Add basic part movement mechanism.

app/src/main/java/com/codigoparallevar/minicards/PartCanvasView.java

@@ -4,36 +4,43 @@ import android.content.Context;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Paint;
+import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.util.Log;
 import android.view.MotionEvent;
 import android.view.View;
 
 import com.codigoparallevar.minicards.parts.Part;
+import com.codigoparallevar.minicards.parts.Placeholder;
 import com.codigoparallevar.minicards.parts.buttons.RoundButton;
 
 import java.util.ArrayList;
 
 class PartCanvasView extends View {
 
+    @NonNull
     ArrayList<Part> parts = new ArrayList<>();
 
+    @Nullable
+    Part selectedPart;
+
     public PartCanvasView(Context context) {
         super(context);
         this.setBackgroundColor(Color.rgb(4, 69, 99));
+        parts.add(new Placeholder(50, 50, 750, 500));
         parts.add(new RoundButton(500, 1200, 80, 100));
     }
 
     @Override
     public void onDraw(Canvas canvas){
-        long time = System.currentTimeMillis();
+        final long renderStartTime = System.currentTimeMillis();
         drawBackground(canvas);
 
         for (Part part : parts){
             part.draw(canvas);
         }
 
-        Log.d("Render time", System.currentTimeMillis() - time + "ms");
+        Log.d("Render time", System.currentTimeMillis() - renderStartTime + "ms");
     }
 
     private void drawBackground(Canvas canvas) {
@@ -58,16 +65,42 @@ class PartCanvasView extends View {
 
     @Override
     public boolean onTouchEvent(MotionEvent event){
-        int x = (int) event.getX() - this.getLeft();
+        final int x = (int) event.getX() - this.getLeft();
-        int y = (int) event.getY() - this.getTop();
+        final int y = (int) event.getY() - this.getTop();
 
-        Part touchedPart = getPartOn(x, y);
+        switch (event.getAction()){
-        if (touchedPart == null){
+            case MotionEvent.ACTION_DOWN:
+            {
+                selectedPart = getPartOn(x, y);
+                if (selectedPart == null) {
                     Log.d("Touched part", "not found");
                     return false;
                 }
 
-        Log.d("Touched part", "Part: " + touchedPart);
+                Log.d("Touched part", "Part: " + selectedPart);
+            }
+            break;
+
+            case MotionEvent.ACTION_UP:
+            {
+                selectedPart = null;
+            }
+            break;
+
+            case MotionEvent.ACTION_MOVE:
+            {
+                if (selectedPart != null){
+                    selectedPart.move(x, y);
+                }
+            }
+            break;
+
+            default:
+            {
+                Log.d("PartCanvasView", "Unhandled action: " + event.getAction());
+            }
+        }
+
         invalidate();
         return true;
     }
@@ -76,7 +109,7 @@ class PartCanvasView extends View {
     private Part getPartOn(int x, int y) {
         // Look in the list, in reverse so top-most elements are checked before
         for (int i = parts.size() - 1; i >= 0; i--){
-            Part part = parts.get(i);
+            final Part part = parts.get(i);
             if ((x >= part.getLeft()) && (part.getRight() >= x)
                     && (y >= part.getTop()) && (part.getBottom() >= y)){
                 return part;

app/src/main/java/com/codigoparallevar/minicards/parts/Part.java

@@ -9,4 +9,6 @@ public interface Part {
     public int getBottom();
 
     public void draw(Canvas canvas);
+
+    void move(int x, int y);
 }

app/src/main/java/com/codigoparallevar/minicards/parts/Placeholder.java

@@ -5,10 +5,10 @@ import android.graphics.Color;
 import android.graphics.Paint;
 
 public class Placeholder implements Part {
-    private final int _left;
+    private int _left;
-    private final int _top;
+    private int _top;
-    private final int _right;
+    private int _right;
-    private final int _bottom;
+    private int _bottom;
 
     public Placeholder(int left, int top, int right, int bottom) {
         _left = left;
@@ -55,4 +55,16 @@ public class Placeholder implements Part {
         // Cross, top-right, bottom-left
         canvas.drawLine(_right, _top, _left, _bottom, paint);
     }
+
+    @Override
+    public void move(int x, int y) {
+        final int width = _right - _left;
+        final int height = _bottom - _top;
+
+        _left = x - width / 2;
+        _right = _left + width;
+
+        _top = y - height / 2;
+        _bottom = _top + height;
+    }
 }

app/src/main/java/com/codigoparallevar/minicards/parts/buttons/RoundButton.java

@@ -9,8 +9,8 @@ import com.codigoparallevar.minicards.parts.Part;
 public class RoundButton implements Part {
 
 
-    private final int _xCenter;
+    private int _xCenter;
-    private final int _yCenter;
+    private int _yCenter;
     private final int _innerRadius;
     private final int _outerRadius;
     private final int _outerRadiusThickness = 10;
@@ -54,4 +54,10 @@ public class RoundButton implements Part {
         canvas.drawCircle(_xCenter, _yCenter, _outerRadius - _outerRadiusThickness, backgroundPaint);
         canvas.drawCircle(_xCenter, _yCenter, _innerRadius, foregroundPaint);
     }
+
+    @Override
+    public void move(int x, int y) {
+        _xCenter = x;
+        _yCenter = y;
+    }
 }