Add a fallback Drawable to display for null models

Fixes #268

library/src/androidTest/java/com/bumptech/glide/request/GenericRequestTest.java

@@ -77,6 +77,8 @@ private static class RequestHarness {
         int placeholderResourceId = 0;
         Drawable placeholderDrawable = null;
         int errorResourceId = 0;
+        Drawable fallbackDrawable = null;
+        int fallbackResourceId = 0;
         Transformation transformation = mock(Transformation.class);
         Drawable errorDrawable = null;
         LoadProvider<Number, Object, Object, List> loadProvider = mock(LoadProvider.class);
@@ -122,6 +124,8 @@ public GenericRequest<Number, Object, Object, List> getRequest() {
                     placeholderResourceId,
                     errorDrawable,
                     errorResourceId,
+                    fallbackDrawable,
+                    fallbackResourceId,
                     requestListener,
                     requestCoordinator,
                     engine,
@@ -331,7 +335,8 @@ public void testCanHandleNullResources() {
 
         assertTrue(request.isFailed());
         verify(harness.requestListener)
-                .onException(any(Exception.class), any(Number.class), eq(harness.target), anyBoolean());
+                .onException(any(Exception.class), any(Number.class), eq(harness.target),
+                    anyBoolean());
     }
 
     @Test
@@ -357,7 +362,8 @@ public void testCanHandleNonConformingResources() {
         assertTrue(request.isFailed());
         verify(harness.engine).release(eq(harness.resource));
         verify(harness.requestListener)
-                .onException(any(Exception.class), any(Number.class), eq(harness.target), anyBoolean());
+                .onException(any(Exception.class), any(Number.class), eq(harness.target),
+                    anyBoolean());
     }
 
     @Test
@@ -483,9 +489,10 @@ public void testIgnoresOnSizeReadyIfNotWaitingForSize() {
         request.onSizeReady(100, 100);
         request.onSizeReady(100, 100);
 
-        verify(harness.engine, times(1)).load(eq(harness.signature), eq(100), eq(100), any(DataFetcher.class),
-                any(DataLoadProvider.class), any(Transformation.class), any(ResourceTranscoder.class),
-                any(Priority.class), anyBoolean(), any(DiskCacheStrategy.class), any(ResourceCallback.class));
+        verify(harness.engine, times(1)).load(eq(harness.signature), eq(100), eq(100),
+            any(DataFetcher.class), any(DataLoadProvider.class), any(Transformation.class),
+            any(ResourceTranscoder.class), any(Priority.class), anyBoolean(),
+            any(DiskCacheStrategy.class), any(ResourceCallback.class));
     }
 
     @Test
@@ -506,8 +513,8 @@ public void testEngineLoadPassedCorrectPriority() {
         request.onSizeReady(100, 100);
 
         verify(harness.engine).load(any(Key.class), anyInt(), anyInt(), any(DataFetcher.class),
-                any(DataLoadProvider.class), any(Transformation.class), any(ResourceTranscoder.class),
-                eq(expected), anyBoolean(), any(DiskCacheStrategy.class), any(ResourceCallback.class));
+            any(DataLoadProvider.class), any(Transformation.class), any(ResourceTranscoder.class),
+            eq(expected), anyBoolean(), any(DiskCacheStrategy.class), any(ResourceCallback.class));
     }
 
     @Test
@@ -602,7 +609,7 @@ public void testErrorDrawableIsSetOnLoadFailed() {
     }
 
     @Test
-    public void setTestPlaceholderDrawableSetOnNullModel() {
+    public void testPlaceholderDrawableSetOnNullModelWithNoErrorDrawable() {
         Drawable placeholder = new ColorDrawable(Color.RED);
 
         MockTarget target = new MockTarget();
@@ -618,7 +625,7 @@ public void setTestPlaceholderDrawableSetOnNullModel() {
     }
 
     @Test
-    public void testErrorDrawableSetOnNullModel() {
+    public void testErrorDrawableSetOnNullModelWithErrorDrawable() {
         Drawable placeholder = new ColorDrawable(Color.RED);
         Drawable errorPlaceholder = new ColorDrawable(Color.GREEN);
 
@@ -635,6 +642,26 @@ public void testErrorDrawableSetOnNullModel() {
         assertEquals(errorPlaceholder, target.currentPlaceholder);
     }
 
+    @Test
+    public void testFallbackDrawableSetOnNullModelWithErrorAndFallbackDrawables() {
+        Drawable placeholder = new ColorDrawable(Color.RED);
+        Drawable errorPlaceholder = new ColorDrawable(Color.GREEN);
+        Drawable fallback = new ColorDrawable(Color.BLUE);
+
+        MockTarget target = new MockTarget();
+
+        harness.placeholderDrawable = placeholder;
+        harness.errorDrawable = errorPlaceholder;
+        harness.fallbackDrawable = fallback;
+        harness.target = target;
+        harness.model = null;
+        GenericRequest request = harness.getRequest();
+
+        request.begin();
+
+        assertEquals(fallback, target.currentPlaceholder);
+    }
+
     @Test
     public void testIsNotRunningBeforeRunCalled() {
         assertFalse(harness.getRequest().isRunning());

library/src/main/java/com/bumptech/glide/BitmapRequestBuilder.java

@@ -369,6 +369,18 @@ public BitmapRequestBuilder<ModelType, TranscodeType> placeholder(Drawable drawa
         return this;
     }
 
+    @Override
+    public BitmapRequestBuilder<ModelType, TranscodeType> fallback(Drawable drawable) {
+        super.fallback(drawable);
+        return this;
+    }
+
+    @Override
+    public BitmapRequestBuilder<ModelType, TranscodeType> fallback(int resourceId) {
+        super.fallback(resourceId);
+        return this;
+    }
+
     /**
      * {@inheritDoc}
      */

library/src/main/java/com/bumptech/glide/DrawableRequestBuilder.java

@@ -329,6 +329,18 @@ public DrawableRequestBuilder<ModelType> placeholder(Drawable drawable) {
         return this;
     }
 
+    @Override
+    public DrawableRequestBuilder<ModelType> fallback(Drawable drawable) {
+        super.fallback(drawable);
+        return this;
+    }
+
+    @Override
+    public DrawableRequestBuilder<ModelType> fallback(int resourceId) {
+        super.fallback(resourceId);
+        return this;
+    }
+
     /**
      * {@inheritDoc}
      */

library/src/main/java/com/bumptech/glide/GenericRequestBuilder.java

@@ -77,6 +77,8 @@ public class GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeT
     private Transformation<ResourceType> transformation = UnitTransformation.get();
     private boolean isTransformationSet;
     private boolean isThumbnailBuilt;
+    private Drawable fallbackDrawable;
+    private int fallbackResource;
 
     GenericRequestBuilder(LoadProvider<ModelType, DataType, ResourceType, TranscodeType> loadProvider,
             Class<TranscodeType> transcodeClass, GenericRequestBuilder<ModelType, ?, ?, ?> other) {
@@ -447,6 +449,49 @@ public GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeType> p
         return this;
     }
 
+    /**
+     * Sets an {@link android.graphics.drawable.Drawable} to display if the model provided to
+     * {@link #load(Object)} is {@code null}.
+     *
+     * <p>
+     *   If a fallback is not set, null models will cause the error drawable to be displayed. If
+     *   the error drawable is not set, the placeholder will be displayed.
+     * </p>
+     *
+     * @see #placeholder(Drawable)
+     * @see #placeholder(int)
+     *
+     * @param drawable The drawable to display as a placeholder.
+     * @return This request builder.
+     */
+    public GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeType> fallback(
+            Drawable drawable) {
+        this.fallbackDrawable = drawable;
+
+        return this;
+    }
+
+    /**
+     * Sets a resource to display if the model provided to {@link #load(Object)} is {@code null}.
+     *
+     * <p>
+     *   If a fallback is not set, null models will cause the error drawable to be displayed. If
+     *   the error drawable is not set, the placeholder will be displayed.
+     * </p>
+     *
+     * @see #placeholder(Drawable)
+     * @see #placeholder(int)
+     *
+     * @param resourceId The id of the resource to use as a fallback.
+     * @return This request builder.
+     */
+    public GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeType> fallback(
+            int resourceId) {
+        this.fallbackResource = resourceId;
+
+        return this;
+    }
+
     /**
      * Sets a resource to display if a load fails.
      *
@@ -802,6 +847,8 @@ private Request obtainRequest(Target<TranscodeType> target, float sizeMultiplier
                 placeholderId,
                 errorPlaceholder,
                 errorId,
+                fallbackDrawable,
+                fallbackResource,
                 requestListener,
                 requestCoordinator,
                 glide.getEngine(),

library/src/main/java/com/bumptech/glide/GifRequestBuilder.java

@@ -319,6 +319,18 @@ public GifRequestBuilder<ModelType> placeholder(Drawable drawable) {
         return this;
     }
 
+    @Override
+    public GifRequestBuilder<ModelType> fallback(Drawable drawable) {
+        super.fallback(drawable);
+        return this;
+    }
+
+    @Override
+    public GifRequestBuilder<ModelType> fallback(int resourceId) {
+        super.fallback(resourceId);
+        return this;
+    }
+
     /**
      * {@inheritDoc}
      */

library/src/main/java/com/bumptech/glide/request/GenericRequest.java

@@ -59,6 +59,8 @@ private enum Status {
     private final String tag = String.valueOf(hashCode());
 
     private Key signature;
+    private Drawable fallbackDrawable;
+    private int fallbackResourceId;
     private int placeholderResourceId;
     private int errorResourceId;
     private Context context;
@@ -99,6 +101,8 @@ public static <A, T, Z, R> GenericRequest<A, T, Z, R> obtain(
             int placeholderResourceId,
             Drawable errorDrawable,
             int errorResourceId,
+            Drawable fallbackDrawable,
+            int fallbackResourceId,
             RequestListener<? super A, R> requestListener,
             RequestCoordinator requestCoordinator,
             Engine engine,
@@ -125,6 +129,8 @@ public static <A, T, Z, R> GenericRequest<A, T, Z, R> obtain(
                 placeholderResourceId,
                 errorDrawable,
                 errorResourceId,
+                fallbackDrawable,
+                fallbackResourceId,
                 requestListener,
                 requestCoordinator,
                 engine,
@@ -150,6 +156,7 @@ public void recycle() {
         target = null;
         placeholderDrawable = null;
         errorDrawable = null;
+        fallbackDrawable = null;
         requestListener = null;
         requestCoordinator = null;
         transformation = null;
@@ -171,6 +178,8 @@ private void init(
             int placeholderResourceId,
             Drawable errorDrawable,
             int errorResourceId,
+            Drawable fallbackDrawable,
+            int fallbackResourceId,
             RequestListener<? super A, R> requestListener,
             RequestCoordinator requestCoordinator,
             Engine engine,
@@ -184,6 +193,8 @@ private void init(
         this.loadProvider = loadProvider;
         this.model = model;
         this.signature = signature;
+        this.fallbackDrawable = fallbackDrawable;
+        this.fallbackResourceId = fallbackResourceId;
         this.context = context.getApplicationContext();
         this.priority = priority;
         this.target = target;
@@ -371,12 +382,22 @@ public boolean isFailed() {
         return status == Status.FAILED;
     }
 
+    private Drawable getFallbackDrawable() {
+      if (fallbackDrawable == null && fallbackResourceId > 0) {
+        fallbackDrawable = context.getResources().getDrawable(fallbackResourceId);
+      }
+      return fallbackDrawable;
+    }
+
     private void setErrorPlaceholder(Exception e) {
         if (!canNotifyStatusChanged()) {
             return;
         }
 
-        Drawable error = getErrorDrawable();
+        Drawable error = model == null ? getFallbackDrawable() : null;
+        if (error == null) {
+          error = getErrorDrawable();
+        }
         if (error == null) {
             error = getPlaceholderDrawable();
         }