Develop Reference

onTouch: detect ACTION_UP without blocking other touch events

I have a custom view which acts as a button. I am drawing all the canvas myself. Now I'm making an outline when ACTION_DOWN and remove it after ACTION_UP or ACTION_CANCEL.
#Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
Log.e("test", "ACTION_DOWN");
break;
case MotionEvent.ACTION_UP:
Log.e("test", "ACTION_UP");
break;
case MotionEvent.ACTION_CANCEL:
Log.e("test", "ACTION_CANCEL");
break;
}
return true;
}
This can work for me, except now it is blocking another gesture behind this view which is detecting ACTION_MOVE (scroll left).
If I return false, then it is working fine but now ACTION_UP is not called.
I want to call ACTION_UP if finger is lifted, but pass events down otherwise.

Have you tried overriding dispatchTouchEvent?
https://developer.android.com/reference/android/view/View.html#dispatchTouchEvent(android.view.MotionEvent)
UPDATE:
So touch events are a bit of a beast. The rundown of it is this...
They bubble up at first from your root container in your Activity. This is done by calling dispatchTouchEvent and then onInterceptTouchEvent assuming intercepting wasn't blocked by a child view.
If no view intercepts the event, it will bubble to the leaf node (such as a button) where onTouch is called. If the node doesn't handle it (returns true) its parent gets a chance and so on.
This means that you can use dispatchTouchEvent or onInterceptTouchEvent to spy on touch events without changing the behavior. Unless you're actually going to intercept the event I suggest using dispatchTouchEvent as it's guaranteed to run whereas intercepting may be blocked (example: DrawerLayout will intercept touch events near the edge in order to open the drawer).
So the final result is:
public class MyView extends Button {
#Override
public boolean dispatchTouchEvent(MotionEvent event) {
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
Log.e("test", "ACTION_DOWN");
break;
case MotionEvent.ACTION_UP:
Log.e("test", "ACTION_UP");
break;
case MotionEvent.ACTION_CANCEL:
Log.e("test", "ACTION_CANCEL");
break;
}
return super.dispatchTouchEvent(event);
}
}
UPDATE:
Sorry, so I've been under the impression for some reason (mostly my poor reading) that we were dealing with the parent. Here's what I would do...
Go ahead and implement onTouch and return true to consume all the events. This means that any touch events that start on your view will be eaten up. What we'll do then is translate the point to the parent's coordinate space and manually pass the touch event up, it'll look like this inside your custom view...
private boolean passingTouchEventToParent = true;
final private Rect hitRect = Rect();
#Override
public boolean onTouch(MotionEvent event) {
// Handle your custom logic here
final ViewParent viewParent = getParent();
if (passingTouchEventToParent &&
viewParent != null &&
viewParent instanceof View) {
// Gets this view's hit rectangle in the parent's space
getHitRect(hitRect);
event.offsetLocation((float) hitRect.left, (float) hitRect.top);
passingTouchEventToParent = viewParent.onTouchEvent(event);
}
if (event.getActionMasked() == MotionEvent.ACTION_UP) {
// Motion event finished, reset passingTouchEventToParent
passingTouchEventToParent = true;
}
return true;
}

How to handle click in the child Views, and touch in the parent ViewGroups?

In my layout I have a structure like that:
--RelativeLayout
|
--FrameLayout
|
--Button, EditText...
I want to handle touch events in the RelativeLayout and in the FrameLayout, so I set the onTouchListener in these two view groups. But only the touch in the RelativeLayout is captured.
To try solve this, I wrote my own CustomRelativeLayout, and override the onInterceptTouchEvent, now the click in the child ViewGroup (FrameLayout) is captured, but the click in the buttons and other views doesn't make any effect.
In my own custom layout, I have this:
public boolean onInterceptTouchEvent(MotionEvent ev) {
return true;
}

You need to override the onInterceptTouchEvent() for each child, otherwise it will remain an onTouchEvent for the parent.
Intercept Touch Events in a ViewGroup
#Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
/*
* This method JUST determines whether we want to intercept the motion.
* If we return true, onTouchEvent will be called and we do the actual
* scrolling there.
*/
...
// In general, we don't want to intercept touch events. They should be
// handled by the child view.
return false;
}
You need to return false to have the child handle it, otherwise you are returning it to the parent.

Your custom solution will capture touch events from anywhere in your relative layout since the overridden method is set to always throw true.
For your requirement I guess its better to use
the onClick method rather than using onTouch.
OnTouch method invokes different threads on every TouchEvent and I guess that is the cause of your problem
Rather than handling these events its better to try onClick method.

I was able to solve this problem with the following code:
Step 1: declare the EditText above the onCreate () method
public EditText etMyEdit;
Step 2: in the onResume () method the configuration ends:
etMyEdit = (EditText) findViewById (R.id.editText);
etMyEdit.setOnTouchListener(new View.OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
v.getParent().requestDisallowInterceptTouchEvent(true);
switch (event.getAction() & MotionEvent.ACTION_MASK){
case MotionEvent.ACTION_UP:
v.getParent().requestDisallowInterceptTouchEvent(false);
return false;
}
return false;
}
});
Hope it helps someone!

Handling onTouch events in android

So I have an autoScrolling scrollView in my class and I want to intercept the user onTouch event so that it stops the scrolling when they click on the scrollView. How will I implement this functionality? I know it has something to do with Overriding the onTouchEvent function, but when I Override this it doesn't work.
#Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_POINTER_1_DOWN:
stopAutoScrolling();
case MotionEvent.ACTION_POINTER_1_UP:
startAutoScrolling();
}
return true;
}

I believe when you return true, you are saying you have handled the onTouchEvent. If you want the normal touch behavior to occur do something like:
return super.onTouchEvent(ev);
That way you call the native code which in your case would perform the scrolling as normal.

OnTouchEvent not working on child views

I have a Linear Layout that has a Button and a TextView on it. I have written a OnTouchEvent for the activity. The code works fine if I touch on the screen, but if I touch the button the code does not work. What is the possible solution for this?
public boolean onTouchEvent(MotionEvent event) {
int eventaction=event.getAction();
switch(eventaction)
{
case MotionEvent.ACTION_MOVE:
reg.setText("hey");
break;
}
return true;
}

The problem is the order of operations for how Android handles touch events. Each touch event follows the pattern of (simplified example):
Activity.dispatchTouchEvent()
ViewGroup.dispatchTouchEvent()
View.dispatchTouchEvent()
View.onTouchEvent()
ViewGroup.onTouchEvent()
Activity.onTouchEvent()
But events only follow the chain until they are consumed (meaning somebody returns true from onTouchEvent() or a listener). In the case where you just touch somewhere on the screen, nobody is interested in the event, so it flows all the way down to your code. However, in the case of a button (or other clickable View) it consumes the touch event because it is interested in it, so the flow stops at Line 4.
If you want to monitor all touches that go into your Activity, you need to override dispatchTouchEvent() since that what always gets called first, onTouchEvent() for an Activity gets called last, and only if nobody else captured the event. Be careful to not consume events here, though, or the child views will never get them and your buttons won't be clickable.
public boolean dispatchTouchEvent(MotionEvent event) {
int eventaction=event.getAction();
switch(eventaction) {
case MotionEvent.ACTION_MOVE:
reg.setText("hey");
break;
default:
break;
}
return super.dispatchTouchEvent(event);
}
Another option would be to put your touch handling code into a custom ViewGroup (like LinearLayout) and use its onInterceptTouchEvent() method to allow the parent view to steal away and handle touch events when necessary. Be careful though, as this interaction is one that cannot be undone until a new touch event begins (once you steal one event, you steal them all).
HTH

Let me add one more comment to this excellent post by #Devunwired.
If you've also set an onTouchListener on your View, then its onTouch() method will be called AFTER the dispatch methods, but BEFORE any onTouchEvent() method, i.e. in between no.3 and no.4 on #Devunwired's answer.

Try to set the descendantFocusability attribute of your layout to blocksDescendants

Activity::onTouchEvent will be called only when non of the views in the Activity WIndow consumes/handles the event. If you touch the Button, the Button will consume the events, so the Activity won't be able to handle it.
Check out following articles for more about Android Touch Event handling pipeline.
http://pierrchen.blogspot.jp/2014/03/pipeline-of-android-touch-event-handling.html

you can also try onUserInteraction():
#Override
public void onUserInteraction(){
//your code here
super.onUserInteraction();
}
works well for me!

RecyclerView list_view = findViewById(R.id.list_view);
list_view.addOnItemTouchListener(new RecyclerView.SimpleOnItemTouchListener(){
#Override
public boolean onInterceptTouchEvent(#NonNull RecyclerView rv, #NonNull MotionEvent e) {
View child = rv.findChildViewUnder(e.getX(), e.getY());
Log.i("Hello", "World");
return false;
}
});

use public boolean dispatchTouchEvent(MotionEvent event) instead on onTouchEvent()

Let parent View assume MotionEvents if child returns false

I have a application that need event handling on a unusual way.
For my question, let me first explain a simple case that the current event handling system of Android don't fits for me.
Supposing that I have a FrameLayout (that I'll call ViewSwiper since now) that all Views added on it are MATCH_PARENT X MATCH_PARENT (that I'll call PageView), it's handles events by translating the actual View and replace it based on the direction of moving.
This component I already have done and work properly ( Using Animation to swipe views ).
But the problem is on that PageView I add on top of it, in case of ImageViews that return false on it's onTouchEvent, the ViewSwiper will handle the events and let another PageView enter the screen, but if I add a ScrollView on that, all the events will be consumed by the Scroll and the ViewSwiper will not have chance to replace the PageView.
So I figured out that returning false onTouchEvent of the ScrollView the parent can assume it's events, I wrote this sub-class of ScrollView to test it:
public class ScrollViewVertical extends ScrollView {
public ScrollViewVertical(Context context) {
super(context);
setOverScrollMode(OVER_SCROLL_ALWAYS);
setVerticalScrollBarEnabled(false);
}
public boolean onTouchEvent(MotionEvent evt) {
super.onTouchEvent(evt);
return false;
}
}
But returning false make any further events to get dispatched to the parent, but I need these events for VERTICAL scrolling, so I have the idea to return falses only if the user are moving HORIZONTAL, that's what my code looks like:
public class ScrollViewVertical extends ScrollView {
private MovementTracker moveTracker;
public ScrollViewVertical(Context context) {
super(context);
setOverScrollMode(OVER_SCROLL_ALWAYS);
setVerticalScrollBarEnabled(false);
moveTracker = new MovementTracker();
}
public boolean onTouchEvent(MotionEvent evt) {
if (moveTracker.track(evt))
if (moveTracker.getDirection() == Direction.HORIZONTAL)
return false;
return super.onTouchEvent(evt);
}
}
PS: MovementTracker will returns true on track() after some events and tell on which direction the user is moving.
But in that case, the ScrollView keep receiving events since it's returns true on the first events.
Any ideas on how can I handle the events on ViewSwiper when it's child returns false (even if some trues are returned).
PS: I can give more info about this if needed, and accept different solutions also.
Based on answers I tried the following:
#Override
public boolean dispatchTouchEvent(MotionEvent ev) {
onTouchEvent(ev);
return intercept;
}
public boolean onTouchEvent(MotionEvent evt) {
boolean x = super.onTouchEvent(evt);
if (moveTracker.track(evt)) {
intercept = moveTracker.getDirection() != Direction.VERTICAL;
if (!intercept)
getParent().requestDisallowInterceptTouchEvent(false);
}
return x;
}
Still nothing.

try this in onTouchEvent() of the scrollview
//if (evt.getAction() == MotionEvent.ACTION_MOVE) {
if (moveTracker.track(evt)){
if (moveTracker.getDirection() == Direction.VERTICAL){
//Or the direction you want the scrollview keep moving
getParent().requestDisallowInterceptTouchEvent(true);
}
}
return true;
Update
Please try the following to the custom Scrollview
#Override
public boolean dispatchTouchEvent(MotionEvent ev) {
super.dispatchTouchEvent(ev);
return false;
}
And nothing else
This way i assume the MotionEvent will perform on both views. And since they don't conflict (One is vertical the other one is Horizontal) this could work

Based on the answer from weakwire, I came to the following solution:
On ViewSwiper
#Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if(!super.dispatchTouchEvent(ev))
onTouchEvent(ev);
return true;
}
And on ScrollHorizontal I return false on dispatchTouchEvent when I don't need then anymore.