Added clear canvas functionality

Method "clearCanvas" added to class MyCanvas. It will clear the path list and update the canvas status on screen.

app/src/main/java/com/simplemobiletools/draw/MyCanvas.java

@@ -85,6 +85,13 @@ public class MyCanvas extends View {
         canvas.drawPath(mPath, mPaint);
     }
 
+    public void clearCanvas(){
+        mPath = new Path();
+        mPaths = new LinkedHashMap<>();
+        pathsUpdated();
+        invalidate();
+    }
+
     private void actionDown(float x, float y) {
         mPath.reset();
         mPath.moveTo(x, y);

app/src/main/java/com/simplemobiletools/draw/activities/MainActivity.java

@@ -84,6 +84,9 @@ public class MainActivity extends SimpleActivity implements MyCanvas.PathsChange
             case R.id.settings:
                 startActivity(new Intent(getApplicationContext(), SettingsActivity.class));
                 return true;
+            case R.id.clear:
+                mMyCanvas.clearCanvas();
+                return true;
             case R.id.about:
                 startActivity(new Intent(getApplicationContext(), AboutActivity.class));
                 return true;

app/src/main/res/menu/menu.xml

@@ -15,6 +15,10 @@
         android:id="@+id/settings"
         android:title="@string/settings"
         app:showAsAction="never"/>
+    <item
+        android:id="@+id/clear"
+        android:title="@string/clear"
+        app:showAsAction="never"/>
     <item
         android:id="@+id/about"
         android:title="@string/about"

app/src/main/res/values/strings.xml

@@ -12,6 +12,7 @@
 
     <!-- Settings -->
     <string name="settings">Settings</string>
+    <string name="clear">Clear</string>
     <string name="dark_theme">Dark theme</string>
 
     <!-- About -->