TFragments.05-Solution-InterfaceCommunication

Author: cezannec

app/src/main/java/com/example/android/android_me/ui/MainActivity.java

@@ -18,12 +18,13 @@
 
 import android.os.Bundle;
 import android.support.v7.app.AppCompatActivity;
+import android.widget.Toast;
 
 import com.example.android.android_me.R;
 
 // This activity is responsible for displaying the master list of all images
-// TODO (4) Implement the MasterListFragment callback, OnImageClickListener
-public class MainActivity extends AppCompatActivity {
+// Implement the MasterListFragment callback, OnImageClickListener
+public class MainActivity extends AppCompatActivity implements MasterListFragment.OnImageClickListener{
 
 
     @Override
@@ -33,6 +34,10 @@ protected void onCreate(Bundle savedInstanceState) {
 
     }
 
-    // TODO (5) Define the behavior for onImageSelected; create a Toast that displays the position clicked
+    // Define the behavior for onImageSelected
+    public void onImageSelected(int position) {
+        // Create a Toast that displays the position that was clicked
+        Toast.makeText(this, "Position clicked = " + position, Toast.LENGTH_SHORT).show();
+    }
 
 }

app/src/main/java/com/example/android/android_me/ui/MasterListFragment.java

@@ -16,11 +16,13 @@
 
 package com.example.android.android_me.ui;
 
+import android.content.Context;
 import android.os.Bundle;
 import android.support.v4.app.Fragment;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.AdapterView;
 import android.widget.GridView;
 
 import com.example.android.android_me.R;
@@ -31,11 +33,28 @@
 // The list appears as a grid of images
 public class MasterListFragment extends Fragment {
 
-    // TODO (1) Define a new interface OnImageClickListener that triggers a callback in the host activity
-        // The callback is a method named onImageSelected(int position) that contains information about
-        // which position on the grid of images a user has clicked
+    // Define a new interface OnImageClickListener that triggers a callback in the host activity
+    OnImageClickListener mCallback;
 
-    // TODO (2) Override onAttach to make sure that the container activity has implemented the callback
+    // OnImageClickListener interface, calls a method in the host activity named onImageSelected
+    public interface OnImageClickListener {
+        void onImageSelected(int position);
+    }
+
+    // Override onAttach to make sure that the container activity has implemented the callback
+    @Override
+    public void onAttach(Context context) {
+        super.onAttach(context);
+
+        // This makes sure that the host activity has implemented the callback interface
+        // If not, it throws an exception
+        try {
+            mCallback = (OnImageClickListener) context;
+        } catch (ClassCastException e) {
+            throw new ClassCastException(context.toString()
+                    + " must implement OnImageClickListener");
+        }
+    }
 
 
     // Mandatory empty constructor
@@ -59,7 +78,14 @@ public View onCreateView(LayoutInflater inflater, ViewGroup container,
         // Set the adapter on the GridView
         gridView.setAdapter(mAdapter);
 
-        // TODO (3) Set a click listener on the gridView and trigger the callback onImageSelected when an item is clicked
+        // Set a click listener on the gridView and trigger the callback onImageSelected when an item is clicked
+        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
+            @Override
+            public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
+                // Trigger the callback method and pass in the position that was clicked
+                mCallback.onImageSelected(position);
+            }
+        });
 
         // Return the root view
         return rootView;