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POdrawArc not drawing properly when startAngle > endAngle in android
 

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  1. POdrawArc not drawing properly when startAngle > endAngle in android
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    <p>I am trying to draw an arc between two points in a circle using touch listener. Here is my code:</p> <pre><code>public class MainActivity extends Activity implements OnTouchListener { ImageView whiteCircle, centreCircle, slideArcFrame; int xStart = 0, yStart = 0, xEnd = 0, yEnd = 0, centerIx = 0, centerIy = 0; Bitmap output; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); whiteCircle = (ImageView) findViewById(R.id.centerImageWhite); centreCircle = (ImageView) findViewById(R.id.centerImage2); slideArcFrame = (ImageView) findViewById(R.id.centerImage); slideArcFrame.setOnTouchListener(this); slideArcFrame.setDrawingCacheEnabled(true); slideArcFrame.measure( MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED)); slideArcFrame.layout(0, 0, slideArcFrame.getMeasuredWidth(), slideArcFrame.getMeasuredHeight()); slideArcFrame.buildDrawingCache(true); output = Bitmap.createBitmap(slideArcFrame.getDrawingCache()); centerIx = 100; centerIy = 100; } @Override public boolean onTouch(View arg0, MotionEvent arg1) { if (arg1.getAction() == MotionEvent.ACTION_DOWN) { xStart = (int) arg1.getX(); yStart = (int) arg1.getY(); } if (arg1.getAction() == MotionEvent.ACTION_MOVE) { xEnd = (int) arg1.getX(); yEnd = (int) arg1.getY(); drawArc(); } if (arg1.getAction() == MotionEvent.ACTION_UP) { xEnd = (int) arg1.getX(); yEnd = (int) arg1.getY(); } return true; } private void drawArc() { Bitmap outp = Bitmap.createBitmap(output.getWidth(), output.getHeight(), Config.ARGB_8888); Canvas can = new Canvas(outp); final Paint paint = new Paint(); RectF rect = new RectF(0, 0, output.getWidth(), output.getHeight()); can.drawARGB(0, 0, 0, 0); paint.setAntiAlias(true); paint.setColor(getResources().getColor(R.color.white)); double quadXS, quadYS, quadXE, quadYE; double quadrantS = 0, quadrantE = 0; quadXS = xStart - centerIx; quadYS = yStart - centerIy; quadXE = xEnd - centerIx; quadYE = yEnd - centerIy; if (quadXS &gt;= 0 &amp;&amp; quadYS &gt;= 0) quadrantS = 1; if (quadXS &lt; 0 &amp;&amp; quadYS &gt;= 0) quadrantS = 2; if (quadXS &lt; 0 &amp;&amp; quadYS &lt; 0) quadrantS = 3; if (quadXS &gt;= 0 &amp;&amp; quadYS &lt; 0) quadrantS = 4; if (quadXE &gt;= 0 &amp;&amp; quadYE &gt;= 0) quadrantE = 1; if (quadXE &lt; 0 &amp;&amp; quadYE &gt;= 0) quadrantE = 2; if (quadXE &lt; 0 &amp;&amp; quadYE &lt; 0) quadrantE = 3; if (quadXE &gt;= 0 &amp;&amp; quadYE &lt; 0) quadrantE = 4; double startAngle = 0, endAngle = 0; if (quadrantS == 1) { startAngle = Math.toDegrees(Math.atan((double) (quadYS) / quadXS)); } if (quadrantS == 2) { startAngle = 180 - Math.toDegrees(Math.atan((double) (quadYS) / -quadXS)); } if (quadrantS == 3) { startAngle = 180 + Math.toDegrees(Math.atan((double) (-quadYS) / -quadXS)); } if (quadrantS == 4) { startAngle = 360 - Math.toDegrees(Math.atan((double) (-quadYS) / quadXS)); } if (quadrantE == 1) { endAngle = Math.toDegrees(Math.atan((double) (quadYE) / quadXE)); } if (quadrantE == 2) { endAngle = 180 - Math.toDegrees(Math.atan((double) (quadYE) / -quadXE)); } if (quadrantE == 3) { endAngle = 180 + Math.toDegrees(Math.atan((double) (-quadYE) / -quadXE)); } if (quadrantE == 4) { endAngle = 360 - Math.toDegrees(Math.atan((double) (-quadYE) / quadXE)); } can.drawArc(rect, (float) startAngle, (float) endAngle - (float) startAngle, true, paint); slideArcFrame.setImageBitmap(outp); } } </code></pre> <p>When the start angle is greater than end angle, the arc is drawn from end angle to start angle. Can anyone explain please?</p>
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