Question

在此行中出现null错误

mFragmentTransaction.replace(R.id.containerView,new TabFragment()).commit();

在下面的代码中获取android错误。

DrawerLayout mDrawerLayout;
NavigationView mNavigationView;
FragmentManager mFragmentManager;
FragmentTransaction mFragmentTransaction;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    /**
     *Setup the DrawerLayout and NavigationView
     */

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
    mNavigationView = (NavigationView) findViewById(R.id.shitstuff);

    /**
     * Lets inflate the very first fragment
     * Here , we are inflating the TabFragment as the first Fragment
     */


    mFragmentManager = getSupportFragmentManager();
    mFragmentTransaction = mFragmentManager.beginTransaction();
    mFragmentTransaction.replace(R.id.containerView,new TabFragment()).commit();
    /**
     * Setup click events on the Navigation View Items.
     */

    mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(MenuItem menuItem) {
            mDrawerLayout.closeDrawers();



            if (menuItem.getItemId() == R.id.nav_item_sent) {
                FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
                fragmentTransaction.replace(R.id.containerView,new SentFragment()).commit();

            }

            if (menuItem.getItemId() == R.id.nav_item_inbox) {
                FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
               // xfragmentTransaction.replace(R.id.containerView,new TabFragment()).commit();
            }

            return false;
        }

    });

    /**
     * Setup Drawer Toggle of the Toolbar
     */

    android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
    ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(this,mDrawerLayout, toolbar,R.string.app_name,
            R.string.app_name);

    mDrawerLayout.setDrawerListener(mDrawerToggle);

    mDrawerToggle.syncState();

}

logcat错误日志

    .tabproject E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.kpgames.tabproject, PID: 22961
java.lang.NullPointerException: Attempt to write to field 'android.support.v4.app.FragmentManagerImpl android.support.v4.app.Fragment.mFragmentManager' on a null object reference
    at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:418)
    at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:413)
    at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:99)
    at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:943)
    at android.support.v4.view.ViewPager.populate(ViewPager.java:1157)
    at android.support.v4.view.ViewPager.populate(ViewPager.java:1025)
    at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1545)
    at android.view.View.measure(View.java:18788)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
    at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
    at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
    at android.view.View.measure(View.java:18788)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
    at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
    at android.view.View.measure(View.java:18788)
    at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:1075)
    at android.view.View.measure(View.java:18788)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
    at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
    at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
    at android.view.View.measure(View.java:18788)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
    at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
    at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
    at android.view.View.measure(View.java:18788)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
    at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
    at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
    at android.view.View.measure(View.java:18788)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
    at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
    at android.view.View.measure(View.java:18788)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
    at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
    at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
    at android.view.View.measure(View.java:18788)
    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
    at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
    at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643)
    at android.view.View.measure(View.java:18788)
    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2100)
    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1216)
    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1452)
    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013)
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
    at android.view.Choreographer.doCallbacks(Choreographer.java:670)
    at android.view.Choreographer.doFrame(Choreographer.java:606)
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5417)
    at java.lang.ref

Answer 1

您收到 NullPointerException 。

尝试写入'android.support.v4.app.FragmentManagerImpl字段空对象上的android.support.v4.app.Fragment.mFragmentManager' 参考

当应用程序尝试使用时抛出NullPointerException 具有空值的对象引用。

检查如何传递newFragment

Fragment tabFragment = new TabFragment();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack if needed
transaction.replace(R.id.fragment_container, tabFragment );
transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();

FYI

调用 android.support.v4.app.Fragment ，而不是 android.app.Fragment 。

Answer 2

这只是我身边的问题。我把它包含在我的标签片段中并且设置了2个片段但项目计数设置为3.这就是为什么它给出了空问题..谢谢你的帮助和见证

在android选项卡项目中获取null错误

2 个答案:

FYI