I'm having trouble using a path to create a diamond shape on Android studio. It looks like I have a little more than half of the diamond, but I don't know what I am doing wrong and why the rest of it isn't printing out. I've been trying to change my code for hours and nothing is working. Could anyone please point out what I am doing wrong? Here is my code so far:
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.drawable.shapes.Shape;
public class Diamond extends Shape {
private int strokeWidth;
private final int fillColor;
private int strokeColor;
private Path path;
private Paint strokePaint;
private Paint fillPaint;
public Diamond(int strokeWidth, int fillColor, int strokeColor) {
this.strokeWidth = strokeWidth;
this.fillColor = fillColor;
this.strokeColor = strokeColor;
this.strokePaint = new Paint();
this.strokePaint.setStyle(Paint.Style.STROKE);
this.strokePaint.setStrokeWidth(strokeWidth);
this.fillPaint = new Paint();
this.fillPaint.setStyle(Paint.Style.FILL);
this.fillPaint.setColor(fillColor);
}
#Override
public void draw(Canvas canvas, Paint paint) {
canvas.drawPath(path, fillPaint);
canvas.drawPath(path, strokePaint);
}
#Override
protected void onResize(float width, float height) {
super.onResize(width, height);
path = new Path();
path.moveTo(width/2, 0);
path.lineTo(width, height);
path.lineTo(width/2, height*4);
path.lineTo(0, height);
path.close();
}
}
I think you should just need to change path.lineTo(width/2, height*4); to instead multiply the height by 2 as in path.lineTo(width/2, height*2);, using 4 makes the bottom half skewed longer than the top. There's also an example on this page drawing a rhombus which you can modify to draw a diamond by using the full width like:
public void drawRhombus(Canvas canvas, Paint paint, int x, int y, int width) {
int halfWidth = width / 2;
Path path = new Path();
path.moveTo(x, y + width); // Top
path.lineTo(x - halfWidth, y); // Left
path.lineTo(x, y - width); // Bottom
path.lineTo(x + halfWidth, y); // Right
path.lineTo(x, y + width); // Back to Top
path.close();
canvas.drawPath(path, paint);
}
Related
I need to implement curved text which draw text on circular path on canvas.
It does draw circular path using
canvas.drawTextOnPath(QUOTE, circle, 485, 20, tPaint);
but it is not working for different length of the text.
Following is my Class to draw circular text on the canavs.
public class CircularTextVie extends View {
private String QUOTE = "";
private Path circle;
private Paint cPaint;
private Paint tPaint;
public CircularTextVie(Context context) {
super(context);
circle = new Path();
cPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
cPaint.setStyle(Paint.Style.STROKE);
cPaint.setColor(Color.LTGRAY);
cPaint.setStrokeWidth(3);
tPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
tPaint.setStyle(Paint.Style.FILL_AND_STROKE);
tPaint.setColor(Color.BLACK);
}
#Override
protected void onDraw(Canvas canvas) {
canvas.restore();
int xPos = (canvas.getWidth() /3);
int yPos = (int) ((canvas.getHeight() / 3) - ((tPaint.descent() + tPaint.ascent()) / 3)) ;
circle.addCircle(xPos, yPos, 150, Path.Direction.CW);
canvas.drawTextOnPath(QUOTE, circle, 485, 20, tPaint);
QUOTE="";
}
public void SetText(String text) {
this.QUOTE = text;
}
public void SetTypeFace(Typeface face) {
cPaint.setTypeface(face);
tPaint.setTypeface(face);
}
public void SetColor(int color) {
cPaint.setColor(color);
tPaint.setColor(color);
}
}
Thanks.
This can be done by varying the x and y positions based on textwidth
Define variables
private Rect textBounds;
private int mTextWidth, mTextHeight,centerX,centerY;
Add the below in the constructor of customview
textBounds = new Rect();
tPaint.getTextBounds(QUOTE, 0, QUOTE.length(), textBounds);
mTextWidth = Math.round(tPaint.measureText(QUOTE.toString())); // Use measureText to calculate width
mTextHeight = textBounds.height(); // Use height from getTextBounds()
Then in onDraw
canvas.drawCircle(centerX,centerY,150,mCirlcePaint);
circle.addCircle(centerX, centerY, 150, Path.Direction.CW);
// Note the 0 that's y offset. textdraw at circumference of the circle. Changing y you probably need to change the radius as well i guess.
canvas.drawTextOnPath(QUOTE, circle, (centerX)-(mTextWidth / 2f), 0, tPaint);
centerX,centerY are the center of the circle ie canvaswidht/2 and canvasHeight/2. I drew a circle for reference
The results for hello
The result for a bigger text
For numbers
Edit: To the question in comment
The math involved is in calculating the semi circle using text length
radius = (float) ((mTextWidth) / (Math.PI)). If text length is greater than your canvas you need to reduce the text size or use the full circle radius = (float) ((mTextWidth) / (2*(Math.PI))). Few other edge case you can consider to draw the text properly.
public class GraphicsView extends View {
private String QUOTE = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
private Path circle;
private Paint mCirlcePaint;
private Paint tPaint;
private Rect textBounds;
private int mTextWidth, mTextHeight, centerX, centerY;
private float radius;
public GraphicsView(Context context) {
super(context);
circle = new Path();
tPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
tPaint.setStyle(Paint.Style.FILL_AND_STROKE);
tPaint.setColor(Color.BLACK);
tPaint.setTextSize(100f);
textBounds = new Rect();
tPaint.getTextBounds(QUOTE, 0, QUOTE.length(), textBounds);
mTextWidth = Math.round(tPaint.measureText(QUOTE.toString())); // Use measureText to calculate width
mTextHeight = textBounds.height(); // Use height from getTextBounds()
mCirlcePaint = new Paint();
mCirlcePaint.setStyle(Paint.Style.FILL);
mCirlcePaint.setColor(Color.GREEN);
radius = (float) ((mTextWidth) / (Math.PI));
}
#Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
centerX = w / 2;
centerY = h / 2;
}
#Override
protected void onDraw(Canvas canvas) {
canvas.rotate(180, getWidth() / 2, getHeight() / 2);
canvas.drawCircle(centerX, centerY, radius, mCirlcePaint);
circle.addCircle(centerX, centerY, radius, Path.Direction.CW);
canvas.drawTextOnPath(QUOTE, circle, 0, 0, tPaint);
}
}
By making a custom ImageView and override the onDraw method with the following will make the ImageView to have rounded corners. Reference
#Override
protected void onDraw(Canvas canvas) {
float radius = getContext().getResources().getDimension(R.dimen.round_corner_radius);
Path path = new Path();
RectF rect = new RectF(0, 0, this.getWidth(), this.getHeight());
path.addRoundRect(rect, radius, radius, Path.Direction.CW);
canvas.clipPath(path);
super.onDraw(canvas);
}
How can I selectively make the round corners instead of making all four corners round. For example, only making the top left and top right corners round and leave the bottom corners intact. Here is a solution to do to through Bitmap. I am looking for doing it in this onDraw method and only using Path and RectF.
There is a Path#addRoundRect() overload that takes a float array of eight values wherein we can specify the x- and y-radius for each of the four corners. These values are in [x, y] pairs, starting at the top-left corner, and going clockwise around the rest. For those corners we want rounded, we set both values of the pair to the radius value, and leave them at zero for those we don't.
As an illustrative example, a simple method that will return a Path that can be used in your snippet:
private Path getPath(float radius, boolean topLeft, boolean topRight,
boolean bottomRight, boolean bottomLeft) {
final Path path = new Path();
final float[] radii = new float[8];
if (topLeft) {
radii[0] = radius;
radii[1] = radius;
}
if (topRight) {
radii[2] = radius;
radii[3] = radius;
}
if (bottomRight) {
radii[4] = radius;
radii[5] = radius;
}
if (bottomLeft) {
radii[6] = radius;
radii[7] = radius;
}
path.addRoundRect(new RectF(0, 0, getWidth(), getHeight()),
radii, Path.Direction.CW);
return path;
}
Per your example description, rounding the top-left and top-right corners:
#Override
protected void onDraw(Canvas canvas) {
float radius = getContext().getResources().getDimension(R.dimen.round_corner_radius);
Path path = getPath(radius, true, true, false, false);
canvas.clipPath(path);
super.onDraw(canvas);
}
As always, I would recommend keeping the onDraw() method as tight as possible, moving anything that doesn't absolutely have to be there elsewhere. The resource value for the radius, for instance, could be retrieved in the constructor, and kept in a field. Furthermore, the Path could be constructed only when necessary; i.e., when the View's size changes, or when the radius or chosen corners change.
Since I put together a simple custom ImageView to test this, I'll include it here, as it demonstrates the above points. This custom View also offers XML attributes that allow the corner radius and the rounded corners to be set in your layout.
public class RoundishImageView extends ImageView {
public static final int CORNER_NONE = 0;
public static final int CORNER_TOP_LEFT = 1;
public static final int CORNER_TOP_RIGHT = 2;
public static final int CORNER_BOTTOM_RIGHT = 4;
public static final int CORNER_BOTTOM_LEFT = 8;
public static final int CORNER_ALL = 15;
private static final int[] CORNERS = {CORNER_TOP_LEFT,
CORNER_TOP_RIGHT,
CORNER_BOTTOM_RIGHT,
CORNER_BOTTOM_LEFT};
private final Path path = new Path();
private int cornerRadius;
private int roundedCorners;
public RoundishImageView(Context context) {
this(context, null);
}
public RoundishImageView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public RoundishImageView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RoundishImageView);
cornerRadius = a.getDimensionPixelSize(R.styleable.RoundishImageView_cornerRadius, 0);
roundedCorners = a.getInt(R.styleable.RoundishImageView_roundedCorners, CORNER_NONE);
a.recycle();
}
public void setCornerRadius(int radius) {
if (cornerRadius != radius) {
cornerRadius = radius;
setPath();
invalidate();
}
}
public int getCornerRadius() {
return cornerRadius;
}
public void setRoundedCorners(int corners) {
if (roundedCorners != corners) {
roundedCorners = corners;
setPath();
invalidate();
}
}
public boolean isCornerRounded(int corner) {
return (roundedCorners & corner) == corner;
}
#Override
protected void onDraw(Canvas canvas) {
if (!path.isEmpty()) {
canvas.clipPath(path);
}
super.onDraw(canvas);
}
#Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
setPath();
}
private void setPath() {
path.rewind();
if (cornerRadius >= 1f && roundedCorners != CORNER_NONE) {
final float[] radii = new float[8];
for (int i = 0; i < 4; i++) {
if (isCornerRounded(CORNERS[i])) {
radii[2 * i] = cornerRadius;
radii[2 * i + 1] = cornerRadius;
}
}
path.addRoundRect(new RectF(0, 0, getWidth(), getHeight()),
radii, Path.Direction.CW);
}
}
}
For the XML attributes to work, the following needs to be in your <resources>, which you can do by putting this file in your project's res/values/ folder, or adding to the one that might already be there.
attrs.xml
<resources>
<declare-styleable name="RoundishImageView">
<attr name="cornerRadius" format="dimension" />
<attr name="roundedCorners">
<flag name="topLeft" value="1" />
<flag name="topRight" value="2" />
<flag name="bottomRight" value="4" />
<flag name="bottomLeft" value="8" />
<flag name="all" value="15" />
</attr>
</declare-styleable>
</resources>
The cornerRadius is a dimension attribute, and should be specified as a dp or px value. The roundedCorners is a flag attribute, and multiple corners can be chosen using the pipe character, |. For example:
<com.mycompany.myapp.RoundishImageView
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/riv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:scaleType="fitXY"
android:src="#drawable/magritte"
app:cornerRadius="#dimen/round_corner_radius"
app:roundedCorners="topLeft|topRight" />
I also spent a half-day to solve the problem; the key point here is how to use mPath.arcTo make a corner. The basic knowledge is E direction is 0 degree, then the second param means which degree start; the third param means how many degrees to show.
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PathMeasure;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.DecelerateInterpolator;
public class RectangleConerView extends View {
private Path mPath;
private Paint mPaint;
private PathMeasure mPathMeasure;
private float mAnimatorValue;
private Path mDst;
private float mLength;
private float left = 300;
private float top = 200;
private float width = 800;
private float height = 300;
private float checkWidth = 100;
private float checkHeight = 60;
private float cornerRadius = 30;
public RectangleConerView(Context context) {
super(context);
}
public RectangleConerView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
public RectangleConerView(Context context, AttributeSet attrs)
{
super(context, attrs);
mPathMeasure = new PathMeasure();
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(5);
mPath = new Path();
mPath.moveTo(left + width, top + checkHeight/2);
//bottom-right
mPath.lineTo(left + width, top + height - cornerRadius);
mPath.arcTo(new RectF(left + width-cornerRadius, top + height - cornerRadius, left + width, top + height), 0, 90); //start degree is E direct, then CW 90 degree, which is the bottom-right corner.
//bottom-left
mPath.lineTo(left + cornerRadius, top + height);
mPath.arcTo(new RectF(left, top + height - cornerRadius, left + cornerRadius, top + height), 90, 90);//start degree is the S, then CW 90 degree, which is the bottom-left corner.
//top-left
mPath.lineTo(left, top + cornerRadius);
mPath.arcTo(new RectF(left, top, left + cornerRadius, top + cornerRadius), 180, 90);//start degree W
//top-right
mPath.lineTo(left + width - checkWidth/2, top);
mPathMeasure.setPath(mPath, false);
mLength = mPathMeasure.getLength();
mDst = new Path();
final ValueAnimator valueAnimator = ValueAnimator.ofFloat(0, 1);
valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
#Override
public void onAnimationUpdate(ValueAnimator valueAnimator) {
mAnimatorValue = (float) valueAnimator.getAnimatedValue();
invalidate();
}
});
valueAnimator.setDuration(1000);
valueAnimator.setRepeatCount(ValueAnimator.INFINITE);
valueAnimator.setInterpolator(new DecelerateInterpolator());
valueAnimator.start();
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
mDst.reset();
// 硬件加速的BUG
mDst.lineTo(0,0);
float stop = mLength * mAnimatorValue;
mPathMeasure.getSegment(0, stop, mDst, true);
canvas.drawPath(mDst, mPaint);
}
}
I created my own TextView by extending the TextView class in order to improve its display. I created various Paint and stuff to add a kind of margin. Then text has to be displayed right after the margin. If I set
android:layout_width="fill_parent"
the display is ok and my line is fully filled with a white background (as defined in my layout).
BUT if I set
android:layout_width="wrap_content"
the display goes wrong and the end of the text of my TextView is cropped. I guess this is due to the fact that I made a Translate in the onDraw method of my TextView but I don't know how to fix it.
Please note that I need the set wrap_content because I want to add another TextBox right after, and a LinearLayout around both, but for the moment the other TextBox erase a part of the content of the first one.
The code of my new TextBox is the following one :
package com.flo.ui;
import android.content.Context;
import android.content.res.Configuration;
import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.widget.TextView;
import com.flo.musicalnotes.R;
public class NoteItemTextView extends TextView {
// Properties
private Paint marginPaint;
private Paint linePaint;
private Paint circlePaint;
private int paperColor;
private float margin;
private float marginEnd;
private float textStart;
// Initialization
public NoteItemTextView(Context context) {
super(context);
this.Init(context);
}
public NoteItemTextView(Context context, AttributeSet attrs)
{
super(context, attrs);
this.Init(context);
}
private void Init(Context context)
{
// Resources retrieval
Resources myResources = getResources();
// Brush definition
this.marginPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
this.marginPaint.setColor(myResources.getColor(R.color.marginColor));
this.marginPaint.setStrokeWidth((float) 1.8);
this.linePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
this.linePaint.setColor(myResources.getColor(R.color.underlineColor));
this.circlePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
this.circlePaint.setColor(myResources.getColor(R.color.marginColor));
this.circlePaint.setStyle(Paint.Style.FILL_AND_STROKE);
// various resources
this.paperColor = myResources.getColor(R.color.bgColor);
this.margin = myResources.getDimension(R.dimen.marginSize);
DisplayMetrics metrics = context.getResources().getDisplayMetrics();
int ot = getResources().getConfiguration().orientation;
switch(ot)
{
case Configuration.ORIENTATION_LANDSCAPE:
this.marginEnd = this.margin + metrics.widthPixels / 100;
this.textStart = this.marginEnd + metrics.widthPixels / 100;
case Configuration.ORIENTATION_PORTRAIT:
this.marginEnd = this.margin + metrics.heightPixels / 100;
this.textStart = this.marginEnd + metrics.heightPixels / 100;
default:
this.marginEnd = this.margin + 5;
this.textStart = this.marginEnd + 10;
}
}
//#Override
protected void onDraw(Canvas canvas) {
// paper color
canvas.drawColor(this.paperColor);
// lines drawing
canvas.drawLine(0, getMeasuredHeight(), getMeasuredWidth(), getMeasuredHeight(), this.linePaint);
// marge drawing
canvas.drawLine(this.margin, 0, this.margin, getMeasuredHeight(), this.marginPaint);
canvas.drawLine(this.marginEnd, 0, this.marginEnd, getMeasuredHeight(), this.marginPaint);
double x = (this.textStart + this.marginEnd) / 1.8;
float y1 = getMeasuredHeight() / 3;
float y2 = getMeasuredHeight() * 2 / 3;
float radius = (float) 2.5;
canvas.drawCircle((float) x, y1, radius, this.circlePaint);
canvas.drawCircle((float) x, y2, radius, this.circlePaint);
canvas.save();
canvas.translate(this.textStart, 0);
super.onDraw(canvas);
canvas.restore();
}
}
Thanks for your help !
Try to add this code to your custom textview class
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int height = getMeasuredHeight();
int width = getMeasuredWidth();
Log.e(getClass().getSimpleName() , String.format("height x %s ::: width x %s ",height , width));
float density = getResources().getDisplayMetrics().density;
//Extra space after last letter.
float px = 2 * density;
int adjustedWidth = (int) (width + textStart + px);
setMeasuredDimension(adjustedWidth, height);
}
add this to your textview
android:paddingRight="25dp"
I want to paint graphics onto a Canvas such that the colors are additive. For example, I want to produce this:
But instead, I get this:
Note that the half white, half black background is intentional, just to see how alpha interacts with both backgrounds. I will be happy to have this work with either background. Here is my code:
public class VennColorsActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
class VennView extends View {
public VennView(Context context) {
super(context);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
int alpha = 60, val = 255;
int ar = Color.argb(alpha, val, 0, 0);
int ag = Color.argb(alpha, 0, val, 0);
int ab = Color.argb(alpha, 0, 0, val);
float w = canvas.getWidth();
float h = canvas.getHeight();
float cx = w / 2f;
float cy = h / 2;
float r = w / 5;
float tx = (float) (r * Math.cos(30 * Math.PI / 180));
float ty = (float) (r * Math.sin(30 * Math.PI / 180));
float expand = 1.5f;
Paint paint = new Paint();
paint.setColor(Color.WHITE);
canvas.drawRect(new Rect(0, 0, (int) w, (int) (h / 2)), paint);
PorterDuff.Mode mode = android.graphics.PorterDuff.Mode.ADD;
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColorFilter(new PorterDuffColorFilter(ar, mode));
paint.setColor(ar);
canvas.drawCircle(cx, cy - r, expand * r, paint);
paint.setColorFilter(new PorterDuffColorFilter(ag, mode));
paint.setColor(ag);
canvas.drawCircle(cx - tx, cy + ty, expand * r, paint);
paint.setColorFilter(new PorterDuffColorFilter(ab, mode));
paint.setColor(ab);
canvas.drawCircle(cx + tx, cy + ty, expand * r, paint);
}
}
this.setContentView(new VennView(this));
}
}
Can someone please help me understand how to paint with additive colors in Android graphics?
You are on the right track. There are 3 major issues in your code:
You need to set xfer mode iso color filter
Use temp bitmap for rendering your image
Alpha should be 0xFF in order to get results you are looking for
Here is what I've got by using xfer mode. What I'm doing - is drawing everything into temporary bitmap and then rendering entire bitmap to main canvas.
You ask why do you need temp bitmap? Good question! If you are drawing everything on a main canvas, your colors will be blended with main canvas background color, so all colors will get messed up. Transparent temp bitmap helps to keep your colors away of other parts of UI
Please make sure you are not allocating anything in onDraw() - you will run out memory very soon in this way.. Also make sure you have recycled your temp bitmap when you no longer need it.
package com.example.stack2;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.os.Bundle;
import android.view.View;
public class YouAreWelcome extends Activity {
Bitmap tempBmp = Bitmap.createBitmap(1, 1, Config.ARGB_8888);
Canvas c = new Canvas();
Paint paint = new Paint();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
class VennView extends View {
public VennView(Context context) {
super(context);
}
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if(tempBmp.isRecycled() || tempBmp.getWidth()!=canvas.getWidth() || tempBmp.getHeight()!=canvas.getHeight())
{
tempBmp.recycle();
tempBmp = Bitmap.createBitmap(canvas.getWidth(), canvas.getHeight(), Config.ARGB_8888);
c.setBitmap(tempBmp);
}
//clear previous drawings
c.drawColor(Color.TRANSPARENT, Mode.CLEAR);
int alpha = 255, val = 255;
int ar = Color.argb(alpha, val, 0, 0);
int ag = Color.argb(alpha, 0, val, 0);
int ab = Color.argb(alpha, 0, 0, val);
float w = canvas.getWidth();
float h = canvas.getHeight();
float cx = w / 2f;
float cy = h / 2;
float r = w / 5;
float tx = (float) (r * Math.cos(30 * Math.PI / 180));
float ty = (float) (r * Math.sin(30 * Math.PI / 180));
float expand = 1.5f;
paint.setAntiAlias(true);
paint.setXfermode(new PorterDuffXfermode(Mode.ADD));
paint.setColor(ar);
c.drawCircle(cx, cy - r, expand * r, paint);
paint.setColor(ag);
c.drawCircle(cx - tx, cy + ty, expand * r, paint);
paint.setColor(ab);
c.drawCircle(cx + tx, cy + ty, expand * r, paint);
canvas.drawBitmap(tempBmp, 0, 0, null);
}
}
this.setContentView(new VennView(this));
}
}
Thanks again Pavel. That would have been very difficult for me to have figured out on my own. I am answering my own question to better drill into details, but I've accepted yours as the best answer.
You are right that I prefer not to have to create and manage an off-screen Bitmap (and Canvas). That is essentially why I mentioned that a black or white background would be fine to make this work.
I'm never concerned with performance before I see something working but I share your caution after that point. Editing your version to fix that and remove those members gives the implementation below.
Is this robust? Note the two calls to Canvas.drawColor() which I suspect could also be combined into one.
package com.superliminal.android.test.venn;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.os.Bundle;
import android.view.View;
public class VennColorsActivity extends Activity {
private Paint paint = new Paint();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
class VennView extends View {
public VennView(Context context) {
super(context);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawColor(Color.BLACK);
canvas.drawColor(Color.TRANSPARENT, Mode.CLEAR);
int alpha = 255, val = 255;
int ar = Color.argb(alpha, val, 0, 0);
int ag = Color.argb(alpha, 0, val, 0);
int ab = Color.argb(alpha, 0, 0, val);
float w = canvas.getWidth();
float h = canvas.getHeight();
float cx = w / 2f;
float cy = h / 2;
float r = w / 5;
float tx = (float) (r * Math.cos(30 * Math.PI / 180));
float ty = (float) (r * Math.sin(30 * Math.PI / 180));
float expand = 1.5f;
paint.setAntiAlias(true);
paint.setXfermode(new PorterDuffXfermode(Mode.ADD));
paint.setColor(ar);
canvas.drawCircle(cx, cy - r, expand * r, paint);
paint.setColor(ag);
canvas.drawCircle(cx - tx, cy + ty, expand * r, paint);
paint.setColor(ab);
canvas.drawCircle(cx + tx, cy + ty, expand * r, paint);
}
}
setContentView(new VennView(this));
}
}
I have drawn a graphic object ,say rectangle. I would like write some text at each corner of the rectangle. How to achieve this ?
private static class SimpleView extends View {
private ShapeDrawable mDrawable = new ShapeDrawable();
public SimpleView(Context context) {
super(context);
setFocusable(true);
this.mDrawable = new ShapeDrawable(new RectShape());
this.mDrawable.getPaint().setColor(0xFF0F00FF);
}
#Override
protected void onDraw(Canvas canvas) {
int x1 = 50;
int y1 = 150;
int width = 400;
int height = 50;
this.mDrawable.setBounds(x1, y1, x1 + width, y1 + height);
this.mDrawable.draw(canvas);
int x = 0;
int y = 0;
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
etc
If you are using Canvas thenjust use the drawText() method.
drawText(String text, int start, int end, float x, float y, Paint paint)
Source: http://developer.android.com/reference/android/graphics/Canvas.html
Use canvas.drawText with the coordinates of the corners, and with Paint set at the appropriate alignment. i.e. you'd drawText at each corner, with the right corners having paint.align = RIGHT, and the left corners having paint.align = LEFT. That way, the text is drawn to the side of the square.