I want to know how to move a view from top to bottom continuously without animation. I am asking this because I want to get the position of the view at every step so that I can check that if there is any collision between that view and any other view.
With animation you can move (not exactly move) a view from one position to another position (Animator class), but animation produces an illusion to the user that it is moving but it's position is fixed all the time. So this can't be done using animation?
Second approach is incrementing position of view. I applied this method in onCreate(). If I used it without Thread.sleep(50) then the activity doesn't show the view, if I applied it with Thread.sleep(50) then activity doesn't start for some period.
Property animation (subclasses of Animator class) actually move the view, as they update the actual property of the view. It is the view animations (subclasses of Animation class) that don't move the actual view and instead just where it appears to the user.
Source:http://developer.android.com/guide/topics/graphics/prop-animation.html
Quote: With the property animation system, these constraints are completely removed, and you can animate any property of any object (Views and non-Views) and the object itself is actually modified.
You also shouldn't start moving things around in the onCreate method as things are still initializing (onwindowfocuschanged is recommened). Also if you call thread.sleep, you are going the sleep the main UI thread, hence freezing the application for a time.
Solved the problem using ValueAnimator :-
CodeSnippet :-
va=ValueAnimator.ofFloat(0.0f,size.y);
va.setDuration(5000);
va.setRepeatCount(va.INFINITE);
va.setRepeatMode(va.REVERSE);
va.start();
va.addUpdateListener(new AnimatorUpdateListener() {
#Override
public void onAnimationUpdate(ValueAnimator animation) {
// TODO Auto-generated method stub
bullet[0].setTranslationY((Float) va.getAnimatedValue());
Rect R11=new Rect(bullet[0].getLeft(),bullet[0].getTop()+(int)bullet[0].getTranslationY(),bullet[0].getRight(),bullet[0].getBottom()+(int)bullet[0].getTranslationY());
Rect R21=new Rect(ball.getLeft(), ball.getTop(), ball.getRight(), ball.getBottom());
if(R11.intersect(R21))
va.cancel();
}
});
Related
I am using 'com.android.support.constraint:constraint-layout:2.0.0-alpha5'.
I have a fragment using MotionLayout inside an activity that also carries a BottomNavigationView inside a CoordinatorLayout with a custom behaviour allowing to show and hide when the content is scrolled.
With all fragments, where there is no MotionLayout, this behaviour works perfectly. Only with the MotionLayout, which has a NestedScrollView as a child, and makes use of an onSwipe transition, this swipe seems to be consumed, and does not arrive at the activity's coordinator layout.
Is this a current limitation of how MotionLayout works, and is it possible to extend it to support my use case?
I want to add a new View to a Layout dynamically by layout.addView(view) method. The new View is not supposed to be visible, but I want it's Display List to be created so it doesn't have to redraw (call onDraw method) itself when I decide to show it (by animation, for example fade in).
I run this code:
customView = new CustomView(this.getContext());
customView .setAlpha(0.0f);
this.addView(customView ); // 'this' is RelativeLayout instance in this case
onDraw method gets called for customView and everything is fine. However, when I change anything in my layout (push a button, scroll, anything that invalidates layout), the onDraw method for my customView is called second time. After that, it isn't called any more if I don't invalidate my customView (correct behaviour).
I don't know why Android behaves this way. I want it to create customView, call onDraw, create a Display List for it, and not call onDraw any more until I invalidate my view. To sum up, onDraw is supposed to be called once.
And it has nothing to do with initial invisibility of customView, if alpha is set to 0.5f, behaviour is the same.
My question is, how to make Android call onDraw only once?
And if Android really has to call onDraw twice, then what should I do to enforce it to do it in some code right after this.addView(view); without setting up any timers because THAT would be totally ugly.
The behavior you are describing is ok and is a part of the android framework for view object -
Drawing
Drawing is handled by walking the tree and rendering each view that
intersects the invalid region. Because the tree is traversed in-order,
this means that parents will draw before (i.e., behind) their
children, with siblings drawn in the order they appear in the tree. If
you set a background drawable for a View, then the View will draw it
for you before calling back to its onDraw() method. Note that the
framework will not draw views that are not in the invalid region. To
force a view to draw, call invalidate()
(Taken from the official google android API docs).
Meaning your custom view is contained by the same view that contains the button\scrollbar etc. If you don't want it to be rendered everytime the onDraw method is called for the subtree your view resides in you can set the view's boolean flag to false - use setWillNotDraw() to do that. (you should place it on the activity's onCreate in order to render the view set this flag to false (which is also the default) and use invalidate() whenever you want to render the view).You can read the official google docs for further information.
In Swing you have paint or update(Graphics g) method for each UI component which executes every frame. You can put your drawing logic in the overrided method and draw whatever you want. What is the paint method for JavaFX2 UI?
What I want to do is my UI receives control information from a socket server (another thread). Whenever a control information is received, I should update the UI.
There are two problems:
1. The control information is received from a different thread, it can not access the rendering thread directly.
2. How to update the UI constantly?
For Q1, I have a solution if I know where the update function is (Q2).
I can declare a List object, and insert the new control command received from the socket into the list. In the rendering loop, I can just observe the List object, retrieve the unprocessed command, and delete the already processed command.
However, where can I find such a rendering loop function? I guess maybe I can also do it with javax.concurrent.Task, but I don't find a way to do it.
I think i find the method, I use the following method and it can work. I don't know if there is a better solution
final Duration oneFrameAmt = Duration.millis(1000/10);
final KeyFrame oneFrame = new KeyFrame(oneFrameAmt,new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent actionEvent) {
//put UI update here
}
});
TimelineBuilder.create().cycleCount(Animation.INDEFINITE)
.keyFrames(oneFrame)
.build()
.play();
I am trying to implement a similar effect like the iPhone-alike sliding header in the iPhone contact app (the sliding header that group the contacts by it's starting letter).
This is the screen of my app, and what I want to achieve is the following:
I have a 'guide header' and three 'tabs' for sorting the list. When the user scrolls the list up, I want everything to scroll up (guide header, tabs, list). However, when the tabs reach the top of the screen (and the guide header will just be gone off the screen), I want the tabs to stop and stay there (remain as "sticky header"), and only the list items scroll as in any regular list view.
I have a view group (guide header) above a list view.
First of all, I want to have the guide header adjust it's position depending on the scrolling position of the list view.
First approach:
My idea was to set an onScrollListener to the list view and change the top margin of the guide header to whatever the scroll position of the first item in the list view is (which would be a negative value).
The logic is correct, but the problem I'm facing is that the guide header view doesn't get redrawn fast enough while I'm scrolling in the list view. The guide header view only updates (to my changed top margin value) when the list view fling comes to an end. Even slow scrolling doesn't work. Invalidating (invalidate()) the guide header view or it's parent also doesn't help, since it would just put an invalidation request to the queue, but the invalidation and redrawing doesn't happen immediately, but only when the UI thread becomes idle, which doesn't seem to happen while the user still has his fingers on the scroll list view. Seems that flinging the list view blocks the whole UI thread or keeps it busy for itself.
So the main problem is: changing the margin of the guide header view doesn't become visible immediately while the user is scrolling the list view. The code I'm using it this:
#Override
public void onScroll(final AbsListView view, final int firstVisibleItem,
final int visibleItemCount, final int totalItemCount) {
// Get the first list item and check it's scroll position. This will be the value (top), that we also
// use the scroll the header parallel.
View v = mainList.getChildAt(0);
final int top = (v==null)?0:v.getTop();
// This logs the current scroll position of the first list item element/view group.
Log.d("onScroll", "onScroll: " + top);
// Here we finally change the margin (setting a negative margin) to the header element.
((LinearLayout.LayoutParams)(findViewById(R.id.header_container).getLayoutParams())).setMargins(0, top, 0, 0);
// was just a test: invalidating the outer container/view group, doesn't help
// findViewById(R.id.ll_container).invalidate();
}
I do see the "onScroll:" log output I inserted in the code above in the logcat, but the following adjustment of the top margin just doesn't become visible.
My second approach: is to use a scrollview for the guide header + tabs and work with those. Scrolling the guide header (which is then a scroll view) from code with scrollView.scrollTo(0,Math.abs(Math.abs(top)) from the onScroll method of the list view does work and almost immediately shows on the screen, however, it's not very accurate/stable when the user flings the list view very fast - meaning it jumps in intervals and doesn't look smooth; it's only accurate/stable when scrolling slowly.
My question is now: is there any best practice to accomplish such a sliding header effect, and more concrete: is there a way to force the guide header view to be redrawn while the user is still scrolling the list view (in my first mentioned approach).
For this you should use some tricks (afaik there is no ready-to-use implementation of such a feature).
For instance, you could detect gestures on your view, and
if the current gesture matches a
scroll down, and the first list item
is visible, animate-shrink the
header's size to 0, the tab view's
size to match_parent. Start scrolling
the list only when the header is not
present anymore.
if the current gesture matches scroll
up, and the first is already visible,
animate-expand the header to it's
original size.
So using Animation on the header view might be your solution.
Update
An other workaround would be to extend your List (the value array of your adapter):
Inster a new (dummy) item at the top for the header representation, and modify your ListAdapter's getView method:
#Override
public View getView(int position, View convertView, ViewGroup parent)
{
if (position == 0)
{
convertView = inflater.inflate(R.layout.sliding_header, parent,
false);
return convertView;
}
//TODO: your original method body comes here
}
where the xml referenced by R.layout.sliding_header should contain the header layout of your list.
A custom OnScrollListener implementation applied to the ListView would make unnoticeable that the header actually is an item of the list, since it would hide the scrollbar.
You should add this listener to your listView in the activity's onCreate method:
listView.setOnScrollListener(new MyScrollListener());
where MyScrollListener is:
/**
* Custom OnScrollListener
*/
private final class MyScrollListener implements OnScrollListener
{
#Override
public void onScrollStateChanged(AbsListView view, int scrollState)
{}
#Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount)
{
if (view.getFirstVisiblePosition() == 0)
view.setVerticalScrollBarEnabled(false);
else if (!view.isVerticalScrollBarEnabled())
view.setVerticalScrollBarEnabled(true);
}
}
I think you can also try and use my ExpandAnimation for that.
http://udinic.wordpress.com/2011/09/03/expanding-listview-items/
Just pass the animation class that "guide header" view, and let the animation do the work for you, no scrolling is needed in that case, and it's smooth.
I am implementing a custom surface view, which is called from other activity by setContentView(new SurfaceViewClass(Context)). This class is extending the surfaceView. In the Draw() method which I have added in the surface view, I am displaying an animation that gets triggered, say, every 200 milliseconds, which means that the surfaceview thread gets triggered every 200 msecs.
My requirement is I want to add a button at the bottom of the animation that can respond to events when user has pressed it. How it is possible to do this?
Thank you!
The idea is to have surfaceView(i.e. your graphics) inside a FrameLayout. See the xml layout in the following link.
In the following questions, i have posted the code for the same.
Android:Crash: Binary XML file line : Error inflating class (using SurfaceView)
Let us know if it works!