feat: 优化代码

app/src/main/assets/updateLog.md

@@ -4,7 +4,8 @@
 
 **2020/02/28**
 * 解决阅读界面部分字体超出范围的问题
-* 
+* 修复背景切换有时空白的bug
+* 修复滚动翻页问题
 
 **2020/02/27**
 * 修复bug,边距调节,换源等一些bug,记不清了

app/src/main/java/io/legado/app/ui/book/read/page/ContentTextView.kt

@@ -164,15 +164,23 @@ class ContentTextView(context: Context, attrs: AttributeSet?) : View(context, at
 
         pageOffset += offset
         if (pageOffset > 0) {
-            pageFactory.moveToPrev()
-            textPage = pageFactory.currentPage
-            pageOffset -= textPage.height
-            upView?.invoke(textPage)
+            if (!pageFactory.hasPrev()) {
+                pageOffset = 0f
+            } else {
+                pageFactory.moveToPrev()
+                textPage = pageFactory.currentPage
+                pageOffset -= textPage.height
+                upView?.invoke(textPage)
+            }
         } else if (pageOffset < -textPage.height) {
-            pageOffset += textPage.height
-            pageFactory.moveToNext()
-            textPage = pageFactory.currentPage
-            upView?.invoke(textPage)
+            if (!pageFactory.hasNext()) {
+                pageOffset = -textPage.height.toFloat()
+            } else {
+                pageOffset += textPage.height
+                pageFactory.moveToNext()
+                textPage = pageFactory.currentPage
+                upView?.invoke(textPage)
+            }
         }
         invalidate()
     }