将 onCreate 传递给 Activity 的 Bundle 和 Child Fragment 是否不同？

Question

是否将 Bundle 的私有副本传递给 Fragment 和父级 Activity？

我尝试在 Fragment 的 onSaveInstanceState 中保存键值对，并尝试在 Activity 的 onCreate 中检索它。那里没有。

但两者之间似乎也存在联系。当我将 null 传递给 Activity 的 super.onCreate 时，传递给 Fragment 的 onCreate 的 Bundle 也是 null。

Answer 1

Bundle wich 被发送到 onCreate 因为 Activity 和 Fragment 是完全不同的。如果您将 null 发送到 super.onCreate -> activity 将从头开始重新创建所有 fragments。所以你的 Fragment 也会收到 null ->。因为这是新的 fragment

这是FragmentActivity的部分代码：

/**
 * Perform initialization of all fragments and loaders.
 */
@SuppressWarnings("deprecation")
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    mFragments.attachHost(null /*parent*/);

    super.onCreate(savedInstanceState);

    NonConfigurationInstances nc =
            (NonConfigurationInstances) getLastNonConfigurationInstance();
    if (nc != null) {
        mFragments.restoreLoaderNonConfig(nc.loaders);
    }
    if (savedInstanceState != null) {
        Parcelable p = savedInstanceState.getParcelable(FRAGMENTS_TAG);
        mFragments.restoreAllState(p, nc != null ? nc.fragments : null);

        // Check if there are any pending onActivityResult calls to descendent Fragments.
        if (savedInstanceState.containsKey(NEXT_CANDIDATE_REQUEST_INDEX_TAG)) {
            mNextCandidateRequestIndex =
                    savedInstanceState.getInt(NEXT_CANDIDATE_REQUEST_INDEX_TAG);
            int[] requestCodes = savedInstanceState.getIntArray(ALLOCATED_REQUEST_INDICIES_TAG);
            String[] fragmentWhos = savedInstanceState.getStringArray(REQUEST_FRAGMENT_WHO_TAG);
            if (requestCodes == null || fragmentWhos == null ||
                        requestCodes.length != fragmentWhos.length) {
                Log.w(TAG, "Invalid requestCode mapping in savedInstanceState.");
            } else {
                mPendingFragmentActivityResults = new SparseArrayCompat<>(requestCodes.length);
                for (int i = 0; i < requestCodes.length; i++) {
                    mPendingFragmentActivityResults.put(requestCodes[i], fragmentWhos[i]);
                }
            }
        }
    }

    if (mPendingFragmentActivityResults == null) {
        mPendingFragmentActivityResults = new SparseArrayCompat<>();
        mNextCandidateRequestIndex = 0;
    }

    mFragments.dispatchCreate();
}

将 onCreate 传递给 Activity 的 Bundle 和 Child Fragment 是否不同？

Is the Bundle passed on onCreate to Activity and Child Fragment different?

android

android-fragments

android-activity

activity-lifecycle

fragment-lifecycle