I am making a canvas and setting its background which is an image
I am adding text on it by canvas. Drawtext method which works perfectly alright
now I want these text to be clickable but i couldn't find any method
The other method I could think of was to add text box on canvas add write on click event of these text box but could not find any example related to this can anybody suggest what to do.
Canvas is a space where you can just draw some graphics, thus the only way to do what you want is detecting when the user click the surface the canvas is drawn on (e.g. a SurfaceView), and using the coordenates you just fire an event. Of course, you need to verify whether the click was done on the specific part you want (e.g. the area where you drew a button or something).
Use the onTouchEvent method. Here is an example I used for finding out if the user's click coordinates are in a List of rectangles (aka buttons):
#Override
public boolean onTouchEvent( MotionEvent event) {
super.onTouchEvent(event);
int x = (int)event.getX();
int y = (int)event.getY();
xStored = x; yStored=y;
if (event.getAction()==MotionEvent.ACTION_UP){
}else if(event.getAction()==MotionEvent.ACTION_DOWN){
System.out.println("Touching down!");
for(Rect rect : rectangles){
if(rect.contains(x,y)){
System.out.println("Touched Rectangle, start activity."+x+","+y);
invalidate();
}else{
}
}
}else if(event.getAction()==MotionEvent.ACTION_MOVE){
}
this.postInvalidate();
return true;
}
Related
This is a basic code for detecting touch + drawing a custom view :
public boolean onTouchEvent(MotionEvent event) { //Basic onTouch code for scrolling along the Y axis
super.onTouchEvent(event);
if(event.getActionMasked()==MotionEvent.ACTION_DOWN){
mPrevious = event.getY();
}
if(event.getActionMasked()==MotionEvent.ACTION_MOVE){
float distance = mPrevious - event.getY();
scrollBy(0,Math.round(distance));
mPrevious = event.getY();
}
return true;
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
//Basic drawing of a circle at (200,200)
canvas.drawCircle(200f,200f,50f, defaultPaint);
//canvas.setMatrix(new Matrix());
Log.d("CANVAS", "("+canvas.getMatrix().toString()+")");
}
I'm working with a custom view, I'm trying to implement user scrolling functionality using scrollBy, but it looks like I'll have to create the logic myself.
I still want to understand how this function works. When I print log the canvas matrix in the last line, it correctly displays the new coordinates, and onDraw is called every time the touch moves.
But if I uncomment canvas.setMatrix, suprisingly nothing changes functionality-wise. The only difference now is that the console log shows that the canvas matrix is always equal to identity mx, even if it's correctly being scrolled. Why? How can scrollBy completely overwrite canvas drawing?
I'm working on an app that plots nodes on a map, and each node has edges that are represented by a line between them. I've drawn the edges using Canvas and drawLine(), but it would be useful if the lines themselves could be clickable. By that I mean a method of allowing the user to touch the line or think they're touching the line and an event can trigger. (like display edge info, etc...)
I can't rightly attach a touch event to a line I've drawn with Canvas, so I was thinking of placing ImageViews inbetween the ends of each edge line that's drawn. The ImageView could be a dot so it's clear where the touch event triggers.
Does anyone have any other suggestions? I'm mainly looking for ideas that I've missed. Maybe there's something in the Android API that can help with this that I'm unaware of.
Thanks in advance for any tips!
Use a path to draw the line:
Path linePath;
Paint p;
RectF rectF;
float point1X, point1Y, point2X, point2Y;
// initialize components
// draw the line
linePath.moveTo(point1X, point1Y);
linePath.lineTo(point2X, point2Y);
canvas.drawPath(linePath, p);
linePath.computeBounds(rectF, true);
Override onTouchEvent(MotionEvent):
#Override
public boolean onTouchEvent(MotionEvent event) {
float touchX = event.getX();
float touchY = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
if (rectF.contains(touchX, touchY)) {
// line has been clicked
}
break;
}
return true;
}
I have to draw text annotations on Image. It should also have choice of moving the text over the Image. Is it possible to move the text by using the Canvas? I searched google and found a suggestion to use a TextView on ImageView and take a screenshot. But when I move the TextView, it is not proper. I mean if I touch the textview, then it is moving somewhere, it is not being exactly below the finger.
One way to do this, is to create a custom view and set a bitmap with Your picture to canvas:
canvas.drawBitmap(yourBitmap, new Rect(0,0,100,100), rectangle, null);
and then draw text:
canvas.drawText("Your Text", textX, textY, paint);
and in the custom view´s onTouch:
public boolean onTouch(View view, MotionEvent event) {
if(event.getAction() == MotionEvent.ACTION_DOWN){
textX = event.getX();
textY = event.getY();
invalidate();
return true;
}
return super.onTouchEvent(event);
}
With that code You are moving only the text. By moving a textView like You described, it depends on the textView´s behavihour how the text is aligned inside the textView.
I cannot test this code for now, but it should give You an idea how to do it
I have created panel with collection of different colors, pencil, eraser and different shapes similar to MS-Paint. I could be able to draw or write on a screen using Touch Event method. But when I draw something on a screen (when I touch the screen), MotionEvent.ACTION_Down method is calling. So it works fine. When I release my finger from the screen, MotionEvent.ACTION_up method is calling and works fine.
So, my problem is, like MS-PAINT I am not able to see what I drew or wrote before I release my finger from the screen. For an example, see this video. User can see when he dragged the shapes or trying to draw a pencil. Also, in this link user draws using pencil and it is visible without releasing a finger on the screen.
But, when I draw something on the screen, once I released the finger only it appears.
What I need is, when user touch the screen itself if he/she moves the finger on the screen, user must be able to see what they are trying to draw or write on the screen.
For an example: if I try to write some word like "Apple" on a screen, I am trying to put "A" . But when I write letter "A", it is invisible unless I take my finger from the screen. Once if I released my finger from the screen after I drew letter"A" then only the text or picture has been appeared on a screen what I drew.
So, I have done MotionEvent.ACTION_DOWN and MotionEVent.ACTION_UP. It works fine.
But, MotionEvent.ACTION_MOVE is not working properly at all.
This is my Code,
#Override
public boolean onTouchEvent(MotionEvent event)
{
if(event.getAction() == MotionEvent.ACTION_DOWN)
{
if(Shape == ShapeLine)
{
GraphicObject = new Line();
((Line) GraphicObject).getBegin().setX(event.getX());
((Line) GraphicObject).getBegin().setY(event.getY());
}
if(Shape== ShapeRect)
{
GraphicObject = new Rectangle();
Point temp = new Point(event.getX(), event.getY());
endPoint = new Point();
((Rectangle) GraphicObject).settemppointOfOneEndRectangle(temp);
}
else if(event.getAction() == MotionEvent.ACTION_MOVE){
if(Shape== ShapeLine)
{
final float x=event.getX();
final float y=event.getY();
}
if(Shape == ShapeRect)
{
endPoint.x=event.getX();
endPoint.y=event.getY();
invalidate();
}
Anyone suggest me, about ACTION_MOVE. I have tried a lot in a code but no changes and I didn't find any solution while moving.
Basic idea is when you tap record that point in a variable,then inside ACTION_MOVE record the current point and draw a line in between these 2 points.Once done save this point in the previous point. Sudo code:
Point last;
Point current;
...
case ACTION_DOWN:
last=mouse.position;
break;
case ACTION_MOVE:
current=mouse.position;
drawLine(current,last);
last=current;
break;
Do this way,your drawing should be fine.
N.B. Remember,this is a sudo code. :P
EDIT. Example from one of my app. Basically I pointed out what you should do:
public boolean onTouchEvent(MotionEvent event)
{
int action = event.getAction();
switch(action & MotionEvent.ACTION_MASK)
{
case MotionEvent.ACTION_DOWN:
initial.x=(int)event.getX();
initial.y=(int)event.getY();
break;
case MotionEvent.ACTION_MOVE:
current.x=(int)event.getX();
current.y=(int)event.getY();
//draw line using initial as start and current as end point
//sudo code: drawLine(initial,current)
//now set initial to current
initial=current// for the continuity of drawing.
break;
}
return true;
}
initial and current both are Point objects.
I have an ImageView with an image loaded,
I want that when the user clicks in a point of the image, another little image(used as pin) is overlapped in this point and the coordinates of the point are returned.
But I haven't idea of how could I do this.
To place a image at a certain coordinates you will have to draw the image on the canvas .
To get the coordinates of the touch event use the following code:
#Override
public void onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_MOVE) {
mTouchX = event.getX();
mTouchY = event.getY();//stores touch event
} else {
mTouchX = -1;
mTouchY = -1;
}
super.onTouchEvent(event);
}
Here is the code for drawing the image on canvas Image in Canvas with touch events
hope it helps.
Try this,
It will help you to place image based on the co-ordinates. So it can be overlapped
Link 1