使用bundle，seListAdapter运行时错误将ArrayList从片段传递到另一个片段（扩展ListFragment）
我已尝试使用静态变量为ArrayList但在ListFragment类中，而调试它的值为null。
我认为ListFragment是在初始化ArrayList之前创建的，这就是为什么它是null，但不确定。
建议我是否可以使用任何其他方式将膨胀的ArrayList从Fragment类发送到扩展ListFragment的其他Fragment类。
提前致谢。
目标（这是线索，需要做什么）
在Monday_fragment的onStart（）方法中，使用findByView（）方法在页面视图中查找保存条目按钮的标签。 使用对按钮的引用将setOnClickListener（）方法附加到保存按钮。 您需要在此方法中保存页面上EditText字段中包含的时间和日记条目字符串。
使用findViewById（）也可以获得对第一个EditText字段的引用，并使用它来获取字段的文本作为字符串并将其保存为字符串。 对下一个EditText – 日记条目重复此操作。 您将需要一个可公开访问的变量来存储当天（星期一……星期五）的参考，日期时间字符串和日记条目字符串。 使用这些字段创建一个新类（diaryLogs）来保存值和一个构造函数，它接受一个int（0 Mon，1 Tue，2 Wed etc）和两个字符串作为日期时间和日记条目来初始化一个对象的实例。 由于将在同一天进行多个条目，因此请使用ArrayList 来存储值。 由于此值将在片段之间共享，因此在MainActivity类中将变量声明为static。 使用ArrayList的.add（）方法将新的diaryLog添加到setOnClickListener（）方法中的ArrayList。 对其他日记页面片段重复此操作。
monday_list片段由ListView和用于返回Monday_fragment页面的按钮组成。 在monday_list xml文件中创建这些对象。 创建一个扩展ListFragment类的Monday_list_fragment。 在onCreateView（）方法中inflate（）monday_list资源。
在onCreate（）方法中，您需要提供单个字符串数组作为用于填充页面上ListView的setListAdapter（）方法中列表的源。 字符串位于MainActivity中的静态ListArray变量中。 但是，它们不是必需的forms，您必须解压缩diaryLog元素才能获得所需的字符串。 要做到这一点，你必须创建一个足够大的String数组来保存要显示的字符串。 由于这包含日期/时间字符串后跟日记条目字符串，因此每个diaryLog元素将有两个这样的字符串。 使用迭代器迭代ListArray。 将日期字符串和日记字符串字符串复制到本地字符串中。 然后使用此本地字符串作为setListAdapter（）的相关参数，以便ListView显示所需的字符串。
在MainActivity java文件中添加单击处理程序，以便单击Monday片段页面中的Save Diary Entries按钮可以使用FragmentManager使Monday_list_fragment可见。 还要在MainActivity中添加一个单击处理程序，以便单击Return to Monday Diary按钮返回到Monday_fragment页面。
UPDATE 类MainActivity
public class MainActivity extends Activity { public static int Monday=0; /*public static int Tuesday=1; public static int Wednesday=2; public static int Thursday=3; public static int Friday=4; public static String timeEntry; public static String entryEntered;*/ // public static ArrayList logs; //public static String[] entry; //public static String time; //public static String text; //public static String totalEntry; //public static ArrayList diaryLogs; //public static ArrayList test; //public static DiaryLogs[] entryLogs; //public static ArrayAdapter monAdapter; //public static ArrayList myStringList; //public static ArrayList entryLogs; public static ArrayList myStringList; public static ArrayList getMyStringList() { return myStringList; } public void setMyStringList(ArrayList myStringList) { this.myStringList = myStringList; } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Home_fragment hf = new Home_fragment(); fragmentTransaction.replace(android.R.id.content, hf); fragmentTransaction.commit(); setContentView(R.layout.activity_main); } public void monClick(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Monday_fragment mf = new Monday_fragment(); fragmentTransaction.replace(android.R.id.content, mf); fragmentTransaction.commit(); } public void tuesClick(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Tuesday_fragment tf = new Tuesday_fragment(); fragmentTransaction.replace(android.R.id.content, tf); fragmentTransaction.commit(); } public void wedClick(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Wednesday_fragment wf = new Wednesday_fragment(); fragmentTransaction.replace(android.R.id.content, wf); fragmentTransaction.commit(); } public void thursClick(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Thursday_fragment thf = new Thursday_fragment(); fragmentTransaction.replace(android.R.id.content, thf); fragmentTransaction.commit(); } public void friClick(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Friday_fragment ff = new Friday_fragment(); fragmentTransaction.replace(android.R.id.content, ff); fragmentTransaction.commit(); } public void next_Home_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Monday_fragment mf = new Monday_fragment(); fragmentTransaction.replace(android.R.id.content, mf); fragmentTransaction.commit(); } public void previous_Home_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Friday_fragment ff = new Friday_fragment(); fragmentTransaction.replace(android.R.id.content, ff); fragmentTransaction.commit(); } public void next_Mon_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Tuesday_fragment tf = new Tuesday_fragment(); fragmentTransaction.replace(android.R.id.content, tf); fragmentTransaction.commit(); } public void previous_Mon_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Friday_fragment ff = new Friday_fragment(); fragmentTransaction.replace(android.R.id.content, ff); fragmentTransaction.commit(); } public void next_Tues_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Wednesday_fragment wf = new Wednesday_fragment(); fragmentTransaction.replace(android.R.id.content, wf); fragmentTransaction.commit(); } public void previous_Tues_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Monday_fragment mf = new Monday_fragment(); fragmentTransaction.replace(android.R.id.content, mf); fragmentTransaction.commit(); } public void next_Wed_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Thursday_fragment thf = new Thursday_fragment(); fragmentTransaction.replace(android.R.id.content, thf); fragmentTransaction.commit(); } public void previous_Wed_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Tuesday_fragment tf = new Tuesday_fragment(); fragmentTransaction.replace(android.R.id.content, tf); fragmentTransaction.commit(); } public void next_Thurs_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Friday_fragment ff = new Friday_fragment(); fragmentTransaction.replace(android.R.id.content, ff); fragmentTransaction.commit(); } public void previous_Thurs_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Wednesday_fragment wf = new Wednesday_fragment(); fragmentTransaction.replace(android.R.id.content, wf); fragmentTransaction.commit(); } public void next_Fri_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Monday_fragment ff = new Monday_fragment(); fragmentTransaction.replace(android.R.id.content, ff); fragmentTransaction.commit(); } public void previous_Fri_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Thursday_fragment wf = new Thursday_fragment(); fragmentTransaction.replace(android.R.id.content, wf); fragmentTransaction.commit(); } public void home_Click(View view) { FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Home_fragment hf = new Home_fragment(); fragmentTransaction.replace(android.R.id.content, hf); fragmentTransaction.commit(); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // TODO Auto-generated method stub switch (item.getItemId()) { case R.id.action_profile: FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Profile_fragment pf = new Profile_fragment(); fragmentTransaction.replace(android.R.id.content, pf); fragmentTransaction.commit(); break; case R.id.action_saveEntries: break; case R.id.action_sendAllEntries: //call delete dialog deleteDialog(); break; } return false; } @Override public void onBackPressed() { new AlertDialog.Builder(this).setIcon(R.drawable.ic_launcher) .setTitle("Save entries to DB first?") .setNegativeButton("No", new OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { // TODO Auto-generated method stub // if no, close app MainActivity.this.finish(); } }) .setPositiveButton(android.R.string.ok, new OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { // TODO Auto-generated method stub // if ok, save entries to Database } }) .create().show(); } public void deleteDialog() { new AlertDialog.Builder(this).setIcon(R.drawable.ic_launcher) .setTitle("Are you sure? This will delete all entries.") .setNegativeButton(android.R.string.cancel, new OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { // TODO Auto-generated method stub } }) .setPositiveButton(android.R.string.ok, new OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { // TODO Auto-generated method stub } }) .create().show(); } } 自定义对象类DiaryLogs
public class DiaryLogs { //public static ArrayList entryLogs; String timeEntry, entryEntered; int day; // single constructor that takes an integer and two string public DiaryLogs(int day, String timeEntry, String entryEntered) { super(); this.day = day; this.timeEntry = timeEntry; this.entryEntered = entryEntered; } public String getTimeEntry() { return timeEntry; } public void setTimeEntry(String timeEntry) { this.timeEntry = timeEntry; } public String getEntryEntered() { return entryEntered; } public void setEntryEntered(String entryEntered) { this.entryEntered = entryEntered; } public int getDay() { return day; } public void setDay(int day) { this.day = day; } @Override public String toString() { // TODO Auto-generated method stub return this.timeEntry + "\n" + this.entryEntered; } }
UPDATE 类Monday_fragment
public class Monday_fragment extends Fragment { //public ArrayList myStringList; Bundle bundle; ArrayList entryLogs; EditText timeText; EditText entryText; DiaryLogs dl; String timeEntry; String entryEntered; ArrayList myStringList; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { return inflater.inflate(R.layout.monday_fragment, container, false); } @Override public void onViewCreated(View view, Bundle savedInstanceState) { currentDateTime(); super.onViewCreated(view, savedInstanceState); } public void currentDateTime() { EditText timeText = (EditText) getView().findViewById( R.id.dateTimeEText); SimpleDateFormat df = new SimpleDateFormat("d/M/yyyy:H:m"); String dateTime = df.format(Calendar.getInstance().getTime()); timeText.setText(dateTime); } /*public ArrayList toStringList(Collection entryLogs) { ArrayList stringList = new ArrayList(); for (DiaryLogs myobj : entryLogs) { stringList.add(myobj.toString()); } return stringList; }*/ public ArrayList toStringList(Collection entryLogs) { ArrayList stringList = MainActivity.getMyStringList(); for (DiaryLogs myobj : entryLogs) { String objctString = myobj.toString(); stringList.add(objctString); } ((MainActivity)getActivity()).setMyStringList(stringList); return stringList; } @Override public void onStart() { entryLogs = new ArrayList(); timeText = (EditText) getView().findViewById(R.id.dateTimeEText); entryText = (EditText) getView().findViewById(R.id.diaryEntryEText); Button saveBtn = (Button) getView() .findViewById(R.id.saveDiaryEntryBtn); saveBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub timeEntry = timeText.getText().toString(); entryEntered = entryText.getText().toString(); dl = new DiaryLogs(1, timeEntry, entryEntered); entryLogs.add(dl); //convert entryLogs to string array list //myStringList = toStringList(entryLogs); myStringList= MainActivity.getMyStringList(); myStringList = toStringList(entryLogs); //myStringList.addAll(toStringList(entryLogs)); Toast.makeText(getActivity(), "Entry added \n" + dl, Toast.LENGTH_SHORT).show(); entryText.setText(""); } } ); System.out.println(entryLogs); Button showBtn = (Button) getView().findViewById( R.id.showDiaryEntriesBtn); showBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub if (myStringList != null) { bundle = new Bundle(); FragmentManager fragmentManager = getFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Monday_list_fragment mlf = new Monday_list_fragment(); bundle.putStringArrayList("list", myStringList); mlf.setArguments(bundle); fragmentTransaction.replace(android.R.id.content, mlf); fragmentTransaction.commit(); } if (myStringList == null) { Toast.makeText(getActivity(), "No entry have been added yet", Toast.LENGTH_SHORT) .show(); } } }); super.onStart(); } @Override public void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); } }
类Monday_list_fragment
public class Monday_list_fragment extends ListFragment { ArrayList test; Bundle bundle; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); bundle = getArguments(); System.out.println(bundle); //test = bundle.getStringArrayList("list"); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // TODO Auto-generated method stub return inflater .inflate(R.layout.monday_list_fragment, container, false); } @Override public void onViewCreated(View view, Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); /* ArrayAdapter adapter = new ArrayAdapter(getActivity(), android.R.layout.simple_list_item_1, test); // once adapter set throws runtime error setListAdapter(adapter);*/ } }
当对象是Parcelable或Serializable时，您只能通过Bundle(or Intent)传递自定义对象的自定义对象或ArrayList。 如果您的片段处于相同的活动，那么还有一件事就是您传递数组的原因。 您只需在Activity为列表创建getter和setter ，然后在((Activity)getActivity).getArraylist()像((Activity)getActivity).getArraylist()一样访问它们。 用于创建对象Parcelable执行类似下面的操作。
import android.os.Parcel; import android.os.Parcelable; public class Address implements Parcelable { private String name, address, city, state, phone, zip; @Override public int describeContents() { return 0; } /* THE ORDER YOU READ OBJECT FROM AND WRITE OBJECTS TO YOUR PARCEL MUST BE THE SAME */ @Override public void writeToParcel(Parcel parcel, int i) { parcel.writeString(name); parcel.writeString(address); parcel.writeString(city); parcel.writeString(state); parcel.writeString(phone); parcel.writeString(zip); } public Address(Parcel p){ name = p.readString(); address = p.readString(); city = p.readString(); state = p.readString(); phone = p.readString(); zip = p.readString(); } // THIS IS ALSO NECESSARY public static final Creator CREATOR = new Creator() { @Override public Address createFromParcel(Parcel parcel) { return new Address(parcel); } @Override public Address[] newArray(int i) { return new Address[0]; } }; }
我已经看到了您给定链接的代码，这就是我发布新Ans的原因。 如果仔细阅读代码，有一点是在Monday_fragment声明了ArrayAdapter ，因此每次将此片段替换为其他时，此列表都会初始化。 因此，只需在MainActivity创建一个ArrayAdapter ，然后在相同的getter, setter创建getter, setter ，并在Monday_fragment更改您的方法ArrayList ，如下所示
public ArrayList toStringList(Collection entryLogs) { ArrayList stringList = ((MainActivity)getActivity()).getMyStringList(); for (DiaryLogs myobj : entryLogs) { String objctString = myobj.toString(); stringList.add(objctString); } ((MainActivity)getActivity()).setMyStringList(stringList); return stringList; }