这是我的主要活动,我想将城市名称的文本传递给我
TabFragment1。我正在获取空指针异常。请帮助我解决问题。即使事务commit()也不能解决问题,代码有什么问题。
public class MainActivity extends AppCompatActivity {
EditText cityname;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
cityname = findViewById(R.id.cityname);
tabLayout.addTab(tabLayout.newTab().setText("Tab1"));
tabLayout.addTab(tabLayout.newTab().setText("Tab2"));
tabLayout.addTab(tabLayout.newTab().setText("Tab3"));
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
final PagerAdapter adapter = new PagerAdapter
(getSupportFragmentManager(), tabLayout.getTabCount());
viewPager.setAdapter(adapter);
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
String cn = cityname.getText().toString();
Bundle bundle = new Bundle();
bundle.putString("city",cn);
TabFragment1 fobj = new TabFragment1();
fobj.setArguments(bundle);
}
}
以下是我的TabFragment1.java文件
public class TabFragment1 extends Fragment {
TextView tx;
String s="Hello";
Intent it;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.tab_fragment_1 , container, false);
tx=(TextView)view.findViewById(R.id.textView1);
s=this.getArguments().getString("city");
tx.setText(s);
return view;
}
}
随附tab_fragment1.xml文件
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/colorPrimary">
<TextView
android:id="@+id/textView1"
android:layout_width="161dp"
android:layout_height="66dp"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:text="TextView" />
</RelativeLayout>
我收到以下错误:
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
at com.example.ps.trial1.TabFragment1.onCreateView(TabFragment1.java:19)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2354)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1419)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1740)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1809)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:799)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:2199)
at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:651)
at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:167)....
最佳答案
似乎您正在尝试将值传递给TabFragment1实例。最好的方法是使用newInstance()
public static TabFragment1 newInstance(String someCity) {
TabFragment1 myFragment = new TabFragment1();
Bundle args = new Bundle();
args.putString("city", someCity);
myFragment.setArguments(args);
return myFragment;
}
在您的TabFragment1类中编写此方法,并在尝试将值传递给Fragment时使用此方法。
编辑:我建议这样做,因为您必须在将片段附加到活动之前调用“ setArguments()”