What steps are required to create a shape e.g. rectangle with a shadow from scratch using a Canvas?
Adding a shadow layer to the paint used to draw the rectangle yielded no success.
No need for a Bitmap, just needed to set the layer type to LAYER_TYPE_SOFTWARE the original approach worked.
public class TestShapeShadow extends View
{
Paint paint;
public TestShapeShadow(Context context)
{
super(context);
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setShadowLayer(12, 0, 0, Color.YELLOW);
// Important for certain APIs
setLayerType(LAYER_TYPE_SOFTWARE, paint);
}
#Override
protected void onDraw(Canvas canvas)
{
canvas.drawRect(20, 20, 100, 100, paint);
}
}
I followed the ideas in #pskink's answer and found a solution.
I put the code snippet here for anyone in need.
public class MyViewWithShadow extends View {
Paint paint;
int mainColor;
int shadowColor;
// shadow properties
int offsetX = -25;
int offsetY = 30;
int blurRadius = 5;
public MyViewWithShadow(Context context)
{
super(context);
mainColor = Color.RED;
shadowColor = Color.BLACK; // this color can also have alpha
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setStyle(Paint.Style.FILL);
}
#Override
protected void onDraw(Canvas canvas)
{
// Create paint for shadow
paint.setColor(shadowColor);
paint.setMaskFilter(new BlurMaskFilter(
blurRadius /* shadowRadius */,
BlurMaskFilter.Blur.NORMAL));
// Draw shadow before drawing object
canvas.drawRect(20 + offsetX, 20 + offsetY, 100 + offsetX, 100 + offsetY, paint);
// Create paint for main object
paint.setColor(mainColor);
paint.setMaskFilter(null);
// Draw main object
canvas.drawRect(20, 20, 100, 100, paint);
}
}
[Link is now broken:]
If you wonder what shadow properties are, you can refer to this tester:
https://okawa-h.github.io/box-shadow_tester/~
create. a Path, add some elements to it
set BlurMaskFilter to a Paint
draw a path with dx, dy shadow offset
unset mask filter
draw a path again with no. offset
Related
I have made a paint app in which i have used ImageView in layout to show image that can be taken from camera or gallery.I want to draw transparent line over image so that image can be seen after drawing.please help me.
Thanks for support
I have used the code to make draw line transparent is :
myPaint.setAlpha(50);
My code is:
protected void onDraw(Canvas canvas) {
Toast.makeText(PaintScreen.this, "onDraw is called", Toast.LENGTH_SHORT).show();
// myPaint.setAlpha(100);
canvas.drawBitmap(PaintScreen.this.localBitmap, 0,0,null);
// canvas.drawPath(myPath, paintBlur);
canvas.drawPath(myPath, myPaint); Log.i("OnDRAWING", "REACH ON DRAW"); }
public class CustomView extends ImageView {
private float mX, mY;
public CustomView(Context context) {
super(context);
localBitmap = Bitmap.createBitmap(myBitmap.getWidth(), myBitmap.getHeight(), Config.ARGB_8888);
myCanvas = new Canvas(localBitmap);
myPaint = new Paint(); setPaintForDraw(paintcolor, false, 30);
setFocusable(true);
setFocusableInTouchMode(true); myPath = new Path();
}
}
private void setPaintForDraw(int color, boolean eraseMode, int brushSize) {
//myPaint.setAlpha(100);
myPaint.setAntiAlias(true);
myPaint.setDither(true);
myPaint.setStyle(Paint.Style.STROKE);
myPaint.setColor(color);
myPaint.setStrokeCap(Paint.Cap.ROUND);
myPaint.setStrokeJoin(Paint.Join.ROUND);
myPaint.setStrokeWidth(brushSize);
myPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
if (eraseMode) {
myPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
}
else { myPaint.setXfermode(null); }
}
see this thread How to maintain multi layers of ImageViews and keep their aspect ratio based on the largest one?, here you can use multiple Draeable layers that are drawn over the image
First, you have to check that your Bitmap is mutable. If it is not, make a copy of it. And here is how you can draw a line on your image:
Bitmap copyBmp = yourBMP.copy(Bitmap.Config.ARGB_8888, true); //Copy if yourBMP is not mutable
Canvas canvas = new Canvas(copyBmp);
Paint paint = new Paint();
paint.setAlpha(50); //Put a value between 0 and 255
paint.setColor(Color.GRAY); //Put your line color
paint.setStrokeWidth(5); //Choose the width of your line
canvas.drawLine(startX, startY, stopX, stopY, paint); //Set the coordinates of the line
Now, if you display copyBmp, you should see a line drawn over it.
Hello i added rectangle in my canvas now i want to add textview or some other view in that rectangle.Suggest me some tutorial also. Thanks in advance
public class DrawView extends View {
public DrawView(Context context) {
super(context);
}
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Rect rect = new Rect();
rect.set(20 ,10 ,canvas.getWidth()/2, canvas.getHeight()/2);
Paint paint = new Paint();
paint.setColor(Color.GREEN);
canvas.drawRect(rect, paint);
}
}
You can draw text on your canvas.
Paint mpaint= new Paint();
mpaint.setColor(Color.RED);//set red color for rectangle
mpaint.setStyle(Paint.Style.FILL);//mpaint will fill the rectangle
Paint paint2 = new Paint();
paint2.setColor(Color.GREEN);//green color for text
paint2.setTextSize(30f);//set text size. you can change the stroke width also
#Override
protected void onDraw(Canvas canvas)
{
canvas.drawRect(30, 30, 600, 600, mpaint);
canvas.drawText("hello", 150, 150, paint2);//change x and y according to your needs
}
Resulting snapshot on samsung galaxy s3
Adding a View of any kind is out of question here since you are simply drawing on a canvas. But Canvas.drawText(...) might be exactly what you are looking for.
I am trying to move a rectangle that i created to the center of the screen as I am using an accelerometer to allow it to move, is there a way to move the shape to the center of the screen without using android xml?
public class CustomDrawableView extends View
{
static final int width = 150;
static final int height = 250;
public CustomDrawableView(Context context)
{
super(context);
mDrawable = new ShapeDrawable(new RectShape());
mDrawable.getPaint().setColor(0xff74AC23);
mDrawable.setBounds(x, y, x + width, y + height);
}
protected void onDraw(Canvas canvas)
{
RectF rect = new RectF(AccelActivity.x, AccelActivity.y, AccelActivity.x + width, AccelActivity.y
+ height); // set bounds of rectangle
Paint p = new Paint(); // set some paint options
p.setColor(Color.BLUE);
canvas.drawRect(rect, p);
invalidate();
}
}
}
Yes, check this example, no use of xml there: How can I use the animation framework inside the canvas?
Use on sizeChanged to find the actual size of your canvas...
I think I'm a bit confused about how to use custom views. I'm following along with slides from a talk given by Eric Burke from Square (from this year's anddevcon, slides here: http://www.andevcon.com/AndevCon_II/downloadpresentation.aspx?aid=Taming_Android__User_Experience_Lessons_from_Square_pdf.zip&sid=2).
His code, or at least the part he showed in the slides, went something like this:
public class EditablePhoto extends View {
private Bitmap framedPhoto;
private Bitmap image;
private Drawable placeholder;
public EditablePhoto(Context context) {
super(context);
}
#Override protected void onMeasure(int widthMeasureSpec,
int heightMeasureSpec) {
int measuredWidth = getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec);
int measuredHeight = getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec);
//ensure view always square
int min = Math.min(measuredHeight, measuredWidth);
setMeasuredDimension(min, min);
}
#Override
protected void onDraw(Canvas canvas) {
if(placeholder == null && image==null) return;
if(framedPhoto == null) {
createFramedPhoto(Math.min(getWidth(), getHeight()));
}
canvas.drawBitmap(framedPhoto, 0, 0, null);
}
private void createFramedPhoto(int size) {
Drawable imageDrawable = (image!=null)
? new BitmapDrawable(image) : placeholder;
Bitmap output = Bitmap.createBitmap(size, size,
Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(output);
RectF outerRect = new RectF(0, 0, size, size);
float outerRadius = size / 18f;
//Red rectangle
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.RED);
canvas.drawRoundRect(outerRect, outerRadius, outerRadius, paint);
paint.setXfermode(new PorterDuffXfermode(
PorterDuff.Mode.SRC_IN));
imageDrawable.setBounds(0, 0, size, size);
canvas.saveLayer(outerRect, paint, Canvas.ALL_SAVE_FLAG);
imageDrawable.draw(canvas);
canvas.restore();
}
}
What I don't get is how to actually use this View now.... Where and when do you set the bitmaps, which are private fields in this class...?
Generally confused and would love some enlightenment.
More than one year passed, but I hope this will help anyone who looking for the right answer. In my case, I putted this line of code
framedPhoto = output;
as the last one in createFramedPhoto() method. It works.
In the example, the author created a rounded rectangle as background then he draw the bitmap on it with XOR mode, so all pixel outside the rounded rectangle will be trim off.
OnDraw() is the method where you will Draw your view on canvas. here too you can analyze onDraw() will fisrt call CreateFramePhoto then draw this Bitmap on canvas .
You can add this customView in layout Either from xml or in Java Class
1) Through Xml :
<EditablePhoto android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
..........................
/>
dont forgate to add constructor EditablePhoto(Context context, AttributeSet attributeSet) for this case
2) through Java class :
EditablePhoto editablePhoto = new EditablePhoto(this);
addView(editablePhoto) // or do anthing you want with this
Given a closed Path object result is like this:
Although that is a rectangle I'm looking for something which works with any closed Path.
While steelbytes' answer will probably give you more control over the individual sections of the gradient, you can do it without the path:
Paint m_Paint = new Paint();
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
// start at 0,0 and go to 0,max to use a vertical
// gradient the full height of the screen.
m_Paint.setShader(new LinearGradient(0, 0, 0, getHeight(), Color.BLACK, Color.WHITE, Shader.TileMode.MIRROR));
canvas.drawPaint(m_Paint);
}
this may help.
Note: it's not efficient to create the Paint etc in every call to onDraw. This is just an demonstration of LinearGradient shader
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
int w = getWidth();
int h = getHeight();
Paint p = new Paint(Paint.ANTI_ALIAS_FLAG|Paint.FILTER_BITMAP_FLAG);
Path pth = new Path();
pth.moveTo(w*0.27f,0);
pth.lineTo(w*0.73f,0);
pth.lineTo(w*0.92f,h);
pth.lineTo(w*0.08f,h);
pth.lineTo(w*0.27f,0);
p.setColor(0xff800000);
p.setShader(new LinearGradient(0,0,0,h,0xff000000,0xffffffff,Shader.TileMode.CLAMP));
canvas.drawPath(pth,p);
}