Develop Reference

AndroidStudio MotionEvent: detect only ACTION_UP on a second view, starting ACTION_DOWN on first view

Solved it by using emandt's suggestion. My personal Solution added below.
I'm using Android Studio for this.
I searched for solutions but couldn't find anything resembling this.
I want to know on which ImageView an UP action occurs while starting the DOWN action on a different ImageView (to eventually be able to drag one image over the other and make it snap to the same position by getting the position of the image I dragged over).
My example has two ImageViews with the id imageView (left) and imageView2(right).
In my example I'm not dragging anything yet, I just want to touch the left image, see "Action was down" in the log and lift the finger over the right image showing "Action was up2".
I don't know if this is easily possible.
As far as I can tell from testing, the MotionEvent.ACTION_UP only fires for an ImageView when you also pressed down on it beforehand. So when I release on top of imageView2 it only shows "Action was up" from the left image.
I wondered if it was possible by playing with return false, since the return value tells if an ActionEvent is consumed so I thought if the UP event of imageView returns false, maybe it does trigger the UP event of imageView2 but no. (Either complete misunderstanding on my part or it doesn't recognise UP on the second because it didn't start with a DOWN and MotionEvents probably always have to start with a DOWN).
public class MainActivity extends Activity {
ImageView imageView;
ImageView imageView2;
String DEBUG_TAG = "action";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = findViewById(R.id.imageView);
imageView2 = findViewById(R.id.imageView2);
imageView.setOnTouchListener(new View.OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
//int action = MotionEventCompat.getActionMasked(event);
int action = event.getActionMasked();
switch(action) {
case (MotionEvent.ACTION_DOWN) :
Log.d(DEBUG_TAG,"Action was DOWN"+v.toString());
return true;
case (MotionEvent.ACTION_MOVE) :
//Log.d(DEBUG_TAG,"Action was MOVE");
return true;
case (MotionEvent.ACTION_UP) :
Log.d(DEBUG_TAG,"Action was UP"+v.toString());
return false;
default :
//return true;
}
return true;
}
});
imageView2.setOnTouchListener(new View.OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
//int action = MotionEventCompat.getActionMasked(event);
int action = event.getActionMasked();
switch(action) {
case (MotionEvent.ACTION_DOWN) :
Log.d(DEBUG_TAG,"Action was DOWN2"+v.toString());
return true;
case (MotionEvent.ACTION_MOVE) :
//Log.d(DEBUG_TAG,"Action was MOVE");
return true;
case (MotionEvent.ACTION_UP) :
Log.d(DEBUG_TAG,"Action was UP2"+v.toString());
return true;
default :
//return true;
}
return true;
}
});
}
}
If there is no simple way to do this, I'm thinking about solving this mathematically, but maybe some of you can help.
So my question is, is there a way to recognise an UP action on a second ImageView while currently being in a MotionEvent of another ImageView?
SOLUTION (see emandt's answer)
I ditched the second OnClickListener because I realised that the 2nd image doesn't need any, I just need its position.
Added this method:
#Nullable
private View getDroppedView(View droppedView, int x, int y, List<View> arrayOfPossibilities) {
Rect cVisibleBoundsRect = new Rect();
for (View cView : arrayOfPossibilities) {
//if currently iterated view doesn't have values for getGlobalVisibleRect, skip the .contains part
//ignore the item which is your current active item (which would potentially be dropped)
//getGlobalVisibleRect sets cVisibleBoundsRect immediately to the Rect given as parameter
if (!cView.getGlobalVisibleRect(cVisibleBoundsRect)||(cView.equals(droppedView))) continue;
if (cVisibleBoundsRect.contains(x, y)) {
Log.d(DEBUG_TAG,"Found something");
//THIS "cView" IS THE VIEW WHERE YOU RELEASED THE FINGER
return cView;
}
}
Log.d(DEBUG_TAG,"Found nothing");
return null;
}
And added this in onUP:
case (MotionEvent.ACTION_UP) :
View dropTarget;
Log.d(DEBUG_TAG,"Action was UP"+v.toString());
dropTarget = getDroppedView(v, (int)event.getRawX(), (int)event.getRawY(), listOfViews);
if (dropTarget != null){
v.setX(dropTarget.getX());
v.setY(dropTarget.getY());
}

I think you want to know which is the View where you release the finger from the screen, am I right?
To do this you can use the same "View.OnTouchListener()" for all of your Views and in the ACTION_UP you have to call a new method similar to this (pseudo-code):
....
case (MotionEvent.ACTION_UP) :
View[] cArrayOfPossibileViews = new View[]{ findViewById(IMAGE_1), findViewById(IMAGE2) }
getDroppedView(v, event.getRawX(), event.getRawY(), cArrayOfPossibileViews);
break;
}
....
#Nullable
private View getDroppedView(View view, int x, int y, View[] arrayOfPossibilities) {
Rect cVisibleBoundsRect = new Rect();
for (View cView : arrayOfPossibilities) {
if (!cView.getGlobalVisibleRect(cVisibleBoundsRect)) continue;
if (cVisibleBoundsRect.contains(x, y)) {
//THIS "cView" IS THE VIEW WHERE YOU RELEASED THE FINGER
return cView;
}
}
return null;
}
This method get View bounds and compare them avains X and Y of your Touch Event. If X and Y are contained inside a View bounds it means that View is the one you need.

How to distinct between a tap on the right/ left side of the display?

I thought this is a pretty relevant and common question, but I couldnt find an answer.
At the moment I have this method:
public boolean onTouchEvent (MotionEvent evt){
if (evt.getAction() == MotionEvent.ACTION_DOWN) {
do stuff ...
}
}
So if the user taps on the screen (wherever) the code is executed. Now I want the distinction between the right side of the display and the left side (left side means --> go back).

You can do this many ways. Here is one of them:
Attach onTouch listener to the view, which stretches to its edges. (For example your RelativeLayout which holds rest of views)
private View.OnTouchListener onTouchListener = new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
float halfOfAScreen = mainLayout.getMaxWidth() / 2;
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
float fingerPosition = event.getX();
if(fingerPosition < halfOfAScreen) {
onBackPressed();
}
return true;
default:
return false;
}
}
};

Refer to this post on how to get touch position.
It seems in your case you will use
int x = (int)event.getX();
int y = (int)event.getY();
and work within the bounds of your layout that you want the app to react to.

Override single tap of Photoview

I have an ImageView inside of a view pager with an ActionBar at the top. I would like to be able to single tap to hide the action bar, and I would also like to be able to pinch zoom and pan on each ImageView.
To implement the single tap to hide the action bar I have a simple OnClickListener that hides it.
To implement the pinch zoom and pan on each ImageView I am using the PhotoView Library Project.
I am having issues because only one touch event listener can be associated with an ImageView, and the implementing the PhotoView Library project overwrites my OnClickListener to hide the ActionBar with,
parent.requestDisallowInterceptTouchEvent(true);
I am not sure how to go about getting both implemented at the same time. It seems like the only solution is to create my own Pinch Zoom ImageView in order to control touch events myself.

Found out that the PhotoView library actually allows me to set onViewTap for the PhotoViewAttacher object which is exactly what I wanted.
To create the PhotoViewAttacher in the current Fragment/Activity have it implement PhotoViewAttacher.OnViewTapListener, create the attacher,
PhotoViewAttacher mAttacher = new PhotoViewAttacher(imageView);
mAttacher.setOnViewTapListener(this);
and add the following function,
public void onViewTap(View view, float x, float y) {
// your code here
}
Source

You'll have to override the PhotoView library itself. If you look at the source code, the PhotoViewAttacher class is the one that handles the onTouch events.
You'll have to add the special funcionality you're looking for at this part of the code (specially, the ACTION_DOWN) event:
#Override
public final boolean onTouch(View v, MotionEvent ev) {
boolean handled = false;
if (mZoomEnabled && hasDrawable((ImageView) v)) {
ViewParent parent = v.getParent();
switch (ev.getAction()) {
case ACTION_DOWN:
// First, disable the Parent from intercepting the touch
// event
if (null != parent)
parent.requestDisallowInterceptTouchEvent(true);
else
Log.i(LOG_TAG, "onTouch getParent() returned null");
// If we're flinging, and the user presses down, cancel
// fling
cancelFling();
break;
case ACTION_CANCEL:
case ACTION_UP:
// If the user has zoomed less than min scale, zoom back
// to min scale
if (getScale() < mMinScale) {
RectF rect = getDisplayRect();
if (null != rect) {
v.post(new AnimatedZoomRunnable(getScale(), mMinScale,
rect.centerX(), rect.centerY()));
handled = true;
}
}
break;
}
// Check to see if the user double tapped
if (null != mGestureDetector && mGestureDetector.onTouchEvent(ev)) {
handled = true;
}
if (!handled && null != parent) {
parent.requestDisallowInterceptTouchEvent(false);
}
// Finally, try the Scale/Drag detector
if (null != mScaleDragDetector
&& mScaleDragDetector.onTouchEvent(ev)) {
handled = true;
}
}
return handled;
}

Android - Drag and Drop only vertical

I have got a textView or small Icon and I want to drag it only vertical.
What I tried:
Create an own ShadowBuilder but make him invisible. So others views get called over the OnDragListener but the ShadowView is not visible.
Instead I display an own view which is moved like here:
How to make the TextView drag in LinearLayout smooth, in android? with the different, only in vertical direction. The Problem is, the onTouchListener is only called twice if dragging is activated. So no moving could be done.
That solution does not work for me I think.
Drag an image only horizontally or vertically in android?
Maybe any idea? Thanks for reading.

try out my solution here, but only change the top&bottom margins instead.

findViewById(R.id.btn_submit).setOnTouchListener(new View.OnTouchListener()
{
int prevX,prevY;
#Override
public boolean onTouch(final View v,final MotionEvent event)
{
final LinearLayout.LayoutParams par=(LinearLayout.LayoutParams)v.getLayoutParams();
switch(event.getAction())
{
case MotionEvent.ACTION_MOVE:
{
par.topMargin+=(int)event.getRawY()-prevY;
prevY=(int)event.getRawY();
prevX=(int)event.getRawX();
v.setLayoutParams(par);
return true;
}
case MotionEvent.ACTION_UP:
{
par.topMargin+=(int)event.getRawY()-prevY;
v.setLayoutParams(par);
return true;
}
case MotionEvent.ACTION_DOWN:
{
prevX=(int)event.getRawX();
prevY=(int)event.getRawY();
par.bottomMargin=-2*v.getHeight();
v.setLayoutParams(par);
return true;
}
}
return false;
}
});

Custom horizontal scroll animation to track finger on view in android

So this is not a tecnical question with code but more on some thoughts. I am new to android developing and because of that I am not completely familiar with a lot of what it has to offer.
I have a list of items on the screen and you can scroll up and down to view the different items.
My issue came up when I decided to have the items be able to slide left and right to reveal a settings like panal with a few optons below them(each item has its own settings below it, not a setting screen for all items kind of deal). I looked around for different ways to do this but cant seem to find one that works. What I am thinking so far is to have a HorizonalScrollView with my item in it with the setting menu to the left or right off the screen, but when I put my text area in the HorizonalScrollView, it only takes up half the screen, so I can fit two side by side, not what I wanted and the end result wont be what I imagined. I really would like a solution that allows for the setting to be under the item, so when you push it out of the way it reveals the settings.
Is there a better way or should I just continue trying to make my HorizonalScrollView work, any guides or thought on how I could go about this would be greatly appreciated.
Went though my apps to see if I could find one that has something similar, gmail app has it. Here is a link to an image that gives you an idea, after you slide the item to the side it brings up an undo or archive buttons in the place of the item as if they were hiding under the list item you swiped away

it's quite an interesting topic this question. And be prepared to do a certain amount of custo stuff.
First of all, drop the HorizonalScrollView, I don't think it will help you. The layout of each item should be something like this (pseudo-code, you can build the XML yourself =] ):
FrameLayout
RelativeLayout id:topContent background:someSolidColor
// inside this RelativeLayout, the stuff that is visible on the ListView
RelativeLayout id:bottomContent
// inside this RelativeLayout, the stuff that is behind the content
/FrameLayout
that way you will be literally putting one thing on top of the other. Also note that the topContent have a background with a solid color. If you do not specify any background, both RelativeLayouts will be visible. Also note that I used RelativeLayout, just because I like them, and I like their flexibility, but this will depend on the content of your list view and your settings.
And now is when things get fun, you'll need a GestureDetector to detect the finger sliding and you'll use that value to generate a margin offset on the id:topContent.
You can create a TouchListener like this:
public class MySlideListener extends View.OnTouchListener{
private View v;
private GestureDetector gestureDetector;
public MySlideListener (View v){
this.v = v;
gestureDetector = new GestureDetector(v.getContext(), myGestureListener);
}
public boolean onTouch (View v, MotionEvent event){
return gestureDetector.onTouchEvent(event);
}
private SimpleOnGestureListener myGestureListener = new SimpleOnGestureListener(){
#Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY){
// now here we make the view scroll
MarginLayoutParams lp = (MarginLayoutParams) view.getLayoutParams();
lp.leftMargin = distanceX;
lp.rightMargin = -distanceX;
// You might need to call view.requestLayout();
// but first give it a try without it
// This part of the method for processing the horizontal
// offset can (and should) be further developed to add some
// 'snap-in' or transparency functionality to make the whole
// concept work better.
// But this code should give you a proof of concept on how to deal with stuff.
// The important part is that now you have a call back that have access
// to the view during onScroll.
// Also might be necessary to enable/disable the bottomContent view
// in order for it to be not clickable whilst not visible.
return true;
}
}
}
and then set a new of those listeners for each topContent of your ListView (probably inside the getView from the adapter) with topContentView.setOnTouchListener(new MySlideListener(topContentView));
Please keep in mind that I typed all this code by heart and is 100% untested!
edit:
The above code is the correct direction, but it's a 100% untested thing.
Now the code below, I've just compiled, tested, and this code works!
This class is also a bit more efficient as you can create only one and apply the same instance to all the items created on your adapter. You can see it's getting the view to scroll on the touch event.
public class MySlideListener implements View.OnTouchListener {
private View view;
private ListView listView;
private GestureDetector gestureDetector;
public MySlideListener(ListView lv) {
listView = lv;
gestureDetector = new GestureDetector(lv.getContext(), myGestureListener);
}
#Override
public boolean onTouch(View v, MotionEvent event) {
view = v;
gestureDetector.onTouchEvent(event);
return true;
}
private SimpleOnGestureListener myGestureListener = new SimpleOnGestureListener() {
private int origLeft, origRight;
public boolean onDown(MotionEvent e) {
MarginLayoutParams lp = (MarginLayoutParams) view.getLayoutParams();
origLeft = lp.leftMargin;
origRight = lp.rightMargin;
return true;
};
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
listView.requestDisallowInterceptTouchEvent(true);
MarginLayoutParams lp = (MarginLayoutParams) view.getLayoutParams();
lp.leftMargin = (int) (origLeft + (e2.getRawX() - e1.getRawX()));
lp.rightMargin = (int) (origRight - (e2.getRawX() - e1.getRawX()));
view.requestLayout();
return true;
};
};
}