Implement request group and pause/resume support

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

@@ -10,6 +10,8 @@
 import android.widget.ListView;
 import android.widget.ToggleButton;
 
+import com.squareup.picasso.Picasso;
+
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
 
@@ -40,6 +42,12 @@ public void onItemClick(AdapterView<?> adapterView, View view, int position, lon
     });
   }
 
+  @Override
+  protected void onDestroy() {
+    super.onDestroy();
+    Picasso.with(this).cancelTag(this);
+  }
+
   @Override public void onBackPressed() {
     if (showHide.isChecked()) {
       showHide.setChecked(false);

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

@@ -42,6 +42,7 @@ public class SampleContactsActivity extends PicassoSampleActivity
 
     ListView lv = (ListView) findViewById(android.R.id.list);
     lv.setAdapter(adapter);
+    lv.setOnScrollListener(new SampleScrollListener(this));
 
     getSupportLoaderManager().initLoader(ContactsQuery.QUERY_ID, null, this);
   }

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

@@ -61,6 +61,7 @@ public SampleContactsAdapter(Context context) {
     Picasso.with(context)
         .load(contactUri)
         .placeholder(R.drawable.contact_picture_placeholder)
+        .tag(context)
         .into(holder.icon);
   }
 

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

@@ -10,5 +10,6 @@ public class SampleGridViewActivity extends PicassoSampleActivity {
 
     GridView gv = (GridView) findViewById(R.id.grid_view);
     gv.setAdapter(new SampleGridViewAdapter(this));
+    gv.setOnScrollListener(new SampleScrollListener(this));
   }
 }

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

@@ -44,6 +44,7 @@ public SampleGridViewAdapter(Context context) {
         .placeholder(R.drawable.placeholder) //
         .error(R.drawable.error) //
         .fit() //
+        .tag(context) //
         .into(view);
 
     return view;

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

@@ -43,6 +43,7 @@ public static ListFragment newInstance() {
       ListView listView = (ListView) LayoutInflater.from(activity)
           .inflate(R.layout.sample_list_detail_list, container, false);
       listView.setAdapter(adapter);
+      listView.setOnScrollListener(new SampleScrollListener(activity));
       listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
         @Override
         public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
@@ -83,6 +84,7 @@ public static DetailFragment newInstance(String url) {
       Picasso.with(activity)
           .load(url)
           .fit()
+          .tag(activity)
           .into(imageView);
 
       return view;

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

@@ -45,6 +45,7 @@ public SampleListDetailAdapter(Context context) {
         .error(R.drawable.error)
         .resizeDimen(R.dimen.list_detail_image_size, R.dimen.list_detail_image_size)
         .centerInside()
+        .tag(context)
         .into(holder.image);
 
     return view;

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

@@ -0,0 +1,30 @@
+package com.example.picasso;
+
+import android.content.Context;
+import android.widget.AbsListView;
+
+import com.squareup.picasso.Picasso;
+
+public class SampleScrollListener implements AbsListView.OnScrollListener {
+  private final Context context;
+
+  public SampleScrollListener(Context context) {
+    this.context = context;
+  }
+
+  @Override
+  public void onScrollStateChanged(AbsListView view, int scrollState) {
+    final Picasso picasso = Picasso.with(context);
+    if (scrollState == SCROLL_STATE_IDLE || scrollState == SCROLL_STATE_TOUCH_SCROLL) {
+      picasso.resumeTag(context);
+    } else {
+      picasso.pauseTag(context);
+    }
+  }
+
+  @Override
+  public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,
+                       int totalItemCount) {
+    // Do nothing.
+  }
+}

picasso/src/main/java/com/squareup/picasso/Action.java

@@ -39,12 +39,13 @@ public RequestWeakReference(Action action, T referent, ReferenceQueue<? super T>
   final int errorResId;
   final Drawable errorDrawable;
   final String key;
+  final Object tag;
 
   boolean willReplay;
   boolean cancelled;
 
   Action(Picasso picasso, T target, Request request, boolean skipCache, boolean noFade,
-      int errorResId, Drawable errorDrawable, String key) {
+      int errorResId, Drawable errorDrawable, String key, Object tag) {
     this.picasso = picasso;
     this.request = request;
     this.target = new RequestWeakReference<T>(this, target, picasso.referenceQueue);
@@ -53,6 +54,7 @@ public RequestWeakReference(Action action, T referent, ReferenceQueue<? super T>
     this.errorResId = errorResId;
     this.errorDrawable = errorDrawable;
     this.key = key;
+    this.tag = (tag != null ? tag : this);
   }
 
   abstract void complete(Bitmap result, Picasso.LoadedFrom from);
@@ -90,4 +92,8 @@ Picasso getPicasso() {
   Priority getPriority() {
     return request.priority;
   }
+
+  Object getTag() {
+    return tag;
+  }
 }

picasso/src/main/java/com/squareup/picasso/Dispatcher.java

@@ -27,10 +27,12 @@
 import android.os.Looper;
 import android.os.Message;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.WeakHashMap;
 import java.util.concurrent.ExecutorService;
 
@@ -45,6 +47,7 @@
 import static com.squareup.picasso.Utils.VERB_DELIVERED;
 import static com.squareup.picasso.Utils.VERB_ENQUEUED;
 import static com.squareup.picasso.Utils.VERB_IGNORED;
+import static com.squareup.picasso.Utils.VERB_PAUSED;
 import static com.squareup.picasso.Utils.VERB_REPLAYING;
 import static com.squareup.picasso.Utils.VERB_RETRYING;
 import static com.squareup.picasso.Utils.getLogIdsForHunter;
@@ -67,6 +70,9 @@ class Dispatcher {
   static final int HUNTER_BATCH_COMPLETE = 8;
   static final int NETWORK_STATE_CHANGE = 9;
   static final int AIRPLANE_MODE_CHANGE = 10;
+  static final int TAG_PAUSE = 11;
+  static final int TAG_RESUME = 12;
+  static final int REQUEST_BATCH_RESUME = 13;
 
   private static final String DISPATCHER_THREAD_NAME = "Dispatcher";
   private static final int BATCH_DELAY = 200; // ms
@@ -77,6 +83,8 @@ class Dispatcher {
   final Downloader downloader;
   final Map<String, BitmapHunter> hunterMap;
   final Map<Object, Action> failedActions;
+  final Map<Object, Action> pausedActions;
+  final Set<Object> pausedTags;
   final Handler handler;
   final Handler mainThreadHandler;
   final Cache cache;
@@ -95,6 +103,8 @@ class Dispatcher {
     this.service = service;
     this.hunterMap = new LinkedHashMap<String, BitmapHunter>();
     this.failedActions = new WeakHashMap<Object, Action>();
+    this.pausedActions = new WeakHashMap<Object, Action>();
+    this.pausedTags = new HashSet<Object>();
     this.handler = new DispatcherHandler(dispatcherThread.getLooper(), this);
     this.downloader = downloader;
     this.mainThreadHandler = mainThreadHandler;
@@ -121,6 +131,14 @@ void dispatchCancel(Action action) {
     handler.sendMessage(handler.obtainMessage(REQUEST_CANCEL, action));
   }
 
+  void dispatchPauseTag(Object tag) {
+    handler.sendMessage(handler.obtainMessage(TAG_PAUSE, tag));
+  }
+
+  void dispatchResumeTag(Object tag) {
+    handler.sendMessage(handler.obtainMessage(TAG_RESUME, tag));
+  }
+
   void dispatchComplete(BitmapHunter hunter) {
     handler.sendMessage(handler.obtainMessage(HUNTER_COMPLETE, hunter));
   }
@@ -143,6 +161,15 @@ void dispatchAirplaneModeChange(boolean airplaneMode) {
   }
 
   void performSubmit(Action action) {
+    if (pausedTags.contains(action.getTag())) {
+      pausedActions.put(action.getTarget(), action);
+      if (action.getPicasso().loggingEnabled) {
+        log(OWNER_DISPATCHER, VERB_PAUSED, action.request.logId(),
+            "because tag '" + action.getTag() + "' is paused");
+      }
+      return;
+    }
+
     BitmapHunter hunter = hunterMap.get(action.getKey());
     if (hunter != null) {
       hunter.attach(action);
@@ -178,12 +205,101 @@ void performCancel(Action action) {
         }
       }
     }
+
+    if (pausedTags.contains(action.getTag())) {
+      pausedActions.remove(action.getTarget());
+      if (action.getPicasso().loggingEnabled) {
+        log(OWNER_DISPATCHER, VERB_CANCELED, action.getRequest().logId(),
+            "because paused request got canceled");
+      }
+    }
+
     Action remove = failedActions.remove(action.getTarget());
     if (remove != null && remove.getPicasso().loggingEnabled) {
       log(OWNER_DISPATCHER, VERB_CANCELED, remove.getRequest().logId(), "from replaying");
     }
   }
 
+  void performPauseTag(Object tag) {
+    // Trying to pause a tag that is already paused.
+    if (!pausedTags.add(tag)) {
+      return;
+    }
+
+    // Go through all active hunters and detach/pause the requests
+    // that have the paused tag.
+    for (Iterator<BitmapHunter> it = hunterMap.values().iterator(); it.hasNext();) {
+      BitmapHunter hunter = it.next();
+      boolean loggingEnabled = hunter.getPicasso().loggingEnabled;
+
+      Action single = hunter.getAction();
+      List<Action> joined = hunter.getActions();
+      boolean hasMultiple = joined != null && !joined.isEmpty();
+
+      // Hunter has no requests, bail early.
+      if (single == null && !hasMultiple) {
+        continue;
+      }
+
+      if (single != null && single.getTag().equals(tag)) {
+        hunter.detach(single);
+        pausedActions.put(single.getTarget(), single);
+        if (loggingEnabled) {
+          log(OWNER_DISPATCHER, VERB_PAUSED, single.request.logId(),
+              "because tag '" + tag + "' was paused");
+        }
+      }
+
+      if (hasMultiple) {
+        for (int i = joined.size() - 1; i >= 0; i--) {
+          Action action = joined.get(i);
+          if (!action.getTag().equals(tag)) {
+            continue;
+          }
+
+          hunter.detach(action);
+          pausedActions.put(action.getTarget(), action);
+          if (loggingEnabled) {
+            log(OWNER_DISPATCHER, VERB_PAUSED, action.request.logId(),
+                "because tag '" + tag + "' was paused");
+          }
+        }
+      }
+
+      // Check if the hunter can be cancelled in case all its requests
+      // had the tag being paused here.
+      if (hunter.cancel()) {
+        it.remove();
+        if (loggingEnabled) {
+          log(OWNER_DISPATCHER, VERB_CANCELED, getLogIdsForHunter(hunter), "all actions paused");
+        }
+      }
+    }
+  }
+
+  void performResumeTag(Object tag) {
+    // Trying to resume a tag that is not paused.
+    if (!pausedTags.remove(tag)) {
+      return;
+    }
+
+    List<Action> batch = null;
+    for (Iterator<Action> i = pausedActions.values().iterator(); i.hasNext();) {
+      Action action = i.next();
+      if (action.getTag().equals(tag)) {
+        if (batch == null) {
+          batch = new ArrayList<Action>();
+        }
+        batch.add(action);
+        i.remove();
+      }
+    }
+
+    if (batch != null) {
+      mainThreadHandler.sendMessage(mainThreadHandler.obtainMessage(REQUEST_BATCH_RESUME, batch));
+    }
+  }
+
   void performRetry(BitmapHunter hunter) {
     if (hunter.isCancelled()) return;
 
@@ -350,6 +466,16 @@ public DispatcherHandler(Looper looper, Dispatcher dispatcher) {
           dispatcher.performCancel(action);
           break;
         }
+        case TAG_PAUSE: {
+          Object tag = msg.obj;
+          dispatcher.performPauseTag(tag);
+          break;
+        }
+        case TAG_RESUME: {
+          Object tag = msg.obj;
+          dispatcher.performResumeTag(tag);
+          break;
+        }
         case HUNTER_COMPLETE: {
           BitmapHunter hunter = (BitmapHunter) msg.obj;
           dispatcher.performComplete(hunter);

picasso/src/main/java/com/squareup/picasso/FetchAction.java

@@ -18,8 +18,8 @@
 import android.graphics.Bitmap;
 
 class FetchAction extends Action<Void> {
-  FetchAction(Picasso picasso, Request data, boolean skipCache, String key) {
-    super(picasso, null, data, skipCache, false, 0, null, key);
+  FetchAction(Picasso picasso, Request data, boolean skipCache, String key, Object tag) {
+    super(picasso, null, data, skipCache, false, 0, null, key, tag);
   }
 
   @Override void complete(Bitmap result, Picasso.LoadedFrom from) {

picasso/src/main/java/com/squareup/picasso/GetAction.java

@@ -18,8 +18,8 @@
 import android.graphics.Bitmap;
 
 class GetAction extends Action<Void> {
-  GetAction(Picasso picasso, Request data, boolean skipCache, String key) {
-    super(picasso, null, data, skipCache, false, 0, null, key);
+  GetAction(Picasso picasso, Request data, boolean skipCache, String key, Object tag) {
+    super(picasso, null, data, skipCache, false, 0, null, key, tag);
   }
 
   @Override void complete(Bitmap result, Picasso.LoadedFrom from) {

picasso/src/main/java/com/squareup/picasso/ImageViewAction.java

@@ -25,8 +25,9 @@ class ImageViewAction extends Action<ImageView> {
   Callback callback;
 
   ImageViewAction(Picasso picasso, ImageView imageView, Request data, boolean skipCache,
-      boolean noFade, int errorResId, Drawable errorDrawable, String key, Callback callback) {
-    super(picasso, imageView, data, skipCache, noFade, errorResId, errorDrawable, key);
+      boolean noFade, int errorResId, Drawable errorDrawable, String key, Object tag,
+      Callback callback) {
+    super(picasso, imageView, data, skipCache, noFade, errorResId, errorDrawable, key, tag);
     this.callback = callback;
   }