[英]Unable to send Strings from one Fragment to another via Bundles
我試圖通過捆綁將兩個字符串發送到下一個片段,但應用程序甚至在我到達第一個片段之前就崩潰了。
我在第二個片段中收到此錯誤:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.android.guessit, PID: 22360
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.android.guessit.GameFlow.FragmentAnswer1.onCreateView(FragmentAnswer1.java:125)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2600)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:881)
at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1238)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1303)
at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:439)
at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManagerImpl.java:2079)
at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1869)
at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1824)
at androidx.fragment.app.FragmentManagerImpl.execSingleAction(FragmentManagerImpl.java:1696)
at androidx.fragment.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:299)
at androidx.fragment.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:259)
at androidx.viewpager.widget.ViewPager.populate(ViewPager.java:1244)
at androidx.viewpager.widget.ViewPager.setCurrentItemInternal(ViewPager.java:669)
at androidx.viewpager.widget.ViewPager.setCurrentItemInternal(ViewPager.java:631)
at androidx.viewpager.widget.ViewPager.setCurrentItem(ViewPager.java:612)
at com.example.android.guessit.GameFlow.GameActivity.setViewPager(GameActivity.java:152)
at com.example.android.guessit.GameFlow.FragmentOneCategory$6.onClick(FragmentOneCategory.java:190)
at android.view.View.performClick(View.java:7352)
at android.view.View.performClickInternal(View.java:7318)
at android.view.View.access$3200(View.java:846)
at android.view.View$PerformClick.run(View.java:27800)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7050)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)
我知道這意味着我嘗試在第二個片段中接收的字符串值意味着該字符串沒有值,但我不知道這里的問題出在哪里,因為我嘗試發送的字符串不為空.
這是我在第一個片段中用於包的代碼(在onCreatView
):
FragmentAnswer1 frag1 = new FragmentAnswer1();
Bundle args = new Bundle();
args.putString("question_1", question);
args.putString("answer_1", answer);
frag1.setArguments(args);
getFragmentManager().beginTransaction().add(R.id.container, frag1).commit(); // there is a message that says that "beginTransaction" may produce a nullPointer
這是在第二個片段中接收字符串的代碼(目前也在onCreateView
)
question = getArguments().getString("question_1"); // error is in this line
answer = getArguments().getString("answer_1");
question1.setText(question);
rightAnswer.setText(answer);
我已經嘗試將上面的代碼移動到onStart
方法中,但我仍然遇到相同的錯誤。 我也嘗試使用此解決方案,但它對我不起作用。 我沒有找到有關如何解決問題的任何其他解決方案或方法。
如果您需要更多信息,請告訴我。 任何幫助深表感謝!
我現在找到了在擁有 ViewPager 的同時將數據從一個 Fragment 發送到另一個 Fragment 的正確方法。 我們必須使用 ViewModel。
首先,我們必須創建一個 ViewModel,在這種情況下,我們的目標是將一個 String 從 Fragment 1 發送到 Fragment 2。這是帶有 Getter 和 Setter 方法的 ViewModel 的代碼:
public class ViewModelString extends ViewModel {
private MutableLiveData<String> mString = new MutableLiveData<>();
public MutableLiveData<String> getmString() {
return mString;
}
public void setmString(MutableLiveData<String> mString) {
this.mString = mString;
}
}
然后在我們想要發送字符串的片段 1 中,我們需要首先在onCreate
初始化 ViewModel 。
public class Fragment1 extends Fragment {
private ViewModelString viewModel;
public Fragment1() {
// Required empty public constructor
}
public static Fragment1 newInstance() {
return new Fragment1();
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// initialize ViewModel here
viewModel = ViewModelProviders.of(requireActivity()).get(ViewModelString.class);
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
String hello = "hello";
viewModel.setmString(hello);
}
}
然后在第二個 Fragment 中,我們還必須首先初始化 viewModel,然后創建一個觀察者。 在這里,我們然后獲取存儲在 ViewModel 中的 String 並將 TextView 設置為其值:
public class Fragment2 extends Fragment {
private ViewModelString viewModel;
public Fragment2() {
// Required empty public constructor
}
public static Fragment2 newInstance() {
return new Fragment2();
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// initialize ViewModel here
viewModel = ViewModelProviders.of(requireActivity()).get(ViewModelString.class);
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
TextView textView = findViewById(R.id.yourTextViewId);
// Gets the string
viewModel.getmString().observe(requireActivity(), new Observer<String>() {
@Override
public void onChanged(@Nullable String s) {
textView.setText(s);
}
});
}
...
}
我希望這可以幫助任何人! 請隨時編輯我的帖子。
使用 Bundle 發送字符串:
//Put the value
Bundle args = new Bundle();
args.putString("YourKey", "YourValue");
YourFragmentName ldf = new YourFragmentName ();
ldf.setArguments(args);
//Inflate the fragment
getActivity().getSupportFragmentManager().beginTransaction().add(R.id.container, ldf).commit();
在新 Fragment 的 onCreateView 中:
//Retrieve the value
Bundle bundle = this.getArguments();
if (bundle != null) {
String value = bundle.getString("YourKey");
}
使用捆綁包。 下面是一個例子:
Fragment fragment = new Fragment();
Bundle bundle = new Bundle();
bundle.putInt("Key", "value");
fragment.setArguments(bundle);
fragmentManager.beginTransaction().replace(R.id.container, frag1).commit()
Bundle 為許多數據類型提供了 put 方法。 看到 這個
然后在您的 Fragment 中,在 onCreate() 方法中檢索數據,例如:
Bundle bundle = this.getArguments();
if (bundle != null) {
int myInt = bundle.getString(Key);
}
嘗試這個。
var fragment: MainFragment =MainFragment()
val args = Bundle()
args.putString("question_1", "My question")
args.putString("answer_1", "My answer")
fragment.setArguments(args)
fragmentManager.beginTransaction().add(R.id.fragment_content, fragment).commit()
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.