fix #40, add an eraser

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

@@ -30,6 +30,8 @@ class MyCanvas(context: Context, attrs: AttributeSet) : View(context, attrs) {
     private var mStartY = 0f
     private var mIsSaving = false
     private var mIsStrokeWidthBarEnabled = false
+    private var mIsEraserOn = false
+    private var mBackgroundColor = 0
 
     init {
         mPaint.apply {
@@ -59,8 +61,10 @@ class MyCanvas(context: Context, attrs: AttributeSet) : View(context, attrs) {
         invalidate()
     }
 
-    fun toggleEraser() {
-
+    fun toggleEraser(isEraserOn: Boolean) {
+        mIsEraserOn = isEraserOn
+        mPaintOptions.isEraser = isEraserOn
+        invalidate()
     }
 
     fun setColor(newColor: Int) {
@@ -70,6 +74,12 @@ class MyCanvas(context: Context, attrs: AttributeSet) : View(context, attrs) {
         }
     }
 
+    fun updateBackgroundColor(newColor: Int) {
+        mBackgroundColor = newColor
+        setBackgroundColor(newColor)
+        mBackgroundBitmap = null
+    }
+
     fun setStrokeWidth(newStrokeWidth: Float) {
         mPaintOptions.strokeWidth = newStrokeWidth
         if (mIsStrokeWidthBarEnabled) {
@@ -152,7 +162,7 @@ class MyCanvas(context: Context, attrs: AttributeSet) : View(context, attrs) {
         var y = height - res.getDimension(R.dimen.preview_dot_offset_y)
         canvas.drawCircle((width / 2).toFloat(), y, mPaintOptions.strokeWidth / 2, mPaint)
         mPaint.style = Paint.Style.STROKE
-        mPaint.color = mPaintOptions.color.getContrastColor()
+        mPaint.color = if (mPaintOptions.isEraser) mBackgroundColor.getContrastColor() else mPaintOptions.color.getContrastColor()
         mPaint.strokeWidth = res.getDimension(R.dimen.preview_dot_stroke_size)
 
         y = height - res.getDimension(R.dimen.preview_dot_offset_y)
@@ -162,7 +172,11 @@ class MyCanvas(context: Context, attrs: AttributeSet) : View(context, attrs) {
     }
 
     private fun changePaint(paintOptions: PaintOptions) {
-        mPaint.color = paintOptions.color
+        if (paintOptions.isEraser)
+            mPaint.color = mBackgroundColor
+        else
+            mPaint.color = paintOptions.color
+
         mPaint.strokeWidth = paintOptions.strokeWidth
     }
 

app/src/main/kotlin/com/simplemobiletools/draw/PaintOptions.kt

@@ -2,18 +2,6 @@ package com.simplemobiletools.draw
 
 import android.graphics.Color
 
-class PaintOptions {
-    var color = Color.BLACK
-    var strokeWidth = 5f
-    var isEraser = false
-
-    constructor()
-
-    constructor(color: Int, strokeWidth: Float, isEraser: Boolean) {
-        this.color = color
-        this.strokeWidth = strokeWidth
-        this.isEraser = isEraser
-    }
-
+data class PaintOptions(var color: Int = Color.BLACK, var strokeWidth: Float = 5f, var isEraser: Boolean = false) {
     fun getColorToExport() = if (isEraser) "none" else Integer.toHexString(color).substring(2)
 }

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

@@ -44,6 +44,7 @@ class MainActivity : SimpleActivity(), MyCanvas.PathsChangedListener {
     private var strokeWidth = 0f
     private var suggestedFileExtension = PNG
     private var openFileIntentPath = ""
+    private var isEraserOn = false
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -60,7 +61,7 @@ class MainActivity : SimpleActivity(), MyCanvas.PathsChangedListener {
 
         color_picker.setOnClickListener { pickColor() }
         undo.setOnClickListener { my_canvas.undo() }
-        eraser.setOnClickListener { my_canvas.toggleEraser() }
+        eraser.setOnClickListener { eraserClicked() }
         storeStoragePaths()
 
         if (intent?.action == Intent.ACTION_VIEW && intent.data != null) {
@@ -159,6 +160,16 @@ class MainActivity : SimpleActivity(), MyCanvas.PathsChangedListener {
         }
     }
 
+    private fun eraserClicked() {
+        isEraserOn = !isEraserOn
+        updateEraserState()
+    }
+
+    private fun updateEraserState() {
+        eraser.setImageDrawable(resources.getDrawable(if (isEraserOn) R.drawable.ic_eraser_on else R.drawable.ic_eraser_off))
+        my_canvas.toggleEraser(isEraserOn)
+    }
+
     private fun changeBackgroundClicked() {
         val oldColor = (my_canvas.background as ColorDrawable).color
         ColorPickerDialog(this, oldColor) {
@@ -232,8 +243,7 @@ class MainActivity : SimpleActivity(), MyCanvas.PathsChangedListener {
     fun setBackgroundColor(pickedColor: Int) {
         undo.setColorFilter(pickedColor.getContrastColor(), PorterDuff.Mode.SRC_IN)
         eraser.setColorFilter(pickedColor.getContrastColor(), PorterDuff.Mode.SRC_IN)
-        my_canvas.setBackgroundColor(pickedColor)
-        my_canvas.mBackgroundBitmap = null
+        my_canvas.updateBackgroundColor(pickedColor)
         suggestedFileExtension = PNG
     }
 
@@ -241,6 +251,8 @@ class MainActivity : SimpleActivity(), MyCanvas.PathsChangedListener {
         color = pickedColor
         color_picker.setBackgroundColor(color)
         my_canvas.setColor(color)
+        isEraserOn = false
+        updateEraserState()
     }
 
     override fun pathsChanged(cnt: Int) {

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

@@ -17,7 +17,7 @@
         android:layout_height="@dimen/normal_icon_size"
         android:layout_toLeftOf="@+id/color_picker"
         android:padding="@dimen/normal_margin"
-        android:src="@drawable/ic_eraser"/>
+        android:src="@drawable/ic_eraser_off"/>
 
     <ImageView
         android:id="@+id/color_picker"