angle == 90) {
stripeSize = rect.height() / stripes;
} else {
stripeSize = ?
}
canvas.save();
canvas.rotate(angle, rect.centerX(), rect.centerY());
float offset = 0;
for (int i = 0; i < stripes; i++) {
if (angle == 0) {
reusableRect.set(offset, rect.top, offset + stripeSize, rect.bottom);
} else if (angle == 90) {
reusableRect.set(rect.left, offset, rect.right, offset + stripeSize);
} else {
reusableRect.set(?, ?, ?, ?);
}
canvas.drawRect(reusableRect, paint);
offset += stripeSize;
}
canvas.restore();

Let's pretend you have one stripe. Depending on the angle, the stripe width is going to be a value between the shorter dimension (the height in your case) and the longer dimension (the width in your case). The formula for the stripe width calculation should look something like this:
height + ((width - height) * ?)
where ? varies between 0 and 1 based on the angle of rotation. To me that sounds like the sine function might be a good candidate: sine(0) = 0 and sine(90) = 1. You can use Math.sin(), but be aware that the argument it takes is in radians, not degrees, so you need to use Math.toRadians() on your angle first. Then just divide by the number of stripes:
double radians = Math.toRadians(angle);
float stripeTotal = height + ((width - height) * Math.sin(radians));
float stripeWidth = stripeTotal / 4; // or however many stripes you have
If it's not perfect, you can adjust the formula. One last point, since these values only need to be calculated once, I would do that separately every time the angle changes (if it ever changes), not inside of onDraw().

How can I achieve this ListView animation?

What's up guys, I need a little help with this one. I'm trying to achieve a simple(but not really) folding animation on a listview that is being scrolled. Basically, I'm attempting to fold the listview's first visible child backward as if a sheet of paper is being folded downward along the X axis. This goes on on continuously as the user scrolls up and down the list. This is my first time playing around with Matrix animations and Android's camera from the graphics api, so I'm definitely off the mark here.
This is the effect I'm trying to achieve
And this is the effect I'm getting.
I want the animation to begin at the origin(0,0) but both the left and right side, animating from the top of the list item instead of the upper left corner. I'm not very familiar with matrix translations or animations so If anyone much more experience with these techniques than myself can shed some knowledge, it'll be greatly appreciated.
Basically I'm overriding the onDrawChild method of ListView, grabbing the child's bitmap from a drawing cache, and using a matrix to perform the animation. The lighting and camera implementation is code that I took from another sample app in order to get the animation to look as 3D as possible.
I tried playing around with the ListView animations library, but without much luck. I also tried to hack together a solution using code from the developer guides here that uses object animators to achieve a nice little card flip animation, but it started feeling a bit hacky and I couldn't quite get it the way I wanted.
Here's my current implementation. If anyone can shed some light or direction on this one, or maybe if anyone wrote an awesome library that I didn't come across on my searches, please feel free to share. Thanks
#Override
protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
View first = getChildAt(0);
if (child == first) {
if (child.getTop() < 0) {
Bitmap bitmap = getChildDrawingCache(child);
final int top = child.getTop();
child.getRight();
child.getBottom();
child.getLeft();
final int childCenterY = child.getHeight() / 2;
// final int childCenterX = child.getWidth() / 2;
final int parentCenterY = getHeight() / 2; // center point of
// child relative to list
final int absChildCenterY = child.getTop() + childCenterY;
// final int bottom = child.getBottom();
// distance of child center to the list center final int
int distanceY = parentCenterY - absChildCenterY;
final int r = getHeight() / 2;
if (mAnimate) {
prepareMatrix(mMatrix, distanceY, r);
mMatrix.preTranslate(0, top);
mMatrix.postTranslate(0, -top);
}
canvas.drawBitmap(bitmap, mMatrix, mPaint);
}
else {
super.drawChild(canvas, child, drawingTime);
}
} else {
super.drawChild(canvas, child, drawingTime);
}
return false;
}
private void prepareMatrix(final Matrix outMatrix, int distanceY, int r) { // clip
// the
// distance
final int d = Math.min(r, Math.abs(distanceY)); //
// circle formula
final float translateZ = (float) Math.sqrt((r * r) - (d * d));
double radians = Math.acos((float) d / r);
double degree = 45 - (180 / Math.PI) * radians;
// double degree = -180;
mCamera.save();
mCamera.translate(0, 0, r - translateZ);
mCamera.rotateX((float) degree);
if (distanceY < 0) {
degree = 360 - degree;
}
mCamera.rotateY((float) degree);
mCamera.getMatrix(outMatrix);
mCamera.restore();
// highlight elements in the middle
mPaint.setColorFilter(calculateLight((float) degree));
}
private Bitmap getChildDrawingCache(final View child) {
Bitmap bitmap = child.getDrawingCache();
if (bitmap == null) {
child.setDrawingCacheEnabled(true);
child.buildDrawingCache();
bitmap = child.getDrawingCache();
}
return bitmap;
}
private LightingColorFilter calculateLight(final float rotation) {
final double cosRotation = Math.cos(Math.PI * rotation / 180);
int intensity = AMBIENT_LIGHT + (int) (DIFFUSE_LIGHT * cosRotation);
int highlightIntensity = (int) (SPECULAR_LIGHT * Math.pow(cosRotation,
SHININESS));
if (intensity > MAX_INTENSITY) {
intensity = MAX_INTENSITY;
}
if (highlightIntensity > MAX_INTENSITY) {
highlightIntensity = MAX_INTENSITY;
}
final int light = Color.rgb(intensity, intensity, intensity);
final int highlight = Color.rgb(highlightIntensity, highlightIntensity,
highlightIntensity);
return new LightingColorFilter(light, highlight);
}

JazzyListView
has a lot of stuff that's similar to what you want if not exactly what you want. Take a look at how they're defined under jazzy effect and mix and match. I think reverse fly or maybe flip is close to what you want.

How do I zoom in a GridLayout view group centered at the focus point where multi-touch takes place?

For study purpose I am trying to write an Android app that can load pictures in any size (e.g. 8000x8000px). To do so I have to preprocess a picture into smaller pieces and load only the pieces that need to be displayed into the cells of a GridLayout view group.
I am able follow the instruction and make this view scroll (i.e. panning). Now I am trying to add zooming to this GridLayout view, but it doesn't seem to be as straightforward. Basically the view keeps shrink to (0, 0) instead of the focus point where multi-touch happens. The zooning behavior I need is something like Google Map. However my implementation does not really work. It always zoom to the upper left conner (0,0), because for zoom in/out, only the size scale is changed.
My code looks like
private final class onScaleListener implements OnScaleListener {
#Override
public void onScale(float scaleFactor, float focusX, float focusY)
{
for (int x = 0; x < GRID_DENSITY; x++)
{
Spec columnSpec = GridLayout.spec(x);
for (int y = 0; y < GRID_DENSITY; y++)
{
Spec rowSpec = GridLayout.spec(y);
LayoutParams l = new LayoutParams(rowSpec, columnSpec);
l.height = (int) (_gridHeight * scaleFactor);
l.width = (int) (_gridWidth * scaleFactor);
_gridLayout.updateViewLayout(_imageViewMatrix[x][y], l);
}
}
}
}
#Override
public boolean onScale(ScaleGestureDetector arg0)
{
_scaleFactor *= _scaleGestureDetector.getScaleFactor();
// Don't let the object get too small or too large.
_scaleFactor = Math.max(0.1f, Math.min(_scaleFactor, 5.0f));
_onScaleListener.onScale(_scaleFactor, _scaleGestureDetector.getFocusX(), _scaleGestureDetector.getFocusY());
return true;
}
Thanks!

Android touch direction northwest, northeast for UP direction

Sorry if the title sounds confusing - but this is what I am trying to do:
I have a large circular button on which I detect touch direction. I am able to find the UP/DOWN/LEFT/RIGHT from the dy and dx of the change in touch input coordinates like this:
if(Math.abs(dX) > Math.abs(dY)) {
if(dX>0) direction = 1; //left
else direction = 2; //right
} else {
if(dY>0) direction = 3; //up
else direction = 4; //down
}
But now I would like to handle cases where the button can be slightly rotated and thus the touch direction will also need to adjust for this. For example, if the button is rotated slightly to the left, then UP is now the finger moving northwest instead of just pure north. How do I handle this?

Use Math.atan2(dy, dx) to get the angle anticlockwise from the positive horizontal of the coordinate in radians
double pressed = Math.atan2(dY, dX);
subtract the rotation amount (anticlockwise rotation amount in radians) from this angle, putting the angle into the coordinate system of the button
pressed -= buttonRotation;
or if you have your angle in degrees, convert it to radians
pressed -= Math.toRadians(buttonRotation);
You can then calculate an easier direction number from this angle
int dir = (int)(Math.round(2.0d*pressed/Math.PI) % 4);
This gives right 0, up 1, left 2 and down 3. We need to correct the case where the angle is negative, as the modulo result will also be negative.
if (dir < 0) {
dir += 4;
}
Now supposing that these numbers are bad and you don't want to use them, you can just switch on the result to return whatever you like for each direction. Putting that all together:
/**
* #param dY
* The y difference between the touch position and the button
* #param dX
* The x difference between the touch position and the button
* #param buttonRotationDegrees
* The anticlockwise button rotation offset in degrees
* #return
* The direction number
* 1 = left, 2 = right, 3 = up, 4 = down, 0 = error
*/
public static int getAngle(int dY, int dX, double buttonRotationDegrees)
{
double pressed = Math.atan2(dY, dX);
pressed -= Math.toRadians(buttonRotationDegrees);
// right = 0, up = 1, left = 2, down = 3
int dir = (int)(Math.round(2.0d*pressed/Math.PI) % 4);
// Correct negative angles
if (dir < 0) {
dir += 4;
}
switch (dir) {
case 0:
return 2; // right
case 1:
return 3; // up
case 2:
return 1; // left;
case 3:
return 4; // down
}
return 0; // Something bad happened
}