I have a problem I am struggling with a while now.
I have a Layout with a Button and a container in it.
<FrameLayout ... >
<Button
android:id="#+id/button"
...
/>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/overlayContainer"/>
</FrameLayout>
My goal is that as I long-press the button, I attach a custom view MyCustomViewto the container and keep the finger pressed.
All the following (ACTION_MOVE, ACTION_UP) events should then ideally be dispatched to and evaluated by MyCustomView.
MyCustomView works like a circular flyout menu: it overlays, dims the background, and shows some options. You then slide your pressed finger to the option, lift it up, and it triggers a result.
mButton.setOnLongClickListener(new View.OnLongClickListener() {
#Override
public boolean onLongClick(View v) {
// attach custom view to overlayContainer
// simplified code for demonstration
overlayContainer.addView(new MyCustomView());
return true;
}
});
Right now I don't see any option to "steal" the ACTION_DOWN-Event (which is required to start the event flow to a view) from the Button as I'm above it.
Nor does it work to manually generate and dispatch a ACTION_DOWN-Event in MyCustomView as I attach it.
While researching I found this post here, it basically is the same requirement, but for iOS (also does not provide an elegant solution, other that an click capturing overlay view) ): How to preserve touch event after new view is added by long press
Note that I want to avoid some kind of global overlay over the main view, I would like the solution to be as pluggable and portable as possible.
Thanks for any suggestions.
To answer my own question after the hint in the comments:
I solved it using a bare stripped version of TouchDelegate (had to extend it, since it unfortunetaly is no interface - setTouchDelegate only accepts TouchDelegate (sub)classes. Not 100% clean, but works great.
public class CustomTouchDelegate extends TouchDelegate {
private View mDelegateView;
public CustomTouchDelegate(View delegateView) {
super(new Rect(), delegateView);
mDelegateView = delegateView;
}
public boolean onTouchEvent(MotionEvent event) {
return mDelegateView.dispatchTouchEvent(event);
}
}
Then in my onLongClick method:
mButton.setOnLongClickListener(new View.OnLongClickListener() {
#Override
public boolean onLongClick(View v) {
// attach custom view to overlayContainer, simplified for demonstration
MyCustomView myMenuView = new MyCustomView()
mButton.setTouchDelegate(new CustomTouchDelegate(myMenuView));
// What's left out here is to mButton.setTouchDelegate = null,
// as soon as the temporary Overlay View is removed
overlayContainer.addView(myMenuView);
return true;
}
});
This way, all my ACTION_MOVE events from the Button are delegated to MyCustomView (and may or may not need some translation of the coordinates) - et voilà.
Thanks to pskink for the hint.
Related
When I try to add onTouchListner() to a button, it gets me the
Button has setOnTouchListener called on it but does not override
performClick
warning. Does anyone know how to fix it?
btnleftclick.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View view, MotionEvent motionEvent) {
return false;
}
});
Error:
Custom view has setOnTouchListener called on it but does not override
performClick If a View that overrides onTouchEvent or uses an
OnTouchListener does not also implement performClick and call it when
clicks are detected, the View may not handle accessibility actions
properly. Logic handling the click actions should ideally be placed in
View#performClick as some accessibility services invoke performClick
when a click action should occur.
This warning comes up because Android wants to remind you to think about the blind or visually impaired people who may be using your app. I suggest you watch this video for a quick overview about what that is like.
The standard UI views (like Button, TextView, etc.) are all set up to provide blind users with appropriate feedback through Accessibility services. When you try to handle touch events yourself, you are in danger of forgetting to provide that feedback. This is what the warning is for.
Option 1: Create a custom view
Handling touch events is normally something that is done in a custom view. Don't dismiss this option too quickly. It's not really that difficult. Here is a full example of a TextView that is overridden to handle touch events:
public class CustomTextView extends AppCompatTextView {
public CustomTextView(Context context) {
super(context);
}
public CustomTextView(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
super.onTouchEvent(event);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
return true;
case MotionEvent.ACTION_UP:
performClick();
return true;
}
return false;
}
// Because we call this from onTouchEvent, this code will be executed for both
// normal touch events and for when the system calls this using Accessibility
#Override
public boolean performClick() {
super.performClick();
doSomething();
return true;
}
private void doSomething() {
Toast.makeText(getContext(), "did something", Toast.LENGTH_SHORT).show();
}
}
Then you would just use it like this:
<com.example.myapp.CustomTextView
android:id="#+id/textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="20dp"
android:text="Click me to do something"/>
See my other answer for more details about making a custom view.
Option 2: Silencing the warning
Other times it might be better to just silence the warning. For example, I'm not sure what it is you want to do with a Button that you need touch events for. If you were to make a custom button and called performClick() in onTouchEvent like I did above for the custom TextView, then it would get called twice every time because Button already calls performClick().
Here are a couple reasons you might want to just silence the warning:
The work you are performing with your touch event is only visual. It doesn't affect the actual working of your app.
You are cold-hearted and don't care about making the world a better place for blind people.
You are too lazy to copy and paste the code I gave you in Option 1 above.
Add the following line to the beginning of the method to suppress the warning:
#SuppressLint("ClickableViewAccessibility")
For example:
#SuppressLint("ClickableViewAccessibility")
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button myButton = findViewById(R.id.my_button);
myButton.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View view, MotionEvent motionEvent) {
return false;
}
});
}
Solution:
Create a class that extends Button or whatever view you are using and override performClick()
class TouchableButton extends Button {
#Override
public boolean performClick() {
// do what you want
return true;
}
}
Now use this TouchableButton in xml and/or code and the warning will be gone!
Have you tried adding :
view.performClick()
or adding suppresslint annotation :
#SuppressLint("ClickableViewAccessibility")
?
Custom view controls may require non-standard touch event behavior.
For example, a custom control may use the onTouchEvent(MotionEvent)
listener method to detect the ACTION_DOWN and ACTION_UP events and
trigger a special click event. In order to maintain compatibility with
accessibility services, the code that handles this custom click event
must do the following:
Generate an appropriate AccessibilityEvent for the interpreted click
action. Enable accessibility services to perform the custom click
action for users who are not able to use a touch screen. To handle
these requirements in an efficient way, your code should override the
performClick() method, which must call the super implementation of
this method and then execute whatever actions are required by the
click event. When the custom click action is detected, that code
should then call your performClick() method.
https://developer.android.com/guide/topics/ui/accessibility/custom-views#custom-touch-events
At the point in the overridden OnTouchListener, where you interprete the MotionEvent as a click, call view.performClick(); (this will call onClick()).
It is to give the user feedback, e.g. in the form of a click sound.
you can suppress a warning
#SuppressLint("ClickableViewAccessibility")
or call performClick()
[Example]
I have a RecyclerView (with LinearLayoutManager) and a custom RecyclerView.ItemDecoration for it.
Let's say, I want to have buttons in the decoration view (for some reason..).
I inflate the layout with button, it draws properly. But I can't make the button clickable. If I press on it, nothing happening(it stays the same, no pressing effect) and onClick event is not firing.
The structure of ItemDecoration layout is
<LinearLayout>
<TextView/>
<Button/>
</LinearLayout>
And I'm trying to set listener in ViewHolder of the decoration
class ItemDecorationHolder extends RecyclerView.ViewHolder {
public TextView header;
public Button button;
public HeaderHolder(View itemView) {
super(itemView);
header = (TextView)itemView.findViewById(R.id.header);
button = (Button)itemView.findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//.. Show toast, etc.
}
});
}
}
And i'm drawing the decoration in onDrawOver method. (actually, I'm modifying this codebase: https://github.com/edubarr/header-decor )
Any ideas? Is it doable?
Thanks!
While the real header is scroll off the screen, the visible one is drawing on canvas directly ,not like a normal interactive widget.
You have these options
Override RecyclerView.onInterceptTouchEvent(), though with some invasiveness so I prefer the next one.
Make use of RecyclerView.addOnItemTouchListener(), remember the motion event argument has been translated into RecyclerView's coordinate system.
Use a real header view, but that will go a little far I think.
If you take option 1/2, Button.setPressed(true) and redraw the header will have a visual press effect.
In addition to what Neil said,
the answer here might help.
Passing MotionEvents from RecyclerView.OnItemTouchListener to GestureDetectorCompat
And then you just need to calculate the height of the header and see if the click falls onto that header view and handle the event yourself.
private class RecyclerViewOnGestureListener extends GestureDetector.SimpleOnGestureListener {
#Override
public boolean onSingleTapConfirmed(MotionEvent e) {
float touchY = e.getY();
ALLog.i(this, "Recyclerview single tap confirmed y: " + touchY);
//mGroupHeaderHeight is the height of the header which is used to determine whether the click is inside of the view, hopefully it's a fixed size it would make things easier here
if(touchY < mGroupHeaderHeight) {
int itemAdapterPosition = mRecyclerView.getLayoutManager().getPosition(mRecyclerView.findChildViewUnder(0, mGroupHeaderHeight));
//Do stuff here no you have the position of the item that's been clicked
return true;
}
return super.onSingleTapConfirmed(e);
}
#Override
public boolean onDown(MotionEvent e) {
float touchY = e.getY();
if(touchY < mGroupHeaderHeight) {
return true;
}
return super.onDown(e);
}
#Override
public boolean onSingleTapUp(MotionEvent e) {
float touchY = e.getY();
if(touchY < mGroupHeaderHeight) {
return true;
}
return super.onSingleTapUp(e);
}
}
As Neil is pointing out, things are getting more complicated than that. However by definition you can't.
So, why not including good libraries that do that and more?
I propose my hard work for clickable sticky header in my FlexibleAdapter project, which uses a real view (not decorators) to handle click events on headers when sticky.
There's also a working demo and a Wiki page on that part (and not only).
i have a blank screen on mainactivity.
when i tap everywhere on the screen it will do an action. such as opening a new activity or making and event. is it possible to make it on an imageview too? what is the listener that listens to the tapping and how can i get a method such as "OnTap"?
I know little about android but sure this can help:
create an ImageView with height and width set to match_parent
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:onClick="tap_me"
/>
then in your java code you can do this
public void tap_me(View v){
//do something
}
View.onClickListener should do the work for you.
Update:
Check out similar problem: How to Set onClicklistener Method of ImageView in Android?
You can only detect clicks within your app. Make the imageview to cover the entire screen. Then click on any point will be picked up by the onClickListener.
You could also do something like this:
ImageView imageView = (ImageView) findViewById(R.drawable.YourImage);
imageView.setOnTouchListener(new OnTouchListener) {
#Override
public boolean onTouch(View view, MotionEvent me) {
switch(me.getAction()) {
case(MotionEvent.ACTION_DOWN):
//do stuff here
}
}
}
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()
Okey, so I've implemented a button on a Sliding drawer in a android application I'm building. The only problem is that when I press the button the whole sliding drawer is pressed and it slides up.
I know I can disable 'press to slide up' in the XML, but that does not seem to work as the sliding drawer still is pressed just without the slide up.
If I call the slidingDrawer.lock(); function the button actually works but then the sliding drawer can't slide up or even be pressed up.
Any one have a simple solution to this problem?
If I understand well you have added buttons on your SlidingDrawer handle and you want them to work like buttons when the user press them with keeping a standard SlidingDrawer behaviour when the handle is pressed/dragged?
I just solved a similar problem.
My Handle was looking something like that:
It's composed of two buttons and a center TextView which will be the real handle (reacting as a standard SlidingDrawer handle).
To make the buttons work independently of the SlidingDrawer I changed a bit of source code in the onInterceptTouchEvent method of the standard SlidingDrawer.java class (copy paste the source file from the android code source):
public boolean onInterceptTouchEvent(MotionEvent event) {
//...
final Rect frame = mFrame;
final View handle = mHandle;
// original behaviour
//mHandle.getDrawingRect(frame);
// New code
View trackHandle = mTrackHandle;
// set the rect frame to the mTrackHandle view borders instead of the hole handle view
// getParent() => The right and left are valid, but we need to get the parent top and bottom to have absolute values (in screen)
frame.set(trackHandle.getLeft(), ((ViewGroup) trackHandle.getParent()).getTop(), trackHandle.getRight(), ((ViewGroup) trackHandle.getParent()).getBottom());
if (!mTracking && !frame.contains((int) x, (int) y)) {
return false;
}
//...
}
I also added a setter for the mTrackHandle attribute to set, during the activity creation, the real hanlde to use:
protected void onCreate(Bundle savedInstanceState) {
//...
mSlidingDrawer.setTrackHandle((View) findViewById(R.id.menu_handle_TextView_Title));
//...
}
After that you can set standard listener on your two buttons. They will work like a charm.
in response to Joakim Engstrom:
Yes that's possible!
to do that you have to override onInterceptTouchEvent as follow.
#Override
public boolean onInterceptTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
rect = new Rect(handle.getLeft(), ((View) handle.getParent()).getTop(),
handle.getRight(), ((View) handle.getParent()).getBottom());
if (!rect.contains((int) event.getX(), (int) event.getY())) {
if (event.getAction() == MotionEvent.ACTION_UP)
this.lock();
else
this.unlock();
return false;
} else {
this.unlock();
return super.onInterceptTouchEvent(event);
}
}
you have also to add a setter to set handle to actual handle view during activity creation.
may be this code can help you
https://github.com/xPutnikx/SlidingDrawerWithButtons