fix: play with range

Author: yangqingren

Diff for: SVGAPlayer.podspec

@@ -1,7 +1,7 @@
 
 Pod::Spec.new do |s|
   s.name         = "SVGAPlayer"
-  s.version      = "2.5.5"
+  s.version      = "2.5.6"
   s.summary      = "SVGAPlayer 是一个高性能的动画播放器"
   s.description  = <<-DESC
                    SVGA 是一种全新的动画格式，由 YY UED 团队主导开发；

Diff for: SVGAPlayer/ViewController.m

@@ -67,12 +67,13 @@ - (IBAction)onChange:(id)sender {
                                                 NSParagraphStyleAttributeName: para,
                                             }];
                  [self.aPlayer setAttributedText:str forKey:@"banner"];
-                 
-//                 self.aPlayer.mianRunLoopMode = NSDefaultRunLoopMode;
+
                  [self.aPlayer startAnimation];
+                 
+//                 [self.aPlayer startAnimationWithRange:NSMakeRange(10, 25) reverse:YES];
              }
          } failureBlock:nil];
-
+//
 //        [parser parseWithURL:[NSURL URLWithString:@"https://github.com/svga/SVGA-Samples/raw/master_aep/BitmapColorArea1.svga"] completionBlock:^(SVGAVideoEntity * _Nullable videoItem) {
 //            if (videoItem != nil) {
 //                self.aPlayer.videoItem = videoItem;

Diff for: Source/SVGAPlayer.m

@@ -89,6 +89,19 @@ - (void)startAnimation {
 }
 
 - (void)startAnimationWithRange:(NSRange)range reverse:(BOOL)reverse {
+    if (self.videoItem == nil) {
+        NSLog(@"videoItem could not be nil！");
+        return;
+    } else if (self.drawLayer == nil) {
+        self.videoItem = _videoItem;
+    }
+    [self stopAnimation:NO];
+    self.loopCount = 0;
+    if (self.videoItem.FPS == 0) {
+        NSLog(@"videoItem FPS could not be 0！");
+        return;
+    }
+    
     self.currentRange = range;
     self.reversing = reverse;
     if (reverse) {
@@ -97,7 +110,10 @@ - (void)startAnimationWithRange:(NSRange)range reverse:(BOOL)reverse {
     else {
         self.currentFrame = MAX(0, range.location);
     }
-    [self startAnimation];
+    self.forwardAnimating = !self.reversing;
+    self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(next)];
+    self.displayLink.frameInterval = 60 / self.videoItem.FPS;
+    [self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:self.mainRunLoopMode];
 }
 
 - (void)pauseAnimation {