Refine undo

src/main/scala/com/github/shadowsocks/widget/UndoSnackbarManager.scala

@@ -0,0 +1,45 @@
+package com.github.shadowsocks.widget
+
+import android.support.design.widget.Snackbar
+import android.view.View
+import com.github.shadowsocks.R
+
+import scala.collection.mutable.ArrayBuffer
+
+/**
+  * @author Mygod
+  * @param view The view to find a parent from.
+  * @param undo Callback for undoing removals.
+  * @param commit Callback for committing removals.
+  * @tparam T Item type.
+  */
+class UndoSnackbarManager[T](view: View, undo: Iterator[(Int, T)] => Unit,
+                             commit: Iterator[(Int, T)] => Unit = null) {
+  private val recycleBin = new ArrayBuffer[(Int, T)]
+  private val removedCallback = new Snackbar.Callback {
+    override def onDismissed(snackbar: Snackbar, event: Int) = {
+      event match {
+        case Snackbar.Callback.DISMISS_EVENT_MANUAL | Snackbar.Callback.DISMISS_EVENT_TIMEOUT =>
+          if (commit != null) commit(recycleBin.iterator)
+          recycleBin.clear
+        case _ =>
+      }
+      last = null
+    }
+  }
+  private var last: Snackbar = _
+
+  def remove(index: Int, item: T) = {
+    recycleBin.append((index, item))
+    val count = recycleBin.length
+    last = Snackbar
+      .make(view, view.getResources.getQuantityString(R.plurals.removed, count, count: Integer), Snackbar.LENGTH_LONG)
+      .setCallback(removedCallback).setAction(R.string.undo, (_ => {
+      undo(recycleBin.reverseIterator)
+      recycleBin.clear
+    }): View.OnClickListener)
+    last.show
+  }
+
+  def flush = if (last != null) last.dismiss
+}