同时它们还是实现了 LifecycleOwner 接口，里面的 getLifecycle() 就是返回这个 mLifecycleRegistry 用的。

SupportActivity.java（用于support库）
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public class SupportActivity extends Activity implements LifecycleOwner {

private LifecycleRegistry mLifecycleRegistry = new LifecycleRegistry(this);


ComponentActivity.java（用于androidx库）
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public class ComponentActivity extends Activity
implements LifecycleOwner, KeyEventDispatcher.Component {

private LifecycleRegistry mLifecycleRegistry = new LifecycleRegistry(this);


Fragment.java
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public class Fragment implements ComponentCallbacks, OnCreateContextMenuListener, LifecycleOwner {

LifecycleRegistry mLifecycleRegistry = new LifecycleRegistry(this);





LifecycleOwner.java
------------------------------
public interface LifecycleOwner {
@NonNull
Lifecycle getLifecycle();
}
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来源：https://www.cnblogs.com/liyanyan665/p/11379438.html