Develop Reference

Android Screen Touch Action

I am working on an android project where I need to know if user is Touch Down the screen or Touch Up the screen and I frequently need this. How can I do that?
I used on Touch Event in switch case for action Up and action down but that works for only one time. I also tried the bellow code but it gives me the the value of var(int variable) for first touch only.
my code:
int var=-1;
#Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction();
if(action==MotionEvent.ACTION_DOWN)var=1;
if(action==MotionEvent.ACTION_UP)var=0;
if(action==MotionEvent.ACTION_MOVE)var=1;
return super.onTouchEvent(event);
}
I need the value of var again and again.

Since onTouchEvent is the last point of touch event traversal, it might not be called if one of the children has consumed touch event already (of if you returned false for MotionEvent.ACTION_DOWN event indicating that you are not interested in this gesture at all).
For your problem I would rather use dispatchTouchEvent() instead of onTouchEvent() and track touches there.
For more information I highly recommend getting yourself familiar with talk from Dave Smith about Android Touch System

How do I allow clicks to bubble up in onTouchEvent

I have a ViewPager that can contain two types of views. One of the view types has buttons, one of the view types does not. The buttonless view type does have to trap touches in onTouchEvent in order to pan and zoom an image. But I want to let clicks bubble to the ViewPager (that has a clickListener attached to it)
I have to return true in the view's onTouchEvent ACTION_DOWN or else it won't see future events.
I can't use onInterceptTouchEvent() in the ViewPager to capture clicks because one of the views does have buttons and those buttons need their clicks
So how can my view trap swipes, and let clicks bubble up?

proper way is probably to intercept only the events you want to intercept, by returning true in onInterceptTouchEvent only when needed.
but if you want to go with the dark side, there's a dirty alternative, that probably will lure you and you'll probably regret later: intercept all the events, then if needed pass them down.
e.g. have inside your views something like
public boolean canInterceptTouch(MotionEvent ev) {
// return true if you are interested in this touch event, e.g. it falls into
// a clickable area
}
and something that handle the touch event like
public void interceptTouch(MotionEvent ev) {
// here you react to the event
}
inside your viewpager you have
#Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return true;
}
thien the view pager will handle the events in a dirty way like this:
#Override
public boolean onTouchEvent(MotionEvent ev) {
if (yourView.canInterceptTouch(ev))) {
yourView.interceptTouch(ev);
return true;
} else {
return doSomethingElse();
}
}
note: although I've done something similar, with decent result, I do NOT reccomend it as a solution unless you've very simple logic in the handling of the motion events, otherwise it becomes a mess. Your future self will be happier if you spend some time now to do it properly.
EDIT: code has not been tested, just to give you an idea of what you need. Sorry for any typo.

Try using this ViewGroup.onInterceptTouchEvent(MotionEvent).This allows a ViewGroup to watch events as they are dispatched to child Views`

OnClick and onTouch

I have a activity where I have two imagesViews.
This to imagesViews has onClickListener, because I need to know which imageView was clicked. After when I click choosen picture I get result which picture was clicked.
I Know need the same result but I need to know where exacly I click on this image. I need precise coordinates where this imageView was clicked. I know that in onTouch method I have functions like I need.
Can I change onClick method on onTouch? Or in onClick can get precise coordinates?

There is no need for you to use the onClick event, since you can easily capture the click using the onTouch callback. A click is a sequence of one ACTION_DOWN action, several ACTION_MOVE actions and one ACTION_UP action. These can be acquired using the event.getAction() method. If you get an ACTION_DOWN event and then an ACTION_UP event - it means that the user has just clicked your View. You can also measure time spent between these events to be sure that it was a simple click, not a long one. And, of course, you can use the event.getX() and event.getY() methods to get the exact touch point. Hope this helps.

you can use onTouch() method for getting touch coordinates
touchView.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
System.out.println("Touch coordinates : " +
String.valueOf(event.getX()) + "x" + String.valueOf(event.getY()));
return true;
}
});

onclick cannot do this. You can get them only from an onTouchListener.
a question with this info

How can I get all of touch events in my activity even in drag mode?

I want to get x and y position of every touch point in my activity even in drag mode. When I implement onTouchEvent method of my activity, it does not get all of touch events. How can I do that?
Thanks in advance,
public class MyActivity extends Activity {
#Override
public boolean onTouchEvent(MotionEvent event) {
// my Code
return super.onTouchEvent(event);
}
}
This onTouchEvent method just rises when you touch around the activity.

Do you have any other View which handle touch events?
The documentation says:
Called when a touch screen event was not handled by any of the views
under it. This is most useful to process touch events that happen
outside of your window bounds, where there is no view to receive it.
So when you say you don't get any events when you are in drag mode, this implies that you're dragging some thing. So you already handling the events somewhere else and therefore the onTouchEvent() method won't be notified.
You can try to return false in the other TouchListener's onTouch() method so the event will bubble up further more.

Touch events leaking up the hierarchy despite "return true"

I have a project using a ViewPager which works correctly:
I can page from view to view by flicking left and right.
On one page of the ViewPager, I have a custom view and I am trying to add below it another view (LinearLayout) that is touch sensitive and that will not "page" the ViewPager. Like this:
<LinearLayout >
<myView />
<LinearLayout> // The touch sensitive region
</LinearLayout>
</LinearLayout>
After my view has been inflated and added to the ViewPager, I call setOnTouchListener() to attach a listener to the internal LinearLayout. The listener returns "true".
Unfortunateley when I move horizontally in that view, I move to another page.
The events I get are:
ACTION_DOWN, ACTION_MOVE (n times) and finally ACTION_CANCEL. Although I stayed within the view.
It seems that the event has gone up the view hierarchy and processed by the ViewPager.
Is there a logical explanation to this behaviour ?

I have found a workaround by intercepting events at the Activity level, overriding dispatchTouchEvent().
In there, I call super.dispatchTouchEvent() for processing all events unless the user is touching my touch sensitive view. I test if the user is on the correct page and at the right location. In that case I process the event myself.
#Override
public boolean dispatchTouchEvent (MotionEvent ev) {
if ( pager.getCurrentPosition()!=0 ) { // Test ViewPager page
super.dispatchTouchEvent(ev);
}
else {
int[] xy = new int[2];
findViewById(R.id.myTouchControl).getLocationOnScreen(xy);
int topOfView = xy[1];
if ( ev.getY() > topOfView ) {
// Custom processing
...
} else {
// Standard processing
super.dispatchTouchEvent(ev);
}
}
return false;
}

No need to override dispatchTouchEvent(). Instead, in the ACTION_DOWN event, use View.getParent().requestDisallowInterceptTouchEvent(true).
requestDisallowInterceptTouchEvent(true) requests the parent view (ViewPager) not to intercept this specific touch event. It will clear this flag after the MotionEvent ends, so you must call it in ACTION_DOWN.