Fix for media thumbnails flickering on model updates.

Only update ImageView contents when they have changed.

Fixes #1004
Fixes #2663
Closes #3184

// FREEBIE

src/org/thoughtcrime/securesms/mms/AudioSlide.java

@@ -42,12 +42,12 @@ public class AudioSlide extends Slide {
   }
 
   @Override
-    public boolean hasImage() {
+  public boolean hasImage() {
     return true;
   }
 
   @Override
-    public boolean hasAudio() {
+  public boolean hasAudio() {
     return true;
   }
 

src/org/thoughtcrime/securesms/mms/Slide.java

@@ -20,6 +20,7 @@ import android.content.Context;
 import android.content.res.Resources.Theme;
 import android.net.Uri;
 import android.support.annotation.DrawableRes;
+import android.support.annotation.NonNull;
 import android.util.Log;
 
 import org.thoughtcrime.securesms.crypto.MasterSecret;
@@ -36,28 +37,16 @@ public abstract class Slide {
   protected final Context      context;
   protected       MasterSecret masterSecret;
 
-  public Slide(Context context, PduPart part) {
+  public Slide(Context context, @NonNull PduPart part) {
     this.part    = part;
     this.context = context;
   }
 
-  public Slide(Context context, MasterSecret masterSecret, PduPart part) {
+  public Slide(Context context, @NonNull MasterSecret masterSecret, @NonNull PduPart part) {
     this(context, part);
     this.masterSecret = masterSecret;
   }
 
-  protected byte[] getPartData() {
-    try {
-      if (part.getData() != null)
-        return part.getData();
-
-      return Util.readFully(PartAuthority.getPartStream(context, masterSecret, part.getDataUri()));
-    } catch (IOException e) {
-      Log.w("Slide", e);
-      return new byte[0];
-    }
-  }
-
   public String getContentType() {
     return new String(part.getContentType());
   }
@@ -107,4 +96,28 @@ public abstract class Slide {
       if (size > MmsMediaConstraints.MAX_MESSAGE_SIZE) throw new MediaTooLargeException("Media exceeds maximum message size.");
     }
   }
+
+  @Override
+  public boolean equals(Object other) {
+    if (!(other instanceof Slide)) return false;
+
+    Slide that = (Slide)other;
+
+    return Util.equals(this.getContentType(), that.getContentType()) &&
+           this.hasAudio() == that.hasAudio()                        &&
+           this.hasImage() == that.hasImage()                        &&
+           this.hasVideo() == that.hasVideo()                        &&
+           this.isDraft() == that.isDraft()                          &&
+           Util.equals(this.getUri(), that.getUri())                 &&
+           Util.equals(this.getThumbnailUri(), that.getThumbnailUri());
+  }
+
+  @Override
+  public int hashCode() {
+    return Util.hashCode(getContentType(), hasAudio(), hasImage(),
+                         hasVideo(), isDraft(), getUri(), getThumbnailUri());
+  }
+
+
+
 }

src/org/thoughtcrime/securesms/mms/TextSlide.java

@@ -17,16 +17,9 @@
 package org.thoughtcrime.securesms.mms;
 
 import android.content.Context;
-import android.net.Uri;
 import android.util.Log;
 
-import org.thoughtcrime.securesms.crypto.MasterSecret;
-import org.thoughtcrime.securesms.util.LRUCache;
-
 import java.io.UnsupportedEncodingException;
-import java.lang.ref.SoftReference;
-import java.util.Collections;
-import java.util.Map;
 
 import ws.com.google.android.mms.ContentType;
 import ws.com.google.android.mms.pdu.CharacterSets;
@@ -34,14 +27,6 @@ import ws.com.google.android.mms.pdu.PduPart;
 
 public class TextSlide extends Slide {
 
-  private static final int MAX_CACHE_SIZE = 10;
-  private static final Map<Uri, SoftReference<String>> textCache =
-      Collections.synchronizedMap(new LRUCache<Uri, SoftReference<String>>(MAX_CACHE_SIZE));
-
-  public TextSlide(Context context, MasterSecret masterSecret, PduPart part) {
-    super(context, masterSecret, part);
-  }
-
   public TextSlide(Context context, String message) {
     super(context, getPartForMessage(message));
   }