add wave start shift

Author: Alex1989Wang

Example/JWWaveView/TestExamples/MultiCycles/JWMultiCylceWaveTestViewController.m

@@ -68,6 +68,7 @@ - (JWWaveView *)waveView {
         [UIColor colorWithRed:0 green:0 blue:0.5 alpha:1.0];
         _waveView.waveCycles = 2;
         _waveView.waveDuration = 2;
+        _waveView.waveShift = 1.5 * M_PI;
     }
     return _waveView;
 }

JWWaveView/Classes/JWWaveView.h

@@ -49,6 +49,18 @@
  */
 @property (nonatomic, assign) CGFloat waveDuration;
 
+/**
+ The wave path is modeled using the mathmatical sin(x) function. The default value
+ for x starts at 0, which yeilds an amplitude of 0.
+ This propery adds a shift to the x value.
+ 
+ The effective range for this property is [0, 2 * M_PI]. The default value is 0,
+ which means no shift is added to the wave.
+ 
+ @note changing this value after animation has no effect.
+ */
+@property (nonatomic, assign) CGFloat waveShift;
+
 /**
  Start the water waving animation if all conditions are met.
  */

JWWaveView/Classes/JWWaveView.m

@@ -19,10 +19,9 @@ @implementation JWWaveView
 
 #pragma mark - Public
 - (void)startWavingIfNeeded {
-    CAReplicatorLayer *replicatorLayer = [self replicatorLayer];
-    CGRect replicatorRect = replicatorLayer.bounds;
-    self.waveShapeLayer.frame = replicatorRect;
-    
+    //force layout sublayers if layouts are pending
+    [self layoutIfNeeded];
+
     //setup shape
     [self renewWavePathWithForceRenew:NO animated:NO];
 
@@ -65,6 +64,7 @@ - (void)configureIntialSetup {
     _waveDuration = 1.0;
     _waveColor = [UIColor blueColor];
     _waveCycles = 1;
+    _waveShift = 0;
 }
 
 #pragma mark - Override
@@ -165,7 +165,7 @@ - (void)renewWavePathWithForceRenew:(BOOL)forceRenew animated:(BOOL)animated {
         for (CGFloat xPos = 0.f; xPos <= canvasWidth; xPos += 1.f) {
             //wave path starts at the canvasMidY and uses (canvasHeight * 0.5) as amplitude
             CGFloat halfAmplitude = canvasHeight / 4.f;
-            yPos = canvasMidY + sin((xPos)/canvasWidth * M_PI * 2 * _waveCycles) * halfAmplitude;
+            yPos = canvasMidY + sin((xPos/canvasWidth) * M_PI * 2 * _waveCycles + _waveShift) * halfAmplitude;
             if (fpclassify(xPos) == FP_ZERO) {
                 [sinPath moveToPoint:(CGPoint){xPos, yPos}];
             }
@@ -209,6 +209,13 @@ - (void)setWaveDuration:(CGFloat)waveDuration {
     }
 }
 
+- (void)setWaveShift:(CGFloat)waveShift {
+    if (waveShift < 0 || waveShift > 2 * M_PI) {
+        return;
+    }
+    _waveShift = waveShift;
+}
+
 #pragma mark - Lazy Loading 
 - (CAShapeLayer *)waveShapeLayer {
     if (!_waveShapeLayer) {