Develop Reference

Android: Screen bottom coordinate is beyond visible area

I'm trying to create the control, that allows moving view with the finger. To do this, I follow recommendations from this post.
But presented method needs some modification, to prevent my view from being moved beyond the screen. I found out how to get maxY and maxY coordinates - for my Samsung Galaxy A6 it's 1080x1920. But the problem is, that my maxY is deep beyond the visible bottom edge of the device.
So my control almost disappears, when reaches Y about 1650. What 300 more pixels go for. I can suppose, that this is NavigationBar height + my control view height, but this also doesn't place my control as expected.
I define max coordinates with this method.
private void setMaxCoordinates(int viewWidth, int viewHeight) {
Display display = getWindowManager().getDefaultDisplay();
Point displaySize = new Point();
display.getSize(displaySize);
maxX = displaySize.x - viewWidth;
maxY = displaySize.y - viewHeight;
}
Please, help me to define the correct formula to detect bottom edge coordinate.

I've found a solution. First of all I was wrong with getting bottom coordinates with the help of WindowManager. This just gives you height of your screen in pixels, that is not related to the container. So to detect your bottom coordinate this way, you have to consider:
StatusBar height.
NavigationBar height.
Height of all views that lokated higher, then your container.
Height of your own control view (ImageView in my case).
So formula will look like this.
maxY = windowHeight - (statusBarHeight + navBarheight + allUpperViewsHeight + yourViewHeight)
The correct way to define the bootom of your container, is to get the container's height and deduct your control height.
maxY = containerHeight - yourViewHeight;

View coordinate in Screen

I have the next question:
Im developing an app that when i move a imageView and drop it, if the view drops under the half height of the screen goes to a (X,Y) position and if is over the half height screen, goes to another position.
I need to calculate the half of the screen generic, so i use the next code:
DisplayMetrics displaymetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
halfHeight = displaymetrics.heightPixels / 2;
This works great, im trying in a screen 1920x1080, the code returns 540.
But when im going to see if when i drop the view is under or over the half, here is what i dont understand. i get the Y position of the view and is ok, what i dont understand is why the Y = 0 is not on the TOP of the screen, if i move the view to the top, i get a negative Y position like -260.
Someone can explain me why this happen?
Is there i way that the (0,0) position starts in the top left of the screen?
Greets, hope you understand

If you call getX() or getY() then you are getting relative values for x and y (relative to the view that the call was dispatched from). If you call getRawX() or getRawY() it will give you the absolute position of the view relative to the device's screen.
Most likely you are getting negative values of -260 because you are dragging the ImageView 260 away from the view in which the call was made (perhaps the view on the top of the screen has a height of 260). If you are trying to use getX() or getY() to calculate the middle of the screen then you would have to take all sizes of all views into consideration but I think you want to use getRawX() and getRawY()

An angle of 0 degrees correspond to the geometric angle of 0 degrees (3 o'clock on a watch.)
try using translate to translate the co-ordinates to top of the screen.
http://developer.android.com/reference/android/graphics/Canvas.html#translate(float, float)

Android barrier detection of accelerating object

my app contains an object moving on a surfaceview. I am able to move it around via accelerometer.
Here's the movement code of the player object:
if(x + mx*speed > 0 && x + mx*speed < GameView.WIDTH) {
x += mx*speed;
}
if(y+ my*speed > 0 && y+ my*speed < GameView.HEIGHT) {
y+=my*speed;
}
x and y are the player's coordinates
mx is the value the player gets from the accelerometer, for example: when tilting to the left, mx is -2, when tilting more, mx is -4, -5, -6 etc. --> my is the same for the y-axis
the speed is a variable to modify and play around when i want to have a faster movement.
as you can see I tried to limit the movement to only move when the player is inside of the view.
Now my problem is: when tilting the device intensively to the right, mx turns to something like 6. speed is set to 5. This means, when the player's position + 6 * 5 is bigger than the game view it should not move any more. But this results in the player stopping pixels in front of the right side of the view... when tilting lightly to the right, the object stops perfectly at the border of the view...
Now how should i change the code to achieve an object that stops it's movement perfectly at borders of the screen?
On this picture you can see the circle not stopping quite at the bottom, as there are some pixels between the circle and the bottom border. when going slightly back with the accelerometer, the circle aligns itself to the bottom of the screen:
But now, i can only reach the screen borders when moving slowly, which means with a low mx or my.
the screenshots you can see the mY values. On the first picture my = ca. 8 and on the second ca. 6.
Any ideas?
Thanks in advance

Try to instead cap the value to the border like so
x = Math.max(Math.min(x + mx*speed, GameView.WIDTH), 0.0f));
y = Math.max(Math.min(y + my*speed, GameView.HEIGHT, 0.0f));

Get Y coordinate of top and bottom of ImageView

I have an image view which is contained within a relative layout. I am trying to get the screen y coordinates of the top of the image view and the screen y coordinates of the bottom of the image view. I have tried this:
float yMin = (float)levelH.getTop();
float yMax = (float)levelH.getBottom();
float yMin seems almost correct. I am translating another image view (IM2) up and down this image view(IM1). So I am trying to set a limit on how far (IM2) can translate up and down. So my thinking was to get the y top and bottom of (IM1) I can set those as max and min.
Anyone know how to do this?
ps Im using android accelometer to move (IM2)

getTop() ansd getBottom() look at coordinates within it's parent. To get coordinates of it's position on the screen you can use getLocationOnScreen
Use it like this:
int[] coords = {0,0};
view.getLocationOnScreen(coords);
int absoluteTop = coords[1];
int absoluteBottom = coords[1] + view.getHeight();

Use View.getLocationOnScreen() and/or getLocationInWindow()

Smoothly move Image with accelerometer in android

I am building an android application similar to x-ray scanner (Play Store Link), which moves images smoothly on screen by moving the device left,right top and bottom.
I am using accelerometer for this, but problem is that image is not moving smoothly.
My code is below
int x1 = (int) sensorEvent.values[0]*(screenW/10);
int y1 = (int) sensorEvent.values[1]*(screenH/14);
and then in on Draw
canvas.drawBitmap(bmp, x, y, mPaint);

This is not how you use them. You should take current value and ADD to current position instead of setting position from value directly. The more you tilt - the bigger values you will get and hence the faster the image will appear to move.
You can then also apply some linear interpolation to the movement so that it appears smoother.
Here is a link to learn more about lerp (linear interpolation) in code: http://en.wikipedia.org/wiki/Linear_interpolation#Programming_language_support