[core] Some fixes

> EditText crash because gravity
> Move LinearAnimation to animation package
> Fix absolute layout crash because invalid cast

core/res/ex-layout/main.xml

@@ -68,6 +68,7 @@
         background="#C00"
         src="@drawable/default_window_icon"
         scaleType="fill"
+        rotation="45"
         margin="10dp"/>
 
       <ImageView

core/src/br/nullexcept/mux/view/anim/AlphaAnimation.java

@@ -1,6 +1,5 @@
 package br.nullexcept.mux.view.anim;
 
-import br.nullexcept.mux.utils.LinearAnimation;
 import br.nullexcept.mux.view.View;
 
 public class AlphaAnimation extends LinearAnimation {

core/src/br/nullexcept/mux/view/anim/LinearAnimation.java

@@ -0,0 +1,68 @@
+package br.nullexcept.mux.view.anim;
+
+import br.nullexcept.mux.app.Looper;
+import br.nullexcept.mux.view.View;
+
+public abstract class LinearAnimation {
+    private int duration;
+    private boolean loop  = false;
+    private final Looper looper;
+    private final Runnable update = this::update;
+    private final long[] times = new long[3];
+    private boolean playing = false;
+
+    public LinearAnimation(View view, int duration) {
+        this.duration = duration;
+        this.looper = view.getContext().getMainLooper();
+    }
+
+    protected void setDuration(int duration) {
+        this.duration = duration;
+    }
+
+    private void update() {
+        if (times[1] > times[0]) {
+            playing = false;
+            onEnd();
+            if (loop) {
+                play();
+            }
+            return;
+        }
+        playing = true;
+        onFrame((double) times[1]/ times[0]);
+        times[1] += (System.currentTimeMillis() - times[2]);
+        times[2] = System.currentTimeMillis();
+        looper.post(update);
+    }
+
+    public void play() {
+        looper.cancel(update);
+        playing = true;
+        times[0] = duration;
+        times[1] = 0;
+        times[2] = System.currentTimeMillis();
+
+        onBegin();
+        looper.post(update);
+    }
+
+    public boolean isPlaying() {
+        return playing;
+    }
+
+    public void stop() {
+        if (playing) {
+            looper.cancel(update);
+            onEnd();
+        }
+    }
+
+    public void setLoop(boolean loop) {
+        this.loop = loop;
+    }
+
+    public abstract void onBegin();
+    public abstract void onFrame(double delta);
+    public abstract void onEnd();
+}

core/src/br/nullexcept/mux/view/anim/RotationAnimation.java

@@ -1,6 +1,5 @@
 package br.nullexcept.mux.view.anim;
 
-import br.nullexcept.mux.utils.LinearAnimation;
 import br.nullexcept.mux.view.View;
 
 public class RotationAnimation extends LinearAnimation {

core/src/br/nullexcept/mux/widget/AbsoluteLayout.java

@@ -19,13 +19,11 @@ public AbsoluteLayout(Context context, AttributeList attrs) {
 
     @Override
     public void addChild(View view, ViewGroup.LayoutParams params) {
-        if (params == null) {
-            params = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
+        LayoutParams newParams = new LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
+        if (params != null) {
+            newParams.from(params);
         }
-        if (!(params instanceof LayoutParams)) {
-            params = new LayoutParams(params.width, params.height);
-        }
-        super.addChild(view, params);
+        super.addChild(view, newParams);
     }
 
     @Override
@@ -49,6 +47,9 @@ public void from(ViewGroup.LayoutParams params) {
             if (params instanceof MarginLayoutParams) {
                 x = ((MarginLayoutParams) params).getMarginLeft();
                 y = ((MarginLayoutParams) params).getMarginTop();
+            } else if (params instanceof LayoutParams) {
+                x = ((LayoutParams) params).x;
+                y = ((LayoutParams) params).y;
             }
             super.from(params);
         }

core/src/br/nullexcept/mux/widget/EditText.java

@@ -191,8 +191,10 @@ public void setEditable(boolean editable) {
     @Override
     public void setGravity(int gravity) {
         super.setGravity(gravity);
-        measureText(true);
-        checkMeasure();
+        if (text != null) {
+            measureText(true);
+            checkMeasure();
+        }
     }
 
     @Override

core/src/br/nullexcept/mux/widget/ImageView.java

@@ -18,7 +18,7 @@ public class ImageView extends View {
     public static final int SCALE_FIT = 1;
     public static final int SCALE_CROP = 2;
     public static final int SCALE_WRAP = 3;
-    
+
     private Drawable image;
     private final Rect rect = new Rect();
     private int scaleType = SCALE_FIT;