ScrollListener to improve performance

picasso-sample/AndroidManifest.xml

@@ -34,9 +34,12 @@
       </intent-filter>
     </activity>
 
+
+    <activity android:name=".SampleGridViewScrollingActivity" android:label="@string/view_pager_activity"/>
     <activity android:name=".SampleContactsActivity"/>
     <activity android:name=".SampleGalleryActivity"/>
     <activity android:name=".SampleListDetailActivity"/>
+    <activity android:name=".SampleListDetailScrollingActivity"/>
 
     <receiver android:name="SampleWidgetProvider">
       <intent-filter>

picasso-sample/res/layout/sample_gridview_activity_scrolling.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/viewPager"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"/>
+

picasso-sample/res/layout/sample_gridview_fragment_scrolling.xml

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+  <GridView
+      android:id="@+id/grid_view"
+      android:layout_width="match_parent"
+      android:layout_height="match_parent"
+      android:numColumns="@integer/column_count"
+      android:scrollbarStyle="insideOverlay"
+      android:scrollbars="none"
+      android:listSelector="@null"
+      />
+
+  <Button
+      style="?android:attr/buttonStyleSmall"
+      android:layout_width="wrap_content"
+      android:layout_height="wrap_content"
+      android:text="toggle Skip memory cache"
+      android:id="@+id/skipMemoryCacheButton"
+      android:layout_gravity="right|bottom"
+      />
+
+</FrameLayout>

picasso-sample/res/layout/sample_list_detail_list_scrolling.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+  <ListView
+      android:id="@+id/listView"
+      android:layout_width="match_parent"
+      android:layout_height="match_parent"
+      android:paddingTop="@dimen/faux_action_bar_size"
+      android:clipToPadding="false"
+      />
+
+  <Button
+      style="?android:attr/buttonStyleSmall"
+      android:layout_width="wrap_content"
+      android:layout_height="wrap_content"
+      android:text="toggle Skip memory cache"
+      android:id="@+id/skipMemoryCacheButton"
+      android:layout_gravity="right|bottom"
+      />
+
+</FrameLayout>

picasso-sample/res/values/strings.xml

@@ -11,4 +11,5 @@
     image.\n\nTo enable this functionality on pre-ICS use a standalone HTTP client with caching such
     as OkHttp.
   </string>
+  <string name="view_pager_activity">ViewPager and Scrolling</string>
 </resources>

picasso-sample/src/main/java/com/example/picasso/PicassoSampleAdapter.java

@@ -20,12 +20,44 @@
 final class PicassoSampleAdapter extends BaseAdapter {
 
   private static final int NOTIFICATION_ID = 666;
+  private final LayoutInflater inflater;
+
+  public PicassoSampleAdapter(Context context) {
+    inflater = LayoutInflater.from(context);
+  }
+
+  @Override public int getCount() {
+    return Sample.values().length;
+  }
+
+  @Override public Sample getItem(int position) {
+    return Sample.values()[position];
+  }
+
+  @Override public long getItemId(int position) {
+    return position;
+  }
+
+  @Override public View getView(int position, View convertView, ViewGroup parent) {
+    TextView view = (TextView) convertView;
+    if (view == null) {
+      view = (TextView) inflater.inflate(R.layout.picasso_sample_activity_item, parent, false);
+    }
+
+    view.setText(getItem(position).name);
+
+    return view;
+  }
 
   enum Sample {
     GRID_VIEW("Image Grid View", SampleGridViewActivity.class),
+    GRID_VIEW_SCROLLING("View Pager with Image Grid View and ScrollListener",
+        SampleGridViewScrollingActivity.class),
     GALLERY("Load from Gallery", SampleGalleryActivity.class),
     CONTACTS("Contact Photos", SampleContactsActivity.class),
     LIST_DETAIL("List / Detail View", SampleListDetailActivity.class),
+    LIST_DETAIL_SCROLLING("List / Detail with ScrollListener",
+        SampleListDetailScrollingActivity.class),
     SHOW_NOTIFICATION("Sample Notification", null) {
       @Override public void launch(Activity activity) {
         RemoteViews remoteViews =
@@ -70,33 +102,4 @@ public void launch(Activity activity) {
       activity.finish();
     }
   }
-
-  private final LayoutInflater inflater;
-
-  public PicassoSampleAdapter(Context context) {
-    inflater = LayoutInflater.from(context);
-  }
-
-  @Override public int getCount() {
-    return Sample.values().length;
-  }
-
-  @Override public Sample getItem(int position) {
-    return Sample.values()[position];
-  }
-
-  @Override public long getItemId(int position) {
-    return position;
-  }
-
-  @Override public View getView(int position, View convertView, ViewGroup parent) {
-    TextView view = (TextView) convertView;
-    if (view == null) {
-      view = (TextView) inflater.inflate(R.layout.picasso_sample_activity_item, parent, false);
-    }
-
-    view.setText(getItem(position).name);
-
-    return view;
-  }
 }

picasso-sample/src/main/java/com/example/picasso/SampleGridViewActivity.java

@@ -9,6 +9,6 @@ public class SampleGridViewActivity extends PicassoSampleActivity {
     setContentView(R.layout.sample_gridview_activity);
 
     GridView gv = (GridView) findViewById(R.id.grid_view);
-    gv.setAdapter(new SampleGridViewAdapter(this));
+    gv.setAdapter(new SampleGridViewAdapter(this, false));
   }
 }

picasso-sample/src/main/java/com/example/picasso/SampleGridViewAdapter.java

@@ -5,6 +5,7 @@
 import android.view.ViewGroup;
 import android.widget.BaseAdapter;
 import com.squareup.picasso.Picasso;
+import com.squareup.picasso.RequestCreator;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -14,11 +15,11 @@
 final class SampleGridViewAdapter extends BaseAdapter {
   private final Context context;
   private final List<String> urls = new ArrayList<String>();
+  private boolean skipMemoryCache;
 
-  public SampleGridViewAdapter(Context context) {
+  public SampleGridViewAdapter(Context context, boolean skipMemoryCache) {
     this.context = context;
-
-    // Ensure we get a different ordering of images on each run.
+    this.skipMemoryCache = skipMemoryCache;
     Collections.addAll(urls, Data.URLS);
     Collections.shuffle(urls);
 
@@ -39,12 +40,17 @@ public SampleGridViewAdapter(Context context) {
     String url = getItem(position);
 
     // Trigger the download of the URL asynchronously into the image view.
-    Picasso.with(context) //
+
+    RequestCreator creator = Picasso.with(context) //
         .load(url) //
         .placeholder(R.drawable.placeholder) //
         .error(R.drawable.error) //
-        .fit() //
-        .into(view);
+        .fit();
+
+    if (skipMemoryCache) {
+      creator.skipMemoryCache();
+    }
+    creator.into(view);
 
     return view;
   }
@@ -60,4 +66,9 @@ public SampleGridViewAdapter(Context context) {
   @Override public long getItemId(int position) {
     return position;
   }
+
+  public boolean toggleSkipMemoryCache() {
+    this.skipMemoryCache = !this.skipMemoryCache;
+    return this.skipMemoryCache;
+  }
 }

picasso-sample/src/main/java/com/example/picasso/SampleGridViewScrollingActivity.java

@@ -0,0 +1,78 @@
+package com.example.picasso;
+
+import android.os.Bundle;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentManager;
+import android.support.v4.app.FragmentPagerAdapter;
+import android.support.v4.view.ViewPager;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.GridView;
+import android.widget.Toast;
+import com.squareup.picasso.scrolling.PicassoScrollListener;
+
+public class SampleGridViewScrollingActivity extends PicassoSampleActivity {
+
+  @Override protected void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    setContentView(R.layout.sample_gridview_activity_scrolling);
+
+    ViewPager viewPager = (ViewPager) findViewById(R.id.viewPager);
+    viewPager.setAdapter(new GridFragmentAdapter(getSupportFragmentManager()));
+    viewPager.setPageMargin(30);
+
+    Toast.makeText(this,
+        "ViewPager with GridView\n"
+            + "Fades loaded images only if GridView is NOT scrolling and NOT flinging",
+        Toast.LENGTH_SHORT).show();
+  }
+
+  public static class GridFragmentAdapter extends FragmentPagerAdapter {
+
+    public GridFragmentAdapter(FragmentManager fm) {
+      super(fm);
+    }
+
+    @Override public Fragment getItem(int position) {
+      return new GridFragment();
+    }
+
+    @Override public int getCount() {
+      return 10;
+    }
+  }
+
+  public static class GridFragment extends Fragment {
+
+    private Button skipMemoryCacheButton;
+
+    public View onCreateView(LayoutInflater inflater, ViewGroup container,
+        Bundle savedInstanceState) {
+      View v = inflater.inflate(R.layout.sample_gridview_fragment_scrolling, container, false);
+
+      boolean skipMemory = true;
+
+      GridView gv = (GridView) v.findViewById(R.id.grid_view);
+      final SampleGridViewAdapter adapter = new SampleGridViewAdapter(getActivity(), skipMemory);
+      gv.setAdapter(adapter);
+      gv.setOnScrollListener(new PicassoScrollListener(getActivity()));
+      skipMemoryCacheButton = (Button) v.findViewById(R.id.skipMemoryCacheButton);
+      updateButton(skipMemory);
+      skipMemoryCacheButton.setOnClickListener(new View.OnClickListener() {
+        @Override
+        public void onClick(View v) {
+          boolean skip = adapter.toggleSkipMemoryCache();
+          updateButton(skip);
+        }
+      });
+
+      return v;
+    }
+
+    private void updateButton(boolean skip) {
+      skipMemoryCacheButton.setText("skip memory cache = " + skip);
+    }
+  }
+}

picasso-sample/src/main/java/com/example/picasso/SampleListDetailActivity.java

@@ -10,6 +10,7 @@
 import android.widget.ImageView;
 import android.widget.ListView;
 import android.widget.TextView;
+
 import com.squareup.picasso.Picasso;
 
 public class SampleListDetailActivity extends PicassoSampleActivity {
@@ -38,7 +39,7 @@ public static ListFragment newInstance() {
     @Override public View onCreateView(LayoutInflater inflater, ViewGroup container,
         Bundle savedInstanceState) {
       final SampleListDetailActivity activity = (SampleListDetailActivity) getActivity();
-      final SampleListDetailAdapter adapter = new SampleListDetailAdapter(activity);
+      final SampleListDetailAdapter adapter = new SampleListDetailAdapter(activity, false);
 
       ListView listView = (ListView) LayoutInflater.from(activity)
           .inflate(R.layout.sample_list_detail_list, container, false);

picasso-sample/src/main/java/com/example/picasso/SampleListDetailAdapter.java

@@ -8,16 +8,19 @@
 import android.widget.ImageView;
 import android.widget.TextView;
 import com.squareup.picasso.Picasso;
+import com.squareup.picasso.RequestCreator;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
 final class SampleListDetailAdapter extends BaseAdapter {
   private final Context context;
   private final List<String> urls = new ArrayList<String>();
+  private boolean skipMemoryCache;
 
-  public SampleListDetailAdapter(Context context) {
+  public SampleListDetailAdapter(Context context, boolean skipMemoryCache) {
     this.context = context;
+    this.skipMemoryCache = skipMemoryCache;
     Collections.addAll(urls, Data.URLS);
   }
 
@@ -39,13 +42,17 @@ public SampleListDetailAdapter(Context context) {
     holder.text.setText(url);
 
     // Trigger the download of the URL asynchronously into the image view.
-    Picasso.with(context)
+    RequestCreator creator = Picasso.with(context)
         .load(url)
         .placeholder(R.drawable.placeholder)
         .error(R.drawable.error)
         .resizeDimen(R.dimen.list_detail_image_size, R.dimen.list_detail_image_size)
-        .centerInside()
-        .into(holder.image);
+        .centerInside();
+
+    if (skipMemoryCache) {
+      creator.skipMemoryCache();
+    }
+    creator.into(holder.image);
 
     return view;
   }
@@ -62,6 +69,11 @@ public SampleListDetailAdapter(Context context) {
     return position;
   }
 
+  public boolean toggleSkipMemoryCache() {
+    this.skipMemoryCache = !this.skipMemoryCache;
+    return this.skipMemoryCache;
+  }
+
   static class ViewHolder {
     ImageView image;
     TextView text;