added InputFilter that performs a substation of insertion+AztecImageS…

…pan when an insertion right before an AztecImageSpan is about to happen, to prevent a crash on Android 8.x

aztec/src/main/kotlin/org/wordpress/aztec/AztecText.kt

@@ -420,7 +420,7 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
         // triggers ClickableSpan onClick() events
         movementMethod = EnhancedMovementMethod
 
-        setupBackspaceAndEnterDetection()
+        setupKeyListenersAndInputFilters()
 
         //disable auto suggestions/correct for older devices
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
@@ -440,12 +440,44 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
     // Setup the keyListener(s) for Backspace and Enter key.
     // Backspace: If listener does return false we remove the style here
     // Enter: Ask the listener if we need to insert or not the char
-    private fun setupBackspaceAndEnterDetection() {
+    private fun setupKeyListenersAndInputFilters() {
         //hardware keyboard
         setOnKeyListener { _, _, event ->
             handleBackspaceAndEnter(event)
         }
 
+        // This InputFilter created only for the purpose of avoiding crash described here:
+        // https://android-review.googlesource.com/c/platform/frameworks/base/+/634929
+        // https://github.com/wordpress-mobile/AztecEditor-Android/issues/729
+        // the rationale behind this workaround is that the specific crash happens only when adding/deleting text right
+        // before an AztecImageSpan, so we detect the specific case and re-create the contents only when that happens.
+        // This is indeed tackling the symptom rather than the actual problem, and should be removed once the real
+        // problem is fixed at the Android OS level as described in the following url
+        // https://android-review.googlesource.com/c/platform/frameworks/base/+/634929
+        val dynamicLayoutCrashPreventer = InputFilter { source, start, end, dest, dstart, dend ->
+            var temp = source
+            if (dest.length > dend+1) {
+                // if there are any images right after the destination position, hack the text
+                val spans = dest.getSpans(dstart, dend+1, AztecImageSpan::class.java)
+                if (spans.isNotEmpty()) {
+                    // test: is this an insertion?
+                    if (dstart == dend) {
+                        // take the source (that is, what is being inserted), and append the Image to it. We will delete
+                        // the original Image later so to not have a duplicate.
+                        // use Spannable to copy / keep the current spans
+                        temp = SpannableStringBuilder(source).append(dest.subSequence(dend, dend+1))
+
+                        // delete the original AztecImageSpan
+                        text.delete(dend, dend+1)
+                        // now insert both the new insertion _and_ the original AztecImageSpan
+                        text.insert(dend, temp)
+                        temp = "" // discard the original source parameter as an ouput from this InputFilter
+                    }
+                }
+            }
+            temp
+        }
+
         val emptyEditTextBackspaceDetector = InputFilter { source, start, end, dest, dstart, dend ->
             if (selectionStart == 0 && selectionEnd == 0
                     && end == 0 && start == 0
@@ -462,7 +494,12 @@ open class AztecText : AppCompatEditText, TextWatcher, UnknownHtmlSpan.OnUnknown
             source
         }
 
-        filters = arrayOf(emptyEditTextBackspaceDetector)
+        if (Build.VERSION.SDK_INT == Build.VERSION_CODES.O || Build.VERSION.SDK_INT == Build.VERSION_CODES.O_MR1) {
+            // dynamicLayoutCrashPreventer needs to be first in array as these are going to be chained when processed
+            filters = arrayOf(dynamicLayoutCrashPreventer, emptyEditTextBackspaceDetector)
+        } else {
+            filters = arrayOf(emptyEditTextBackspaceDetector)
+        }
     }
 
     private fun handleBackspaceAndEnter(event: KeyEvent): Boolean {