我正在通过代码以编程方式创建ViewPager，但在生成的活动中，我没有得到ToolBar。我在xml文件和代码中都设置了工具栏，但我的代码一直说工具栏为空。
工具栏显示在我的主活动中，其中包含我的列表片段。每当我点击列表项时，应用程序就会崩溃，列表项会打开viewpager中包含的片段....或者至少我认为它是这样的。我完全失去了，任何帮助都会很棒。
这是堆栈跟踪：
03-24 00:33:50.128 26423-26423/com.fisheradelakin.criminalintent E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.fisheradelakin.criminalintent, PID: 26423
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.fisheradelakin.criminalintent/com.fisheradelakin.criminalintent.CrimePagerActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.support.v7.widget.Toolbar.getTitle()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
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:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.support.v7.widget.Toolbar.getTitle()' on a null object reference
at android.support.v7.internal.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:95)
at android.support.v7.internal.widget.ToolbarWidgetWrapper.<init>(ToolbarWidgetWrapper.java:88)
at android.support.v7.internal.app.ToolbarActionBar.<init>(ToolbarActionBar.java:82)
at android.support.v7.app.ActionBarActivityDelegateBase.setSupportActionBar(ActionBarActivityDelegateBase.java:189)
at android.support.v7.app.ActionBarActivity.setSupportActionBar(ActionBarActivity.java:92)
at com.fisheradelakin.criminalintent.CrimePagerActivity.onCreate(CrimePagerActivity.java:31)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
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:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
这是CrimePagerActivity.java
public class CrimePagerActivity extends ActionBarActivity {
private ViewPager mViewPager;
private ArrayList<Crime> mCrimes;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// create content view programmatically
mViewPager = new ViewPager(this);
mViewPager.setId(R.id.viewPager);
setContentView(mViewPager);
Toolbar toolbar = (Toolbar)(findViewById(R.id.toolbar));
setSupportActionBar(toolbar);
getSupportActionBar().setHomeButtonEnabled(true);
mCrimes = CrimeLab.get(this).getCrimes();
FragmentManager fm = getSupportFragmentManager();
mViewPager.setAdapter(new FragmentStatePagerAdapter(fm) {
@Override
public Fragment getItem(int position) {
Crime crime = mCrimes.get(position);
return CrimeFragment.newInstance(crime.getId());
}
@Override
public int getCount() {
return mCrimes.size();
}
});
mViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
Crime crime = mCrimes.get(position);
if(crime.getTitle() != null) {
getSupportActionBar().setTitle(crime.getTitle());
}
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
// set the current item of viewpager to the id of the crime selected rather than the first
UUID crimeId = (UUID)getIntent().getSerializableExtra(CrimeFragment.EXTRA_CRIME_ID);
for(int i = 0; i < mCrimes.size(); i++) {
if(mCrimes.get(i).getId().equals(crimeId)) {
mViewPager.setCurrentItem(i);
break;
}
}
}
}
我显示的片段的xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<include layout="@layout/toolbar"/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/crime_title_label"
style="?android:listSeparatorTextViewStyle"/>
<EditText
android:id="@+id/crime_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/crime_title_hint"/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/crime_details_label"
style="?android:listSeparatorTextViewStyle"/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/crime_date"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"/>
<CheckBox
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/crime_solved"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
android:text="@string/crime_solved_label"/>
</LinearLayout>
最后但并非最不重要的是，我的CrimeFragment.java类：
public class CrimeFragment extends Fragment {
public static final String EXTRA_CRIME_ID = "com.fisheradelakin.android.criminalintent.crime_id";
private Crime mCrime;
private EditText mTitleField;
private Button mDateButton;
private CheckBox mSolvedCheckBox;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
UUID crimeId = (UUID) getArguments().getSerializable(EXTRA_CRIME_ID);
mCrime = CrimeLab.get(getActivity()).getCrime(crimeId);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_crime, container, false);
mTitleField = (EditText) v.findViewById(R.id.crime_title);
mTitleField.setText(mCrime.getTitle());
mTitleField.addTextChangedListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
mCrime.setTitle(s.toString());
}
@Override
public void afterTextChanged(Editable s) {
}
});
mDateButton = (Button)v.findViewById(R.id.crime_date);
SimpleDateFormat sdf = new SimpleDateFormat("EEEE, MMM F, yyyy", Locale.US);
mDateButton.setText(sdf.format(mCrime.getDate()));
mDateButton.setEnabled(false);
mSolvedCheckBox = (CheckBox)v.findViewById(R.id.crime_solved);
mSolvedCheckBox.setChecked(mCrime.isSolved());
mSolvedCheckBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
// set the crime's solved property
mCrime.setSolved(isChecked);
}
});
return v;
}
public static CrimeFragment newInstance(UUID crimeId) {
Bundle args = new Bundle();
args.putSerializable(EXTRA_CRIME_ID, crimeId);
CrimeFragment fragment = new CrimeFragment();
fragment.setArguments(args);
return fragment;
}
}
ViewPager活动由我的列表片段调用，我已经包含了以下代码
public class CrimeListFragment extends ListFragment {
private static final String TAG = "CrimeListFragment";
private ArrayList<Crime> mCrimes;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getActivity().setTitle(R.string.crimes_title);
mCrimes = CrimeLab.get(getActivity()).getCrimes();
CrimeAdapter adapter = new CrimeAdapter(mCrimes);
setListAdapter(adapter);
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
Crime c = ((CrimeAdapter)getListAdapter()).getItem(position);
// start crime pager activity
Intent i = new Intent(getActivity(), CrimePagerActivity.class);
i.putExtra(CrimeFragment.EXTRA_CRIME_ID, c.getId());
startActivity(i);
}
private class CrimeAdapter extends ArrayAdapter<Crime> {
public CrimeAdapter(ArrayList<Crime> crimes) {
super(getActivity(), 0, crimes);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// if we weren't given a view, inflate one
if(convertView == null) {
convertView = getActivity().getLayoutInflater().inflate(R.layout.list_item_crime, null);
}
// configure the view for this crime
Crime c = getItem(position);
TextView titleTextView = (TextView) convertView.findViewById(R.id.crime_list_item_titleTextView);
titleTextView.setText(c.getTitle());
TextView dateTextView = (TextView) convertView.findViewById(R.id.crime_list_item_dateTextView);
dateTextView.setText(c.getDate().toString());
CheckBox solvedCheckBox = (CheckBox) convertView.findViewById(R.id.crime_list_item_solvedCheckBox);
solvedCheckBox.setChecked(c.isSolved());
return convertView;
}
}
@Override
public void onResume() {
super.onResume();
((CrimeAdapter)getListAdapter()).notifyDataSetChanged();
}
}
答案 0 :(得分：0)
我明白了。我需要在片段中设置工具栏，而不是像我一样在viewpager活动中设置工具栏。