优化

app/src/main/java/io/legado/app/help/config/ReadBookConfig.kt

@@ -218,7 +218,9 @@ object ReadBookConfig {
             config.paragraphSpacing = value
         }
 
-    //标题位置 0:居左 1:居中 2:隐藏
+    /**
+     * 标题位置 0:居左 1:居中 2:隐藏
+     */
     var titleMode: Int
         get() = config.titleMode
         set(value) {
@@ -230,6 +232,11 @@ object ReadBookConfig {
             config.titleSize = value
         }
 
+    /**
+     * 是否标题居中
+     */
+    val isMiddleTitle get() = titleMode == 1
+
     var titleTopSpacing: Int
         get() = config.titleTopSpacing
         set(value) {

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

@@ -136,7 +136,7 @@ object ChapterProvider {
                     stringBuilder,
                     titlePaint,
                     isTitle = true,
-                    isTitleWithNoContent = contents.isEmpty(),
+                    emptyContent = contents.isEmpty(),
                     isVolumeTitle = bookChapter.isVolume
                 ).let {
                     absStartX = it.first
@@ -295,7 +295,7 @@ object ChapterProvider {
         stringBuilder: StringBuilder,
         textPaint: TextPaint,
         isTitle: Boolean = false,
-        isTitleWithNoContent: Boolean = false,
+        emptyContent: Boolean = false,
         isVolumeTitle: Boolean = false,
         srcList: LinkedList<String>? = null
     ): Pair<Int, Float> {
@@ -307,7 +307,7 @@ object ChapterProvider {
         }
         var durY = when {
             //标题y轴居中
-            isTitleWithNoContent && textPages.size == 1 -> {
+            emptyContent && textPages.size == 1 -> {
                 val textPage = textPages.last()
                 if (textPage.lineSize == 0) {
                     val ty = (visibleHeight - layout.lineCount * textPaint.textHeight) / 2
@@ -368,9 +368,9 @@ object ChapterProvider {
                     textLine.text = words
                     textLine.isParagraphEnd = true
                     //标题x轴居中
-                    val startX = if (isTitle && ReadBookConfig.titleMode == 1
+                    val startX = if (
-                        || isTitleWithNoContent
+                        isTitle &&
-                        || isVolumeTitle
+                        (ReadBookConfig.isMiddleTitle || emptyContent || isVolumeTitle)
                     ) {
                         (visibleWidth - layout.getLineWidth(lineIndex)) / 2
                     } else {
@@ -382,6 +382,17 @@ object ChapterProvider {
                     )
                 }
                 else -> {
+                    if (
+                        isTitle &&
+                        (ReadBookConfig.isMiddleTitle || emptyContent || isVolumeTitle)
+                    ) {
+                        //标题居中
+                        val startX = (visibleWidth - layout.getLineWidth(lineIndex)) / 2
+                        addCharsToLineNatural(
+                            book, absStartX, textLine, words.toStringArray(),
+                            textPaint, startX, srcList
+                        )
+                    } else {
                         //中间行
                         textLine.text = words
                         addCharsToLineMiddle(
@@ -390,6 +401,7 @@ object ChapterProvider {
                         )
                     }
                 }
+            }
             stringBuilder.append(words)
             if (textLine.isParagraphEnd) {
                 stringBuilder.append("\n")
@@ -412,6 +424,7 @@ object ChapterProvider {
         textLine: TextLine,
         words: Array<String>,
         textPaint: TextPaint,
+        /**自然排版长度**/
         desiredWidth: Float,
         srcList: LinkedList<String>?
     ) {
@@ -436,7 +449,8 @@ object ChapterProvider {
         if (words.size > bodyIndent.length) {
             val words1 = words.copyOfRange(bodyIndent.length, words.size)
             addCharsToLineMiddle(
-                book, absStartX, textLine, words1, textPaint, desiredWidth, x, srcList
+                book, absStartX, textLine, words1,
+                textPaint, desiredWidth, x, srcList
             )
         }
     }
@@ -450,7 +464,9 @@ object ChapterProvider {
         textLine: TextLine,
         words: Array<String>,
         textPaint: TextPaint,
+        /**自然排版长度**/
         desiredWidth: Float,
+        /**起始x坐标**/
         startX: Float,
         srcList: LinkedList<String>?
     ) {
@@ -458,9 +474,10 @@ object ChapterProvider {
             addCharsToLineNatural(book, absStartX, textLine, words, textPaint, startX, srcList)
             return
         }
+        val residualWidth = visibleWidth - desiredWidth
         val spaceSize = words.filter { it == " " }.size
         if (spaceSize > 0) {
-            val d = (visibleWidth - desiredWidth) / spaceSize
+            val d = residualWidth / spaceSize
             var x = startX
             words.forEachIndexed { index, char ->
                 val cw = StaticLayout.getDesiredWidth(char, textPaint)
@@ -469,17 +486,23 @@ object ChapterProvider {
                 } else {
                     (x + cw)
                 }
-                addCharToLine(book, absStartX, textLine, char, x, x1, index + 1 == words.size, srcList)
+                addCharToLine(
+                    book, absStartX, textLine, char,
+                    x, x1, index + 1 == words.size, srcList
+                )
                 x = x1
             }
         } else {
             val gapCount: Int = words.lastIndex
-            val d = (visibleWidth - desiredWidth) / gapCount
+            val d = residualWidth / gapCount
             var x = startX
             words.forEachIndexed { index, char ->
                 val cw = StaticLayout.getDesiredWidth(char, textPaint)
                 val x1 = if (index != words.lastIndex) (x + cw + d) else (x + cw)
-                addCharToLine(book, absStartX, textLine, char, x, x1, index + 1 == words.size, srcList)
+                addCharToLine(
+                    book, absStartX, textLine, char,
+                    x, x1, index + 1 == words.size, srcList
+                )
                 x = x1
             }
         }