[Carousel] Add full screen strategy

PiperOrigin-RevId: 544471620

lib/java/com/google/android/material/carousel/FullScreenCarouselStrategy.java

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+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.android.material.carousel;
+
+import static com.google.android.material.carousel.CarouselStrategyHelper.createLeftAlignedKeylineState;
+import static java.lang.Math.min;
+
+import androidx.recyclerview.widget.RecyclerView.LayoutParams;
+import android.view.View;
+import androidx.annotation.NonNull;
+
+/**
+ * A {@link CarouselStrategy} that fits one full-width or full-height item into a container to
+ * create a layout to browse one item at a time.
+ *
+ * <p>Note that the item masks will be based on the items encompassing the full width or full height
+ * of the carousel. The carousel item dimensions should reflect this with `match_parent` dimensions.
+ *
+ * <p>This class will automatically be reversed by {@link CarouselLayoutManager} if being laid out
+ * right-to-left and does not need to make any account for layout direction itself.
+ */
+public class FullScreenCarouselStrategy extends CarouselStrategy {
+
+  @Override
+  @NonNull
+  KeylineState onFirstChildMeasuredWithMargins(@NonNull Carousel carousel, @NonNull View child) {
+    float availableSpace;
+    LayoutParams childLayoutParams = (LayoutParams) child.getLayoutParams();
+    float childMargins;
+    if (carousel.isHorizontal()) {
+      availableSpace = carousel.getContainerWidth();
+      childMargins = childLayoutParams.leftMargin + childLayoutParams.rightMargin;
+    } else {
+      availableSpace = carousel.getContainerHeight();
+      childMargins = childLayoutParams.topMargin + childLayoutParams.bottomMargin;
+    }
+    float targetChildSize = min(availableSpace + childMargins, availableSpace);
+    Arrangement arrangement = new Arrangement(
+        /* priority= */ 0,
+        /* targetSmallSize= */ 0,
+        /* minSmallSize= */ 0,
+        /* maxSmallSize= */ 0,
+        /* smallCount= */ 0,
+        /* targetMediumSize= */ 0,
+        /* mediumCount= */ 0,
+        targetChildSize,
+        /* largeCount= */ 1,
+        availableSpace);
+    return createLeftAlignedKeylineState(
+        child.getContext(), childMargins, availableSpace, arrangement);
+  }
+}

lib/javatests/com/google/android/material/carousel/FullScreenCarouselStrategyTest.java

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+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.material.carousel;
+
+import com.google.android.material.test.R;
+
+import static com.google.android.material.carousel.CarouselHelper.createCarouselWithWidth;
+import static com.google.android.material.carousel.CarouselHelper.createViewWithSize;
+import static com.google.common.truth.Truth.assertThat;
+
+import androidx.recyclerview.widget.RecyclerView.LayoutParams;
+import android.view.View;
+import androidx.test.core.app.ApplicationProvider;
+import com.google.android.material.carousel.KeylineState.Keyline;
+import java.util.List;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+/** Tests for {@link FullScreenCarouselStrategy}. */
+@RunWith(RobolectricTestRunner.class)
+public class FullScreenCarouselStrategyTest {
+
+  @Test
+  public void testItemSmallerThanContainer_showsOneLarge() {
+    Carousel carousel = createCarouselWithWidth(400);
+    FullScreenCarouselStrategy config = new FullScreenCarouselStrategy();
+    View view = createViewWithSize(ApplicationProvider.getApplicationContext(), 100, 400);
+
+    KeylineState keylineState = config.onFirstChildMeasuredWithMargins(carousel, view);
+
+    // A fullscreen layout should be [xSmall-large-xSmall] where the xSmall items are
+    // outside the bounds of the carousel container and the large center item takes up the
+    // container's full width.
+    assertThat(keylineState.getKeylines()).hasSize(3);
+    assertThat(keylineState.getKeylines().get(0).locOffset).isLessThan(0F);
+    assertThat(keylineState.getKeylines().get(1).mask).isEqualTo(0F);
+    assertThat(keylineState.getKeylines().get(2).locOffset)
+        .isGreaterThan((float) carousel.getContainerHeight());
+  }
+
+  @Test
+  public void testKnownArrangement_correctlyCalculatesKeylineLocations() {
+    View view = createViewWithSize(ApplicationProvider.getApplicationContext(), 400, 200);
+
+    FullScreenCarouselStrategy config = new FullScreenCarouselStrategy();
+    float extraSmallSize =
+        view.getResources().getDimension(R.dimen.m3_carousel_gone_size);
+    // Keyline sizes for the fullscreen variant carousel are:
+    // {extraSmallSize, largeSize, extraSmallSize}
+    // The keyline loc offsets are placed so that an item centered on a keyline has the
+    //  keyline size described above.
+    float[] locOffsets = new float[] {-extraSmallSize / 2f, 200, 400 + extraSmallSize / 2f};
+
+    List<Keyline> keylines =
+        config.onFirstChildMeasuredWithMargins(createCarouselWithWidth(400), view).getKeylines();
+    for (int i = 0; i < keylines.size(); i++) {
+      assertThat(keylines.get(i).locOffset).isEqualTo(locOffsets[i]);
+    }
+  }
+
+  @Test
+  public void testKnownArrangementWithMargins_correctlyCalculatesKeylineLocations() {
+    View view = createViewWithSize(ApplicationProvider.getApplicationContext(), 400, 200);
+    LayoutParams layoutParams = (LayoutParams) view.getLayoutParams();
+    layoutParams.leftMargin += 50;
+    layoutParams.rightMargin += 30;
+
+    FullScreenCarouselStrategy config = new FullScreenCarouselStrategy();
+    float extraSmallSize = view.getResources().getDimension(R.dimen.m3_carousel_gone_size);
+    // Keyline sizes for the fullscreen variant carousel are:
+    // {extraSmallSize, largeSize, extraSmallSize}
+    // The keyline loc offsets are placed so that an item centered on a keyline has the
+    //  keyline size described above.
+    // The large size is based on whatever width is left over from the minimum small size.
+    float[] locOffsets =
+        new float[] {-(extraSmallSize + 80) / 2f, 200, 400 + (extraSmallSize + 80) / 2f};
+
+    List<Keyline> keylines =
+        config.onFirstChildMeasuredWithMargins(createCarouselWithWidth(400), view).getKeylines();
+    for (int i = 0; i < keylines.size(); i++) {
+      assertThat(keylines.get(i).locOffset).isEqualTo(locOffsets[i]);
+    }
+  }
+}