Question

我正在使用遗留代码，我在此函数中发现了一个不一致的行为：

@Override
public void openFragment(final Class<? extends BaseFragment> fragmentClass,
                         final boolean addToBackStack,
                         final Bundle args)
{
    long delay = 0;
    if (mDrawerLayout.isDrawerOpen(GravityCompat.START)) {
        delay = getResources().getInteger(android.R.integer.config_shortAnimTime) * 2;
    }
    // FIXME: quick fix, but not all cases
    final Bundle args666 = args != null ? (Bundle) args.clone() : null;
    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            doOpenFragment(fragmentClass, addToBackStack, args666);
        }
    }, delay);
    closeDrawer();
}


protected void doOpenFragment(final Class<? extends BaseFragment> fragmentClass,
                              final boolean addToBackStack,
                              final Bundle args)
{
    try {
        if (getSupportFragmentManager().getBackStackEntryCount() >= 1) {
            showNavigationIcon();
        }
        hideKeyboard();
        BaseFragment fragment = createFragment(fragmentClass, args);
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        fragment.initTransactionAnimation(transaction);
        String tag = getTag(fragment);
        transaction.add(R.id.container, fragment, tag);
        if (addToBackStack) {
            transaction.addToBackStack(tag);
        }
        transaction.commitAllowingStateLoss();
        hideLastFragment(0);
    } catch (Exception e) {
        Sentry.captureException(e, "Error opening fragment");
    }
}

openFragment获取非空的Bundle args，但doOpenFragment将获得空Bundle。通过调用commitAllowingStateLoss()

来提交片段

快速修复可以使用Bundle.clone（）：

    final Bundle args666 = (Bundle) args.clone();
    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            doOpenFragment(fragmentClass, addToBackStack, args666);
        }
    }, delay);

它不会处理所有情况，deepCopy仅在api26中可用。

为什么会这样？
如何解决？

[更新

我玩@ Pavel 的解决方案，事情变得怪异

    final Bundle args666 = args != null ? cloneThroughSerialization(args) : args;
    final Bundle args777 = args != null ? (Bundle) args.clone() : args;

[UPDATE2]

实际上，问题不在postDelayed来电。让我们看一下调用堆栈：

在goRightToTheCollectionScreen中创建并打包了Bundle（没有任何可疑，之后没有变异）。

我想，openFragmentsChain内的两次调用中的问题来源：

public void openRootFragmentsChain(Class<? extends BaseFragment> fragmentClass,
                                   List<Class<? extends BaseFragment>> fragmentClasses,
                                   boolean addToBackStack,
                                   Bundle args)
{
    openFragmentsChain(fragmentClasses, addToBackStack, args);
    openFragment(fragmentClass, true, args);
}

public void openFragmentsChain(List<Class<? extends BaseFragment>> fragmentClasses,
                               boolean addToBackStack,
                               Bundle args)
{
    try {
        for (int i = 0; i < fragmentClasses.size(); i++) {
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            BaseFragment fragment = createFragment(fragmentClasses.get(i), args);
            String tag = getTag(fragment);
            transaction.add(R.id.container, fragment, tag);
            if (addToBackStack) {
                transaction.addToBackStack(tag);
            }
            if (i != fragmentClasses.size() - 1) {
                transaction.hide(fragment);
            }
            transaction.commitAllowingStateLoss();
        }
        if (fragmentClasses.size() >= 1) {
            updateDrawer();
        }
    } catch (Exception e) {
        Sentry.captureException(e, "Error opening fragment chain");
    }
}
protected void doOpenFragment(final Class<? extends BaseFragment> fragmentClass,
                              final boolean addToBackStack,
                              final Bundle args)
{
    try {
        if (getSupportFragmentManager().getBackStackEntryCount() >= 1) {
            showNavigationIcon();
        }
        hideKeyboard();
        BaseFragment fragment = createFragment(fragmentClass, args);
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        fragment.initTransactionAnimation(transaction);
        String tag = getTag(fragment);
        transaction.add(R.id.container, fragment, tag);
        if (addToBackStack) {
            transaction.addToBackStack(tag);
        }
        transaction.commitAllowingStateLoss();
        hideLastFragment(0);
    } catch (Exception e) {
        Sentry.captureException(e, "Error opening fragment");
    }
}

protected BaseFragment createFragment(Class<? extends BaseFragment> fragmentClass, Bundle args) throws Exception {
    BaseFragment fragment = fragmentClass.newInstance();
    fragment.setHasOptionsMenu(true);
    fragment.setArguments(args);
    fragment.setNavigationHandler(BaseFragmentNavigatorActivity.this);
    fragment.setToolbar(mToolbar);
    fragment.setMenuLoadService(mMenuLoaderService);
    return fragment;
}

Answer 1

在调用run（）之前，其他一些代码会修改相同的Bundle。问题在于您的代码。

您可以深入克隆序列化。

    public static Bundle cloneThroughSerialization(@NonNull Bundle bundle) {
        Parcel parcel = Parcel.obtain();
        bundle.writeToParcel(parcel, 0);

        Bundle clonedBundle  = new Bundle();
        clonedBundle.readFromParcel(parcel);

        parcel.recycle();
        return clonedBundle;
    }

Answer 2

您发布的代码似乎没问题，因此您的软件包可能会在其他位置进行修改（即使您的postDelayed延迟为0，runnable稍后会执行，可能会同时修改软件包）。尝试直接执行它而不使用postDelayed，以查看问题是否仍然存在。您可以发布更多代码，也许我们可以找出您触摸该捆绑包的其他位置。

如果没有其他帮助，您可以随时将方法从API26复制到您的代码并使用它（边缘情况 - 这似乎是一个简单的问题，所以你不应该这样做）

Answer 3

无法将bundle args建模为“empty”。用片段调用Handler示例和指定的args值制作简单的代码。如果我建模错误请给我提示

public class MainActivity extends FragmentActivity {

private  static final String LOG_TAG = "Main activity";

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.news_articles)

        // Create an instance of ExampleFragment
        final HeadlinesFragment firstFragment = new HeadlinesFragment();

        // Add the fragment to the 'fragment_container' FrameLayout
        getSupportFragmentManager().beginTransaction()
                .add(R.id.fragment_container, firstFragment).commit();

        long delay = 0;
        final boolean addToBackStack = true;
        final Bundle args666 = new Bundle();
        args666.putInt("hi", 666);
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                doOpenFragment(firstFragment, addToBackStack, args666);
            }
        }, delay);
    }

protected void doOpenFragment(HeadlinesFragment firstFragment,
                              final boolean addToBackStack,
                              final Bundle args){
    int value = args.getInt("hi");
    Log.d(LOG_TAG, "The value is " + value);
}
}

Bundle对象的变异

3 个答案: