I want to draw a circle on a canvas and have it leave a trail, rather draw a new circle each time. How would I go about doing this? All I can get it to do is move the circle around.
-CanvasTest Class
package canvas.test;
import android.app.Activity;
import android.os.Bundle;
public class CanvastestActivity extends Activity {
/** Called when the activity is first created. */
float x = 80;
float y = 20;
float r = 15;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Draw2D d = new Draw2D(this, x, y, r);
try {
Thread.sleep(100);
x++;
y++;
} catch(InterruptedException e) {}
setContentView(d);
}
}
--Draw2D Class
package canvas.test;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
public class Draw2D extends View {
float x;
float y;
float r;
public Draw2D(Context context, float x, float y, float r) {
super(context);
this.x = x;
this.y = y;
this.r = r;
}
#Override
protected void onDraw(Canvas c) {
super.onDraw(c);
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.WHITE);
c.drawPaint(paint);
paint.setAntiAlias(true);
paint.setColor(Color.BLUE);
c.drawCircle(x, y, r, paint);
}
}
This is my most recent test. Why would the circle now move? It's does not move at all.
Are you doing something like canvas.drawColor(Color.TRANSPARENT) or canvas.drawColor(Color.BLACK) in the begining of your doDraw method?
If you omit that call it should not clear the canvas and leave the trails you are looking for.
Related
I found some code to draw line and now i wand drawing line progressively so that i cloud see it being drawn.
This is the code
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
public class DrawView extends View {
Paint paint = new Paint();
public DrawView(Context context) {
super(context);
paint.setColor(Color.BLACK);
}
#Override
public void onDraw(Canvas canvas) {
canvas.drawLine(0, 0, 20, 20, paint);
canvas.drawLine(20, 0, 0, 20, paint);
}
}
How can i do that?
Tnx
Did you see that?
Look at source code ;)
http://www.curious-creature.com/2013/12/21/android-recipe-4-path-tracing/
You will want to break up your drawing into multiple steps. Inside your onDraw call, you will want to draw a part of your line, and update a variable so that the next line segment is drawn. Then you will want to make multiple onDraw() calls in an animation loop. You will need to be careful where you make your calls to the animation loop from. Read about the View class for more information, particular event handling and threading. http://developer.android.com/reference/android/view/View.html
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
public class DrawView extends View {
Paint paint = new Paint();
float x1 = 0;
float x2 = 20;
float y1 = 0;
float y2 = 20;
public DrawView(Context context) {
super(context);
paint.setColor(Color.BLACK);
}
#Override
public void onDraw(Canvas canvas) {
if(doClear) {
//clear canvas to begin new animation
}
canvas.drawLine(x1, y1, x2, y2, paint);
}
public void animateLoop() {
while(x1 < 500) {
x1 += 20;
y1 += 20;
x2 += 20;
y2 += 20;
//tell android this view needs to be redrawn
invalidate();
}
//when done set doClear to true so
}
If you really want to learn about animation, you should start with something like this example: http://developer.android.com/guide/topics/graphics/drawable-animation.html.
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.
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.
I am used this from the android developers but don't understand why it force closes:
package com.example.shapedrawable.CustomDrawableView;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.view.View;
public class CustomDrawableViewActivity extends View {
private ShapeDrawable mDrawable;
public CustomDrawableViewActivity(Context context) {
super(context);
int x = 10;
int y = 10;
int width = 300;
int height = 50;
mDrawable = new ShapeDrawable(new OvalShape());
mDrawable.getPaint().setColor(Color.BLUE);
mDrawable.setBounds(x, y, x + width, y + height);
}
protected void onDraw(Canvas canvas) {
mDrawable.draw(canvas);
}
}
You don't say where it force closes which is always useful information, but I assume it's at this line:
mDrawable.getPaint().setColor(Color.BLUE);
getPaint() will return null until you call setPaint(). Try this:
Paint paint = new Paint();
paint.setColor(Color.BLUE);
mDrawable.setPaint(paint);
package com.ewebapps;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.View;
public class Dot extends View {
private final float x;
private final float y;
private final int r;
private final Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final Paint mWhite = new Paint(Paint.ANTI_ALIAS_FLAG);
public Dot(Context context, float x, float y, int r) {
super(context);
mPaint.setColor(0xFF000000); //Black
mWhite.setColor(0xFFFFFFFF); //White
this.x = x;
this.y = y;
this.r = r;
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawCircle(x, y, r+2, mWhite); //White stroke.
canvas.drawCircle(x, y, r, mPaint); //Black circle.
}
}
Well... when creating your own views, the best way to accomplish that is overriding the dispatchTouchEvent method. Trust me, using setOnTouchListener and onTouchEvent don't work well in some scenarios. This is all you have to do in your View:
#Override
public boolean dispatchTouchEvent(MotionEvent event) {
// put your logic here
return super.dispatchTouchEvent(event);
}
documentation with example
View aView = (View)findViewById(R.id.DotView);
aView.setOnTouchListener(this);
Full Example Here
Aaron Saunders answer works for views(like buttons) because an onTouchListener only tells you what view was clicked and not exactly where. If you need to know exactly where the event was without creating buttons try this in your activity class:
#Override
onTouchEvent(MotionEvent event) {
int _x = event.getX();
int _y = event.getY();
// do stuff
}
Note: onTouchEvent is only called when the event is NOT handled by a view.
Documentation
(Can someone tell me how to add line breaks?)