Develop Reference

How to move an object on a SurfaceView without touching the object itself?

I found this question, but it's for iOS development. I'm doing something in Android, so it wasn't any help.
I have a simple white rectangle on a black canvas, and I have an onTouchEvent set up. I can move the rectangle as expected, but this is not the functionality I'm looking for.
I'm needing to know how I can touch anywhere on the screen and move an object? I don't want the object's X and Y to become my touch event's getX() and getY().
For now, I have:
#Override
public boolean onTouchEvent(MotionEvent event) {
switch(event.getAction()) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
myPoint.set((int)event.getX(), (int)event.getY());
}
return true;
}
My reasoning for this is so the object can be seen without a finger hovering over it. Is this possible?
Here is a visual representation of what I'm wanting to achieve:

Why not get and store the previous MotionEvent coordinates in the onTouchEvent callback, then when onTouchEvent fires again (first ACTION_MOVE after ACTION_DOWN and then so on for each ACTION_MOVE callback) work out the offset/difference between the values then get your own myPoint coordinates and add the offset to their current values. This way you're only moving the myPoint object by the position offset, not the actual coordinates.
This code isn't tested and I've not used an IDE but something like this:
private float oldX;
private float oldY;
#Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
oldX = event.getX();
oldY = event.getY();
break;
case MotionEvent.ACTION_MOVE:
float newX = event.getX();
float newY = event.getY();
float offsetX = getOffset(oldX, newX, myPoint.x);
float offsetY = getOffset(oldY, newY, myPoint.y);
myPoint.set((int) offsetX, (int) offsetY);
oldX = newX;
oldY = newY;
break;
}
return true;
}
private float getOffset(float oldVal, float newVal, float current) {
return current + (newVal - oldVal);
}

Move, rotate and resize edittext in android

I need to move, rotate and resize edittext based on user's touch gestures.
Here is what I am doing.
1. Listen for ACTION_DOWN event to detect single finger touch and then use that for movement.
Listen for ACTION_POINTER_DOWN, and get the index count to detect two finger touch and then use ACTION_MOVE for rotation.
I need to make resize work such that only the width gets decreased on resize by touch.
Problem I am facing
Movement is working perfectly fine. But when I apply rotation using the ACTION_POINTER_DOWN, rotation goes all sorts of haywire. Any suggestions on how to make the view movement and rotation work together?
Here is the code for touchListener I have applied
tvMain.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
moving = true;
break;
case MotionEvent.ACTION_POINTER_DOWN:
Log.d("ActionPointerIndex", "" + event.getActionIndex());
int index = event.getActionIndex();
moving = false;
//FOR ROTATION DETAILS
xc = tvMain.getWidth() / 2;
yc = tvMain.getHeight() / 2;
x_ = event.getX();
y_ = event.getY();
Log.d("currentAnglePD", ": " + x_ + "," + y_);
if (index == 1) {
rotate = true;
mCurrAngle = Math.toDegrees(Math.atan2(x_ - xc, yc - y_));
moving = false;
}
break;
case MotionEvent.ACTION_MOVE:
if (moving) {
leftBound = rootView.getX();
topBound = rootView.getY();
rightBound = rootView.getX() + 1280;
bottomBound = rootView.getY() + 618;
x = event.getRawX() - tvMain.getWidth() / 2;
y = event.getRawY() - tvMain.getHeight();
dx = Float.valueOf(rootView.getWidth() - tvMain.getWidth());
dy = Float.valueOf(rootView.getHeight() - tvMain.getHeight());
bottomBound_ = tvMain.getY() + tvMain.getHeight();
rightBound_ = tvMain.getX() + tvMain.getWidth();
if (x >= leftBound && y >= topBound && x <= dx && y <= dy) {
tvMain.setX(x);
tvMain.setY(y);
}
}
if (rotate) {
Log.d("currentAngleMove", ": " + x_ + "," + y_);
mPrevAngle = mCurrAngle;
mCurrAngle = Math.toDegrees(Math.atan2(x_ - event.getX(), yc - event.getY()));
animate(mPrevAngle, mCurrAngle, 0);
System.out.println(mCurrAngle);
}
break;
case MotionEvent.ACTION_POINTER_UP:
rotate = false;
break;
case MotionEvent.ACTION_UP:
rotate = false;
moving = false;
//tvMain.clearAnimation();
break;
}
return true;
}
});
Movement is working fine, but once I move the view, rotation goes haywire, and it does not rotate along its center. Once I stop rotating, the view stops listening for any more touch gestures.

Getting a particular position in canvas after zoom the canvas android

I need to click on particular item on the canvas while zooming and moving functionalities also enable for canvas. I can calculate the rectangle position while moving the canvas. There I just calculate the touch movement distance by (CurrenTouchXPosition - StartXPosition).
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction();
int x = (int) event.getX();
int y = (int) event.getY();
float moveOffsetX = (event.getX() - start.x);
float moveOffsetY = (event.getY() - start.y);
Then,
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
mode = DRAG;
break;
case MotionEvent.ACTION_POINTER_DOWN:
break;
case MotionEvent.ACTION_UP:
Log.d(TAG, "action up");
secondRectUpperX = secondRectUpperX + moveOffsetX;
secondRectBottomX = secondRectBottomX + moveOffsetX;
secondRectUpperY = secondRectUpperY + moveOffsetY;
secondRectBottomY = secondRectBottomY + moveOffsetY;
This can identify the new canvas position of the rectangle. This works perfectly. I can identify the touch event of particular item while moving the canvas by this logic.
But now i need to calculate the rectangle position relative to the canvas, after zoom the canvas. Whats the maths behind the zooming. If anyone knows please help in this.
Thank you.

Finally I come up with a solution.
I translate my touch position screen coordinates to canvas coordinates.
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
...
break;
case MotionEvent.ACTION_POINTER_DOWN:
...
break;
case MotionEvent.ACTION_UP:
float []m = new float[9];
matrix.getValues(m);
float transX = m[Matrix.MTRANS_X] * -1;
float transY = m[Matrix.MTRANS_Y] * -1;
float scaleX = m[Matrix.MSCALE_X];
float scaleY = m[Matrix.MSCALE_Y];
lastTouchX = (int) ((event.getX() + transX) / scaleX);
lastTouchY = (int) ((event.getY() + transY) / scaleY);
lastTouchX = Math.abs(lastTouchX);
lastTouchY = Math.abs(lastTouchY);
Thanks for Andres Cardenas Pardo's answer here
I could able to get the touch position coordinates according to the canvas coordinates. Since i know the coordinates of my drawn object, i check whether the touch position is within the range of drawn object.
if((lastTouchX>=firstRectUpperX && firstRectBottomX>=lastTouchX) && (lastTouchY>=firstRectUpperY && firstRectBottomY>=lastTouchY)) {
isbtn1Clicked = true;
}

Transfer longpress from one android view to another, without releasing finger

We have a longpress detection on a button. When detected, the view should be dismissed (back to the game view) and the object chosen with the button shall be at the coordinates of the longpress. That's the easy part, the hard part is to then change the coordinates with the finger, without releasing it.
Okay so i'm trying to reformulate this: We have two views displayed on top of eachother. What we want is a longclick detected in the top view, to then dismiss the top view, and without releasing the finger, get touchevents in the bottom view.
This is our class gameView: (this code contains a lot of code unneccesay for the problem)
#Override
public boolean onTouchEvent(MotionEvent event) {
gestureDetector.onTouchEvent(event);
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
mode = DRAG;
//We assign the current X and Y coordinate of the finger to startX and startY minus the previously translated
//amount for each coordinates This works even when we are translating the first time because the initial
//values for these two variables is zero.
startX = event.getX() - previousTranslateX;
startY = event.getY() - previousTranslateY;
break;
case MotionEvent.ACTION_MOVE:
translateX = event.getX() - startX;
translateY = event.getY() - startY;
gestureHandler.setTranslation(translateX, translateY);
//We cannot use startX and startY directly because we have adjusted their values using the previous translation values.
//This is why we need to add those values to startX and startY so that we can get the actual coordinates of the finger.
double distance = Math.sqrt(Math.pow(event.getX() - (startX + previousTranslateX), 2) +
Math.pow(event.getY() - (startY + previousTranslateY), 2)
);
if(distance > 0) {
dragged = true;
}
break;
case MotionEvent.ACTION_POINTER_DOWN:
mode = ZOOM;
scaleToX = event.getX();
scaleToY = event.getY();
break;
case MotionEvent.ACTION_UP:
mode = NONE;
dragged = false;
//All fingers went up, so let's save the value of translateX and translateY into previousTranslateX and
//previousTranslate
previousTranslateX = translateX;
previousTranslateY = translateY;
int x = (int)((-translateX/scaleFactorX)+(event.getX()/this.scaleFactorX));
int y = (int)((-translateY/scaleFactorY)+(event.getY()/this.scaleFactorY));
map.click(getContext(), x, y);
for(CastleTile castleTile : map.getCastleTiles()) {
if(castleTile.getRect().contains((int)((-translateX/scaleFactorX)+(event.getX()/this.scaleFactorX)), (int)((-translateY/scaleFactorY)+(event.getY()/this.scaleFactorY)))){
Log.d("Castle to your service", "Boes");
castleSettings.show();
}
}
break;
case MotionEvent.ACTION_POINTER_UP:
mode = DRAG;
//This is not strictly necessary; we save the value of translateX and translateY into previousTranslateX
//and previousTranslateY when the second finger goes up
previousTranslateX = translateX;
previousTranslateY = translateY;
break;
}
detector.onTouchEvent(event);
//We redraw the canvas only in the following cases:
//
// o The mode is ZOOM
// OR
// o The mode is DRAG and the scale factor is not equal to 1 (meaning we have zoomed) and dragged is
// set to true (meaning the finger has actually moved)
if ((mode == DRAG && scaleFactorX != 1f && scaleFactorY != 1f && dragged) || mode == ZOOM) {
invalidate();
}
return true;
}
#Override
public boolean onLongClick(View v) {
castleSettings.dismiss();
return true;
}
And this is the gestureHandler:
public void onLongPress(MotionEvent event) {
map.longClick(context, (int)((-translateX/scaleFactorX)+(event.getX()/this.scaleFactorX)), (int)((-translateY/scaleFactorY)+(event.getY()/this.scaleFactorY)));
}
Sorry for eventual lack of information or bad explaination :)

imageview does not move on touch event android

MY imageview does not move when ontouch event is called...Though I can see ACTION_UP and ACTION_MOVE happening from the log traces.
Here is my code:-
public boolean onTouch(View v, MotionEvent motion) {
float dy ;
float dx;
double r = 0;
float angle = 0;
switch(v.getId())
{
case R.id.arrow:
switch(motion.getActionMasked())
{
case MotionEvent.ACTION_MOVE:
Log.w(this.getClass().getName(),"In MOTION MOVE");
mX1 = motion.getX();
mY1 = motion.getY();
break;
case MotionEvent.ACTION_UP:
Log.w(this.getClass().getName(),"In MOTION UP");
mX2 = motion.getX();
mY2 = motion.getY();
dy = -( mY2-mY1);
dx = -(mX2-mX1);
r = Math.atan2(dy, dx);
angle = (int)Math.toDegrees(r);
updateRotation(angle);
break;
default:
break;
}
Log.d(this.getClass().getName(), "Value of angle in ontouch: " + Double.toString(angle));
break;
default:
break;
}
return true;
}
Basically I am trying to calculate the angular displacement when user touches the imageview and changes its position.
======================================
Edit:- Below is my update rotation function:-
public void updateRotation(double angle)
{
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.arrow);
int w = bitmap.getWidth();
int h = bitmap.getHeight();
String filePath = null;
Matrix mtx = new Matrix();
Log.d(this.getClass().getName(), "Value: " + Double.toString(angle));
if(angle > 90)
angle = 90;
mtx.postRotate((float) angle);
bitmap = Bitmap.createBitmap(bitmap, 0, 0, w, h, mtx, true);
Drawable draw =new BitmapDrawable(bitmap);
mImageView.setBackgroundDrawable(draw);
}
=========================================================
Edit 2: Modified function
public boolean onTouch(View v, MotionEvent motion) {
float dy ;
float dx;
double r = 0;
switch(v.getId())
{
case R.id.arrow:
switch(motion.getActionMasked())
{
case MotionEvent.ACTION_DOWN:
mX1 = motion.getX();
mY1 = motion.getY();
break;
case MotionEvent.ACTION_MOVE:
Log.w(this.getClass().getName(),"In MOTION MOVE");
mX1 = motion.getX();
mY1 = motion.getY();
break;
case MotionEvent.ACTION_UP:
Log.w(this.getClass().getName(),"In MOTION UP");
mX2 = motion.getX();
mY2 = motion.getY();
dy = -( mY2-mY1);
dx = -(mX2-mX1);
r = Math.atan2(dy, dx);
mAngle = (int)Math.toDegrees(r);
updateRotation();
break;
default:
break;
}
Log.d(this.getClass().getName(), "Value of angle in ontouch: " + Float.toString(mAngle));
break;
default:
break;
}
return true;
}
=============================================
Edit 3:- Strange thing is that if i modify my onTouch event and perform all the calculations in ACTION_MOVE the imageview responds for each touch event, but this is not what I want as I cannot do the proper angluar rotation in ACTION_MOVE event

Ruchira,
From looking at your code and working with many onTouch innovations myself, I can tell you that the problem is definitely in your onTouchEvent(). You record the mX1 and mY1 in your ACTION_MOVE without recording the original ACTION_DOWN event. This means that every time you move your finger, the onTouchEvent() method thinks that this is the original position. Try this instead:
public boolean onTouch(View v, MotionEvent motion) {
float dy ;
float dx;
double r = 0;
float angle = 0;
switch(v.getId())
{
case R.id.arrow:
switch(motion.getActionMasked())
{
case MotionEvent.ACTION_DOWN:
mX1 = motion.getX();
mY1 = motion.getY();
break;
case MotionEvent.ACTION_MOVE:
Log.w(this.getClass().getName(),"In MOTION MOVE");
//Just to support real time rotation, you could:
mX2 = motion.getX();
mY2 = motion.getY();
//... some rotation code.
break;
case MotionEvent.ACTION_UP:
Log.w(this.getClass().getName(),"In MOTION UP");
// All of this should be fine.
mX2 = motion.getX();
mY2 = motion.getY();
dy = -( mY2-mY1);
dx = -(mX2-mX1);
r = Math.atan2(dy, dx);
angle = (int)Math.toDegrees(r);
updateRotation(angle);
break;
default:
break;
}
Log.d(this.getClass().getName(), "Value of angle in ontouch: " + Double.toString(angle));
break;
default:
break;
}
return true;
}
That should at least track your numbers correctly, so that they may actually be used.
Additional Considerations
The most common mistake is to make sure that you have not set any of your tracking variables to final. If this is the case, the code will set it once, but not again...
When dealing with Drawables, it is important to get rid of the original Drawable and its callback. The reason for this is a well known issue that was never resolved in Android because a decision couldn't be made as to when exactly it was necessary and when it wasn't. Essentially, Android will eventually run out of memory, but will not necessarily tell you and just fail to update the image. This is how you do this (when replacing an image).
Drawable trash = mImageView.getBackgroundDrawable();
if (trash != null)
{ trash.setCallback(null);
trash.recycle();
trash = null;
}
mImageView.setBackgroundDrawable(draw);
Finally, you have to let the image know that it has to redraw itself. This isn't always the case, but is true more often than not. mImageView.invalidate(); will often resolve the issue, and should be placed on the last line in your updateRotation() method.
FuzzicalLogic