Improve wallpaper load speed.

app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationIntents.java

@@ -159,7 +159,6 @@ public class ConversationIntents {
     }
 
     public @Nullable ChatWallpaper getWallpaper() {
-      // TODO [greyson][wallpaper] Is it worth it to do this beforehand?
       return Recipient.resolved(recipientId).getWallpaper();
     }
 

app/src/main/java/org/thoughtcrime/securesms/conversationlist/ConversationListFragment.java

@@ -163,6 +163,7 @@ import org.thoughtcrime.securesms.util.concurrent.SimpleTask;
 import org.thoughtcrime.securesms.util.task.SnackbarAsyncTask;
 import org.thoughtcrime.securesms.util.views.SimpleProgressDialog;
 import org.thoughtcrime.securesms.util.views.Stub;
+import org.thoughtcrime.securesms.wallpaper.ChatWallpaper;
 import org.whispersystems.signalservice.api.websocket.WebSocketConnectionState;
 
 import java.lang.ref.WeakReference;
@@ -1034,7 +1035,15 @@ public class ConversationListFragment extends MainFragment implements ActionMode
   }
 
   private void handleCreateConversation(long threadId, Recipient recipient, int distributionType) {
+    SimpleTask.run(getLifecycle(), () -> {
+      ChatWallpaper wallpaper = recipient.resolve().getWallpaper();
+      if (wallpaper != null && !wallpaper.prefetch(requireContext(), 250)) {
+        Log.w(TAG, "Failed to prefetch wallpaper.");
+      }
+      return null;
+    }, (nothing) -> {
       getNavigator().goToConversation(recipient.getId(), threadId, distributionType, -1);
+    });
   }
 
   private void startActionMode() {

app/src/main/java/org/thoughtcrime/securesms/wallpaper/ChatWallpaper.java

@@ -1,9 +1,11 @@
 package org.thoughtcrime.securesms.wallpaper;
 
+import android.content.Context;
 import android.os.Parcelable;
 import android.widget.ImageView;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.WorkerThread;
 
 import org.thoughtcrime.securesms.conversation.colors.ChatColors;
 import org.thoughtcrime.securesms.conversation.colors.ChatColorsMapper;
@@ -26,6 +28,11 @@ public interface ChatWallpaper extends Parcelable {
 
   void loadInto(@NonNull ImageView imageView);
 
+  @WorkerThread
+  default boolean prefetch(@NonNull Context context, long maxWaitTime) {
+    return true;
+  }
+
   default boolean isPhoto() {
     return false;
   }

app/src/main/java/org/thoughtcrime/securesms/wallpaper/UriChatWallpaper.java

@@ -1,9 +1,12 @@
 package org.thoughtcrime.securesms.wallpaper;
 
+import android.content.Context;
+import android.graphics.Bitmap;
 import android.graphics.drawable.Drawable;
 import android.net.Uri;
 import android.os.Parcel;
 import android.os.Parcelable;
+import android.util.LruCache;
 import android.widget.ImageView;
 
 import androidx.annotation.NonNull;
@@ -18,11 +21,26 @@ import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.database.model.databaseprotos.Wallpaper;
 import org.thoughtcrime.securesms.mms.DecryptableStreamUriLoader;
 import org.thoughtcrime.securesms.mms.GlideApp;
+import org.thoughtcrime.securesms.util.ByteUnit;
+import org.thoughtcrime.securesms.util.LRUCache;
 
+import java.util.HashMap;
 import java.util.Objects;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 final class UriChatWallpaper implements ChatWallpaper, Parcelable {
 
+  private static final LruCache<Uri, Bitmap> CACHE = new LruCache<Uri, Bitmap>((int) Runtime.getRuntime().maxMemory() / 8) {
+    @Override
+    protected int sizeOf(Uri key, Bitmap value) {
+      return value.getByteCount();
+    }
+  };
+
   private static final String TAG = Log.tag(UriChatWallpaper.class);
 
   private final Uri   uri;
@@ -45,6 +63,12 @@ final class UriChatWallpaper implements ChatWallpaper, Parcelable {
 
   @Override
   public void loadInto(@NonNull ImageView imageView) {
+    Bitmap cached = CACHE.get(uri);
+    if (cached != null) {
+      Log.d(TAG, "Using cached value.");
+      imageView.setImageBitmap(CACHE.get(uri));
+    } else {
+      Log.d(TAG, "Not in cache. Fetching using Glide.");
       GlideApp.with(imageView)
               .load(new DecryptableStreamUriLoader.DecryptableUri(uri))
               .addListener(new RequestListener<Drawable>() {
@@ -62,6 +86,36 @@ final class UriChatWallpaper implements ChatWallpaper, Parcelable {
               })
               .into(imageView);
     }
+  }
+
+  @Override
+  public boolean prefetch(@NonNull Context context, long maxWaitTime) {
+    Bitmap cached = CACHE.get(uri);
+    if (cached != null) {
+      Log.d(TAG, "Already cached, skipping prefetch.");
+      return true;
+    }
+
+    long startTime = System.currentTimeMillis();
+    try {
+      Bitmap bitmap = GlideApp.with(context)
+                              .asBitmap()
+                              .load(new DecryptableStreamUriLoader.DecryptableUri(uri))
+                              .submit()
+                              .get(maxWaitTime, TimeUnit.MILLISECONDS);
+
+      CACHE.put(uri, bitmap);
+      Log.d(TAG, "Prefetched wallpaper in " + (System.currentTimeMillis() - startTime) + " ms.");
+
+      return true;
+    } catch (ExecutionException | InterruptedException e) {
+      Log.w(TAG, "Failed to prefetch wallpaper.", e);
+    } catch (TimeoutException e) {
+      Log.w(TAG, "Timed out waiting for prefetch.");
+    }
+
+    return false;
+  }
 
   @Override
   public @NonNull Wallpaper serialize() {