Merge "[Animations] Add a utility method to get the number of milliseconds for a given number of frames." into tm-dev

packages/SystemUI/src/com/android/systemui/util/animation/AnimationUtil.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2022 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.android.systemui.util.animation
+
+import kotlin.math.roundToLong
+
+/** A generic util class for animations in SysUI. */
+class AnimationUtil {
+    companion object {
+        /**
+         * Returns the number of milliseconds there are in [numFrames] for a 60 fps device.
+         *
+         * Note that this method can be used on any device, not just 60 fps devices. Animation
+         * lengths are typically specified in terms of number of frames for a 60 fps device, and
+         * the value "5 frames" is often more meaningful than "83ms". This method allows us to
+         * write animation code in terms of the more meaningful "5" number.
+         *
+         * @param numFrames must be >= 0.
+         */
+        fun getMsForFrames(numFrames: Int): Long {
+            if (numFrames < 0) {
+                throw IllegalArgumentException("numFrames must be >= 0")
+            }
+            return (numFrames * 1000f / 60f).roundToLong()
+        }
+    }
+}

packages/SystemUI/tests/src/com/android/systemui/util/animation/AnimationUtilTest.kt

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+/*
+ * Copyright (C) 2022 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.android.systemui.util.animation
+
+import androidx.test.filters.SmallTest
+import com.android.systemui.SysuiTestCase
+import com.google.common.truth.Truth.assertThat
+import org.junit.Test
+import java.lang.IllegalArgumentException
+
+@SmallTest
+class AnimationUtilTest : SysuiTestCase() {
+    @Test
+    fun getMsForFrames_5frames_returns83() {
+        assertThat(AnimationUtil.getMsForFrames(5)).isEqualTo(83L)
+    }
+
+    @Test
+    fun getMsForFrames_7frames_returns117() {
+        assertThat(AnimationUtil.getMsForFrames(7)).isEqualTo(117L)
+    }
+
+    @Test
+    fun getMsForFrames_30frames_returns500() {
+        assertThat(AnimationUtil.getMsForFrames(30)).isEqualTo(500L)
+    }
+
+    @Test
+    fun getMsForFrames_60frames_returns1000() {
+        assertThat(AnimationUtil.getMsForFrames(60)).isEqualTo(1000L)
+    }
+
+    @Test(expected = IllegalArgumentException::class)
+    fun getMsForFrames_negativeFrames_throwsException() {
+        AnimationUtil.getMsForFrames(-1)
+    }
+}