add letterSpacingExtra attribute

Author: YvesCheung

app/src/main/java/com/yy/mobile/rollingtext/MainActivity.java

@@ -124,6 +124,7 @@ public void onAnimationEnd(Animator animation) {
 
         final RollingTextView timeView = findViewById(R.id.timeView);
         timeView.setAnimationDuration(300);
+        timeView.setLetterSpacingExtra(10);
         @SuppressLint("SimpleDateFormat") final DateFormat format = new SimpleDateFormat("HH:mm:ss");
         handler.post(new Runnable() {
             @Override

rollingtextview/src/main/java/com/yy/mobile/rollingtextview/RollingTextView.kt

@@ -299,6 +299,15 @@ open class RollingTextView : View {
             }
         }
 
+    /**
+     * px between letter
+     */
+    var letterSpacingExtra: Int
+        set(value) {
+            textManager.letterSpacingExtra = value
+        }
+        get() = textManager.letterSpacingExtra
+
     override fun getBaseline(): Int {
         val fontMetrics = textPaint.fontMetrics
         return (textManager.textHeight / 2 + ((fontMetrics.descent - fontMetrics.ascent) / 2 - fontMetrics.descent)).toInt()

rollingtextview/src/main/java/com/yy/mobile/rollingtextview/TextManager.kt

@@ -26,6 +26,8 @@ internal class TextManager(
 
     private var charListColumns: List<List<Char>> = Collections.emptyList()
 
+    var letterSpacingExtra: Int = 0
+
     init {
         updateFontMatrics()
     }
@@ -68,12 +70,18 @@ internal class TextManager(
     fun draw(canvas: Canvas) {
         textColumns.forEach {
             it.draw(canvas)
-            canvas.translate(it.currentWidth, 0f)
+            canvas.translate(it.currentWidth + letterSpacingExtra, 0f)
         }
     }
 
     val currentTextWidth: Float
-        get() = textColumns.map { it.currentWidth }.fold(0f) { total, next -> total + next }
+        get() {
+            val space = letterSpacingExtra * Math.max(0, textColumns.size - 1)
+            val textWidth = textColumns
+                .map { it.currentWidth }
+                .fold(0f) { total, next -> total + next }
+            return textWidth + space
+        }
 
     private fun Float.isZero(): Boolean = this < FLT_EPSILON && this > -FLT_EPSILON