Drag the Image Pieces Around

app/src/main/java/dragosholban/com/androidpuzzlegame/MainActivity.java

@@ -8,6 +8,7 @@
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.widget.ImageView;
+import android.widget.RelativeLayout;
 
 import java.util.ArrayList;
 
@@ -21,7 +22,7 @@ protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
 
-        final ConstraintLayout layout = findViewById(R.id.layout);
+        final RelativeLayout layout = findViewById(R.id.layout);
         ImageView imageView = findViewById(R.id.imageView);
 
         // run image related code after the view was laid out
@@ -30,9 +31,11 @@ protected void onCreate(Bundle savedInstanceState) {
             @Override
             public void run() {
                 pieces = splitImage();
+                TouchListener touchListener = new TouchListener();
                 for(Bitmap piece : pieces) {
                     ImageView iv = new ImageView(getApplicationContext());
                     iv.setImageBitmap(piece);
+                    iv.setOnTouchListener(touchListener);
                     layout.addView(iv);
                 }
             }

app/src/main/java/dragosholban/com/androidpuzzlegame/TouchListener.java

@@ -0,0 +1,30 @@
+package dragosholban.com.androidpuzzlegame;
+
+import android.view.MotionEvent;
+import android.view.View;
+import android.widget.RelativeLayout;
+
+public class TouchListener implements View.OnTouchListener {
+    private float xDelta;
+    private float yDelta;
+
+    @Override
+    public boolean onTouch(View view, MotionEvent motionEvent) {
+        float x = motionEvent.getRawX();
+        float y = motionEvent.getRawY();
+        RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
+        switch (motionEvent.getAction() & MotionEvent.ACTION_MASK) {
+            case MotionEvent.ACTION_DOWN:
+                xDelta = x - lParams.leftMargin;
+                yDelta = y - lParams.topMargin;
+                break;
+            case MotionEvent.ACTION_MOVE:
+                lParams.leftMargin = (int) (x - xDelta);
+                lParams.topMargin = (int) (y - yDelta);
+                view.setLayoutParams(lParams);
+                break;
+        }
+
+        return true;
+    }
+}

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

@@ -4,8 +4,7 @@
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    tools:context="dragosholban.com.androidpuzzlegame.MainActivity"
-    android:id="@+id/layout">
+    tools:context="dragosholban.com.androidpuzzlegame.MainActivity">
 
     <ImageView
         android:id="@+id/imageView"
@@ -23,4 +22,14 @@
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toTopOf="parent"
         app:srcCompat="@drawable/photo" />
+
+    <RelativeLayout
+        android:id="@+id/layout"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintRight_toRightOf="parent"
+        app:layout_constraintTop_toTopOf="parent">
+    </RelativeLayout>
 </android.support.constraint.ConstraintLayout>