64 lines
2.4 KiB
64 lines
2.4 KiB
/*
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* Copyright (C) 2020 The Dagger Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package dagger.hilt.android.migration;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Target;
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/**
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* When placed on an {@link dagger.hilt.android.AndroidEntryPoint}-annotated activity / fragment /
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* view / etc, allows injection to occur optionally based on whether or not the application is using
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* Hilt.
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*
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* <p>When using this annotation, you can use {@link OptionalInjectCheck#wasInjectedByHilt} to check
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* at runtime if the annotated class was injected by Hilt. Additionally, this annotation will also
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* cause a method, {@code wasInjectedByHilt} to be generated in the Hilt base class as well, that
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* behaves the same as {@link OptionalInjectCheck#wasInjectedByHilt}. The method is available to
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* users that extend the Hilt base class directly and don't use the Gradle plugin.
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*
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* <p>Example usage:
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*
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* <pre><code>
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* {@literal @}OptionalInject
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* {@literal @}AndroidEntryPoint
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* public final class MyFragment extends Fragment {
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*
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* {@literal @}Inject Foo foo;
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*
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* {@literal @}Override
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* public void onAttach(Activity activity) {
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* // Injection will happen here, but only if the Activity and the Application are also
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* // AndroidEntryPoints and were injected by Hilt.
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* super.onAttach(activity);
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* if (!OptionalInjectCheck.wasInjectedByHilt(this)) {
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* // Get Dagger components the previous way and inject.
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* }
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* }
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* }
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* </code></pre>
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*
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* <p>This is useful for libraries that have to support Hilt users as well as non-Hilt users.
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* Injection will happen if the parent type (e.g. the activity of a fragment) is an {@link
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* dagger.hilt.android.AndroidEntryPoint} annotated class and if that parent was also injected via
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* Hilt.
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*
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* @see OptionalInjectCheck
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* @see <a href="https://dagger.dev/hilt/optional-inject">Optional injection</a>
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*/
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@Target(ElementType.TYPE)
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public @interface OptionalInject {}
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