Activity的performDestroy用于执行ActivityDestroy，代码如下：

//frameworks/base/core/java/android/app/Activity.java
public class Activity extends ContextThemeWrapper
        implements LayoutInflater.Factory2,
        Window.Callback, KeyEvent.Callback,
        OnCreateContextMenuListener, ComponentCallbacks2,
        Window.OnWindowDismissedCallback,
        ContentCaptureManager.ContentCaptureClient {
    final void performDestroy() {
        if (Trace.isTagEnabled(Trace.TRACE_TAG_WINDOW_MANAGER)) {
            Trace.traceBegin(Trace.TRACE_TAG_WINDOW_MANAGER, "performDestroy:"
                    + mComponent.getClassName());
        }
        dispatchActivityPreDestroyed();
        mDestroyed = true;
        mWindow.destroy();
        mFragments.dispatchDestroy();
        onDestroy();
        EventLogTags.writeWmOnDestroyCalled(mIdent, getComponentName().getClassName(),
                "performDestroy");
        mFragments.doLoaderDestroy();
        if (mVoiceInteractor != null) {
            mVoiceInteractor.detachActivity();
        }
        dispatchActivityPostDestroyed();
        Trace.traceEnd(Trace.TRACE_TAG_WINDOW_MANAGER);
    }
}

上面方法主要处理如下：

1、调用Activity的dispatchActivityPreDestroyed方法。

2、调用Activity的onDestroy方法。

3、调用Activity的dispatchActivityPostDestroyed方法。

下面分别进行分析：

Activity dispatchActivityPreDestroyed

调用Activity的dispatchActivityPreDestroyed方法：

//frameworks/base/core/java/android/app/Activity.java
public class Activity extends ContextThemeWrapper
        implements LayoutInflater.Factory2,
        Window.Callback, KeyEvent.Callback,
        OnCreateContextMenuListener, ComponentCallbacks2,
        Window.OnWindowDismissedCallback,
        ContentCaptureManager.ContentCaptureClient {
    private void dispatchActivityPreDestroyed() {
        getApplication().dispatchActivityPreDestroyed(this);
        Object[] callbacks = collectActivityLifecycleCallbacks();
        if (callbacks != null) {
            for (int i = callbacks.length - 1; i >= 0; i--) {
                ((Application.ActivityLifecycleCallbacks) callbacks[i])
                        .onActivityPreDestroyed(this);
            }
        }
    }
}

Application.ActivityLifecycleCallbacks onActivityPreDestroyed

调用Application.ActivityLifecycleCallbacks的onActivityPreDestroyed方法，如果应用程序调用了Application的registerActivityLifecycleCallbacks，就会收到onActivityPreDestroyed回调。

void onActivityPreDestroyed(@NonNull Activity activity) ：作为被销毁的活动的第一步调用。这总是在 {@link Activity#onDestroy} 之前调用。

Activity onDestroy

调用Activity的onDestroy方法，在Activity的子类(应用程序实现)的onDestroy会调用super.onDestroy()方法：

//frameworks/base/core/java/android/app/Activity.java
public class Activity extends ContextThemeWrapper
        implements LayoutInflater.Factory2,
        Window.Callback, KeyEvent.Callback,
        OnCreateContextMenuListener, ComponentCallbacks2,
        Window.OnWindowDismissedCallback,
        ContentCaptureManager.ContentCaptureClient {
    protected void onDestroy() {
        if (DEBUG_LIFECYCLE) Slog.v(TAG, "onDestroy " + this);
        mCalled = true;


        getAutofillClientController().onActivityDestroyed();


        // dismiss any dialogs we are managing.
        if (mManagedDialogs != null) {
            final int numDialogs = mManagedDialogs.size();
            for (int i = 0; i < numDialogs; i++) {
                final ManagedDialog md = mManagedDialogs.valueAt(i);
                if (md.mDialog.isShowing()) {
                    md.mDialog.dismiss();
                }
            }
            mManagedDialogs = null;
        }


        // close any cursors we are managing.
        synchronized (mManagedCursors) {
            int numCursors = mManagedCursors.size();
            for (int i = 0; i < numCursors; i++) {
                ManagedCursor c = mManagedCursors.get(i);
                if (c != null) {
                    c.mCursor.close();
                }
            }
            mManagedCursors.clear();
        }


        // Close any open search dialog
        if (mSearchManager != null) {
            mSearchManager.stopSearch();
        }


        if (mActionBar != null) {
            mActionBar.onDestroy();
        }


        dispatchActivityDestroyed();


        notifyContentCaptureManagerIfNeeded(CONTENT_CAPTURE_STOP);


        if (mUiTranslationController != null) {
            mUiTranslationController.onActivityDestroyed();
        }
        if (mDefaultBackCallback != null) {
            getOnBackInvokedDispatcher().unregisterOnBackInvokedCallback(mDefaultBackCallback);
            mDefaultBackCallback = null;
        }
        if (mCallbacksController != null) {
            mCallbacksController.clearCallbacks();
        }
    }
}

Activity dispatchActivityDestroyed

调用Activity的dispatchActivityDestroyed方法：

public class Activity extends ContextThemeWrapper
        implements LayoutInflater.Factory2,
        Window.Callback, KeyEvent.Callback,
        OnCreateContextMenuListener, ComponentCallbacks2,
        Window.OnWindowDismissedCallback,
        ContentCaptureManager.ContentCaptureClient {
    private void dispatchActivityDestroyed() {
        Object[] callbacks = collectActivityLifecycleCallbacks();
        if (callbacks != null) {
            for (int i = callbacks.length - 1; i >= 0; i--) {
                ((Application.ActivityLifecycleCallbacks) callbacks[i]).onActivityDestroyed(this);
            }
        }
        getApplication().dispatchActivityDestroyed(this);
    }
}

Application.ActivityLifecycleCallbacks onActivityDestroyed

调用Application.ActivityLifecycleCallbacks的onActivityDestroyed方法，如果应用程序调用了Application的registerActivityLifecycleCallbacks，就会收到onActivityDestroyed回调。

void onActivityDestroyed(@NonNull Activity activity)：当 Activity 调用 {@link Activity#onDestroy super.onDestroy（）} 时调用。

Activity dispatchActivityPostDestroyed

调用Activity的dispatchActivityPostDestroyed方法：

//frameworks/base/core/java/android/app/Activity.java
public class Activity extends ContextThemeWrapper
        implements LayoutInflater.Factory2,
        Window.Callback, KeyEvent.Callback,
        OnCreateContextMenuListener, ComponentCallbacks2,
        Window.OnWindowDismissedCallback,
        ContentCaptureManager.ContentCaptureClient {
    private void dispatchActivityPostDestroyed() {
        Object[] callbacks = collectActivityLifecycleCallbacks();
        if (callbacks != null) {
            for (int i = callbacks.length - 1; i >= 0; i--) {
                ((Application.ActivityLifecycleCallbacks) callbacks[i])
                        .onActivityPostDestroyed(this);
            }
        }
        getApplication().dispatchActivityPostDestroyed(this);
    }
}

Application.ActivityLifecycleCallbacks onActivityPostDestroyed

调用Application.ActivityLifecycleCallbacks的onActivityPostDestroyed方法，如果应用程序调用了Application的registerActivityLifecycleCallbacks，就会收到onActivityPostDestroyed回调。

void onActivityPostDestroyed(@NonNull Activity activity) ：作为被销毁的活动的第一步调用。这总是在 {@link Activity#onDestroy} 之前调用。