Android的 - 尝试调用虚拟方法无效android.support.v4.app.Fragment.setMenuVisibility(布尔)'上一个空对象引用 [英] Android - Attempt to invoke virtual method 'void android.support.v4.app.Fragment.setMenuVisibility(boolean)' on a null object reference
问题描述
下面是错误的完整堆栈跟踪: http://pastebin.com/5dQHkUw3
错误才开始后,我开始在项目中使用的片段,因为我想给JSON提要出现。这是当我创建标签之前精细,NavigationDrawer等。
MainActivity.java
公共类MainActivity扩展ActionBarActivity实现MaterialTabListener {
工具栏私人mToolbar;
私人NavigationDrawerFragment mDrawerFragment;
私人DrawerLayout mDrawerLayout;私人MaterialTabHost mTabHost;
私人ViewPager mViewPager;公共静态最终诠释SERVICES_ALL = 1;
公共静态最终诠释SERVICES_FEATURED = 2;
公共静态最终诠释SERVICES_NEW = 3;@覆盖
保护无效的onCreate(捆绑savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.activity_main_appbar); mToolbar =(工具栏)findViewById(R.id.app_bar);
setSupportActionBar(mToolbar);
getSupportActionBar()setDisplayShowHomeEnabled(真)。 mDrawerLayout =(DrawerLayout)findViewById(R.id.drawer_layout);
mDrawerFragment =(NavigationDrawerFragment)getSupportFragmentManager()findFragmentById(R.id.fragment_navigation_drawer)。
mDrawerFragment.setUp(R.id.fragment_navigation_drawer,mDrawerLayout,mToolbar); mTabHost =(MaterialTabHost)findViewById(R.id.materialTabHost);
mViewPager =(ViewPager)findViewById(R.id.viewPager); MyPagerAdapter适配器=新MyPagerAdapter(getSupportFragmentManager());
mViewPager.setAdapter(适配器);
mViewPager.setOnPageChangeListener(新ViewPager.SimpleOnPageChangeListener(){
@覆盖
公共无效使用onPageSelected(INT位置){
mTabHost.setSelectedNavigationItem(位置);
}
}); 的for(int i = 0; I< adapter.getCount();我++){
mTabHost.addTab(
mTabHost.newTab()。
的setText(adapter.getPageTitle(I))。
setTabListener(本)
);
}
}@覆盖
公共无效onTabSelected(MaterialTab materialTab){
mViewPager.setCurrentItem(materialTab.getPosition());
}@覆盖
公共无效onTabReselected(MaterialTab materialTab){}@覆盖
公共无效onTabUnselected(MaterialTab materialTab){}私有类MyPagerAdapter扩展FragmentStatePagerAdapter {
FragmentManager fragmentManager; 公共MyPagerAdapter(FragmentManager FM){
超(FM);
fragmentManager =调频;
} @覆盖
公共片段的getItem(INT NUM){
片段片段= NULL;
开关(NUM){
案例SERVICES_ALL:
片段= FragmentAll.newInstance(,);
打破;
案例SERVICES_FEATURED:
片段= FragmentFeatured.newInstance(,);
打破;
案例SERVICES_NEW:
片段= FragmentNew.newInstance(,);
打破;
}
返回片段;
} @覆盖
公众诠释的getCount(){
返回3;
} 公共CharSequence的getPageTitle(INT位置){
返回getResources()getStringArray(R.array.tabs)[位置]。
}
}@覆盖
公共布尔onCreateOptionsMenu(菜单菜单){
。getMenuInflater()膨胀(R.menu.menu_main,菜单);
返回true;
}@覆盖
公共布尔onOptionsItemSelected(菜单项项){
INT ID = item.getItemId(); 如果(ID == R.id.action_settings){
Toast.makeText(这一点,嘿,你只需点击+ item.getTitle(),Toast.LENGTH_LONG).show();
返回true;
} 如果(ID == R.id.action_next){
startActivity(新意图(这一点,DetailActivity.class));
} 返回super.onOptionsItemSelected(项目);
}
}
FragmentAll.java (另外2片段类似于FragmentAll。)
公共类FragmentAll扩展片段{
私有静态最后弦乐ARG_PARAM1 =参数1;
私有静态最后弦乐ARG_PARAM2 =参数2;私人字符串mParam1;
私人字符串mParam2;公共静态的newInstance FragmentAll(字符串参数1,字符串参数2){
FragmentAll片段=新FragmentAll();
捆绑ARGS =新包();
args.putString(ARG_PARAM1,参数1);
args.putString(ARG_PARAM2,参数2);
fragment.setArguments(参数);
返回片段;
}公共FragmentAll(){
//必需的空公共构造
}@覆盖
公共无效的onCreate(捆绑savedInstanceState){
super.onCreate(savedInstanceState);
如果(getArguments()!= NULL){
mParam1 = getArguments()的getString(ARG_PARAM1)。
mParam2 = getArguments()的getString(ARG_PARAM2)。
}
}@覆盖
公共查看onCreateView(LayoutInflater充气器,容器的ViewGroup,
捆绑savedInstanceState){
//充气的布局该片段
返回inflater.inflate(R.layout.fragment_all,集装箱,FALSE);
}
}
该堆栈跟踪:
android.support.v4.app.Fragment.setMenuVisibility(布尔)'上一个空对象引用
在android.support.v4.app.FragmentStatePagerAdapter.instantiateItem(FragmentStatePagerAdapter.java:116)
在android.support.v4.view.ViewPager.addNewItem(ViewPager.java:836)
在android.support.v4.view.ViewPager.populate(ViewPager.java:986)
在android.support.v4.view.ViewPager.populate(ViewPager.java:918)
在android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1440)
在android.view.View.measure(View.java:17430)
在android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
在android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
在android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
在android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
在android.view.View.measure(View.java:17430)
在android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
在android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
在android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124)
在android.view.View.measure(View.java:17430)
在android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
在android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
在android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
在android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
在android.view.View.measure(View.java:17430)
在android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
在android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
在android.view.View.measure(View.java:17430)
在android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
在android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
在android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
在android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
在android.view.View.measure(View.java:17430)
在android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
在android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
在com.android.internal.policy.impl.PhoneWindow $ DecorView.onMeasure(PhoneWindow.java:2560)
在android.view.View.measure(View.java:17430)
在android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2001)
在android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1166)
在android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1372)
在android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
在android.view.ViewRootImpl $ TraversalRunnable.run(ViewRootImpl.java:5779)
在android.view.Choreographer $ CallbackRecord.run(Choreographer.java:767)
在android.view.Choreographer.doCallbacks(Choreographer.java:580)
在android.view.Choreographer.doFrame(Choreographer.java:550)
在android.view.Choreographer $ FrameDisplayEventReceiver.run(Choreographer.java:753)
在android.os.Handler.handleCallback(Handler.java:739)
在android.os.Handler.dispatchMessage(Handler.java:95)
在android.os.Looper.loop(Looper.java:135)
在android.app.ActivityThread.main(ActivityThread.java:5221)
在java.lang.reflect.Method.invoke(本机方法)
在java.lang.reflect.Method.invoke(Method.java:372)
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:899)
在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
公共静态最终诠释SERVICES_ALL = 1;
公共静态最终诠释SERVICES_FEATURED = 2;
公共静态最终诠释SERVICES_NEW = 3;
应
公共静态最终诠释SERVICES_ALL = 0;
公共静态最终诠释SERVICES_FEATURED = 1;
公共静态最终诠释SERVICES_NEW = 2;
的getItem
0为基础的指数,这意味着在你的code时, 0的情况
你的适配器永远不匹配之一,而在这种情况下,你是返回一个空片段导致异常
Here is the full stack trace of the error: http://pastebin.com/5dQHkUw3
The error started to appear only after I started using fragments in the project, because I want to give JSON feeds. It was fine before when I was creating Tabs, NavigationDrawer etc.
MainActivity.java
public class MainActivity extends ActionBarActivity implements MaterialTabListener{
private Toolbar mToolbar;
private NavigationDrawerFragment mDrawerFragment;
private DrawerLayout mDrawerLayout;
private MaterialTabHost mTabHost;
private ViewPager mViewPager;
public static final int SERVICES_ALL = 1;
public static final int SERVICES_FEATURED = 2;
public static final int SERVICES_NEW = 3;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_appbar);
mToolbar = (Toolbar) findViewById(R.id.app_bar);
setSupportActionBar(mToolbar);
getSupportActionBar().setDisplayShowHomeEnabled(true);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerFragment = (NavigationDrawerFragment) getSupportFragmentManager().findFragmentById(R.id.fragment_navigation_drawer);
mDrawerFragment.setUp(R.id.fragment_navigation_drawer, mDrawerLayout, mToolbar);
mTabHost = (MaterialTabHost) findViewById(R.id.materialTabHost);
mViewPager = (ViewPager) findViewById(R.id.viewPager);
MyPagerAdapter adapter = new MyPagerAdapter(getSupportFragmentManager());
mViewPager.setAdapter(adapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener(){
@Override
public void onPageSelected(int position) {
mTabHost.setSelectedNavigationItem(position);
}
});
for(int i=0; i<adapter.getCount(); i++ ){
mTabHost.addTab(
mTabHost.newTab().
setText(adapter.getPageTitle(i)).
setTabListener(this)
);
}
}
@Override
public void onTabSelected(MaterialTab materialTab) {
mViewPager.setCurrentItem(materialTab.getPosition());
}
@Override
public void onTabReselected(MaterialTab materialTab) {
}
@Override
public void onTabUnselected(MaterialTab materialTab) {
}
private class MyPagerAdapter extends FragmentStatePagerAdapter{
FragmentManager fragmentManager;
public MyPagerAdapter(FragmentManager fm) {
super(fm);
fragmentManager = fm;
}
@Override
public Fragment getItem(int num) {
Fragment fragment = null;
switch (num){
case SERVICES_ALL:
fragment = FragmentAll.newInstance("","");
break;
case SERVICES_FEATURED:
fragment = FragmentFeatured.newInstance("","");
break;
case SERVICES_NEW:
fragment = FragmentNew.newInstance("","");
break;
}
return fragment;
}
@Override
public int getCount() {
return 3;
}
public CharSequence getPageTitle(int position){
return getResources().getStringArray(R.array.tabs)[position];
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
Toast.makeText(this, "Hey you just hit " + item.getTitle(), Toast.LENGTH_LONG).show();
return true;
}
if (id == R.id.action_next) {
startActivity(new Intent(this, DetailActivity.class));
}
return super.onOptionsItemSelected(item);
}
}
FragmentAll.java (The other 2 fragments are similar to FragmentAll.)
public class FragmentAll extends Fragment {
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private String mParam1;
private String mParam2;
public static FragmentAll newInstance(String param1, String param2) {
FragmentAll fragment = new FragmentAll();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
public FragmentAll() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_all, container, false);
}
}
The stacktrace:
android.support.v4.app.Fragment.setMenuVisibility(boolean)' on a null object reference
at android.support.v4.app.FragmentStatePagerAdapter.instantiateItem(FragmentStatePagerAdapter.java:116)
at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:836)
at android.support.v4.view.ViewPager.populate(ViewPager.java:986)
at android.support.v4.view.ViewPager.populate(ViewPager.java:918)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1440)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
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:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
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:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
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:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
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:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2560)
at android.view.View.measure(View.java:17430)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2001)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1166)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1372)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
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)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
public static final int SERVICES_ALL = 1;
public static final int SERVICES_FEATURED = 2;
public static final int SERVICES_NEW = 3;
should be
public static final int SERVICES_ALL = 0;
public static final int SERVICES_FEATURED = 1;
public static final int SERVICES_NEW = 2;
getItem
is 0-based-index, which means that in your code, the case 0
of your Adapter never matches one, and in that case you are returning a null fragment causing the exception
这篇关于Android的 - 尝试调用虚拟方法无效android.support.v4.app.Fragment.setMenuVisibility(布尔)'上一个空对象引用的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!