Develop Reference

Android -Measure the Coordinates of texts with the onTouchEvent coordinates

I want to dynamically update the Coordinate values of texts stored in an array when MotionEvent.ACTION_MOVE triggers
The problem is i can manually change the Coordinates, But how to measure the Coordinates of Texts and Coordinates of Event.
package argha.paperzone.papereditor.paperviews;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import androidx.annotation.Nullable;
import java.util.ArrayList;
import java.util.List;
import argha.paperzone.papereditor.models.PaperTextModel;
public class PaperEditorView extends View {
private Paint paint;
private List<PaperTextModel> textModelList = new ArrayList<>();
public PaperEditorView(Context context, #Nullable AttributeSet attrs) {
super(context, attrs);
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setTextSize(60);
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.FILL);
}
public void addText(String text) {
if (textModelList.size() == 0) {
textModelList.add(new PaperTextModel(1, 100, 100));
} else {
int lastId = textModelList.get(textModelList.size() - 1).getId();
int lastX = textModelList.get(textModelList.size() - 1).getXAxis();
int lastY = textModelList.get(textModelList.size() - 1).getYAxis();
textModelList.add(new PaperTextModel(lastId + 1, lastX, lastY + 100));
}
invalidate();
}
public void clearAll() {
textModelList.clear();
invalidate();
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (textModelList.size() > 0) {
for (int i = 0; i < textModelList.size(); i++) {
canvas.drawText("Text " + textModelList.get(i).getId(),
textModelList.get(i).getXAxis(),
textModelList.get(i).getYAxis(),
paint
);
}
}
}
#Override
public boolean onTouchEvent(MotionEvent event) {
int eventAction = event.getAction();
int x = (int) event.getX();
int y = (int) event.getY();
switch (eventAction) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
textModelList.get(2).setXAxis(x);
textModelList.get(2).setYAxis(y);
}
invalidate();
return true;
}
}

Android calculate the area of polygon using canvas drawing(not maps)

I use this codes for draw a polygon on a canvas. But I want to calculate the area of polygon. Of course give the measurements of each line. I see a lot of example on maps but ı don't convert/adapt on canvas. Can anyone showing a way or method ?
Thanks in advance.
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Point;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class MainActivity extends Activity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(new DrawingView(MainActivity.this));
}
class DrawingView extends SurfaceView
{
private SurfaceHolder surfaceHolder;
private final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
private List<Point> pointsList = new ArrayList<Point>();
public DrawingView(Context context)
{
super(context);
surfaceHolder = getHolder();
paint.setColor(Color.BLACK);
paint.setStyle(Style.FILL);
}
#Override
public boolean onTouchEvent(MotionEvent event)
{
if (event.getAction() == MotionEvent.ACTION_DOWN)
{
if (surfaceHolder.getSurface().isValid())
{
// Add current touch position to the list of points
pointsList.add(new Point((int) event.getX(), (int) event.getY()));
// Get canvas from surface
Canvas canvas = surfaceHolder.lockCanvas();
// Clear screen
canvas.drawColor(Color.WHITE);
// Iterate on the list
for (int i = 0; i < pointsList.size(); i++)
{
Point current = pointsList.get(i);
Point first = pointsList.get(0);
// Draw points
canvas.drawCircle(current.x, current.y, 5, paint);
// Draw line with next point (if it exists)
if (i + 1 < pointsList.size())
{
Point next = pointsList.get(i + 1);
canvas.drawLine(current.x, current.y, next.x, next.y, paint);
canvas.drawLine(next.x, next.y, first.x, first.y, paint);
c
}
}
// Release canvas
surfaceHolder.unlockCanvasAndPost(canvas);
}
}
return false;
}
}
}

Here's a method for calculating the area of a polygon.
for (int i = 0; i < points.size(); i++) {
float addX = points.get(i).x;
float addY = points.get(i == points.size() - 1 ? 0 : i + 1).y;
float subX = points.get(i == points.size() - 1 ? 0 : i + 1).x;
float subY = points.get(i).y;
total += (addX * addY * 0.5);
total -= (subX * subY * 0.5);
}
return Math.abs(total);

Move ball back and forth

Trying to get the ball where it moves back and forth across the screen (left-right).
I tried using the draw function to update the ball position using if statements
x += speed_x;
y += speed_y;
canvas.drawCircle(x, y, 20, paint);
if (x == 0)
speed_x=-1;
if (x == getHeight())
speed_x=1;
if (y == 0)
speed_y = -1;
if (y == getWidth())
speed_y = 1;
invalidate();
This did not work.
**game.java*
import android.content.Context;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.graphics.drawable.BitmapDrawable;
import android.os.Handler;
import android.util.AttributeSet;
import android.widget.ImageView;
public class GameWorld extends SurfaceView implements Runnable {
boolean isRunning;
GameObject obj;
SurfaceHolder holder;
Canvas canvas;
Thread gameThread;
Paint paint;
private Context mContext;
int x = -1;
int y = -1;
int speed_x=1, speed_y=1;
private int xVelocity = 10;
private int yVelocity = 5;
private Handler h;
private final int FRAME_RATE = 30;
public GameWorld(Context context, AttributeSet attrs) {
super(context, attrs);
mContext = context;
h = new Handler();
}
private Runnable r = new Runnable() {
#Override
public void run() {
invalidate();
}
};
public GameWorld(Context context){
super(context);
isRunning=true;
obj=new GameObject(BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher),200,300);
paint=new Paint();
gameThread= new Thread(this);
gameThread.start();
holder=getHolder();
}
public void run(){
while(isRunning){
if(!holder.getSurface().isValid()){
continue;
}
update();
draw();
}
}
private void update(){
obj.update();
}
private void draw(){
canvas=holder.lockCanvas();
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.FILL);
canvas.drawRect(0, 0, getWidth(), getHeight(), paint);
obj.draw(canvas);
canvas.drawColor(Color.WHITE);
x+=speed_x;
y+=speed_y;
canvas.drawCircle(x, y, 20, paint);
if(x==0)
speed_x=-1;
if(x== getHeight())
speed_x=1;
if(y==0)
speed_y=-1;
if(y==getWidth())
speed_y=1;
invalidate();
holder.unlockCanvasAndPost(canvas);
}
public boolean onTouchEvent(MotionEvent event){
obj.jump();
return super.onTouchEvent(event);
}
}
**main:**
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class MainActivity extends Activity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new GameWorld(this));
}
}
**gameobject.java**
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
public class GameObject {
int x,y;
int velY;
int width, height;
boolean jump;
Bitmap bitmap;
final int GRAVITY =2;
public GameObject(Bitmap bitmap, int x, int y){
this.x=x;
this.y=y;
this.width=bitmap.getWidth();
this.height=bitmap.getHeight();
this.bitmap=bitmap;
velY=0;
jump=false;
}
public void update(){
//handles input
if (jump){
velY=-30;
}
//add gravity
velY+=GRAVITY;
y+=velY;
//POSITION
if(y>300){
y=300;
velY=0;
}
jump=false;
}
public void jump(){
jump=true;
}
Paint paint = new Paint();
public void draw(Canvas canvas){
canvas.drawBitmap(bitmap,x,y,null);
int x=5; //ball
boolean game = true;
// while(game = true)
// {
int maxx = canvas.getWidth();
if (x <= maxx)
{
paint.setColor(Color.WHITE);
canvas.drawCircle(x, 305, 10, paint);
x= (x+2);
}
///else{
// x= (x-2);
// paint.setColor(Color.WHITE);
// canvas.drawCircle(x, 305, 10, paint);
// game = false;
//}
// }
}
public void moveball()
{
x= (x-2);
}
}

Here is my version of a ball moving based on the swipes it recives
import android.app.Activity;
import android.graphics.Color;
import android.graphics.PorterDuff;
import android.os.Bundle;
import android.view.View;
public class BouncingBallActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
View boundcingBallView = new BouncingBallView(this);
setContentView(boundcingBallView);
}
}
Here is the actual view that will make the ball
package com.example.bouncingball;
import java.util.Formatter;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.DashPathEffect;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Typeface;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;
public class BouncingBallView extends View {
private int xMin=0,xMax,yMin=0,yMax;
private float ballRadius = 80,ballX = ballRadius+20, ballY= ballRadius+40,ballSpeedX=5,ballSpeedY=3,previousX,previousY;
private RectF ballBounds;
private Paint paint;
private StringBuilder statusmsg = new StringBuilder();
private Formatter formatter = new Formatter(statusmsg);
public BouncingBallView(Context context) {
super(context);
ballBounds = new RectF();
paint = new Paint();
paint.setDither(true);
paint.setAntiAlias(true);
paint.setFilterBitmap(true);
paint.setHinting(Paint.HINTING_ON);
paint.setPathEffect(new DashPathEffect(new float[] {1,1}, 0));
paint.setTypeface(Typeface.MONOSPACE);
paint.setTextSize(16);
this.setFocusableInTouchMode(true);
}
#Override
protected void onDraw(Canvas canvas) {
ballBounds.set(ballX-ballRadius , ballY-ballRadius,ballX+ballRadius,ballY+ballRadius);
paint.setColor(Color.GREEN);
canvas.drawOval(ballBounds, paint);
paint.setColor(Color.BLACK);
canvas.drawText(statusmsg.toString(), 10, 30,paint);
update();
invalidate();
}
private void update() {
ballX +=ballSpeedX;
ballY+=ballSpeedY;
if(ballX+ballRadius> yMax) {
ballSpeedX =-ballSpeedX;
ballX = xMax -ballRadius;
}
else if(ballX - ballRadius < xMin) {
ballSpeedX = -ballSpeedX;
ballX = xMin+ballRadius;
}
if(ballY + ballRadius > yMax) {
ballSpeedY = -ballSpeedY;
ballY = yMax-ballRadius;
}
else if (ballY - ballRadius < yMin) {
ballSpeedY = -ballSpeedY;
ballY = yMin+ballRadius;
}
statusmsg.delete(0, statusmsg.length());
formatter.format("Ball#(%3.0f,%3.0f),Speed=(%2.0f,%2.0f)", ballX, ballY,ballSpeedX, ballSpeedY);
}
#Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
xMax = w-1;
yMax = h-1;
}
#Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
switch(keyCode) {
case KeyEvent.KEYCODE_DPAD_RIGHT:
ballSpeedX++;
break;
case KeyEvent.KEYCODE_DPAD_LEFT:
ballSpeedX--;
break;
case KeyEvent.KEYCODE_DPAD_UP:
ballSpeedY--;
break;
case KeyEvent.KEYCODE_DPAD_DOWN:
ballSpeedY++;
break;
case KeyEvent.KEYCODE_DPAD_CENTER:
ballSpeedX = 0;
ballSpeedY = 0;
break;
case KeyEvent.KEYCODE_A:
float maxRadius = (xMax > yMax) ? yMax / 2* 0.9f : xMax / 2 * 0.9f;
if(ballRadius < maxRadius)
ballRadius*=1.05;
break;
case KeyEvent.KEYCODE_Z:
if(ballRadius>20){
ballRadius *=0.95;
}
break;
}
return true;
}
#Override
public boolean onTouchEvent(MotionEvent event) {
float currentX=event.getX();
float currentY = event.getY();
float deltaX,deltaY;
float scalingFactor = 5.0f / ((xMax > yMax) ? yMax : xMax);
switch(event.getAction()) {
case MotionEvent.ACTION_MOVE:
deltaX = currentX - previousX;
deltaY = currentY - previousY;
ballSpeedX += deltaX*scalingFactor;
ballSpeedY += deltaY*scalingFactor;
}
previousX = currentX;
previousY = currentY;
return true;
}
}

implemanting freehand crop in android

i m trying to implement freehand crop in android using canvas. i use drawPath and store it in List and draw it in canvas path drawing ok,
like this
but now i want to make all pixel in that path in side area with this code but i dont no how to do it..
public Bitmap getBitmapWithTransparentBG(Bitmap srcBitmap)
{
Bitmap result = srcBitmap.copy(Bitmap.Config.ARGB_8888, true);
int nWidth = result.getWidth();
int nHeight = result.getHeight();
for (int y = 0; y < nHeight; ++y)
{
for (int x = 0; x < nWidth; ++x)
{
for (int i = 0; i < points.size() ; i++)
{
}
result.setPixel(x, y, Color.TRANSPARENT);
}
}
return result;
}
points is list of path coordinate hear is code for draw path
package com.org;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
public class SomeView extends View implements OnTouchListener {
private Paint paint;
List<Point> points;
int DIST = 2;
boolean flgPathDraw = true;
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.waterlilies);
public SomeView(Context c ) {
super(c);
setFocusable(true);
setFocusableInTouchMode(true);
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(2);
paint.setColor(Color.WHITE);
this.setOnTouchListener(this);
points = new ArrayList<Point>();
}
public SomeView(Context context, AttributeSet attrs) {
super(context, attrs);
setFocusable(true);
setFocusableInTouchMode(true);
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(2);
paint.setColor(Color.WHITE);
this.setOnTouchListener(this);
points = new ArrayList<Point>();
}
public void onDraw(Canvas canvas)
{
canvas.drawBitmap(bitmap, 0, 0, null);
Path path = new Path();
boolean first = true;
for (int i = 0; i < points.size(); i += 2)
{
Point point = points.get(i);
if (first) {
first = false;
path.moveTo(point.x, point.y);
} else if (i < points.size() - 1) {
Point next = points.get(i + 1);
path.quadTo(point.x, point.y, next.x, next.y);
} else {
path.lineTo(point.x, point.y);
}
}
canvas.drawPath(path, paint);
}
public boolean onTouch(View view, MotionEvent event) {
// if(event.getAction() != MotionEvent.ACTION_DOWN)
// return super.onTouchEvent(event);
Point point = new Point();
point.x = (int) event.getX();
point.y = (int) event.getY();
if (flgPathDraw) {
points.add(point);
}
invalidate();
Log.e("Hi ==>", "Size: " + points.size());
return true;
}
public void fillinPartofPath()
{
Point point = new Point();
point.x = points.get(0).x;
point.y = points.get(0).y;
points.add(point);
invalidate();
}
public void resetView()
{
points.clear();
paint.setColor(Color.WHITE);
paint.setStyle(Style.STROKE);
flgPathDraw=true;
invalidate();
}
}
class Point {
public float dy;
public float dx;
float x, y;
#Override
public String toString() {
return x + ", " + y;
}
}

Hi i think below link for your exact solution, what u try?
Android: Free Croping of Image
Don't forget to put your vote and feedback here.

Lets look at a bit more complex example:
The red point is the point you want to test. You have to find the edges that cross the y coordinate of the red point. In this example 4 edges cross the y coordinate (the blue points).
Now test how much intersections you get on the left side and on the right side of the point you want to check. If there is an odd number of intersections on both sides the point is inside the shape.
update: you can find a more detailed description of this algorithm here

You can use Canvas.clipPath to draw only cropped region. But be awared that this method doesn't work with hardware acceleration so you have to turn it off and use software rendering.

This circle only draws once in android

Why does this code only draw a circle once? I cannot for the life of me figure it out. Do I need to do some kind of refresh or something? I am able to get a red dot, to draw once, but any click after does not show a new dot, or even move the previous one.
package ball.test;
import android.app.Activity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.TextView;
public class BallActivity extends Activity {
/** Called when the activity is first created. */
BallView bv;
int i = 0;
TextView tv;
//float x = 20;
//float y = 20;
float r = 20;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
tv = (TextView) findViewById(R.id.top);
LinearLayout main = (LinearLayout) findViewById(R.id.main_view);
//main.addView(new BallView(this, 20, 20, 20));
main.setOnTouchListener(new View.OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
i++;
float x = event.getX();
float y = event.getY();
tv.setText("Clicks: " + i + "X: " + x + "Y: " + y);
LinearLayout ll = (LinearLayout) v;
ll.addView(new BallView(ll.getContext(), x, y, 25));
return false;
}
});
}
}
package ball.test;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.view.View;
public class BallView extends View{
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
float x;// = 20;
float y;// = 20;
float r;// = 20;
public BallView(Context context, float x, float y, float r) {
super(context);
this.x = x;
this.y = y;
this.r = r;
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
paint.setColor(Color.RED);
//paint.setStyle(Style.FILL_AND_STROKE);
//canvas.drawColor(Color.WHITE);
canvas.drawCircle(x, y, r, paint);
}
}

Change your LinearLayout to an AbsoluteLayout. I think what's happening is that your first BallView is actually taking up the entirety of the LinearLayout view group and any other views you add to it are being pushed out of the layout.
Also, look into using addView(View, AbsoluteLayout.LayoutParams) instead, so you can set the size/position of the ball there as opposed to in BallView.onDraw, which will allow smaller regions of your layout to be marked dirty.