Question

我评论了recylerview但我仍然收到以下错误：

    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView$LayoutManager.onMeasure(android.support.v7.widget.RecyclerView$Recycler, android.support.v7.widget.RecyclerView$State, int, int)' on a null object reference
        at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1764)
        at android.view.View.measure(View.java:17440)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5465)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
        at android.view.View.measure(View.java:17440)
        at android.widget.ScrollView.measureChildWithMargins(ScrollView.java:1260)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
        at android.widget.ScrollView.onMeasure(ScrollView.java:337)
        at android.view.View.measure(View.java:17440)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5465)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
        at android.view.View.measure(View.java:17440)
        at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1488)
        at android.view.View.measure(View.java:17440)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:875)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
        at android.view.View.measure(View.java:17440)
        at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727)
        at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463)
        at android.view.View.measure(View.java:17440)
        at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:868)
        at android.view.View.measure(View.java:17440)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5465)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
        at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124)
        at android.view.View.measure(View.java:17440)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5465)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
        at android.view.View.measure(View.java:17440)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5465)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
        at android.view.View.measure(View.java:17440)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5465)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
        at android.view.View.measure(View.java:17440)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5465)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2560)
        at android.view.View.measure(View.java:17440)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2031)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1189)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1402)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1077)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5884)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
        at android.view.Choreographer.doCallbacks(Choreographer.java:580)
        at android.view.Choreographer.doFrame(Choreographer.java:550)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)

此处生成错误：

    public class NextActivity extends AppCompatActivity {

String TITLES[] = {"Workspace","#Recently Used 1","#Recently Used 2","#Recently Used 3",". . .","Scorecard","Starred","Files","Directory","Settings","tag 1","tag 2","tag 3"};
int ICONS[] = {0,0,0,0,0,0,0,0,0,0,R.drawable.back,R.drawable.back,R.drawable.back};
String SETTINGS[] = {"Last synced","Premium"};

String NAME = "Chetan Harithas";
String EMAIL = "chetan.harithas@google.com";
int PROFILE = R.drawable.background;

RecyclerView mRecyclerView;                           // Declaring RecyclerView
RecyclerView.Adapter mAdapter;                        // Declaring Adapter For Recycler View
RecyclerView.LayoutManager mLayoutManager;            // Declaring Layout Manager as a linear layout manager
DrawerLayout Drawer;                                  // Declaring DrawerLayout 

ActionBarDrawerToggle mDrawerToggle;

ViewPager pager;
ViewPagerAdapter adapter;
SlidingTabLayout tabs;
CharSequence Titles[]={"Today","Week","Month","Workspace"};
int Numboftabs =4;

private Toolbar toolbar;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    String username = getSharedPreferences("PREFERENCE", MODE_PRIVATE).getString("username", "");
    String email = getSharedPreferences("PREFERENCE", MODE_PRIVATE).getString("email", "");
    Toast.makeText(getApplicationContext(), email, Toast.LENGTH_LONG).show();
    Toast.makeText(getApplicationContext(), username, Toast.LENGTH_LONG).show();

    setContentView(R.layout.activity_next);

    toolbar = (Toolbar) findViewById(R.id.tool_bar); // Attaching the layout to the toolbar object
    setSupportActionBar(toolbar);


/*    mRecyclerView = (RecyclerView) findViewById(R.id.RecyclerView); // Assigning the RecyclerView Object to the xml View
    mRecyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL_LIST));
    mRecyclerView.setHasFixedSize(true);                            // Letting the system know that the list objects are of fixed size
    mAdapter = new SlideInAdapter(TITLES,ICONS,SETTINGS,NAME,EMAIL,PROFILE,this);       // Creating the Adapter of MyAdapter class(which we are going to see in a bit)
    // And passing the titles,icons,header view name, header view email,
    // and header view profile picture
    mRecyclerView.setAdapter(mAdapter);                              // Setting the adapter to RecyclerView
    mLayoutManager = new LinearLayoutManager(this);                 // Creating a layout Manager
    mRecyclerView.setLayoutManager(mLayoutManager);                 // Setting the layout Manager
    Drawer = (DrawerLayout) findViewById(R.id.DrawerLayout);        // Drawer object Assigned to the view
    mDrawerToggle = new ActionBarDrawerToggle(this,Drawer,toolbar,R.string.navigation_drawer_open,R.string.navigation_drawer_close){
        @Override
        public void onDrawerOpened(View drawerView) {
            super.onDrawerOpened(drawerView);
            // code here will execute once the drawer is opened( As I dont want anything happened whe drawer is
            // open I am not going to put anything here)
        }
        @Override
        public void onDrawerClosed(View drawerView) {
            super.onDrawerClosed(drawerView);
            // Code here will execute once drawer is closed
        }

    }; // Drawer Toggle Object Made
    Drawer.setDrawerListener(mDrawerToggle); // Drawer Listener set to the Drawer toggle
    mDrawerToggle.syncState();               // Finally we set the drawer toggle sync State     */



    final FloatingActionMenu fab_menu = (FloatingActionMenu) findViewById(R.id.fab_menu);
    fab_menu.setClosedOnTouchOutside(true);
    FloatingActionButton fab1 = (FloatingActionButton) findViewById(R.id.fab1);
    fab1.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            Toast.makeText(getApplicationContext(),"New Workspace clicked",Toast.LENGTH_SHORT).show();
        }
    });
    FloatingActionButton fab2 = (FloatingActionButton) findViewById(R.id.fab2);
    fab2.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            Toast.makeText(getApplicationContext(),"Analysis clicked",Toast.LENGTH_SHORT).show();
        }
    });
    FloatingActionButton fab3 = (FloatingActionButton) findViewById(R.id.fab3);
    fab3.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            Toast.makeText(getApplicationContext(),"Tasks clicked",Toast.LENGTH_SHORT).show();
        }
    });
    FloatingActionButton fab4 = (FloatingActionButton) findViewById(R.id.fab4);
    fab4.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            Toast.makeText(getApplicationContext(),"Chatrooms clicked",Toast.LENGTH_SHORT).show();
        }
    });

    adapter =  new ViewPagerAdapter(getSupportFragmentManager(),Titles,Numboftabs);

    // Assigning ViewPager View and setting the adapter
    pager = (ViewPager) findViewById(R.id.pager);
    pager.setAdapter(adapter);

    // Assiging the Sliding Tab Layout View
    tabs = (SlidingTabLayout) findViewById(R.id.tabs);
    tabs.setDistributeEvenly(true);

    // To make the Tabs Fixed set this true, This makes the tabs Space Evenly in Available width

    // Setting Custom Color for the Scroll bar indicator of the Tab View
    tabs.setCustomTabColorizer(new SlidingTabLayout.TabColorizer() {
        @Override
        public int getIndicatorColor(int position) {
            return getResources().getColor(R.color.tabsScrollColor);
        }
    });

    //Setting the ViewPager For the SlidingTabsLayout
    tabs.setViewPager(pager);

}


public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu items for use in the action bar
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu_next, menu);
    return super.onCreateOptionsMenu(menu);
}

public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

}

这是我的ViewPageAdapter：

    public class ViewPagerAdapter extends FragmentStatePagerAdapter {

CharSequence Titles[]; // This will Store the Titles of the Tabs which are Going to be passed when ViewPagerAdapter is created
int NumbOfTabs; // Store the number of tabs, this will also be passed when the ViewPagerAdapter is created


// Build a Constructor and assign the passed Values to appropriate values in the class
public ViewPagerAdapter(FragmentManager fm,CharSequence mTitles[], int mNumbOfTabsumb) {
    super(fm);

    this.Titles = mTitles;
    this.NumbOfTabs = mNumbOfTabsumb;

}

//This method return the fragment for the every position in the View Pager
@Override
public Fragment getItem(int position) {

    if(position == 0) // if the position is 0 we are returning the First tab
    {
        Tab_Day_View tab1 = new Tab_Day_View();
        return tab1;
    }
    else if(position==1)            // As we are having 2 tabs if the position is now 0 it must be 1 so we are returning second tab
    {
        Tab_Week_View tab2 = new Tab_Week_View();
        return tab2;
    }

    else if(position==2)
    {
        Tab_Month_View tab3 = new Tab_Month_View();
        return tab3;
    }
    else
    {
        Tab_Workspace tab4 = new Tab_Workspace();
        return tab4;
    }


}

// This method return the titles for the Tabs in the Tab Strip

@Override
public CharSequence getPageTitle(int position) {
    return Titles[position];
}

// This method return the Number of tabs for the tabs Strip

@Override
public int getCount() {
    return NumbOfTabs;
}
}

我用来制作标签的类：两个课程如下

SlidingTabLayout.java

SlidingTabStrip.java

我在切换每个标签片段的标签时收到错误。

Answer 1

尝试评论这些行还：

RecyclerView mRecyclerView;                           // Declaring RecyclerView
RecyclerView.Adapter mAdapter;                        // Declaring Adapter For Recycler View
RecyclerView.LayoutManager mLayoutManager;            // Declaring Layout Manager as a linear layout manager
DrawerLayout Drawer;

Answer 2

如果XML布局文件中有RecyclerView，那么您的Java代码中没有Adapter和LayoutManager，那么您将会遇到同样的错误。在布局文件中注释掉您未附加到Java代码中RecyclerView和Adapter的任何LayoutManager，然后重试。

Recyclerview onMeasure java null指针异常，即使没有recyclerview

2 个答案: