[Android] Retry strategy for paged lists loading

[Geoffrey Métais]

vlc-android | branch: master | Geoffrey Métais <geoffrey.metais at gmail.com> | Wed Jan  9 15:34:54 2019 +0100| [0fbe8aa8dee1c916b24353d805717ea3190e805a] | committer: Geoffrey Métais

Retry strategy for paged lists loading

> https://code.videolan.org/videolan/vlc-android/commit/0fbe8aa8dee1c916b24353d805717ea3190e805a
---

 .../org/videolan/vlc/viewmodels/paged/MLPagedModel.kt  | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/vlc-android/src/org/videolan/vlc/viewmodels/paged/MLPagedModel.kt b/vlc-android/src/org/videolan/vlc/viewmodels/paged/MLPagedModel.kt
index 18f95b52a..5f7d20ec9 100644
--- a/vlc-android/src/org/videolan/vlc/viewmodels/paged/MLPagedModel.kt
+++ b/vlc-android/src/org/videolan/vlc/viewmodels/paged/MLPagedModel.kt
@@ -1,6 +1,7 @@
 package org.videolan.vlc.viewmodels.paged
 
 import android.content.Context
+import android.os.Handler
 import androidx.lifecycle.MutableLiveData
 import androidx.paging.DataSource
 import androidx.paging.LivePagedListBuilder
@@ -22,11 +23,13 @@ abstract class MLPagedModel<T : MediaLibraryItem>(context: Context) : SortableMo
             .setPageSize(100)
             .setPrefetchDistance(100)
             .setEnablePlaceholders(true)
-            .build()!!
+            .build()
 
     val pagedList = LivePagedListBuilder(MLDatasourceFactory(), pagingConfig)
             .build()
 
+    private val handler by lazy { Handler() }
+
     init {
         medialibrary.apply {
             medialibrary.addOnMedialibraryReadyListener(this at MLPagedModel)
@@ -99,12 +102,21 @@ abstract class MLPagedModel<T : MediaLibraryItem>(context: Context) : SortableMo
     }
 
     inner class MLDataSource : PositionalDataSource<T>() {
+        private var retry = true
 
         override fun loadInitial(params: LoadInitialParams, callback: LoadInitialCallback<T>) {
             val page = getPage(params.requestedLoadSize, params.requestedStartPosition)
             val count = if (page.size < params.requestedLoadSize) page.size else getTotalCount()
-            callback.onResult(page.toList(), params.requestedStartPosition, count)
-            loading.postValue(false)
+            try {
+                callback.onResult(page.toList(), params.requestedStartPosition, count)
+                loading.postValue(false)
+                retry = true
+            } catch (e: IllegalArgumentException) {
+                if (retry) {
+                    retry = false
+                    handler.postDelayed({ loadInitial(params, callback) }, 500L)
+                } else retry = true
+            }
         }
         override fun loadRange(params: LoadRangeParams, callback: LoadRangeCallback<T>) {
             callback.onResult(getPage(params.loadSize, params.startPosition).toList())