1 /* 2 * Copyright (C) 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.os; 18 19 import android.annotation.NonNull; 20 import android.annotation.Nullable; 21 22 import java.util.Objects; 23 24 /** 25 * A value with an associated reference time. The reference time will typically be provided by the 26 * elapsed realtime clock. The elapsed realtime clock can be obtained using methods like 27 * {@link SystemClock#elapsedRealtime()} or {@link SystemClock#elapsedRealtimeClock()}. 28 * If a suitable clock is used the reference time can be used to identify the age of a value or 29 * ordering between values. 30 * 31 * <p>This class implements {@link Parcelable} for convenience but instances will only actually be 32 * parcelable if the value type held is {@code null}, {@link Parcelable}, or one of the other types 33 * supported by {@link Parcel#writeValue(Object)} / {@link Parcel#readValue(ClassLoader)}. 34 * 35 * @param <T> the type of the value with an associated timestamp 36 * @hide 37 */ 38 public final class TimestampedValue<T> implements Parcelable { 39 private final long mReferenceTimeMillis; 40 @Nullable 41 private final T mValue; 42 TimestampedValue(long referenceTimeMillis, @Nullable T value)43 public TimestampedValue(long referenceTimeMillis, @Nullable T value) { 44 mReferenceTimeMillis = referenceTimeMillis; 45 mValue = value; 46 } 47 48 /** Returns the reference time value. See {@link TimestampedValue} for more information. */ getReferenceTimeMillis()49 public long getReferenceTimeMillis() { 50 return mReferenceTimeMillis; 51 } 52 53 /** 54 * Returns the value associated with the timestamp. See {@link TimestampedValue} for more 55 * information. 56 */ 57 @Nullable getValue()58 public T getValue() { 59 return mValue; 60 } 61 62 @Override equals(@ullable Object o)63 public boolean equals(@Nullable Object o) { 64 if (this == o) { 65 return true; 66 } 67 if (o == null || getClass() != o.getClass()) { 68 return false; 69 } 70 TimestampedValue<?> that = (TimestampedValue<?>) o; 71 return mReferenceTimeMillis == that.mReferenceTimeMillis 72 && Objects.equals(mValue, that.mValue); 73 } 74 75 @Override hashCode()76 public int hashCode() { 77 return Objects.hash(mReferenceTimeMillis, mValue); 78 } 79 80 @Override toString()81 public String toString() { 82 return "TimestampedValue{" 83 + "mReferenceTimeMillis=" + mReferenceTimeMillis 84 + ", mValue=" + mValue 85 + '}'; 86 } 87 88 /** 89 * Returns the difference in milliseconds between two instance's reference times. 90 */ referenceTimeDifference( @onNull TimestampedValue<?> one, @NonNull TimestampedValue<?> two)91 public static long referenceTimeDifference( 92 @NonNull TimestampedValue<?> one, @NonNull TimestampedValue<?> two) { 93 return one.mReferenceTimeMillis - two.mReferenceTimeMillis; 94 } 95 96 /** @hide */ 97 public static final @NonNull Parcelable.Creator<TimestampedValue<?>> CREATOR = 98 new Parcelable.ClassLoaderCreator<TimestampedValue<?>>() { 99 100 @Override 101 public TimestampedValue<?> createFromParcel(@NonNull Parcel source) { 102 return createFromParcel(source, null); 103 } 104 105 @Override 106 public TimestampedValue<?> createFromParcel( 107 @NonNull Parcel source, @Nullable ClassLoader classLoader) { 108 long referenceTimeMillis = source.readLong(); 109 Object value = source.readValue(classLoader); 110 return new TimestampedValue<>(referenceTimeMillis, value); 111 } 112 113 @Override 114 public TimestampedValue[] newArray(int size) { 115 return new TimestampedValue[size]; 116 } 117 }; 118 119 @Override describeContents()120 public int describeContents() { 121 return 0; 122 } 123 124 @Override writeToParcel(@onNull Parcel dest, int flags)125 public void writeToParcel(@NonNull Parcel dest, int flags) { 126 dest.writeLong(mReferenceTimeMillis); 127 dest.writeValue(mValue); 128 } 129 } 130