fix #41, add Redo

Author: tibbi

app/src/main/kotlin/com/simplemobiletools/draw/activities/MainActivity.kt

@@ -64,6 +64,7 @@ class MainActivity : SimpleActivity(), CanvasListener {
         color_picker.setOnClickListener { pickColor() }
         undo.setOnClickListener { my_canvas.undo() }
         eraser.setOnClickListener { eraserClicked() }
+        redo.setOnClickListener { my_canvas.redo() }
 
         checkIntents()
         checkWhatsNewDialog()
@@ -342,6 +343,7 @@ class MainActivity : SimpleActivity(), CanvasListener {
         val contrastColor = pickedColor.getContrastColor()
         undo.applyColorFilter(contrastColor)
         eraser.applyColorFilter(contrastColor)
+        redo.applyColorFilter(contrastColor)
         my_canvas.updateBackgroundColor(pickedColor)
         suggestedFileExtension = PNG
     }
@@ -358,6 +360,10 @@ class MainActivity : SimpleActivity(), CanvasListener {
         undo.beVisibleIf(visible)
     }
 
+    override fun toggleRedoVisibility(visible: Boolean) {
+        redo.beVisibleIf(visible)
+    }
+
     private var onStrokeWidthBarChangeListener: SeekBar.OnSeekBarChangeListener = object : SeekBar.OnSeekBarChangeListener {
         override fun onProgressChanged(seekBar: SeekBar, progress: Int, fromUser: Boolean) {
             my_canvas.setStrokeWidth(progress.toFloat())

app/src/main/kotlin/com/simplemobiletools/draw/interfaces/CanvasListener.kt

@@ -2,4 +2,6 @@ package com.simplemobiletools.draw.interfaces
 
 interface CanvasListener {
     fun toggleUndoVisibility(visible: Boolean)
+
+    fun toggleRedoVisibility(visible: Boolean)
 }

app/src/main/kotlin/com/simplemobiletools/draw/views/MyCanvas.kt

@@ -27,9 +27,9 @@ class MyCanvas(context: Context, attrs: AttributeSet) : View(context, attrs) {
     var mBackgroundBitmap: Bitmap? = null
     var mListener: CanvasListener? = null
 
-    // allow undoing Clear
     var mLastPaths = LinkedHashMap<MyPath, PaintOptions>()
     var mLastBackgroundBitmap: Bitmap? = null
+    var mUndonePaths = LinkedHashMap<MyPath, PaintOptions>()
 
     private var mPaint = Paint()
     private var mPath = MyPath()
@@ -67,16 +67,32 @@ class MyCanvas(context: Context, attrs: AttributeSet) : View(context, attrs) {
             return
         }
 
-        if (mPaths.isEmpty())
+        if (mPaths.isEmpty()) {
             return
+        }
 
+        val lastPath = mPaths.values.lastOrNull()
         val lastKey = mPaths.keys.lastOrNull()
 
         mPaths.remove(lastKey)
+        if (lastPath != null && lastKey != null) {
+            mUndonePaths[lastKey] = lastPath
+            mListener?.toggleRedoVisibility(true)
+        }
         pathsUpdated()
         invalidate()
     }
 
+    fun redo() {
+        val lastKey = mUndonePaths.keys.last()
+        addPath(lastKey, mUndonePaths.values.last())
+        mUndonePaths.remove(lastKey)
+        if (mUndonePaths.isEmpty()) {
+            mListener?.toggleRedoVisibility(false)
+        }
+        invalidate()
+    }
+
     fun toggleEraser(isEraserOn: Boolean) {
         mIsEraserOn = isEraserOn
         mPaintOptions.isEraser = isEraserOn
@@ -146,7 +162,7 @@ class MyCanvas(context: Context, attrs: AttributeSet) : View(context, attrs) {
     }
 
     fun addPath(path: MyPath, options: PaintOptions) {
-        mPaths.put(path, options)
+        mPaths[path] = options
         pathsUpdated()
     }
 
@@ -248,6 +264,8 @@ class MyCanvas(context: Context, attrs: AttributeSet) : View(context, attrs) {
                 mStartX = x
                 mStartY = y
                 actionDown(x, y)
+                mUndonePaths.clear()
+                mListener?.toggleRedoVisibility(false)
             }
             MotionEvent.ACTION_MOVE -> actionMove(x, y)
             MotionEvent.ACTION_UP -> actionUp()

app/src/main/res/layout/activity_main.xml

@@ -11,6 +11,15 @@
         android:layout_height="match_parent"
         android:background="@android:color/white"/>
 
+    <ImageView
+        android:id="@+id/redo"
+        android:layout_width="@dimen/normal_icon_size"
+        android:layout_height="@dimen/normal_icon_size"
+        android:layout_toLeftOf="@+id/eraser"
+        android:padding="@dimen/medium_margin"
+        android:src="@drawable/ic_redo"
+        android:visibility="gone"/>
+
     <ImageView
         android:id="@+id/eraser"
         android:layout_width="@dimen/normal_icon_size"