Develop Reference

Compose SwipeToDismiss confirmStateChange applies only >= threshold

I have a SwipeToDismiss instance to delete items with dismissThresholds 75%.
If user swipes row too fast without reaching 75% threshold the row being deleted. How to prevent that?
Here is code where I execute an action:
val dismissState = rememberDismissState(
confirmStateChange = {
if (it == DismissValue.DismissedToStart) {
viewModel.deleteCity(city)
}
true
}
)

I ran into the same issue and found a fix that works for me. My theory is, that when the swipe is very fast but doesn't go very far (doesn't reach the set fractional threshold), the layout just immediately resets. In this case (DismissToStart), meaning the view snaps back to the right screen edge, giving us the value of 1.0f for the threshold and thus triggering the confirmStateChange because the fraction is per definition higher than our threshold. The problem being that our threshold is measured from the right screen edge, and this fracion (in my theory) is measured from the left screen edge.
So my solution is to track the current fractional value, and inside confirmStateChange check if the current value is higher than the threshold, BUT NOT 1.0f. In a real world scenario, I think it's impossible to reach 1.0 with actual swiping the finger from right to left, so the solution seems safe to me.
val dismissThreshold = 0.25f
val currentFraction = remember { mutableStateOf(0f) }
val dismissState = rememberDismissState(
confirmStateChange = {
if (it == DismissValue.DismissedToStart) {
if (currentFraction.value >= dismissThreshold && currentFraction.value < 1.0f) {
onSwiped(item)
}
}
dismissOnSwipe
}
)
SwipeToDismiss(
state = dismissState,
modifier = Modifier.animateItemPlacement(),
directions = setOf(DismissDirection.EndToStart),
dismissThresholds = { direction ->
FractionalThreshold(dismissThreshold)
},
background = {
Box(...) {
currentFraction.value = dismissState.progress.fraction
...
}
}
dismissContent = {...}
)

I'm dealing with the same issue, it seems to be a feature, not a bug, but I did not find the way to disable it.
*If the user has dragged their finger across over 50% of the screen
width, the app should trigger the rest of the swipe back animation. If
it's less than that, the app should snap back to the full app view.
If the gesture is quick, ignore the 50% threshold rule and swipe back.*
https://developer.android.com/training/wearables/compose/swipe-to-dismiss

Android: setTranslationX glitches after view's anchor changed

Using setTranslationX, I'm trying to animate a view as I swipe it across the screen. Then after it passes a threshold-X, I assign the view a new RelativeLayout.RIGHT_OF.
I want it to stop animating (whether or not I continue swiping) at that point and basically lock to that new anchor.
This is where the problem is: suddenly the view jumps X position to the right of its new anchor.
I've tried, when it's >= threshold, to set setTranslationX(0), but then I see the view twitch/flash twice, once to its original 0, then to the new 0.
I would love to get rid of that double twitch/flash, but don't know how at this point.
#Override
public void onChildDraw(Canvas c ... float dX) {
threshold = anchorView.getRight();
if (animate) {
if (dX >= 0) {
translationX = Math.min(dX, threshold);
if (dX >= threshold) {
translationX = 0; // (A) if I do this, then mainView flashs twice: original 0, then new 0
setToRightOf(mainView, anchorView);
mainView.invalidate(); // has no effect
}
} else {
translationX = 0;
}
// if I don't do (A), then mainView will suddenly jump to 2*threshold
mainView.setTranslationX(translationX);
return;
}
super.onChildDraw(c ... dX);
}

Okay, instead of assigning RelativeLayout.RIGHT_OF during onDraw to set the threshold boundary, I took it out and assigned it when my touch left the screen.
But to insure I wouldn't swipe back behind that threshold while swiping, I had to add another case to check translationX and instead of previously trying to rely on the RelativeLayout anchor.
Now, I'm using setTag() and getTag() to help confirm the threshold during the swipe:
if (dX >= 0) {
if ((Object) past != tag)
translationX = Math.min(dX, threshold);
else
translationX = threshold;
if (dX >= threshold) {
if ((Object) past != tag) {
anchorView.setTag(past);
}
}
} else {
...
}
Plus a couple other places to make sure I reset anchorView's tag and the translationX when needed, then it's all good.
It works for now!
(doesn't directly solve the double flash/twitch issue, but a different approach to the same goal)
(any other recommendations besides using setTag()?)
P.S. In my earlier attempts, instead of invalidate(), I later tried mainView.requestLayout() with no success either, thinking requestLayout() also factors in position.

Detect everytime an image is zoomed in or zoomed out

I am using the photoview library of chris banes to handle all zoom events for my gallery.
I want to detect if the image has been zoomed in or has been zoomed out by the user without overriding all those double tap,and touch event methods.Is there an efficient way to achieve this?

To answer my own question:-
I found a much better way to implement zoom detection which works for pinch zoom as well as double tap(any zooming event, without having to override each method).Found it nowhere on the web to detect a zoom event.If there's a much more efficient way, please let me know :)
(Also I am using chris banes photoview library to handle the zooming.)
So to detect a zooming event,get the rectangle of the current photoview and when a zoom event happens , OnMatrixChangeListener gets called and there you compare the rectangles to see .
(Now simply using this listener to handle a zooming event won't work, because the listener gets called, everytime you change your image,(in case you're using it in a gallery) ,it also gets called when the orientation of the screen is changed and also when simple no-zoom intending touches are made to the screen.)
Also, when the screen orientation changes,sometimes the photoview returns a 0 rectangle,so you have to check for that as well,here's my code:-
if (savedInstanceState.getBoolean(Constants.ZOOM)) {
photoViewAttacher = new PhotoViewAttacher(backgroundImage);
mWindowRect = new RectF(photoViewAttacher.getDisplayRect());
photoViewAttacher.setOnMatrixChangeListener(new PhotoViewAttacher.OnMatrixChangedListener() {
#Override
public void onMatrixChanged(RectF rect) {
//need to differentiate between screen orientation
if (mWindowRect.left == 0 && mWindowRect.top == 0 && mWindowRect.right == 0 && mWindowRect.bottom == 0) {
mWindowRect = new RectF(rect);
}
if (Math.abs(mWindowRect.left - rect.left) < 2 && Math.abs(mWindowRect.top - rect.top) < 2 && Math.abs(mWindowRect.right - rect.right) < 2 && Math.abs(mWindowRect.bottom - rect.bottom) < 2) {
viewPager.setLocked(false);
thumbnailsContainer.startAnimation(appear);
thumbnailsContainer.setClickable(true);
} else {
viewPager.setLocked(true);
thumbnailsContainer.startAnimation(disappear);
thumbnailsContainer.setClickable(false);
}
Log.i("ZOOM", "default rect: " + mWindowRect);
Log.i("ZOOM", "zoom rect: " + rect);
}
});
}

I can see a bunch of listeners, that can be notified, when a certain event on a PhotoView occurrs.
Refer to:
IPhotoView
Here I can see the listeners:
void setOnDoubleTapListener(GestureDetector.OnDoubleTapListener newOnDoubleTapListener);
void setOnScaleChangeListener(PhotoViewAttacher.OnScaleChangeListener onScaleChangeListener);
void setOnSingleFlingListener(PhotoViewAttacher.OnSingleFlingListener onSingleFlingListener);
Hope this helps.

Android Cover Flow

I'm using a cover flow in my Android App with this tutorial link http://www.inter-fuser.com/2010/01/android-coverflow-widget.html and I already use it well. But my problem is when the Android version is 4.1 the cover flow semms not working well, because the images is not being centered or aligning well after choosing an image. But if the Android version is below 4.0 it works well like in the video of the link.
Did anyone have a thoughts regards this issue?

UPDATE
A fix for this issue is to make the following change to getChildStaticTransformation(View child, Transformation t)
protected boolean getChildStaticTransformation(View child, Transformation t) {
child.invalidate(); // add this line
final int childCenter = getCenterOfView(child);
final int childWidth = child.getWidth();
int rotationAngle = 0;
t.clear();
t.setTransformationType(Transformation.TYPE_MATRIX);
if (childCenter == mCoveflowCenter) {
transformImageBitmap((ImageView) child, t, 0);
} else {
rotationAngle = (int) (((float) (mCoveflowCenter - childCenter) / childWidth) * mMaxRotationAngle);
if (Math.abs(rotationAngle) > mMaxRotationAngle) {
rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle
: mMaxRotationAngle;
}
transformImageBitmap((ImageView) child, t, rotationAngle);
}
return true;
}
--
I had this same problem recently. This has to do with the Gallery having been deprecated. As an alternative, I implemented something similar to this using a HorizontalScrollView and centering using .scrollTo(). The problem with this solution is that scrollTo() aligns with the left side of the View and so you have to compute the middle y0urself. If the layout fills the screen you're going to have to apply padding to the left and right side of the view to force the selected element to the center.
A word of caution. Horizontal scroll views don't have animatible scrolling so it's going to be a snap-to behavior. You can get around this by scrolling using a timer but it's not a terribly elegant solution.

android: move to touch location after release with libgdx/universal-tween-engine

I'm learning to use libgdx with universal-tween-engine and haven't been able to figure out how to touch (or click on the desktop app) a point on the screen and have a texture move all the way to the touched location without keeping the touch or click active until the end-point is reached.
When the touch event is initiated, the animation begins and the graphic moves towards the location. The graphic will follow the finger/mouse-pointer if a touch and drag is initiated. If I touch a point, the graphic will move towards the point until the touch is released. Then it stops where it was when touch is released.
I'm looking to touch-and-release and have that graphic move to the touched point, and am probably not understanding something about the tween engine implementation. I've pasted the tweening code below.
public void render() {
camera.update();
batch.setProjectionMatrix(camera.combined);
batch.begin();
batch.draw(texture.getTexture(), texture.getBoundingBox().x, texture.getBoundingBox().y);
batch.end();
Tween.registerAccessor(Plane.class, new TextureAccessor());
TweenManager planeManager = new TweenManager();
float newX = 0;
float newY = 0;
boolean animateOn = false;
if(Gdx.input.isTouched()) {
newX = Gdx.input.getX();
newY = Gdx.input.getY();
animateOn = true;
}
if (animateOn == true && (texture.getX() != newX || texture.getY() != newY)) {
Tween.to(texture, TextureAccessor.POSITION_XY, 10)
.target(newX, newY)
.ease(TweenEquations.easeNone)
.start(planeManager);
planeManager.update(1);
if (texture.getX() == newX && texture.getY() == newY) {
animateOn = false;
}
}
}
Originally, I had the tweening code inside the conditional for isTouched() and didn't use the newX, newY or animateOn variables. I thought using isTouched() to only set the new coordinates and animation state would then make the loop trigger the tween. The older code looked like this:
if(Gdx.input.isTouched()) {
newX = Gdx.input.getX();
newY = Gdx.input.getY();
Tween.to(texture, TextureAccessor.POSITION_XY, 10)
.target(newX, newY)
.ease(TweenEquations.easeNone)
.start(planeManager);
planeManager.update(1);
}
I've also tried using justTouched(), but the graphic would only move very slightly toward the touched point.
I've been struggling with this for a few hours, I'd really appreciate it if anyone could point me in the right direction.
Thanks.

Tween.registerAccessor(Plane.class, new TextureAccessor());
TweenManager planeManager = new TweenManager();
These two lines should go in the create() method, not the render() one! Here, you're instantiating a new manager on every frame, you only need one manager, that's all, not an army of them!
Also, you need to update the manager on every frame, not just when animateOn is true, else you'll need to keep your finger pressed...
The correct code is as follows, learn from it, you'll get a better understanding of how the Tween Engine works :)
// Only one manager is needed, like a Spritebatch
private TweenManager planeManager;
public void create() {
Tween.registerAccessor(Plane.class, new TextureAccessor());
planeManager = new TweenManager();
}
public void render() {
// The manager needs to be updated on every frame.
planeManager.update(Gdx.graphics.getDeltaTime());
camera.update();
batch.setProjectionMatrix(camera.combined);
batch.begin();
batch.draw(texture.getTexture(), texture.getBoundingBox().x, texture.getBoundingBox().y);
batch.end();
// When the user touches the screen, we start an animation.
// The animation is managed by the TweenManager, so there is
// no need to use an "animateOn" boolean.
if (Gdx.input.justTouched()) {
// Bonus: if there is already an animation running,
// we kill it to prevent conflicts with the new animation.
planeManager.killTarget(texture);
// Fire the animation! :D
Tween.to(texture, TextureAccessor.POSITION_XY, 10)
.target(Gdx.input.getX(), Gdx.input.getY())
.ease(TweenEquations.easeNone)
.start(planeManager);
}
}

I was trying to implement this behavior in the wrong way. Instead of using isTouched or justTouched(), I needed to use touchDown() from GestureListener.
I created a class that implemented GestureDetector (call it touchListener())inside of my main class (the one that implements ApplicationLisetener )in the main libgdx project and put the x and y capturing code inside of toucDown (I noticed tap() was also being triggered). I moved the tween functions (the actual tweening, the call to registerAccessor(), and the creation of the new tween manager) into the update() method of touchListener().
I added a call to touchListener()'s update function inside the render() loop of the main libgdx class.
I doubt I did this is the best way, but I hope it's helpful to someone else in the future.