[英]Getting Null Pointer Exception when calling an Activity from onMenuItemClick() method
public class MainActivity extends FragmentActivity implements ActionBar.TabListener, OnMenuItemClickListener, OnClickListener {
private PopupMenu popupMenu;
private final static int ONE = 1;
private final static int TWO = 2;
private final static int THREE = 3;
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link android.support.v4.app.FragmentPagerAdapter} derivative, which
* will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Create the adapter that will return a fragment for each of the three
// primary sections of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding
// tab. We can also use ActionBar.Tab#select() to do this if we have
// a reference to the Tab.
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
actionBar.addTab(
actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.action_settings:
/*View menuItemView = findViewById(R.id.action_settings);
PopupMenu popupMenu = new PopupMenu(this, menuItemView);
popupMenu.inflate(R.menu.counters_overflow);
popupMenu.show();*/
popupMenu = new PopupMenu(this, findViewById(R.id.action_settings));
popupMenu.getMenu().add(Menu.NONE, ONE, Menu.NONE, "Set Password");
popupMenu.getMenu().add(Menu.NONE, TWO, Menu.NONE, "About");
//popupMenu.getMenu().add(Menu.NONE, THREE, Menu.NONE, "Item 3");
popupMenu.setOnMenuItemClickListener(this);
findViewById(R.id.action_settings).setOnClickListener(this);
}
return (super.onOptionsItemSelected(item));
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a DummySectionFragment (defined as a static inner class
// below) with the page number as its lone argument.
Fragment fragment = new DummySectionFragment();
Bundle args = new Bundle();
args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, position + 1);
fragment.setArguments(args);
return fragment;
}
@Override
public int getCount() {
// Show 4 total pages.
return 4;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
case 3:
return getString(R.string.title_section4).toUpperCase(l);
}
return null;
}
}
/**
* A dummy fragment representing a section of the app, but that simply
* displays dummy text.
*/
public static class DummySectionFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
public static final String ARG_SECTION_NUMBER = "section_number";
public DummySectionFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main_dummy, container, false);
TextView dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
dummyTextView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
@Override
public boolean onMenuItemClick(MenuItem item) {
// TODO Auto-generated method stub
switch (item.getItemId()) {
case ONE:
getActionBar().hide();
//setContentView(R.layout.setpassword);
Intent intent = new Intent(this, SetPassword.class);
startActivity(intent);
break;
case TWO:
break;
}
return false;
}
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
popupMenu.show();
}
}
LOG CAT 日志猫
06-10 09:38:36.836: E/AndroidRuntime(790): FATAL EXCEPTION: main 06-10 09:38:36.836: E/AndroidRuntime(790): java.lang.RuntimeException: Unable to start activity ComponentInfo{split.pack.doasplit/split.pack.doasplit.SetPassword}: java.lang.NullPointerException 06-10 09:38:36.836: E/AndroidRuntime(790):
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 06-10 09:38:36.836: E/AndroidRuntime(790):
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 06-10 09:38:36.836: E/AndroidRuntime(790):
at android.app.ActivityThread.access$600(ActivityThread.java:141) 06-10 09:38:36.836: E/AndroidRuntime(790):
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 06-10 09:38:36.836: E/AndroidRuntime(790):
at android.os.Handler.dispatchMessage(Handler.java:99) 06-10 09:38:36.836: E/AndroidRuntime(790):
at android.os.Looper.loop(Looper.java:137) 06-10 09:38:36.836: E/AndroidRuntime(790):
at android.app.ActivityThread.main(ActivityThread.java:5041) 06-10 09:38:36.836: E/AndroidRuntime(790):
at java.lang.reflect.Method.invokeNative(Native Method) 06-10 09:38:36.836: E/AndroidRuntime(790):
at java.lang.reflect.Method.invoke(Method.java:511) 06-10 09:38:36.836: E/AndroidRuntime(790):
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 06-10 09:38:36.836: E/AndroidRuntime(790):
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 06-10 09:38:36.836: E/AndroidRuntime(790):
at dalvik.system.NativeStart.main(Native Method) 06-10 09:38:36.836: E/AndroidRuntime(790):
Caused by: java.lang.NullPointerException 06-10 09:38:36.836: E/AndroidRuntime(790):
at split.pack.doasplit.SetPassword.onCreate(SetPassword.java:32) 06-10 09:38:36.836: E/AndroidRuntime(790):
at android.app.Activity.performCreate(Activity.java:5104) 06-10 09:38:36.836: E/AndroidRuntime(790):
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 06-10 09:38:36.836: E/AndroidRuntime(790):
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 06-10 09:38:36.836: E/AndroidRuntime(790):
... 11 more
You are getting a NullPointerException
when you're creating SetPassword
activity, specifically, on line 32 of SetPassword.java
(check the bottom of the logcat). 在创建
SetPassword
活动时,特别是在SetPassword.java
第32行上,您将获得NullPointerException
(请检查logcat的底部)。
In your onMenuItemClick
method, you're creating an intent and starting activity SetPassword
, which throws the exception. 在
onMenuItemClick
方法中,您正在创建一个意图并启动活动SetPassword
,该活动将引发异常。
Edit: 编辑:
The Exception is in your SetPassword class not in this one post the code of setpassword or check the line 32 in the SetPassword class. 例外是在您的SetPassword类中,而不是在此中张贴setpassword的代码或检查SetPassword类中的第32行。
Check the theme you have taken in android manifest file for your application, ie does your current theme is having action bar because you wrote getActionBar().hide(); 检查您在Android清单文件中为应用程序获取的主题,即您当前的主题是否具有操作栏,因为您编写了getActionBar()。hide();。 in the code and it might be throwing exception if the theme you have choosen with no action bar.
在代码中,如果您选择的主题没有操作栏,则可能会引发异常。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.