Develop Reference

Draw on canvas wherever view is dragged

I am trying to create a simple paint app using canvas. The end product would be for the user to select a tool of choice (pen, marker, eraser, etc) and draw or erase accordingly anywhere the tool is dragged on the canvas.
As of now, I only have a pen and I am trying to draw a line wherever the pen is dragged in the canvas. However, I am finding this task challenging. I can drag the pen and I can draw lines, but I can't draw while I am dragging the pen. I am reaching out to the SO community to bridge these two features.
Below is what I have:
MainActivity.java
public class MainActivity extends AppCompatActivity {
private ViewGroup rootLayout;
private int _xDelta;
private int _yDelta;
private RelativeLayout pl;
private ImageView w1;
private boolean clicked1 = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
CanvasView canvasView = new CanvasView(MainActivity.this);
w1 = (ImageView) findViewById(R.id.wand1);
pl = (RelativeLayout) findViewById(R.id.coordAct);
RelativeLayout rootLayout = (RelativeLayout) findViewById(R.id.coordAct);
rootLayout.addView(canvasView);
RelativeLayout.LayoutParams layoutParams1w2 = new RelativeLayout.LayoutParams(getScreenWidth(), getScreenHeight() / 2);
layoutParams1w2.addRule(RelativeLayout.CENTER_IN_PARENT, RelativeLayout.TRUE);
canvasView.setLayoutParams(layoutParams1w2);
w1.setOnTouchListener(new ChoiceTouchListener());
}
public static int getScreenWidth() {
return Resources.getSystem().getDisplayMetrics().widthPixels;
}
public static int getScreenHeight() {
return Resources.getSystem().getDisplayMetrics().heightPixels;
}
public class ChoiceTouchListener implements View.OnTouchListener {
public boolean onTouch(View view, MotionEvent event) {
if (!clicked1){
rootLayout = (ViewGroup) w1.getParent();
if (rootLayout != null) {
// detach the child from parent
rootLayout.removeView(w1);
}
RelativeLayout.LayoutParams layoutParams1 = new RelativeLayout.LayoutParams(300, 300);
pl.addView(w1);
w1.setLayoutParams(layoutParams1);
clicked1 = true;
}
final int X = (int) event.getRawX();
final int Y = (int) event.getRawY();
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
_xDelta = X - lParams.leftMargin;
_yDelta = Y - lParams.topMargin;
break;
case MotionEvent.ACTION_MOVE:
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view
.getLayoutParams();
layoutParams.leftMargin = X - _xDelta;
layoutParams.topMargin = Y - _yDelta;
layoutParams.rightMargin = -250;
layoutParams.bottomMargin = -250;
view.setLayoutParams(layoutParams);
break;
}
rootLayout.invalidate();
return true;
}
}
CanvasView.java
public class CanvasView extends View{
Context context;
int width, height;
Bitmap bitmap;
Path path;
Canvas canvas;
Paint paint;
float mX, mY;
static final float TOLERANCE=4;
public CanvasView(Context context) {
super(context);
this.context=context;
path=new Path();
paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(50);
}
#Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w,h,oldw,oldh);
bitmap=Bitmap.createBitmap(w,h,Bitmap.Config.ARGB_8888);
canvas=new Canvas(bitmap);
}
public void startTouch(float x, float y) {
path.moveTo(x, y);
mX = x;
mY = y;
}
public void moveTouch(float x, float y) {
float dx = Math.abs(x-mX);
float dy = Math.abs(y-mY);
if(dx>=TOLERANCE || dy>= TOLERANCE) {
path.quadTo(mX, mY, (x+mX)/2, (y+mY)/2);
mX=x;
mY=y;
}
}
//To clear canvas
public void clearCanvas() {
path.reset();
invalidate();
}
public void upTouch() {
path.lineTo(mX,mY);
}
#Override
protected void onDraw(Canvas canvas){
super.onDraw(canvas);
canvas.drawPath(path,paint);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction())
{
case MotionEvent.ACTION_DOWN:
startTouch(x,y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
moveTouch(x,y);
invalidate();
break;
case MotionEvent.ACTION_UP:
upTouch();
invalidate();
break;
default:
return false;
}
invalidate();
return true;
}
activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/coordAct"
tools:context="com.simplepaintapp.MainActivity">
<RelativeLayout
android:id="#+id/parLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:weightSum="3"
android:background="#0000ff">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="100dp"
android:layout_alignParentBottom="true"
android:layout_alignParentStart="true"
android:layout_marginBottom="28dp"
android:background="#BA9DF7"
android:gravity="bottom"
android:orientation="vertical">
<HorizontalScrollView
android:id="#+id/backgd"
android:layout_width="match_parent"
android:layout_height="100dp"
android:weightSum="1">
<LinearLayout
android:id="#+id/parentLL"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="horizontal"
android:weightSum="5">
<ImageView
android:id="#+id/wand1"
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_centerInParent="true"
android:layout_gravity="center"
android:src="#drawable/pen" />
</LinearLayout>
</HorizontalScrollView>
</RelativeLayout>
</RelativeLayout>
Current bug after implementing the dispatchTouchEvent() method inside onTouch()

An update to MainActivity and CanvasView is required. See the new source code below:
MainActivity.java
public class MainActivity extends AppCompatActivity {
private ViewGroup rootLayout;
private int _xDelta;
private int _yDelta;
private RelativeLayout pl;
private ImageView w1;
private boolean clicked1 = false;
CanvasView canvasView;
public static int X;
public static int Y;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
canvasView = new CanvasView(MainActivity.this);
w1 = (ImageView) findViewById(R.id.wand1);
pl = (RelativeLayout) findViewById(R.id.coordAct);
RelativeLayout rootLayout = (RelativeLayout) findViewById(R.id.coordAct);
rootLayout.addView(canvasView);
RelativeLayout.LayoutParams layoutParams1w2 = new RelativeLayout.LayoutParams(getScreenWidth(), getScreenHeight() / 2);
layoutParams1w2.addRule(RelativeLayout.CENTER_IN_PARENT, RelativeLayout.TRUE);
canvasView.setLayoutParams(layoutParams1w2);
w1.setOnTouchListener(new ChoiceTouchListener());
}
public static int getScreenWidth() {
return Resources.getSystem().getDisplayMetrics().widthPixels;
}
public static int getScreenHeight() {
return Resources.getSystem().getDisplayMetrics().heightPixels;
}
public class ChoiceTouchListener implements View.OnTouchListener {
public boolean onTouch(View view, MotionEvent event) {
if (!clicked1){
rootLayout = (ViewGroup) w1.getParent();
if (rootLayout != null) {
// detach the child from parent
rootLayout.removeView(w1);
}
RelativeLayout.LayoutParams layoutParams1 = new RelativeLayout.LayoutParams(300, 300);
pl.addView(w1);
w1.setLayoutParams(layoutParams1);
clicked1 = true;
}
X = (int) event.getRawX();
Y = (int) event.getRawY();
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
_xDelta = X - lParams.leftMargin;
_yDelta = Y - lParams.topMargin;
canvasView.dispatchTouchEvent(event);
break;
case MotionEvent.ACTION_MOVE:
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view
.getLayoutParams();
layoutParams.leftMargin = X - _xDelta;
layoutParams.topMargin = Y - _yDelta;
layoutParams.rightMargin = -250;
layoutParams.bottomMargin = -250;
view.setLayoutParams(layoutParams);
canvasView.dispatchTouchEvent(event);
break;
}
rootLayout.invalidate();
return true;
}
}
CanvasView.java:
public class CanvasView extends View{
Context context;
int width, height;
Bitmap bitmap;
Path path;
public Canvas canvas;
Paint paint;
float mX, mY;
static final float TOLERANCE=4;
public static float x;
public static float y;
public CanvasView(Context context) {
super(context);
this.context=context;
path=new Path();
paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(50);
}
#Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w,h,oldw,oldh);
bitmap=Bitmap.createBitmap(w,h,Bitmap.Config.ARGB_8888);
canvas=new Canvas(bitmap);
}
public void startTouch(float x, float y) {
path.moveTo(x, y);
mX = x;
mY = y;
}
public void moveTouch(float x, float y) {
float dx = Math.abs(x-mX);
float dy = Math.abs(y-mY);
if(dx>=TOLERANCE || dy>= TOLERANCE) {
path.quadTo(mX, mY, (x+mX)/2, (y+mY)/2);
mX=x;
mY=y;
}
}
//To clear canvas
public void clearCanvas() {
path.reset();
invalidate();
}
public void upTouch() {
path.lineTo(mX,mY);
}
#Override
protected void onDraw(Canvas canvas){
super.onDraw(canvas);
canvas.drawPath(path,paint);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction())
{
case MotionEvent.ACTION_DOWN:
startTouch(MainActivity.X,MainActivity.Y-380);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
moveTouch(MainActivity.X,MainActivity.Y-380);
invalidate();
break;
case MotionEvent.ACTION_UP:
upTouch();
invalidate();
break;
default:
return false;
}
invalidate();
return true;
}

mLayout.addView() works one time only

I started lately developing for android and got stuck trying to add multiple Views to a Layout. It actually works for the first touch, but after that it does nothing. The Log though keeps working and showing that the touch has been detected and shows the position of the event. I have the following code
public class MainActivity extends Activity {
private LinearLayout mLayout;
private Context con = this;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mLayout = (LinearLayout) findViewById(R.id.lLayout);
mLayout.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
mLayout.addView(createNewView(event.getX(), event.getY()));
Log.d("this ","View has been add." + event.getX()+ ", " + event.getY());
break;
}
return false;
}
});
}
private markerView createNewView(float x, float y) {
final LayoutParams lparams = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
final markerView mView = new markerView(con, 150, x, y);
mView.setLayoutParams(lparams);
return mView;
}}
and
public class markerView extends View implements View.OnTouchListener{
private Paint paint = new Paint();
private int diameter;
private float X,Y;
public markerView(Context context, int dia, float dx, float dy) {
super(context);
diameter = dia;
X = dx; Y = dy;
paint.setColor(Color.GREEN);
paint.setStyle(Style.STROKE);
paint.setStrokeWidth((float) 4.0);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.save();
canvas.drawCircle(X, Y, diameter, paint);
canvas.restore();
}
#Override
public boolean onTouch(View v, MotionEvent event) {
return true;
}}

Try remove final tag on your final markerView mView = new markerView(con, 150, x, y);

i just found that the Views ave been created but never show up because the first one has the size of the parentLayout. so i just add the following methode and it worked. the position needs to be changed because of the RelativeLayout but thats not a problem ;)
here is the code:
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
setMeasuredDimension(2*diameter, 2*diameter);
}

Draw bitmap on canvas by "onTouchListener" at specific position

I use Canvas to draw bitmap by touch screen but they don't show bitmap on apps.
public class MainActivity extends Activity {
public LinearLayout screenlayout;
public void draw (int x, int y){
Bitmap b = BitmapFactory.decodeResource(getResources(),R.drawable.dam);
Canvas canvas=new Canvas(b);
canvas.drawBitmap(b, x, y, null);
}
public void onCreate(Bundle saveInstanceState){
super.onCreate(saveInstanceState);
setContentView(R.layout.activity_main);
final LinearLayout screenlayout= (LinearLayout)findViewById(R.id.screenlayout);
screenlayout.setOnTouchListener(new OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
int x = (int) event.getRawX();
int y = (int) event.getRawY();
draw(x,y);
break;
case MotionEvent.ACTION_MOVE:
break;
default:
break;
}
return true;
}
});
}
}

As Ganpat Kaliya answer, I provide another code to solve this problem. Thanks to Ganpat Kaliya.
public class MainActivity extends Activity {
public static float vtx;
public static float vty;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Test view = new Test(this);
ViewGroup.LayoutParams params = new ViewGroup.LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT);
addContentView(view, params);
view.setOnTouchListener(new OnTouchListener(){
public boolean onTouch(View v, MotionEvent event) {
float a = event.getX();
float b = event.getY();
vtx=a;
vty=b;
v.invalidate();
return true;
}
});
}
}
And:
public class Test extends View {
public Test(Context context) {
super(context);
}
public void draw(Canvas canvas) {
float x=MainActivity.vtx;
float y=MainActivity.vty;
Paint paint = new Paint();
paint.setColor(Color.GREEN);
paint.setStrokeWidth(6);
canvas.drawLine(10,10,50,50,paint);
paint.setColor(Color.RED);
canvas.drawLine(50, 50, 90, 10, paint);
canvas.drawCircle(50, 50, 3, paint);
canvas.drawCircle(x,y,10,paint);
Bitmap b = BitmapFactory.decodeResource(getResources(),R.drawable.dam);
canvas.drawBitmap(b, x, y, null);
}
}

Passing values between activity and view class

I have a problem with passing X and Y coordinates from onTouchEvent in DravingView; I want show these values in MainActivity. I tried use intinity and bundle method, but I did something wrong.
DrawingView.java
public class DrawingView extends View {
private Bitmap cacheBitmap;
private Canvas cacheCanvas;
private Paint paint;
private Paint BitmapPaint;
private Path path;
private int height;
private int width;
/** Last saved X-coordinate */
private float pX;
/** Last saved Y-coordinate*/
private float pY;
/** Initial color */
private int paintColor = Color.BLACK;
private static Paint.Style paintStyle = Paint.Style.STROKE;
/** Paint Point size */
private static int paintWidth = 8;
private Canvas canvas;
/** get the height and width */
#Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
height = h;
width = w;
init();
}
private void init(){
cacheBitmap = Bitmap.createBitmap(width, height, Config.ARGB_8888);
cacheCanvas = new Canvas(cacheBitmap);
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
path = new Path();
BitmapPaint = new Paint();
updatePaint();
}
private void updatePaint(){
paint.setColor(paintColor);
paint.setStyle(paintStyle);
paint.setStrokeWidth(paintWidth);
}
public DrawingView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public DrawingView(Context context){
super(context);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
path.moveTo(event.getX(), event.getY());
pX = event.getX();
pY = event.getY();
break;
case MotionEvent.ACTION_MOVE:
path.quadTo(pX, pY, event.getX(), event.getY());
pX = event.getX();
pY = event.getY();
break;
case MotionEvent.ACTION_UP:
cacheCanvas.drawPath(path, paint);
path.reset();
break;
}
invalidate();
return true;
}
#Override
protected void onDraw(Canvas canvas) {
this.canvas = canvas;
BitmapPaint = new Paint();
canvas.drawBitmap(cacheBitmap, 0,0, BitmapPaint);
canvas.drawPath(path, paint);
}
public void setColor(int color){
paintColor = color;
updatePaint();
}
public void setPaintWidth(int width){
paintWidth = width;
updatePaint();
}
public static final int PEN = 1;
public static final int PAIL = 2;
public void setStyle(int style){
switch(style){
case PEN:
paintStyle = Paint.Style.STROKE;
break;
case PAIL:
paintStyle = Paint.Style.FILL;
break;
}
updatePaint();
}
/** clear your drawing*/
public void clearScreen(){
if(canvas != null){
Paint backPaint = new Paint();
backPaint.setColor(Color.WHITE);
canvas.drawRect(new Rect(0, 0, width, height), backPaint);
cacheCanvas.drawRect(new Rect(0, 0, width, height), backPaint);
}
invalidate();
}
}
MainActivity.java
public class MainActivity extends ActionBarActivity {
private DrawingView drawView;
private ImageButton currPaint;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
drawView = (DrawingView)findViewById(R.id.drawing);
//LinearLayout paintLayout = (LinearLayout)findViewById(R.id.paint_colors);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public void openMenuBack(View view) {
Intent intent = new Intent(this, MainActivityMenu.class);
startActivity(intent);
}
public void openNew(View view) {
Intent intent = new Intent(this, MainActivity.class);
startActivity(intent);
}
}

What you could do is create an interface, that your mainActivity would implement.
public interface MyDrawingViewInterface {
public void onActionFinished(int movedX, int movedY);
}
Then your MainActivity would implement this interface :
public class MainActivity extends ActionBarActivity implements MyDrawingViewInterface{
/* All your other stuff */
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
drawView = (DrawingView)findViewById(R.id.drawing);
drawView.setViewListener(this);
//LinearLayout paintLayout = (LinearLayout)findViewById(R.id.paint_colors);
}
#Override
public void onActionFinished(int movedX, int movedY) {
/*Print it wherever you want here */
}
}
Finally, your DrawView would change as so (notice the new variable, and the call on ACTION_UP) :
public class DrawingView extends View {
private MyDrawingInterface mInterface;
public void setViewListener(MyDrawingView interface) {
mInterface = interface;
}
#Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
path.moveTo(event.getX(), event.getY());
pX = event.getX();
pY = event.getY();
break;
case MotionEvent.ACTION_MOVE:
path.quadTo(pX, pY, event.getX(), event.getY());
pX = event.getX();
pY = event.getY();
break;
case MotionEvent.ACTION_UP:
cacheCanvas.drawPath(path, paint);
path.reset();
mInterface.onActionFinished(pX, pY);
break;
}
invalidate();
return true;
}
}

android-update line between two rotating rectangles

after i draw line between 2 fixed points on two different rectangles i need to rotate them.The problem is that my line is not updated, it stays on the same x1,y1 x2,y2. How to make line to follow this rectangle?
If any of you have any example code or something that can help, it would be great!
Thanks!
I dont think that i will need OnValidateUpdate tho solve this.
This is my example code to demonstrate this problem:
Object that i want to draw:
public class Object {
private int xPos;
private int yPos;
private int width;
private int height;
float xDistance = 0f;
float yDistance = 0f;
double angleToTurn = 0.0;
Matrix matrix = new Matrix();
private Rect rect;
private Paint paint;
private Point point;
Paint p = null;
public Object(int xPos, int yPos){
this.xPos = xPos;
this.yPos = yPos;
this.width = 300;
this.height = 100;
matrix = new Matrix();
rect = new Rect(xPos,yPos,xPos + width,yPos + height);
paint = new Paint();
paint.setStyle(Style.FILL);
paint.setColor(Color.BLUE);
p = new Paint();
p.setStyle(Style.FILL);
p.setStrokeWidth(15);
p.setColor(Color.BLACK);
point = new Point(this.getxPos(), this.getyPos()+this.getHeight());
}
public void rotate(float xEvent, float yEvent){
xDistance = xEvent - this.xPos;
yDistance = yEvent - this.yPos;
int angleToTurn = ((int)Math.toDegrees(Math.atan2(yDistance, xDistance)));
matrix.setRotate((int)(angleToTurn),xPos,yPos + height/2);
}
public void draw(Canvas c){
c.save();
c.setMatrix(matrix);
c.drawRect(rect, paint);
c.drawPoint(point.x,point.y,p);
c.restore();
}
public Point getPoint() {
return point;
}
public void setPoint(Point point) {
this.point = point;
}
public Matrix getMatrix() {
return matrix;
}
public void setMatrix(Matrix matrix) {
this.matrix = matrix;
}
public int getxPos() {
return xPos;
}
public void setxPos(int xPos) {
this.xPos = xPos;
}
public int getyPos() {
return yPos;
}
public void setyPos(int yPos) {
this.yPos = yPos;
}
public int getWidth() {
return width;
}
public void setWidth(int width) {
this.width = width;
}
public int getHeight() {
return height;
}
public void setHeight(int height) {
this.height = height;
}
GameView class where i draw 2 rects:
public class GameView extends SurfaceView implements SurfaceHolder.Callback{
private SurfaceHolder surfaceHolder;
private GameloopThread gameloopThread;
float downx,downy,upx,upy;
private Object object,object1;
Line line;
public GameView(Context context) {
super(context);
gameloopThread = new GameloopThread(this);
surfaceHolder = getHolder();
surfaceHolder.addCallback(this);
object = new Object(500,500);
object1 = new Object(800,700);
line = new Line(object.getPoint(),object1.getPoint());
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
Canvas canvas = surfaceHolder.lockCanvas();
onDraw(canvas);
surfaceHolder.unlockCanvasAndPost(canvas);
gameloopThread.setRunning(true);
gameloopThread.start();
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
boolean retry = true;
gameloopThread.setRunning(false);
while(retry){
try {
gameloopThread.join();
retry=false;
}catch(InterruptedException e){
}
}
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {
}
#SuppressLint("ClickableViewAccessibility")
#Override
public boolean onTouchEvent( MotionEvent event) {
float x = 0f,y=0f;
if(event.getAction() == MotionEvent.ACTION_DOWN){
downx = event.getX();
downy = event.getY();
}
if (event.getAction() == MotionEvent.ACTION_MOVE) {
x = event.getX();
y = event.getY();
object.rotate(x, y);
object1.rotate(x, y);
}
if (event.getAction() == MotionEvent.ACTION_UP) {
}
return true;
}
#Override
public void onDraw(Canvas canvas){
super.onDraw(canvas);
canvas.drawColor(Color.LTGRAY);
if(object != null)
object.draw(canvas);
if(object1 != null)
object1.draw(canvas);
if(line != null){
line._drawLine(canvas);
}
}
}
Line class that should connect two rectangles (i made class for it but it is not needed)
public class Line {
private Point point1,point2;
private Paint p;
Matrix m;
public Line(Point p1,Point p2){
this.point1 = p1;
this.point2 = p2;
p = new Paint();
p.setStyle(Style.FILL);
p.setColor(Color.RED);
m = new Matrix();
}
public void _drawLine(Canvas c){
c.setMatrix(m);
c.save();
c.drawLine(point1.x, point1.y, point2.x, point2.y, p);
c.restore();
}
public Matrix getMatrix(){
return m;
}
}
I would like to use Matrix object if possible to achieve that.There is also MainActivity and Thread class but I dont post them because thay are not relevant to this problem.

You can use ValueAnimator to animate the rectangles. On each
onAnimationUpdate(ValueAnimator animation)
you can invalidate or re-draw the line with the new position.

I found the solution I can just use Matrix.mapPoints, save them and just redraw line !