Android：捆绑NullPointerException [英] Android: Bundle NullPointerException
问题描述
我正在开发一个应用程序，我需要将一些数据从ListFragment发送到ItemFragment。我使用包，但得到nullpointerexception。我应该提到我是新手，这是我的第一个应用程序。因此，请让我知道我的做法是否错误或令人困惑。这是我的代码
I'm working on an app I need to send some data from ListFragment to ItemFragment. I use bundle but I get nullpointerexception. I should mention that i'm a newbie and this is my first app. so let me know if what I did is wrong or confusing. Here are my codes
ListFragment.java
if (child != null && mGestureDetector.onTouchEvent(motionEvent)) {
int position = recyclerView.getChildLayoutPosition(child);
selectedItem = mItems.get(position);
itemId = mItems.get(position).getId();
openFragment(new ItemFragment(), "MyApp");
ItemFragment if = new ItemFragment();
Bundle bundle = new Bundle();
bundle.putLong("selectedId", itemId);
if.setArguments(bundle);
}
return false;
}
ItemFragment.java
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Bundle bundledData = this.getArguments();
selectedId = bundledData.getLong("selectedId");//here is the line 105 in logcat
return mRootView;
}
Logcat
java.lang.NullPointerException
at me.myapp.fragments.ItemFragment.onCreateView(ItemFragment.java:105)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1962)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1613)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:517)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
---添加---
出于某种原因，我当我在这里尝试答案时，仍然会遇到同样的错误，除了阮的。据我对nguyen代码的理解，我使用此
For some reason, I still get the same error when I tried the answers here except for nguyen's. From what I understand in nguyen's code, I use this
ListFragment.java
private long itemId;
if (child != null && mGestureDetector.onTouchEvent(motionEvent)) {
int position = recyclerView.getChildLayoutPosition(child);
selectedItem = mItems.get(position);
itemId = mItems.get(position).getId();
Bundle bundle = new Bundle();
bundle.putLong("selectedId", itemId);
ItemFragment itemFrag = ItemFragment.newInstance(bundle);
openFragment(new ItemFragment(), "Update Item");
Toast.makeText(getActivity(), "id = " + itemId, Toast.LENGTH_SHORT).show();
ItemFragment.java
private long selId;
public static ItemFragment newInstance(Bundle bundle) {
ItemFragment frag = new ItemFragment();
frag.setArguments(bundle);
return frag;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
if (getArguments() != null) {
selId = getArguments().getLong("selectedId");
}
makeToast(""+selId);
return mRootView;
}
这些代码没有任何错误。 ListFragment中的Toast确实显示了正确的值，但ItemFragment中的Toast始终返回0。我在这里缺少什么？
I didn't get any error with these codes. The toast in ListFragment does shows the correct value but the toast in ItemFragment always returns 0. what am i missing here??
推荐答案
经过数小时的时间，弄乱了代码，反复试验，尝试了不同的代码，nguyen的代码以及此处的代码 https://stackoverflow.com/ a / 16036693/5563156 给了我这个主意。这些代码似乎可以完成工作
After hours messing around with the code, trial and error, tried different codes, nguyen's code and the code here https://stackoverflow.com/a/16036693/5563156 gives me the idea. these codes seems to get the job done
ListFragment.java
mRecyclerView.addOnItemTouchListener(new RecyclerView.OnItemTouchListener() {
@Override
public boolean onInterceptTouchEvent(RecyclerView recyclerView, MotionEvent motionEvent) {
View child = recyclerView.findChildViewUnder(motionEvent.getX(), motionEvent.getY());
if (child != null && mGestureDetector.onTouchEvent(motionEvent)) {
int position = recyclerView.getChildLayoutPosition(child);
selectedItem = mItems.get(position);
itemId = mItems.get(position).getId();
//pass selected item's ID to Main Activity
Intent i = new Intent(getActivity(), MainActivity.class);
i.putExtra("selectedId", itemId);
startActivity(i);
Toast.makeText(getActivity(), "id = " + itemId, Toast.LENGTH_SHORT).show();
}
return false;
}
在 MainActivity的OnCreate
if(savedInstanceState == null){
//receives selected item's ID passed from ListFragment
Intent intent = getIntent();
long selId = intent.getLongExtra("selectedId", 0);
if (selId > 0) {
//send the selected item ID to ItemFragment
Bundle bundle = new Bundle();
bundle.putLong("selectedId", 0);
ItemFragment frag = new ItemFragment();
openFragment(ItemFragment.newInstance(selId), "Update Item");
frag.setArguments(bundle);
}}
ItemFragment.java
public static ItemFragment newInstance(long selId) {
ItemFragment fragment = new ItemFragment();
if (selId > 0) {
Bundle bundle = new Bundle();
bundle.putLong("selectedId", selId);
fragment.setArguments(bundle);
}
return fragment;
}
在 ItemFragment的OnCreateView
Bundle args = getArguments();
if (args != null && args.containsKey("selectedId")) {
selId = args.getLong("selectedId");
}
感谢发布代码的每个人！感谢帮助。
Thanks to everyone who posted their codes! Appreciate the help.
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