I am new to android.I am making an app in which I want to get all the dynamic coordinates of scroll gesture. e.g if I draw a line I want to get all the coordinates of that line.How to obtain that?
I have tried to take the values in array like this:
#Override
public boolean onScroll(MotionEvent me1, MotionEvent me2, float distanceX,float distanceY) {
x =me1.getRawX()+me2.getRawX();
xval.add((int) x);
return true;
}
#Override
public boolean onTouchEvent(MotionEvent me) {
this.gDetector.onTouchEvent(me);
onScroll(me,me,x,y);
Intent i=new Intent();
i.putIntegerArrayListExtra("key0", xval );
setResult(RESULT_OK,i);
finish();
}
return gDetector.onTouchEvent(me);
This code is able to fetch only the first coordinate of the scroll gesture
You don't get all the coordinates of the line, its inefficient. Instead you use the mathematical formula for distance from a point to a line, and see if you're close. If you're close enough (never expect the user to tap exactly on a line), then that point counts as on the line.
http://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line
I have list items that have a HorizontalScrollView in each of them. Hence, I should be able to swipe up and down the list and also swipe through the list item horizontally. (e.g. Pulse News App).
What I'm encountering is that, whenever I scroll the HorizontalScrollView, the ListView also gets scrolled by tiny bit but giving out annoying disturbances in terms of User Experience.
So, I was actually thinking to subclass ListView and implement my own ListView widget. However, I don't know which method to override so that I could increase X tolerance and stop the listview from giving these unwanted flickering.
gestureDetector = new GestureDetector(new YScrollDetector());
public boolean onInterceptTouchEvent(MotionEvent ev) {
//Call super first because it does some hidden motion event handling
boolean result = super.onInterceptTouchEvent(ev);
//Now see if we are scrolling vertically with the custom gesture detector
if (gestureDetector.onTouchEvent(ev)) {
return result;
}
//If not scrolling vertically (more y than x), don't hijack the event.
else {
return false;
}
}
// Return false if we're scrolling in the x direction
class YScrollDetector extends SimpleOnGestureListener {
#Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
try {
if (Math.abs(distanceY) > Math.abs(distanceX)) {
return true;
} else {
return false;
}
} catch (Exception e) {
// nothing
}
return false;
}
}
This is will help you, you have to override these in the custom list view you create,i used this to eliminate the problem in my application. Hope this helps.
I have a TabHost hosting 3 Activities. In addition to the tabs, I want support for swipe gestures to change the current tab. My issue is that one of the views holds a horizontal scrollview, and I cannot figure out how to prevent touches in the horizontal scrollview from changing the current tab.
plateView is the horizontal scrollview that needs to be handled. Finding it's bottom with plateView.getBottom() and not counting touches above that works without the TabHost, but now it returns null and crashes, regardless of where it's called.
onTouchEvent counts touches everywhere and dispatchTouchEvent doesn't count touches on any widget. It seems some combination of them would be great, but together they yield the same functionality as onTouchEvent alone. Swipes anywhere count to change the Activity. My understanding of these is a little fuzzy though.
Why does getBottom() return null? How can I get this to work?
gestureDetector = new GestureDetector(new CalcGestureDetector());
gestureListener = new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
Log.d(TAG,"onTOUCH");
if(gestureDetector.onTouchEvent(event)){
return true;
}
return false;
}
};
//Takes the touch and interprets it. Handles it. Changes tabs on fling.
class CalcGestureDetector extends SimpleOnGestureListener{
#Override
public boolean onFling(MotionEvent eOne, MotionEvent eTwo, float velocityX, float velocityY){
Log.d(TAG,"WTF "+plateView.getBottom());
if(false){
}
else{
try{
if (Math.abs(eOne.getY() - eTwo.getY()) > flingMaxOffPath)
return false; //Too much of an arc in the fling.
// right to left swipe
if(eOne.getX() - eTwo.getX() > flingMinDistance && Math.abs(velocityX) > flingMinVelocity) {
tabHost.setAnimation(slideLeftIn);
tabHost.setAnimation(slideLeftOut);
tabHost.setCurrentTab((tabHost.getCurrentTab()+1)%3);
} else if (eTwo.getX() - eOne.getX() > flingMinDistance && Math.abs(velocityX) > flingMinVelocity) {
tabHost.setAnimation(slideRightIn);
tabHost.setAnimation(slideRightOut);
tabHost.setCurrentTab((tabHost.getCurrentTab()+2)%3);
}
}
catch(Exception e){
}
}
return false;
}
}
//This method alone keeps a touch in the weights from changing tabs, but won't register
//touches on ANY widget on any screen (like text views).
public boolean dispatchTouchEvent(MotionEvent event){
super.dispatchTouchEvent(event);
return gestureDetector.onTouchEvent(event);
}
//This method alone counts touches for swipes anywhere and everywhere.
#Override
public boolean onTouchEvent(MotionEvent event) {
if (gestureDetector.onTouchEvent(event))
return true;
else
return false;
}
I'm playing around with an app I have written whose main activity is a TabActivity. I was considering allowing the user to navigate between tabs with a fling gesture, but I find that I can only detect flings on one of my four tabs.
public class WSGesture extends TabActivity implements OnGestureListener {
private GestureDetector gestureScanner;
#Override onCreate(Bundle savedInstanceState)
{
gestureScanner = new GestureDetector(this);
...
}
.
.
.
#Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
Log.v(TAG, "onFling called, velX: " + velocityX + ", velY: " + velocityY);
return true;
}
public boolean onTouchEvent(MotionEvent me)
{
return gestureScanner.onTouchEvent(me);
}
}
When I execute this code, I only see onFling being called when one particular tab is set as the current tab. For the other three, I get nothing. It's always the third out of four, if that matters.
One thing that has worked for me in the past is implementing onDown() and returning true...
When doing this though, be careful... I have found that the behavior when doing this is different between the 1.x and 2.x versions of Android when using your onGestureListener to handle other things like single clicks... so be sure to thoroughly test your app when making changes like this.
If you are only using onFling then you "should" be ok... but test it just to be safe.
I am using the onScroll method of GestureDetector.SimpleOnGestureListener to scroll a large bitmap on a canvas. When the scroll has ended I want to redraw the bitmap in case the user wants to scroll further ... off the edge of the bitmap, but I can't see how to detect when the scroll has ended (the user has lifted his finger from the screen).
e2.getAction() always seems to return the value 2 so that is no help.
e2.getPressure seems to return fairly constant values (around 0.25) until the final onScroll call when the pressure seems to fall to about 0.13. I suppose I could detect this reduction in pressure, but this will be far from foolproof.
There must be a better way: can anyone help, please?
Here is how I solved the problem. Hope this helps.
// declare class member variables
private GestureDetector mGestureDetector;
private OnTouchListener mGestureListener;
private boolean mIsScrolling = false;
public void initGestureDetection() {
// Gesture detection
mGestureDetector = new GestureDetector(new SimpleOnGestureListener() {
#Override
public boolean onDoubleTap(MotionEvent e) {
handleDoubleTap(e);
return true;
}
#Override
public boolean onSingleTapConfirmed(MotionEvent e) {
handleSingleTap(e);
return true;
}
#Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
// i'm only scrolling along the X axis
mIsScrolling = true;
handleScroll(Math.round((e2.getX() - e1.getX())));
return true;
}
#Override
/**
* Don't know why but we need to intercept this guy and return true so that the other gestures are handled.
* https://code.google.com/p/android/issues/detail?id=8233
*/
public boolean onDown(MotionEvent e) {
Log.d("GestureDetector --> onDown");
return true;
}
});
mGestureListener = new View.OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
if (mGestureDetector.onTouchEvent(event)) {
return true;
}
if(event.getAction() == MotionEvent.ACTION_UP) {
if(mIsScrolling ) {
Log.d("OnTouchListener --> onTouch ACTION_UP");
mIsScrolling = false;
handleScrollFinished();
};
}
return false;
}
};
// attach the OnTouchListener to the image view
mImageView.setOnTouchListener(mGestureListener);
}
You should take a look at http://developer.android.com/reference/android/widget/Scroller.html.
Especially this could be of help (sorted by relevance):
isFinished();
computeScrollOffset();
getFinalY(); getFinalX(); and getCurrY() getCurrX()
getDuration()
This implies that you have to create a Scroller.
If you want to use touching you could also use GestureDetector and define your own canvas scrolling. The following sample is creating a ScrollableImageView and in order to use it, you have to define the measurements of your image. You can define your own scrolling range and after finishing your scrolling the image gets redrawn.
http://www.anddev.org/viewtopic.php?p=31487#31487
Depending on your code you should consider invalidating (int l, int t, int r, int b); for the invalidation.
SimpleOnGestureListener.onFling()
It seems to take place when a scroll ends (i.e. the user lets the finger go), that's what I am using and it works great for me.
Coming back to this after a few months I've now followed a different tack: using a Handler (as in the Android Snake sample) to send a message to the app every 125 milliseconds which prompts it to check whether a Scroll has been started and whether more than 100 milliseconds has elapsed since the last scroll event.
This seems to work pretty well, but if anyone can see any drawbacks or possible improvements I should be grateful to hear of them.
The relevant the code is in the MyView class:
public class MyView extends android.view.View {
...
private long timeCheckInterval = 125; // milliseconds
private long scrollEndInterval = 100;
public long latestScrollEventTime;
public boolean scrollInProgress = false;
public MyView(Context context) {
super(context);
}
private timeCheckHandler mTimeCheckHandler = new timeCheckHandler();
class timeCheckHandler extends Handler{
#Override
public void handleMessage(Message msg) {
long now = System.currentTimeMillis();
if (scrollInProgress && (now>latestScrollEventTime+scrollEndInterval)) {
scrollInProgress = false;
// Scroll has ended, so insert code here
// which calls doDrawing() method
// to redraw bitmap re-centred where scroll ended
[ layout or view ].invalidate();
}
this.sleep(timeCheckInterval);
}
public void sleep(long delayMillis) {
this.removeMessages(0);
sendMessageDelayed(obtainMessage(0), delayMillis);
}
}
}
#Override protected void onDraw(Canvas canvas){
super.onDraw(canvas);
// code to draw large buffer bitmap onto the view's canvas
// positioned to take account of any scroll that is in progress
}
public void doDrawing() {
// code to do detailed (and time-consuming) drawing
// onto large buffer bitmap
// the following instruction resets the Time Check clock
// the clock is first started when
// the main activity calls this method when the app starts
mTimeCheckHandler.sleep(timeCheckInterval);
}
// rest of MyView class
}
and in the MyGestureDetector class
public class MyGestureDetector extends SimpleOnGestureListener {
#Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
float distanceY) {
[MyView].scrollInProgress = true;
long now = System.currentTimeMillis();
[MyView].latestScrollEventTime =now;
[MyView].scrollX += (int) distanceX;
[MyView].scrollY += (int) distanceY;
// the next instruction causes the View's onDraw method to be called
// which plots the buffer bitmap onto the screen
// shifted to take account of the scroll
[MyView].invalidate();
}
// rest of MyGestureDetector class
}
This is what worked for me.
I've enriched the existing GestureDetector.OnGestureListener with onFingerUp() method. This listener does everything as the built-in GestureDetector and it can also listen to the finger up event (it's not onFling() as this is called only when the finger is lifted up along with a quick swipe action).
import android.content.Context;
import android.os.Handler;
import android.view.GestureDetector;
import android.view.MotionEvent;
public class FingerUpGestureDetector extends GestureDetector {
FingerUpGestureDetector.OnGestureListener fListener;
public FingerUpGestureDetector(Context context, OnGestureListener listener) {
super(context, listener);
fListener = listener;
}
public FingerUpGestureDetector(Context context, GestureDetector.OnGestureListener listener, OnGestureListener fListener) {
super(context, listener);
this.fListener = fListener;
}
public FingerUpGestureDetector(Context context, GestureDetector.OnGestureListener listener, Handler handler, OnGestureListener fListener) {
super(context, listener, handler);
this.fListener = fListener;
}
public FingerUpGestureDetector(Context context, GestureDetector.OnGestureListener listener, Handler handler, boolean unused, OnGestureListener fListener) {
super(context, listener, handler, unused);
this.fListener = fListener;
}
public interface OnGestureListener extends GestureDetector.OnGestureListener {
boolean onFingerUp(MotionEvent e);
}
public static class SimpleOnGestureListener extends GestureDetector.SimpleOnGestureListener implements FingerUpGestureDetector.OnGestureListener {
#Override
public boolean onFingerUp(MotionEvent e) {
return false;
}
}
#Override
public boolean onTouchEvent(MotionEvent ev) {
if (super.onTouchEvent(ev)) return true;
if (ev.getAction() == MotionEvent.ACTION_UP) {
return fListener.onFingerUp(ev);
}
return false;
}
}
I think this will work as you need
protected class SnappingGestureDetectorListener extends SimpleOnGestureListener{
#Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY){
boolean result = super.onScroll(e1, e2, distanceX, distanceY);
if(!result){
//Do what you need to do when the scrolling stop here
}
return result;
}
}
I am sure it is too late for you, however, it seems I have found the right solution to your original question and not necessarily the intention.
If you are using Scroller/OverScroller Object for scrolling you should check the return value from the following function.
public boolean computeScrollOffset()
I was looking into this same issue. I saw Akos Cz's answer to your question. I created something similar, but with my version, I noticed that it only worked for a regular scroll - meaning one that doesn't generate a fling. But if a fling did get generated - regardless if I processed a fling or not, then it did NOT detect the "ACTION_UP" in "onTouchEvent". Now maybe this was just something with my implementation, but if it was I couldn't figure out why.
After further investigation, I noticed that during a fling, the "ACTION_UP" was passed into "onFling" in "e2" every time. So I figured that must be why it wasn't being handled in "onTouchEvent" in those instances.
To make it work for me I only had to call a method to handle the "ACTION_UP" in "onFling" and then it worked for both types of scrolling. Below are the exact steps I took to implement my app:
-initialized a "gestureScrolling" boolean to "false" in a constructor.
-I set it to "true" in "onScroll"
-created a method to handle the "ACTION_UP" event. Inside that event, I reset "gestureSCrolling" to false and then did the rest of the processing I needed to do.
-in "onTouchEvent", if an "ACTION_UP" was detected and "gestureScrolling" = true, then I called my method to handle "ACTION_UP"
-And the part that I did that was different was: I also called my method to handle "ACTION_UP" inside of "onFling".
I haven't done this myself but looking at onTouch() you always get a sequence 0<2>1, so the end has to be a 1 for finger lift.
I don't know Android, but looking at the documentation it seems Rob is right: Android ACTION_UP constant Try checking for ACTION_UP from getAction()?
Edit: What does e1.getAction() show? Does it ever return ACTION_UP? The documentation says it holds the initial down event, so maybe it'll also notify when the pointer is up
Edit: Only two more things I can think of. Are you returning false at any point? That may prevent ACTION_UP
The only other thing I'd try is to have a seperate event, maybe onDown, and set a flag within onScroll such as isScrolling. When ACTION_UP is given to onDown and isScrolling is set then you could do whatever you want and reset isScrolling to false. That is, assuming onDown gets called along with onScroll, and getAction will return ACTION_UP during onDown
i have not tried / used this but an idea for an approach:
stop / interrupt redrawing canvas on EVERY scroll event wait 1s and then start redrawing canvas on EVERY scroll.
this will lead to performing the redraw only at scroll end as only the last scroll will actually be uninterrupted for the redraw to complete.
hope this idea helps you :)
Extract from the onScroll event from GestureListener API: link text
public abstract boolean onScroll
(MotionEvent e1, MotionEvent e2, float
distanceX, float distanceY) Since: API
Level 1
Returns
* true if the event is consumed, else false
Perhaps once the event has been consumed, the action is finished and the user has taken their finger off the screen or at the least finished this onScroll action
You can then use this in an IF statement to scan for == true and then commence with the next action.
If you're using SimpleGestureDetector to handle your scroll events, you can do this
fun handleTouchEvents(event: MotionEvent): Boolean {
if(event.action == ACTION_UP) yourListener.onScrollEnd()
return gestureDetector.onTouchEvent(event)
}
My attempt at adding additional functionality to the gesture detector. Hope it helps someone put his time to better use... gist