android - FrameLayout.onMeasure() 中的 NullPointerException

Question

编辑:当我对此进行调试并尝试了各种更改时，我意识到我发布的原始代码并不真正相关，所以我删除了它:

我有一个 Activity可以在 3 个不同的 Fragment 之间切换s 当用户按下 3 个 IconButton 之一时s 我已经在自定义布局中插入了 ActionBar，比如在各种模式之间切换:



当我第一次启动应用程序(已将其卸载)时，我默认为 Globe 模式。 Globe 模式在 ViewPager 中有几个 fragment , 这些 fragment 中的大多数是 android.support.v4.app.ListFragment 的子类.我在主 Activity 的 onCreate 方法中创建了所有 8 个选项卡。这按预期工作，一切正常加载。

当我进入“个人资料”模式(通过单击人脸图标按钮)时，我可以登录应用程序并查看我的个人资料。这也按预期工作，一切正常加载。

当我再次从 Android Studio 推送 APK 时，由于我现在已登录(保存的首选项)，它默认我为“ friend 提要”模式(两个人手牵手)。我可以将模式切换到 Profile，一切都按预期工作，但是当我切换到 Globe 模式时，它在 Android 代码中崩溃:

08-14 14:43:22.744  28804-29323/com.trover E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.trover, PID: 28804
    java.lang.NullPointerException
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:309)
            at android.view.View.measure(View.java:16497)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
            at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
            at android.view.View.measure(View.java:16497)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
            at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
            at android.view.View.measure(View.java:16497)
            at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1912)
            at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1109)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1291)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:996)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5600)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
            at android.view.Choreographer.doCallbacks(Choreographer.java:574)
            at android.view.Choreographer.doFrame(Choreographer.java:544)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)

在过去的两周里，我对项目进行了两次重大更改:

我已经删除了 ActionbarSherlock 库。我最初也希望删除 support.v4 库，直到我意识到 ViewPager 需要它。

我从 Eclipse 切换到 Android Studio，其中包括将所有文件移动到新的 Android Studio 结构。

今天早上我重新安装了 Eclipse 并在删除 ActionbarSherlock 后立即进入了这一点，并且无法重新创建此崩溃。

我尝试过的事情:

使用 Gradle 手动构建项目，然后手动安装并运行它。当我执行相同的步骤时，它会以相同的方式崩溃。

通过调试器运行它，并在崩溃时停止。第 309 行如下:

    if (mMeasureAllChildren || child.getVisibility() != GONE) {

此时代码中， child是 null ，然而，调用 getChildCount()在第 296 行返回值 2。我仍然不知道此时哪个 View 实际崩溃了，当我在调试器中浏览它们时，任何变量中都没有定义值。

当您登录/注销时，溢出菜单中的项目会发生变化。当您点击 IconButton s 在上面，我调用 setBackgroundDrawable在 IconButtons 上设置黄色突出显示(或设置 null 如果它不再是 Activity 按钮)。当我注释掉 onCreateOptionsMenu 中的两个代码时和 setHighlightedIconButton() 中的代码，崩溃不再发生

当我从 ViewPager 中删除所有 fragment 时，崩溃不再发生

正如下面提到的@kcoppock，可能是我在某处不正确地膨胀了某些东西。在他链接的文章之后，我修改了我正在调用的应用程序中的每个调用 inflater.inflate(R.layout.somelayout, null)改为 inflater.inflate(R.layout.somelayout, viewGroupContainer, false) ，除非我在选项卡上创建自定义 View (我不知道 viewGroup 是它们的父级)。在这种情况下，我手动设置 LayoutParameters。

在这一点上，我完全不知道接下来要尝试什么。

更新:将应用程序更改为始终以 Globe 模式启动可以防止崩溃，因此如果我们没有启动它，它似乎与切换到 Globe 模式有关。

这是我为主 Activity 的 viewPager 构建选项卡的代码:

    // We HAVE to read this value out before creating the layout, or onTabSelected will set it back to zero
    final SharedPreferences prefs = getApplicationContext().getSharedPreferences(
            Const.Preferences.PREFS_FILE, Context.MODE_PRIVATE);
    boolean deniedLocationServices = prefs.getBoolean(Const.Preferences.LOCATION_SERVICES_DENIED, false);
    int previousTab = prefs.getInt(Const.Preferences.PREVIOUS_TAB, 0);

    setContentView(R.layout.main_browse);

    mFragmentManager = getSupportFragmentManager();

    mActionBar = getActionBar();
    mActionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    // these three lines hide the 'Trover' logo
    mActionBar.setDisplayHomeAsUpEnabled(false);
    mActionBar.setDisplayUseLogoEnabled(false);
    mActionBar.setIcon(new ColorDrawable(android.R.color.black));
    mActionBar.setCustomView(R.layout.action_bar_icons);
    mActionBar.setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM | ActionBar.DISPLAY_SHOW_HOME);
    final int numTabs = 8;

    TabbedBrowsePagerTab[] tabs = new TabbedBrowsePagerTab[numTabs];

    tabs[mAllTabPosition] = buildAllTab();
    tabs[mWhatsHotTabPosition] = buildWhatsHotTab();
    tabs[mWhatsNewTabPosition] = buildWhatsNewTab();
    tabs[mJumpToTabPosition] = buildJumpToTab();
    tabs[mFoodTabPosition] = buildFoodTab();
    tabs[mOutdoorTabPosition] = buildOutdoorTab();
    tabs[mArtTabPosition] = buildArtTab();
    tabs[mLatestTabPosition] = buildLatestTab();

    mPagerAdapter = new TabbedBrowsePagerAdapter(this, tabs);
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mPagerAdapter);

    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
        @Override
        public void onPageSelected(final int position) {
            try {
                mActionBar.setSelectedNavigationItem(position);
            } catch (final IllegalStateException e) {
                TroverApplication.logError(TAG, "IllegalArgumentsException setting tab position in PageChangeListener");
            }
        }
    });

    // Build the actual tabs on the actionbar
    for (int i = 0; i < tabs.length; i++) {
        mActionBar.addTab(mActionBar.newTab()
                .setTabListener(this));

        LayoutInflater inflater = LayoutInflater.from(this);
        View customView = inflater.inflate(R.layout.custom_action_bar_tabs, null);
        customView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
        TextView tabCustom = (TextView) customView.findViewById(R.id.custom_action_bar_tab);
        tabCustom.setText(tabs[i].getTabTitle());
        tabCustom.setGravity(Gravity.CENTER_HORIZONTAL | Gravity.CENTER_VERTICAL);
        tabCustom.setTypeface(TroverApplication.getDefaultFontBold());
        mActionBar.getTabAt(i).setCustomView(tabCustom);
    }

    // Now set up the button listeners for those icons
    mActionBar.getCustomView().findViewById(R.id.action_bar_friend_feed_button).setOnClickListener(this);
    mActionBar.getCustomView().findViewById(R.id.action_bar_me_button).setOnClickListener(this);
    mActionBar.getCustomView().findViewById(R.id.action_bar_nearby_button).setOnClickListener(this);

    mViewPager.setCurrentItem(previousTab);

    TroverLocationManager manger = TroverLocationManager.get();
    if (!manger.isNetworkLocationEnabled() && !deniedLocationServices) {
        showLocationServicesDialog();
    }

    if (AuthManager.get().isAuthenticated()) {
        mCurrentMode = Mode.NEWS_MODE; // <----- if I change this to GLOBE_MODE it doesn't crash
    } else {
        mCurrentMode = Mode.GLOBE_MODE;
    }
    validateView();

这是 main_browse.xml 布局:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="fill_parent"
    android:layout_width="fill_parent" >

    <android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <Button
        android:id="@+id/main_camera_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_marginBottom="15dp"
        android:layout_marginRight="15dp"
        android:background="@drawable/camera_floating" />

</RelativeLayout>

这是 setHighlightedIconButton 函数:

private void setHighlightedIconButton() {
    ImageButton button;
    View iconContainer = mActionBar.getCustomView();

    PaintDrawable selectedBackground = new PaintDrawable(getResources().getColor(R.color.trover_selected_icon_background));

    button = (ImageButton) iconContainer.findViewById(R.id.action_bar_friend_feed_button);
    if (mCurrentMode == Mode.NEWS_MODE) {
        button.setBackgroundDrawable(selectedBackground);
        button.setClickable(false);
    } else {
        button.setBackgroundDrawable(null);
        button.setClickable(true);
    }

    button = (ImageButton) iconContainer.findViewById(R.id.action_bar_nearby_button);
    if (mCurrentMode == Mode.GLOBE_MODE) {
        button.setBackgroundDrawable(selectedBackground);
        button.setClickable(false);
    } else {
        button.setBackgroundDrawable(null);
        button.setClickable(true);
    }

    button = (ImageButton) iconContainer.findViewById(R.id.action_bar_me_button);
    if (mCurrentMode == Mode.PROFILE_MODE) {
        button.setBackgroundDrawable(selectedBackground);
        button.setClickable(false);
    } else {
        button.setBackgroundDrawable(null);
        button.setClickable(true);
    }
}

这是调用它的 validateView() 函数:

/**
 * Handles transitions between different fragments by checking the current mode and authentication state.
 * This function can handle being called multiple times, and will always try to do the least work possible
 * each time.
 */
private void validateView() {
    invalidateOptionsMenu();
    setHighlightedIconButton();

    boolean authenticated = AuthManager.get().isAuthenticated();

    switch(mCurrentMode) {
        case GLOBE_MODE:
            // Note - we don't record a screen here because the tabs will do that
            removeMeFragment();
            removeNewsFragment();
            removeOnboardingFragment();
            mViewPager.setVisibility(View.VISIBLE);
            mActionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
            mPagerAdapter.madeVisible();
            break;
        case NEWS_MODE:
            if (mPreviousTabPosition == mJumpToTabPosition) {
                InputMethodManager imm = (InputMethodManager) getSystemService(
                        Context.INPUT_METHOD_SERVICE);
                imm.hideSoftInputFromWindow(mViewPager.getWindowToken(), 0);
            }
            recordScreen(getCurrentModeTrackingString(), this);
            removeMeFragment();
            removeOnboardingFragment();
            if (mNewsFeedFragment == null) {
                mNewsFeedFragment = DiscoveryListFragment.newNewsFeedInstance();
                mFragmentManager.beginTransaction().add(android.R.id.content, mNewsFeedFragment).commit();
            }
            mActionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
            mViewPager.setVisibility(View.GONE);
            break;
        case PROFILE_MODE:
            if (mPreviousTabPosition == mJumpToTabPosition) {
                InputMethodManager imm = (InputMethodManager) getSystemService(
                        Context.INPUT_METHOD_SERVICE);
                imm.hideSoftInputFromWindow(mViewPager.getWindowToken(), 0);
            }
            if (authenticated) {
                recordScreen(getCurrentModeTrackingString(), this);
                removeNewsFragment();
                removeOnboardingFragment();
                if (mProfileFragment == null) {
                    mProfileFragment = UserDetailFragment.newMeInstance();
                    mFragmentManager.beginTransaction().add(android.R.id.content, mProfileFragment).commit();
                }
            } else {
                recordScreen(getCurrentModeTrackingString() + "/onboarding", this);
                removeMeFragment();
                removeNewsFragment();
                if (mOnboardingFragment == null) {
                    removeOnboardingFragment();
                    mOnboardingFragment = new OnboardingFragment();
                    mFragmentManager.beginTransaction().add(android.R.id.content, mOnboardingFragment).commit();
                }
            }
            mViewPager.setVisibility(View.GONE);
            break;
        default:
            TroverApplication.logError(TAG, "Invalid mode!");
    }
}

这里是 onCreateOptionsMenu对于主要 Activity :

public boolean onCreateOptionsMenu(final Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu, menu);
    if (!AuthManager.get().isAuthenticated()) {
        MenuItem item = menu.findItem(R.id.menu_notifications);
        if (item != null) {
            item.setVisible(false);
        }
        item = menu.findItem(R.id.menu_recommended_users);
        if (item != null) {
            item.setVisible(false);
        }
    }
    return true;
}

这是 FrameLayout.onMeasure() 的一部分它是崩溃的 Android API 19 源代码的一部分的函数:

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    int count = getChildCount();  <-- this is returning 2

    final boolean measureMatchParentChildren =
            MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.EXACTLY ||
            MeasureSpec.getMode(heightMeasureSpec) != MeasureSpec.EXACTLY;
    mMatchParentChildren.clear();

    int maxHeight = 0;
    int maxWidth = 0;
    int childState = 0;

    for (int i = 0; i < count; i++) {
        final View child = getChildAt(i);
        if (mMeasureAllChildren || child.getVisibility() != GONE) { <-- crash happens here
            measureChildWithMargins(child, widthMeasureSpec, 0, heightMeasureSpec, 0);
            final LayoutParams lp = (LayoutParams) child.getLayoutParams();
            maxWidth = Math.max(maxWidth,
                    child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin);
            maxHeight = Math.max(maxHeight,
                    child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin);
            childState = combineMeasuredStates(childState, child.getMeasuredState());
            if (measureMatchParentChildren) {
                if (lp.width == LayoutParams.MATCH_PARENT ||
                        lp.height == LayoutParams.MATCH_PARENT) {
                    mMatchParentChildren.add(child);
                }
            }
        }
    }

Answer 1

View customView = inflater.inflate(R.layout.custom_action_bar_tabs, null);

这可能是您的问题的根源。如果你传入 null ，inflater 不知道要生成什么类型​​的 LayoutParams(它从父 ViewGroup 生成它们)。我相信这会生成默认的 ViewGroup.LayoutParams，但也许它根本不提供任何 LayoutParams。

您应该将其替换为:

View customView = inflater.inflate(R.layout.custom_action_bar_tabs, parent, false);

在哪里 parent是 customView 所在的 ViewGroup将被添加。如果您没有可用的父级，则可以手动设置一些自定义 LayoutParams:

View customView = inflater.inflate(R.layout.custom_action_bar_tabs, null);
customView.setLayoutParams(new ViewGroup.LayoutParams(
    ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));