Develop Reference

How to draw a lines inside a circle angle wise?

In android I have create custom view.I have first drawn circle and now I want to draw a line angle wise within a circle. I want like this with animation.
https://drive.google.com/file/d/1Qx0MBu-77JIlQTByqGTyD-KtGKOB8naG/view?usp=sharing
I have used canvas to draw circle and lines.I have taken viewpager.If I swipe viewpager then pie graphics will rotate.
What I have done uptill now. When animating it's always start from zero:
https://drive.google.com/file/d/12mmAUOeY77jAlj_GmM3Ymcx5m34vli3X/view?usp=sharing
I have done below code:
public class PieView : View
{
int w, h, pl, pr, pt, pb, usableWidth, usableHeight, radius, cx, cy, lineLenght;
Paint paint;
public Canvas canvas;
public float firstLineangle = 0;
public float secondLineangle = 40;
public float thirdLineangle = 120;
float currentAngle,maxAngle;
public override void Draw(Canvas canvas)
{
base.Draw(canvas);
w = Width;
h = Height;
pl = PaddingLeft;
pr = PaddingRight;
pt = PaddingTop;
pb = PaddingBottom;
this.canvas = canvas;
usableWidth = w - (pl + pr);
usableHeight = h - (pt + pb);
radius = Math.Min(usableWidth, usableHeight) / 2;
cx = pl + (usableWidth / 2);
cy = pt + (usableHeight / 2);
lineLenght = radius - (pl * 2) - (pr * 2);
paint = new Paint();
paint.Color = Android.Graphics.Color.White;
paint.SetStyle(Paint.Style.Stroke);
paint.StrokeWidth = 5;
canvas.DrawCircle(cx, cy, radius - 5, paint);
Drawline(canvas, firstLineangle);
Drawline(canvas, secondLineangle);
Drawline(canvas, thirdLineangle);
PostInvalidateDelayed(500);
Invalidate();
}
public void Drawline(Canvas canvas, float angle)
{
float displacedAngle = angle - 90;
float x = cx + ((float)Math.Cos(degreesToRadians(displacedAngle)) * (radius - 5)); //convert angle to radians for x and y coordinates
float y = cy + ((float)Math.Sin(degreesToRadians(displacedAngle)) * (radius - 5));
canvas.DrawLine(cx, cy, x, y, paint); //draw a line from center point back to the point
}
public double degreesToRadians(double degrees)
{
return (degrees * Math.PI) / 180;
}
}
public class PieAnimation : Android.Views.Animations.Animation
{
private PieView pieView;
private float firstLineangle;
private float secondLineangle;
private float thirdLineangle;
public PieAnimation(PieView pieView, float firstLineangle,float secondLineangle,float thirdLineangle)
{
this.pieView = pieView;
this.firstLineangle = firstLineangle;
this.secondLineangle = secondLineangle;
this.thirdLineangle = thirdLineangle;
}
protected override void ApplyTransformation(float interpolatedTime, Transformation t)
{
pieView.firstLineangle = 0 + ((firstLineangle) * interpolatedTime);
pieView.secondLineangle = 0 + ((secondLineangle) * interpolatedTime);
pieView.thirdLineangle = 0 + ((thirdLineangle) * interpolatedTime);
pieView.RequestLayout();
}
}
public class TourPager : Java.Lang.Object, ViewPager.IOnPageChangeListener, ViewPager.IPageTransformer
{
private ViewPager mViewPager;
private float mLastOffset;
public TourView _context;
public TourPager(ViewPager viewpager, TourView context)
{
mViewPager = viewpager;
viewpager.AddOnPageChangeListener(this);
_context = context;
}
public void OnPageSelected(int position)
{
if (position == 0)
{
PieAnimation animation = new PieAnimation(_context._pieView, 0, 40, 120);
animation.Duration = (1000);
_context._pieView.StartAnimation(animation);
}
if (position==1)
{
PieAnimation animation = new PieAnimation(_context._pieView, 100, 140, 200);
animation.Duration=(1000);
_context._pieView.StartAnimation(animation);
}
if(position==2)
{
PieAnimation animation = new PieAnimation(_context._pieView, 180, 270, 10);
animation.Duration = (1000);
_context._pieView.StartAnimation(animation);
}
}

There is running GIF.
There is PieView.cs.
public class PieView:View
{
int w, h, pl, pr, pt, pb, usableWidth, usableHeight, radius, cx, cy, lineLenght;
int handTruncation, hourHandTruncation = 0;
Paint paint;
int[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
Rect rect = new Rect();
public PieView(Context context) : base(context)
{
}
public PieView(Context context, IAttributeSet attrs) : base(context, attrs)
{
}
public PieView(Context context, IAttributeSet attrs, int defStyleAttr) : base(context, attrs, defStyleAttr)
{
}
public PieView(Context context, IAttributeSet attrs, int defStyleAttr, int defStyleRes) : base(context, attrs, defStyleAttr, defStyleRes)
{
}
public override void Draw(Canvas canvas)
{
base.Draw(canvas);
w = Width;
h = Height;
pl = PaddingLeft+10;
pr = PaddingRight+10;
pt = PaddingTop+10;
pb = PaddingBottom+10;
usableWidth = w - (pl + pr);
usableHeight = h - (pt + pb);
radius = Math.Min(usableWidth, usableHeight) / 2;
cx = pl + (usableWidth / 2);
cy = pt + (usableHeight / 2);
int min = Math.Min(usableWidth, usableHeight);
handTruncation = min / 20;
hourHandTruncation = min / 7;
lineLenght = radius - (pl * 2) - (pr * 2);
paint = new Paint();
paint.Color = Android.Graphics.Color.White;
paint.SetStyle(Paint.Style.Stroke);
paint.StrokeWidth = 5;
canvas.DrawCircle(cx, cy, radius , paint);
drawNumeral(canvas);
drawHands(canvas);
PostInvalidateDelayed(200);
Invalidate();
}
private void drawHands(Canvas canvas)
{
Calendar c = Calendar.Instance;
float hour = c.Get(CalendarField.HourOfDay);
hour = hour > 12 ? hour - 12 : hour;
drawHand1(canvas, (hour + c.Get(CalendarField.Minute) / 60) * 5f,true);
drawHand1(canvas, c.Get(CalendarField.Minute),false);
drawHand1(canvas, c.Get(CalendarField.Second),false);
}
private void drawNumeral(Canvas canvas)
{
paint.TextSize=50;
foreach (var number in numbers)
{
string tmp = number.ToString();
paint.GetTextBounds( tmp, 0, tmp.Length, rect); //getTextBounds(tmp, 0, tmp.length(), rect);
double angle = Math.PI / 6 * (number - 3);
int x = (int)(w / 2 + Math.Cos(angle) * radius - rect.Width() / 2);
int y = (int)(h / 2 + Math.Sin(angle) * radius + rect.Height() / 2);
canvas.DrawText(tmp, x, y, paint);
}
}
private void drawHand1(Canvas canvas, double loc, bool isHour)
{
double angle = Math.PI * loc / 30 - Math.PI / 2;
int handRadius = isHour ? radius - handTruncation - hourHandTruncation : radius - handTruncation;
canvas.DrawLine(Width / 2, Height / 2,
(float)(Width / 2 + Math.Cos(angle) * handRadius),
(float)(Height / 2 + Math.Sin(angle) * handRadius),
paint);
}
}
You can use it in MainActivity.cs
RelativeLayout relativeLayout1 = FindViewById<RelativeLayout>
(Resource.Id.relativeLayout1);
relativeLayout1.SetBackgroundColor(Color.Black);
AddContentView(new PieView(this),new ViewGroup.LayoutParams(-1,-1));

Convert sinusoid values to audio in android

I am graphically representing audio on x and y axis. From those y-axis points I want to generate audio again.
Followed https://github.com/billthefarmer/scope this to get points on y-axis. I have all of the values of y-axis points. These points can be used to represent a wave graphically.
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Locale;
// Scope
public class Scope extends View {
private int width;
private int height;
private Path path;
private Canvas cb;
private Paint paint;
private Bitmap bitmap;
private Bitmap graticule;
protected boolean storage;
protected boolean clear;
protected float step;
protected float scale;
protected float start;
protected float index;
protected float yscale;
protected boolean points;
protected MainActivity.Audio audio;
// Scope
public Scope(Context context, AttributeSet attrs) {
super(context, attrs);
// Create path and paint
path = new Path();
paint = new Paint();
}
// On size changed
#Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
// Get dimensions
width = w;
height = h;
// Create a bitmap for trace storage
bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
cb = new Canvas(bitmap);
// Create a bitmap for the graticule
graticule = Bitmap.createBitmap(width, height,
Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(graticule);
// Black background
canvas.drawColor(Color.BLACK);
// Set up paint
paint.setStrokeWidth(2);
paint.setStyle(Paint.Style.STROKE);
paint.setColor(Color.argb(255, 0, 63, 0));
// Draw graticule
for (int i = 0; i < width; i += MainActivity.SIZE)
canvas.drawLine(i, 0, i, height, paint);
canvas.translate(0, height / 2);
for (int i = 0; i < height / 2; i += MainActivity.SIZE) {
canvas.drawLine(0, i, width, i, paint);
canvas.drawLine(0, -i, width, -i, paint);
}
// Draw the graticule on the bitmap
cb.drawBitmap(graticule, 0, 0, null);
cb.translate(0, height / 2);
}
private int max;
// On draw
#Override
protected void onDraw(Canvas canvas) {
// Check for data
if ((audio == null) || (audio.data == null)) {
canvas.drawBitmap(graticule, 0, 0, null);
return;
}
// Draw the graticule on the bitmap
if (!storage || clear) {
cb.drawBitmap(graticule, 0, -height / 2, null);
clear = false;
}
// Calculate x scale etc
float xscale = (float) (2.0 / ((audio.sample / 100000.0) * scale));
int xstart = Math.round(start);
int xstep = Math.round((float) 1.0 / xscale);
int xstop = Math.round(xstart + ((float) width / xscale));
if (xstop > audio.length)
xstop = (int) audio.length;
// Calculate y scale
if (max < 4096)
max = 4096;
yscale = (float) (max / (height / 2.0));
max = 0;
// Draw the trace
path.rewind();
path.moveTo(0, 0);
if (xscale < 1.0) {
for (int i = 0; i < xstop - xstart; i += xstep) {
if (max < Math.abs(audio.data[i + xstart]))
max = Math.abs(audio.data[i + xstart]);
float x = (float) i * xscale;
float y = -(float) audio.data[i + xstart] / yscale;
path.lineTo(x, y);
Log.d("y values", "y = " + String.valueOf(y)); // KING
writeToFile("y = " + String.valueOf(y), getContext());
}
} else {
for (int i = 0; i < xstop - xstart; i++) {
if (max < Math.abs(audio.data[i + xstart]))
max = Math.abs(audio.data[i + xstart]);
float x = (float) i * xscale;
float y = -(float) audio.data[i + xstart] / yscale;
path.lineTo(x, y);
Log.d("y values", "y = " + String.valueOf(y)); // KING
writeToFile("y = " + String.valueOf(y), getContext());
// Draw points at max resolution
if (points) {
path.addRect(x - 2, y - 2, x + 2, y + 2, Path.Direction.CW);
path.moveTo(x, y);
Log.d("y values", "y = " + String.valueOf(y)); // KING
writeToFile("y = " + String.valueOf(y), getContext());
}
}
}
// Green trace
paint.setColor(Color.GREEN);
paint.setAntiAlias(true);
cb.drawPath(path, paint);
// Draw index
if (index > 0 && index < width) {
// Yellow index
paint.setColor(Color.YELLOW);
paint.setAntiAlias(false);
cb.drawLine(index, -height / 2, index, height / 2, paint);
paint.setAntiAlias(true);
paint.setTextSize(height / 48);
paint.setTextAlign(Paint.Align.LEFT);
// Get value
int i = Math.round(index / xscale);
if (i + xstart < audio.length) {
float y = -audio.data[i + xstart] / yscale;
// Draw value
String s = String.format(Locale.getDefault(), "%3.2f",
audio.data[i + xstart] / 32768.0);
cb.drawText(s, index, y, paint);
}
paint.setTextAlign(Paint.Align.CENTER);
// Draw time value
if (scale < 100.0) {
String s = String.format(Locale.getDefault(),
(scale < 1.0) ? "%3.3f" :
(scale < 10.0) ? "%3.2f" : "%3.1f",
(start + (index * scale)) /
MainActivity.SMALL_SCALE);
cb.drawText(s, index, height / 2, paint);
// Log.d("y values", "y = " + String.valueOf(y));
} else {
String s = String.format(Locale.getDefault(), "%3.3f",
(start + (index * scale)) /
MainActivity.LARGE_SCALE);
cb.drawText(s, index, height / 2, paint);
}
}
canvas.drawBitmap(bitmap, 0, 0, null);
}
private void writeToFile(String data, Context context) {
try {
OutputStreamWriter outputStreamWriter = new OutputStreamWriter(context.openFileOutput("Sinusoids.txt", Context.MODE_PRIVATE));
outputStreamWriter.write(data);
outputStreamWriter.close();
} catch (IOException e) {
Log.e("Exception", "File write failed: " + e.toString());
}
}
// On touch event
#Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
// Set the index from the touch dimension
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
index = x;
break;
case MotionEvent.ACTION_MOVE:
index = x;
break;
case MotionEvent.ACTION_UP:
index = x;
break;
}
return true;
}
}
Generate byte array from y-axis points. The array can then be converted to sound.

Paint stroke not covering all the side in android

Hi i am creating indicator for doughnut chart but it is covering only three side. Here i added onDraw method.The selected chart index arc should be highlighted with indicator.The indicator should be cover all the four sides.
Code:
#Override
public void draw(Canvas canvas, int x, int y, int width, int height, Paint paint) {
paint.setAntiAlias(true);
paint.setStyle(Style.FILL);
int legendSize = getLegendSize(mRenderer, height / 5, 0);
int left = x;
int top = y;
int right = x + width;
int sLength = mDataset.getItemCount();
double total = 0;
String[] titles = new String[sLength];
for (int i = 0; i < sLength; i++) {
total += mDataset.getValue(i);
titles[i] = mDataset.getCategory(i);
}
if (mRenderer.isFitLegend()) {
legendSize = drawLegend(canvas, mRenderer, titles, left, right, y, width, height, legendSize, paint, true);
}
int bottom = y + height - legendSize;
drawBackground(mRenderer, canvas, x, y, width, height, paint, false, Renderer.NO_COLOR);
float currentAngle = mRenderer.getStartAngle();
float labelCurrentAngle = mRenderer.getStartAngle();
// int mRadius = Math.min(Math.abs(right - left), Math.abs(bottom - top));
// int radius = (int) (500 * 0.35) + 50;
//Log.i("radius++", "" + radius);
int mRadius = Math.min(Math.abs(right - left), Math.abs(bottom - top));
double rCoef = 0.35 * mRenderer.getScale();
double decCoef = 0.2 / sLength;
int radius = (int) (mRadius * rCoef);
if (mCenterX == 0) {
mCenterX = (left + right) / 2;
}
if (mCenterY == 0) {
mCenterY = (bottom + top) / 2;
}
// Hook in clip detection after center has been calculated
mPieMap.setDimensions(radius, mCenterX, mCenterY);
boolean loadPieCfg = !mPieMap.areAllSegmentPresent(sLength);
if (loadPieCfg) {
mPieMap.clearPieSegments();
}
float shortRadius = radius * 0.9f;
float longRadius = radius * 1.1f;
RectF oval = new RectF(mCenterX - radius, mCenterY - radius, mCenterX + radius, mCenterY + radius);
for (int i = 0; i < sLength; i++) {
float value = (float) mDataset.getValue(i);
float angle = (float) (value / total * 360);
int color = mRenderer.getRenderers().get(i).getColor();
if (mRenderer.getRenderers().get(i).isClicked()) {
ClickedArc.CANVAS = canvas;
ClickedArc.CURRENT_ANGLE = currentAngle;
ClickedArc.ANGLE = angle;
ClickedArc.COLOR = color;
ClickedArc.INDEX = mRenderer.getRenderers().get(i).getDataIndex();
} else {
Paint paint3 = new Paint(Paint.ANTI_ALIAS_FLAG);
paint3.setStrokeCap(Paint.Cap.ROUND);
paint3.setStyle(Style.FILL);
int[] colors = {color, color};
RadialGradient gradient3 = new RadialGradient(mCenterX, mCenterY, radius, colors, null, android.graphics.Shader.TileMode.CLAMP);
paint3.setShader(gradient3);
paint3.setAntiAlias(true);
canvas.drawArc(oval, currentAngle, angle, true, paint3);
}
try {
if (mRenderer.getRenderers().get(ClickedArc.INDEX).isClicked()) {
Paint paint3 = new Paint(Paint.ANTI_ALIAS_FLAG);
paint3.setStyle(Style.FILL);
paint3.setColor(Color.WHITE);
Paint shadow = new Paint(Paint.ANTI_ALIAS_FLAG);
int[] colors = {Color.BLACK, Color.BLACK};
RadialGradient gradient3 = new RadialGradient(mCenterX, mCenterY, radius, colors, null, android.graphics.Shader.TileMode.CLAMP);
shadow.setShader(gradient3);
shadow.setAntiAlias(true);
shadow.setColor(Color.BLACK);
shadow.setStrokeWidth(8);
shadow.setDither(true);
shadow.setStyle(Paint.Style.STROKE);
shadow.setStrokeCap(Paint.Cap.BUTT);
shadow.setAntiAlias(true);
int shadowRadius = radius + 2;
RectF shadowOval = new RectF(mCenterX - shadowRadius, mCenterY - shadowRadius, mCenterX + shadowRadius, mCenterY + shadowRadius);
canvas.drawArc(shadowOval, ClickedArc.CURRENT_ANGLE - 1, ClickedArc.ANGLE + 2, true, shadow);
canvas.drawArc(oval, ClickedArc.CURRENT_ANGLE, ClickedArc.ANGLE, true, paint3);
}
} catch (IndexOutOfBoundsException e) {
e.printStackTrace();
}
if (loadPieCfg) {
mRenderer.getRenderers().get(i).setDataIndex(i);
mPieMap.addPieSegment(i, value, currentAngle, angle + currentAngle);
}
currentAngle += angle;
}
radius -= (int) mRadius * decCoef;
shortRadius -= mRadius * decCoef - 2;
List<RectF> prevLabelsBounds = new ArrayList<RectF>();
for (int i = 0; i < sLength; i++) {
float value = (float) mDataset.getValue(i);
float angle = (float) (value / total * 360);
drawLabel(canvas, mDataset.getCategory(i), mRenderer, prevLabelsBounds, mCenterX, mCenterY, shortRadius / 2 + 50, longRadius / 2 + 50,
labelCurrentAngle, angle, left, right, mRenderer.getLabelsColor(), paint, true, mRenderer.getRenderers().get(i));
Point sPoint = mRenderer.getRenderers().get(i).getCenterPoint();
Point ePoint = new Point((int) mRenderer.getRenderers().get(i).getTextWidth(), (int) mRenderer.getRenderers().get(i).getTextHeight());
mPieMap.addLabelSegment(i, value, sPoint, ePoint);
labelCurrentAngle += angle;
}
prevLabelsBounds.clear();
}

Trying to write a simple drawing program for android

I'm trying to figure out how to wite a simple drawing program in Android. I saw a sample program that stored each stroke in a array, then played back the array when the screen needed to be updated. To me this did not seem to proctical. I would like to draw in a bitmap, and the update would just draw the bitmap instad of every stroke. ( i could not figure out how to do this in android)
Any thoughts
?
Ted

Look at the Android samples: there are a couple of moderately complicated bits, but this is from the Sensors.java api demo in the Android SDK. It demonstrates the bitmap manipulation:
private class GraphView extends View implements SensorEventListener
{
private Bitmap mBitmap;
private Paint mPaint = new Paint();
private Canvas mCanvas = new Canvas();
private Path mPath = new Path();
private RectF mRect = new RectF();
private float mLastValues[] = new float[3*2];
private float mOrientationValues[] = new float[3];
private int mColors[] = new int[3*2];
private float mLastX;
private float mScale[] = new float[2];
private float mYOffset;
private float mMaxX;
private float mSpeed = 1.0f;
private float mWidth;
private float mHeight;
public GraphView(Context context) {
super(context);
mColors[0] = Color.argb(192, 255, 64, 64);
mColors[1] = Color.argb(192, 64, 128, 64);
mColors[2] = Color.argb(192, 64, 64, 255);
mColors[3] = Color.argb(192, 64, 255, 255);
mColors[4] = Color.argb(192, 128, 64, 128);
mColors[5] = Color.argb(192, 255, 255, 64);
mPaint.setFlags(Paint.ANTI_ALIAS_FLAG);
mRect.set(-0.5f, -0.5f, 0.5f, 0.5f);
mPath.arcTo(mRect, 0, 180);
}
#Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.RGB_565);
mCanvas.setBitmap(mBitmap);
mCanvas.drawColor(0xFFFFFFFF);
mYOffset = h * 0.5f;
mScale[0] = - (h * 0.5f * (1.0f / (SensorManager.STANDARD_GRAVITY * 2)));
mScale[1] = - (h * 0.5f * (1.0f / (SensorManager.MAGNETIC_FIELD_EARTH_MAX)));
mWidth = w;
mHeight = h;
if (mWidth < mHeight) {
mMaxX = w;
} else {
mMaxX = w-50;
}
mLastX = mMaxX;
super.onSizeChanged(w, h, oldw, oldh);
}
#Override
protected void onDraw(Canvas canvas) {
synchronized (this) {
if (mBitmap != null) {
final Paint paint = mPaint;
final Path path = mPath;
final int outer = 0xFFC0C0C0;
final int inner = 0xFFff7010;
if (mLastX >= mMaxX) {
mLastX = 0;
final Canvas cavas = mCanvas;
final float yoffset = mYOffset;
final float maxx = mMaxX;
final float oneG = SensorManager.STANDARD_GRAVITY * mScale[0];
paint.setColor(0xFFAAAAAA);
cavas.drawColor(0xFFFFFFFF);
cavas.drawLine(0, yoffset, maxx, yoffset, paint);
cavas.drawLine(0, yoffset+oneG, maxx, yoffset+oneG, paint);
cavas.drawLine(0, yoffset-oneG, maxx, yoffset-oneG, paint);
}
canvas.drawBitmap(mBitmap, 0, 0, null);
float[] values = mOrientationValues;
if (mWidth < mHeight) {
float w0 = mWidth * 0.333333f;
float w = w0 - 32;
float x = w0*0.5f;
for (int i=0 ; i<3 ; i++) {
canvas.save(Canvas.MATRIX_SAVE_FLAG);
canvas.translate(x, w*0.5f + 4.0f);
canvas.save(Canvas.MATRIX_SAVE_FLAG);
paint.setColor(outer);
canvas.scale(w, w);
canvas.drawOval(mRect, paint);
canvas.restore();
canvas.scale(w-5, w-5);
paint.setColor(inner);
canvas.rotate(-values[i]);
canvas.drawPath(path, paint);
canvas.restore();
x += w0;
}
} else {
float h0 = mHeight * 0.333333f;
float h = h0 - 32;
float y = h0*0.5f;
for (int i=0 ; i<3 ; i++) {
canvas.save(Canvas.MATRIX_SAVE_FLAG);
canvas.translate(mWidth - (h*0.5f + 4.0f), y);
canvas.save(Canvas.MATRIX_SAVE_FLAG);
paint.setColor(outer);
canvas.scale(h, h);
canvas.drawOval(mRect, paint);
canvas.restore();
canvas.scale(h-5, h-5);
paint.setColor(inner);
canvas.rotate(-values[i]);
canvas.drawPath(path, paint);
canvas.restore();
y += h0;
}
}
}
}
}
public void onSensorChanged(SensorEvent event) {
//Log.d(TAG, "sensor: " + sensor + ", x: " + values[0] + ", y: " + values[1] + ", z: " + values[2]);
synchronized (this) {
if (mBitmap != null) {
final Canvas canvas = mCanvas;
final Paint paint = mPaint;
if (event.sensor.getType() == Sensor.TYPE_ORIENTATION) {
for (int i=0 ; i<3 ; i++) {
mOrientationValues[i] = event.values[i];
}
} else {
float deltaX = mSpeed;
float newX = mLastX + deltaX;
int j = (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) ? 1 : 0;
for (int i=0 ; i<3 ; i++) {
int k = i+j*3;
final float v = mYOffset + event.values[i] * mScale[j];
paint.setColor(mColors[k]);
canvas.drawLine(mLastX, mLastValues[k], newX, v, paint);
mLastValues[k] = v;
}
if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD)
mLastX += mSpeed;
}
invalidate();
}
}
}
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
}

how to rotate text using canvas in Android

i was draw a pie chart using canvas in android and using the below code i draw a text on each slice of that pie chart (draw arc on path), now i want to draw the text length wise i.e. from center to end of the each slice,so how to rotate the arc using start and sweep angle.
p.addArc(mEventsRect, fStartAngle, fSweepAngle);
mBgPaints.setColor(iTextColor);
canvas.drawTextOnPath(sTextValue, p, fHOffSet, fVOffSet, mBgPaints);

You can try this snippet: (from: http://www.helloandroid.com/tutorials/how-use-canvas-your-android-apps-part-2)
int x = 75;
int y = 185;
paint.setColor(Color.GRAY);
paint.setTextSize(25);
String rotatedtext = "Rotated helloandroid :)";
//Draw bounding rect before rotating text:
Rect rect = new Rect();
paint.getTextBounds(rotatedtext, 0, rotatedtext.length(), rect);
canvas.translate(x, y);
paint.setStyle(Paint.Style.FILL);
canvas.drawText(rotatedtext , 0, 0, paint);
paint.setStyle(Paint.Style.STROKE);
canvas.drawRect(rect, paint);
canvas.translate(-x, -y);
paint.setColor(Color.RED);
canvas.rotate(-45, x + rect.exactCenterX(),y + rect.exactCenterY());
paint.setStyle(Paint.Style.FILL);
canvas.drawText(rotatedtext, x, y, paint);

A bit late to the party but I had to figure this one out and it's a bit simpler than what I found around. You'll already have the x and y for your text, use these to rotate the canvas
canvas.rotate(yourDegrees, x, y)
canvas.drawText(yourText, x, y, yourPaint)
canvas.rotate(-yourDegrees, x, y)
The negative sign negates the first rotation. You could swap it around to rotate in the opposite direction.
You could do this in a loop but the rotation cycle must be done each time either coordinate changes.

may be this will help you,,
here 39.5 is radius,, this will perfectly show result on mdpi screen
protected void onDraw(){
canvas.save();
PointF pf = PointOnCircle(35f, 45f, new PointF(39.5f, 39.5f));
canvas.rotate(-45, pf.x, pf.y);
canvas.drawText("67%", pf.x, pf.y, red);//23.5
canvas.restore();
canvas.save();
PointF pfa = PointOnCircle(35f, 135f, new PointF(39.5f, 39.5f));
canvas.rotate(45, pfa.x, pfa.y);
canvas.drawText("33%", pfa.x, pfa.y, red);//23.5
canvas.restore();
canvas.save();
pfa = PointOnCircle(27.5f, 225f, new PointF(39.5f, 39.5f));
canvas.rotate(-45, pfa.x, pfa.y);
canvas.drawText("45%", pfa.x, pfa.y, red);//23.5
canvas.restore();
canvas.save();
pfa = PointOnCircle(27.5f, 315f, new PointF(39.5f, 39.5f));
canvas.rotate(45, pfa.x, pfa.y);
canvas.drawText("55%", pfa.x, pfa.y, red);//23.5
canvas.restore();}
protected static final PointF PointOnCircle(float radius, float angleInDegrees, PointF origin) {
// Convert from degrees to radians via multiplication by PI/180
float x = (float) (radius * Math.cos(angleInDegrees * Math.PI / 180F)) + origin.x;
float y = (float) (radius * Math.sin(angleInDegrees * Math.PI / 180F)) + origin.y;
return new PointF(x, y);
}

Here's how i finally did it after two days of search with help of this library https://github.com/Ken-Yang/AndroidPieChart
And equations to center text done with help of my friends and alot of search
on MainActivity onCreate or oncreateView if you are using fragments:
PieChart pie = (PieChart) rootView.findViewById(R.id.pieChart);
ArrayList<Float> alPercentage = new ArrayList<Float>();
alPercentage.add(2.0f);
alPercentage.add(8.0f);
alPercentage.add(20.0f);
alPercentage.add(10.0f);
alPercentage.add(10.0f);
alPercentage.add(10.0f);
alPercentage.add(10.0f);
alPercentage.add(10.0f);
alPercentage.add(10.85f);
alPercentage.add(9.15f);
try {
// setting data
pie.setAdapter(alPercentage);
// setting a listener
pie.setOnSelectedListener(new OnSelectedLisenter() {
#Override
public void onSelected(int iSelectedIndex) {
Toast.makeText(getActivity(),
"Select index:" + iSelectedIndex,
Toast.LENGTH_SHORT).show();
}
});
} catch (Exception e) {
if (e.getMessage().equals(PieChart.ERROR_NOT_EQUAL_TO_100)) {
Log.e("kenyang", "percentage is not equal to 100");
}
}
public class PieChart extends View {
public interface OnSelectedLisenter {
public abstract void onSelected(int iSelectedIndex);
}
private OnSelectedLisenter onSelectedListener = null;
private static final String TAG = PieChart.class.getName();
public static final String ERROR_NOT_EQUAL_TO_100 = "NOT_EQUAL_TO_100";
private static final int DEGREE_360 = 360;
private static String[] PIE_COLORS = null;
private static int iColorListSize = 0;
ArrayList<Float> array;
private Paint paintPieFill;
private Paint paintPieBorder;
private Paint paintCenterCircle;
private ArrayList<Float> alPercentage = new ArrayList<Float>();
private int mCenterX = 320;
private int mCenterY = 320;
private int iDisplayWidth, iDisplayHeight;
private int iSelectedIndex = -1;
private int iCenterWidth = 0;
private int iShift = 0;
private int iMargin = 0; // margin to left and right, used for get Radius
private int iDataSize = 0;
private Canvas canvas1;
private RectF r = null;
private RectF centerCircle = null;
private float fDensity = 0.0f;
private float fStartAngle = 0.0f;
private float fEndAngle = 0.0f;
float fX;
float fY;
public PieChart(Context context, AttributeSet attrs) {
super(context, attrs);
PIE_COLORS = getResources().getStringArray(R.array.colors);
iColorListSize = PIE_COLORS.length;
array = new ArrayList<Float>();
fnGetDisplayMetrics(context);
iShift = (int) fnGetRealPxFromDp(30);
iMargin = (int) fnGetRealPxFromDp(40);
centerCircle = new RectF(200, 200, 440, 440);
// used for paint circle
paintPieFill = new Paint(Paint.ANTI_ALIAS_FLAG);
paintPieFill.setStyle(Paint.Style.FILL);
// used for paint centerCircle
paintCenterCircle = new Paint(Paint.ANTI_ALIAS_FLAG);
paintCenterCircle.setStyle(Paint.Style.FILL);
paintCenterCircle.setColor(Color.WHITE);
// used for paint border
paintPieBorder = new Paint(Paint.ANTI_ALIAS_FLAG);
paintPieBorder.setStyle(Paint.Style.STROKE);
paintPieBorder.setStrokeWidth(fnGetRealPxFromDp(3));
paintPieBorder.setColor(Color.WHITE);
Log.i(TAG, "PieChart init");
}
// set listener
public void setOnSelectedListener(OnSelectedLisenter listener) {
this.onSelectedListener = listener;
}
float temp = 0;
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Log.i(TAG, "onDraw");
float centerX = (r.left + r.right) / 2;
float centerY = (r.top + r.bottom) / 2;
float radius1 = (r.right - r.left) / 2;
radius1 *= 0.5;
float startX = mCenterX;
float startY = mCenterY;
float radius = mCenterX;
float medianAngle = 0;
Path path = new Path();
for (int i = 0; i < iDataSize; i++) {
// check whether the data size larger than color list size
if (i >= iColorListSize) {
paintPieFill.setColor(Color.parseColor(PIE_COLORS[i
% iColorListSize]));
} else {
paintPieFill.setColor(Color.parseColor(PIE_COLORS[i]));
}
fEndAngle = alPercentage.get(i);
// convert percentage to angle
fEndAngle = fEndAngle / 100 * DEGREE_360;
// if the part of pie was selected then change the coordinate
if (iSelectedIndex == i) {
canvas.save(Canvas.MATRIX_SAVE_FLAG);
float fAngle = fStartAngle + fEndAngle / 2;
double dxRadius = Math.toRadians((fAngle + DEGREE_360)
% DEGREE_360);
fY = (float) Math.sin(dxRadius);
fX = (float) Math.cos(dxRadius);
canvas.translate(fX * iShift, fY * iShift);
}
canvas.drawArc(r, fStartAngle, fEndAngle, true, paintPieFill);
float angle = (float) ((fStartAngle + fEndAngle / 2) * Math.PI / 180);
float stopX = (float) (startX + (radius/2) * Math.cos(angle));
float stopY = (float) (startY + (radius/2) * Math.sin(angle));
// if the part of pie was selected then draw a border
if (iSelectedIndex == i) {
canvas.drawArc(r, fStartAngle, fEndAngle, true, paintPieBorder);
canvas.drawLine(startX, startY, stopX, stopY, paintPieFill);
canvas.restore();
}
fStartAngle = fStartAngle + fEndAngle;
}
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
// get screen size
iDisplayWidth = MeasureSpec.getSize(widthMeasureSpec);
iDisplayHeight = MeasureSpec.getSize(heightMeasureSpec);
if (iDisplayWidth > iDisplayHeight) {
iDisplayWidth = iDisplayHeight;
}
/*
* determine the rectangle size
*/
iCenterWidth = iDisplayWidth / 2;
int iR = iCenterWidth - iMargin;
if (r == null) {
r = new RectF(iCenterWidth - iR, // top
iCenterWidth - iR, // left
iCenterWidth + iR, // right
iCenterWidth + iR); // bottom
}
if (centerCircle == null) {
// centerCircle=new RectF(left, top, right, bottom);
}
setMeasuredDimension(iDisplayWidth, iDisplayWidth);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
// get degree of the touch point
double dx = Math.atan2(event.getY() - iCenterWidth, event.getX()
- iCenterWidth);
float fDegree = (float) (dx / (2 * Math.PI) * DEGREE_360);
fDegree = (fDegree + DEGREE_360) % DEGREE_360;
// get the percent of the selected degree
float fSelectedPercent = fDegree * 100 / DEGREE_360;
// check which pie was selected
float fTotalPercent = 0;
for (int i = 0; i < iDataSize; i++) {
fTotalPercent += alPercentage.get(i);
if (fTotalPercent > fSelectedPercent) {
iSelectedIndex = i;
break;
}
}
if (onSelectedListener != null) {
onSelectedListener.onSelected(iSelectedIndex);
}
invalidate();
return super.onTouchEvent(event);
}
private void fnGetDisplayMetrics(Context cxt) {
final DisplayMetrics dm = cxt.getResources().getDisplayMetrics();
fDensity = dm.density;
}
private float fnGetRealPxFromDp(float fDp) {
return (fDensity != 1.0f) ? fDensity * fDp : fDp;
}
public void setAdapter(ArrayList<Float> alPercentage) throws Exception {
this.alPercentage = alPercentage;
iDataSize = alPercentage.size();
float fSum = 0;
for (int i = 0; i < iDataSize; i++) {
fSum += alPercentage.get(i);
}
if (fSum != 100) {
Log.e(TAG, ERROR_NOT_EQUAL_TO_100);
iDataSize = 0;
throw new Exception(ERROR_NOT_EQUAL_TO_100);
}
}
in your Layout:
<com.example.piecharts.PieChart
android:id="#+id/pieChart"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</com.example.piecharts.PieChart>

This question is pretty old, but I figured I would write a general answer.Here I assume you want to draw your pie chart in the middle of the canvas and that you have your start and seep angles in an array.
x = canvas.getWidth/2 //Horizontal center of canvas view
y = canvas.getHeight/2 //Vertical center of canvas view
canvas.rotate(fStartAngle[i]+ fSweepAngle[i]/2, x ,y ); //Rotates canvas to a line in the middle
//of start and end of arc
canvas.translate(50f,0);//Moves the text a little out of the center of the circle (50f is arbitrary)
paintText.setStyle(Paint.Style.FILL);
canvas.drawText(rotatedtext, x, y, paintText);
//Undo the translations and rotations so that next arc can be drawn normally
canvas.translate(-50f,0);
canvas.rotate(-(temp+ value_degree[i]/2), x ,y );

it's 2023 there might be other answers out there but here is one that is sure to work
//the path where your text/paint will be drawn across
Path path = new Path();
path.addArc(mEventsRect, fStartAngle, fSweepAngle);//add this if you want your path to be drawn across the arc of your sector
//if you are using a text get the width
float textWidth = mTextPaint.measureText("text");
//this is the y co-ordinate your text will start from
int hOffset = 100;
//this is the x co-ordinate your text will start from
int vOffset = 100;
//we will be using the matrix to rotate the bunds of our current path
Matrix matrix = new Matrix();
//we will use this to get the bounds of our current path
RectF bounds = new RectF();
path.computeBounds(bounds,true);
//we are using the matrix to rotate the bound (with is the bound of the path) by 90 degrees
matrix.setRotate(90,bounds.centerX(),bounds.centerY());
the we transform the points in the path using the matrix
path.transform(matrix);
//you can now draw the text on the path
canvas.drawTextOnPath("text", path, hOffset, vOffset , mBgPaints);