Android Fragment getArguments()返回null

正如标题所示。
我从这里下载了Fragment代码, http://developer.android.com/shareables/training/FragmentBasics.zip 。
这是来自Android官方开发者网站的片段的例子。 http://developer.android.com/training/basics/fragments/fragment-ui.html

这是MainActivity.javaonCreate()

 /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.news_articles); // Check whether the activity is using the layout version with // the fragment_container FrameLayout. If so, we must add the first fragment if (findViewById(R.id.fragment_container) != null) { // However, if we're being restored from a previous state, // then we don't need to do anything and should return or else // we could end up with overlapping fragments. if (savedInstanceState != null) { return; } // Create an instance of ExampleFragment HeadlinesFragment fragment = new HeadlinesFragment(); // In case this activity was started with special instructions from an Intent, // pass the Intent's extras to the fragment as arguments //fragment.setArguments(getIntent().getExtras()); Bundle args= new Bundle(); args.putString("category", "clothes"); args.putString("item", "shirts"); fragment.setArguments(args); // Add the fragment to the 'fragment_container' FrameLayout getSupportFragmentManager().beginTransaction() .replace(R.id.fragment_container, fragment).commit(); } } 

HeadlinesFragment.javaonCreate()

 @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // We need to use a different list item layout for devices older than Honeycomb int layout = Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB ? android.R.layout.simple_list_item_activated_1 : android.R.layout.simple_list_item_1; Bundle args = getArguments(); if (args == null) { Toast.makeText(getActivity(), "arguments is null " , Toast.LENGTH_LONG).show(); } else { Toast.makeText(getActivity(), "text " + args , Toast.LENGTH_LONG).show(); } // Create an array adapter for the list view, using the Ipsum headlines array setListAdapter(new ArrayAdapter<String>(getActivity(), layout, Ipsum.Headlines)); } 

我已经阅读了几个QA,像这样一个片段getArguments()返回null ,和其他许多与setArguments()getArguments() ,但仍然卡住了。

而且我已经将BundleToast代码移到onAttach()onCreateView()了。 我的代码有什么问题? 我想我错过了什么,但不知道是什么。
请帮忙! 谢谢。

编辑
我会更清楚地expression我的意图。 在我下载的FragmentBasic中,有MainActivity.java,HeadlinesFragment.java和ArticlesFragment.java。 从MainActivity.java到ArticlesFragment.java的“通信”在这里不是问题。 我想要的是将数据从MainActivity.java发送到HeadlinesFragment.java。 他们的连接是这样的:

 -------------------------------------- | MainActivity <-> HeadlinesFragment | | | | | |>> ArticlesFragment | -------------------------------------- 

HeadlinesFragment在运行时运行。

*使用<600px宽度的Android小工具时,这些代码有效。 但在平板电脑(> = 600px)上使用时不起作用,如下面的@ Tesla1984所示。 但是,我想要的是小工具<600px和小工具> 600px相同的结果。

Solutions Collecting From Web of "Android Fragment getArguments()返回null"

@tonny

我已经下载了FragmentBasics.zip。 我只更改参数名称。这里是代码和结果图片。

主要活动

 public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.news_articles); // Check whether the activity is using the layout version with // the fragment_container FrameLayout. If so, we must add the first fragment if (findViewById(R.id.fragment_container) != null) { // However, if we're being restored from a previous state, // then we don't need to do anything and should return or else // we could end up with overlapping fragments. if (savedInstanceState != null) { return; } // Create an instance of ExampleFragment HeadlinesFragment fragment = new HeadlinesFragment(); // In case this activity was started with special instructions from an Intent, // pass the Intent's extras to the fragment as arguments // firstFragment.setArguments(getIntent().getExtras()); //test Bundle args= new Bundle(); args.putString("category", "clothes"); args.putString("item", "shirts"); fragment.setArguments(args); // Add the fragment to the 'fragment_container' FrameLayout getSupportFragmentManager().beginTransaction() .replace(R.id.fragment_container, fragment).commit(); } } 

HeadlinesFragment

 public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // We need to use a different list item layout for devices older than Honeycomb int layout = Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB ? android.R.layout.simple_list_item_activated_1 : android.R.layout.simple_list_item_1; Bundle args = getArguments(); if (args == null) { Toast.makeText(getActivity(), "arguments is null " , Toast.LENGTH_LONG).show(); } else { Toast.makeText(getActivity(), "text " + args , Toast.LENGTH_LONG).show(); } // Create an array adapter for the list view, using the Ipsum headlines array setListAdapter(new ArrayAdapter<String>(getActivity(), layout, Ipsum.Headlines)); } 

这是结果

在这里输入图像说明

我有同样的问题,但解决了它:)

我的问题是我在Activity的XML布局中有<fragment android:name="">元素。 因此,在Java代码中的调用之前调用片段的onCreate(),因此不设置参数。

我从我的XML布局中删除了<fragment>元素,它工作!

我解决了它。 看起来像从MainActivity.java发送数据到HeadlinesFragment.java的唯一方法是来自callback(如果其他人知道其他方式,请贡献,然后我们有其他方式,除了这个之外,帮助其他方式这种问题)。

MainActivity.java的函数public Bundle getBundle() {} ,然后在HeadlinesFragment.java上设置interface部分,并添加public Bundle getBundle(); 最后,从HeadlinesFragment.java的onCreate调用它。

什么令我困惑的是fragment.setArguments(getIntent().getExtras()); 在MainActivity.java的onCreate 。 他们把那个代码放在那里,我相信它会起作用,因为它来自Android官方开发者指南和API http://developer.android.com/training/basics/fragments/fragment-ui.html ,但是它没有工作(现在我相信这段代码不会做任何事情)。 所以,任何人阅读教程或从那里取样,拿一粒盐!

下面的代码,所以每个人都可以理解它。

MainActivity.java

  /* * Copyright (C) 2012 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.example.android.fragments; import android.os.Bundle; import android.support.v4.app.FragmentActivity; import android.support.v4.app.FragmentTransaction; import android.widget.Toast; public class MainActivity extends FragmentActivity implements HeadlinesFragment.OnHeadlineSelectedListener { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.news_articles); // Check whether the activity is using the layout version with // the fragment_container FrameLayout. If so, we must add the first fragment if (findViewById(R.id.fragment_container) != null) { // However, if we're being restored from a previous state, // then we don't need to do anything and should return or else // we could end up with overlapping fragments. if (savedInstanceState != null) { return; } Toast.makeText(getApplicationContext(), "activity", Toast.LENGTH_LONG).show(); // Create an instance of ExampleFragment HeadlinesFragment fragment = new HeadlinesFragment(); // In case this activity was started with special instructions from an Intent, // pass the Intent's extras to the fragment as arguments fragment.setArguments(getIntent().getExtras()); // Add the fragment to the 'fragment_container' FrameLayout getSupportFragmentManager().beginTransaction() .replace(R.id.fragment_container, fragment).commit(); } } public void onArticleSelected(int position) { // The user selected the headline of an article from the HeadlinesFragment // Capture the article fragment from the activity layout ArticleFragment articleFrag = (ArticleFragment) getSupportFragmentManager().findFragmentById(R.id.article_fragment); if (articleFrag != null) { // If article frag is available, we're in two-pane layout... // Call a method in the ArticleFragment to update its content articleFrag.updateArticleView(position); } else { // If the frag is not available, we're in the one-pane layout and must swap frags... // Create fragment and give it an argument for the selected article ArticleFragment newFragment = new ArticleFragment(); Bundle args = new Bundle(); args.putInt(ArticleFragment.ARG_POSITION, position); newFragment.setArguments(args); FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); // Replace whatever is in the fragment_container view with this fragment, // and add the transaction to the back stack so the user can navigate back transaction.replace(R.id.fragment_container, newFragment); transaction.addToBackStack(null); // Commit the transaction transaction.commit(); } } public Bundle getBundle() { Bundle args = new Bundle(); args.putString("category", "cloths"); args.putString("item", "shirts"); return args; } } 

HeadlinesFragment.java

  /* * Copyright (C) 2012 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.example.android.fragments; import android.app.Activity; import android.os.Build; import android.os.Bundle; import android.support.v4.app.ListFragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.ArrayAdapter; import android.widget.ListView; import android.widget.Toast; public class HeadlinesFragment extends ListFragment { OnHeadlineSelectedListener mCallback; // The container Activity must implement this interface so the frag can deliver messages public interface OnHeadlineSelectedListener { /** Called by HeadlinesFragment when a list item is selected */ public void onArticleSelected(int position); public Bundle getBundle(); } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Bundle bundle = mCallback.getBundle(); Toast.makeText(getActivity(), "headline fragment " + bundle, Toast.LENGTH_LONG).show(); // We need to use a different list item layout for devices older than Honeycomb int layout = Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB ? android.R.layout.simple_list_item_activated_1 : android.R.layout.simple_list_item_1; // Create an array adapter for the list view, using the Ipsum headlines array setListAdapter(new ArrayAdapter<String>(getActivity(), layout, Ipsum.Headlines)); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { return super.onCreateView(inflater, container, savedInstanceState); } @Override public void onStart() { super.onStart(); // When in two-pane layout, set the listview to highlight the selected list item // (We do this during onStart because at the point the listview is available.) if (getFragmentManager().findFragmentById(R.id.article_fragment) != null) { getListView().setChoiceMode(ListView.CHOICE_MODE_SINGLE); } } @Override public void onAttach(Activity activity) { super.onAttach(activity); // This makes sure that the container activity has implemented // the callback interface. If not, it throws an exception. try { mCallback = (OnHeadlineSelectedListener) activity; } catch (ClassCastException e) { throw new ClassCastException(activity.toString() + " must implement OnHeadlineSelectedListener"); } } @Override public void onListItemClick(ListView l, View v, int position, long id) { // Notify the parent activity of selected item mCallback.onArticleSelected(position); // Set the item as checked to be highlighted when in two-pane layout getListView().setItemChecked(position, true); } } 

它看起来像你插入一个键和值对你的包。 您可能需要引用getArguments().getString(category);中的getArguments().getString(category);

根据putString的文档:插入一个string值到这个Bundle的映射中,replace给定键的任何现有值。 键或值可能为空。

参数key一个String,或者null值一个String,或者null