NoteFragment.java
public class NoteFragment extends Fragment {
private ListView noteListView;
private Note note;
List <Note> notes = new ArrayList<Note>();
private Button add;
private NoteAdapter noteAdapter;
private String title = "title";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_note, container, false);
noteListView = (ListView) view.findViewById(R.id.noteListView);
initWidgets();
loadFromDBtoMemory();
setNoteAdapter();
return view;
}
private void initWidgets() {
noteListView = getActivity().findViewById(R.id.noteListView);
add = getActivity().findViewById(R.id.add_fragment);
}
private void loadFromDBtoMemory() {
SQLiteManager sqLiteManager = new SQLiteManager(getActivity());
sqLiteManager.populateNoteListArray("");
}
private void setNoteAdapter() {
NoteAdapter noteAdapter = new NoteAdapter(getContext().getApplicationContext(), Note.nonDeletedNotes());
noteListView.setAdapter(noteAdapter);
}
@Override
public void onResume() {
super.onResume();
setNoteAdapter();
}
NoteAdapter.java
public class NoteAdapter extends ArrayAdapter<Note> {
public NoteAdapter(Context context, List<Note> notes){
super(context, 0,notes);
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
Note note = getItem(position);
if (convertView == null) {
convertView = LayoutInflater.from(getContext()).inflate(R.layout.note_cell, parent, false);
}
TextView title = convertView.findViewById(R.id.cellTitle);
TextView description = convertView.findViewById(R.id.cellDesc);
TextView realTime = convertView.findViewById(R.id.realTime);
ImageView smallImg = convertView.findViewById(R.id.smallImg);
TextView impTextView = convertView.findViewById(R.id.ImpTextView);
title.setText(note.getTitle());
description.setText(note.getDescription());
String formatedTime = DateFormat.getDateTimeInstance().format(note.getRealTime());
realTime.setText(formatedTime);
Uri uri = Uri.parse(note.getUri());
smallImg.setImageURI(null);
smallImg.setImageURI(uri);
if (Objects.equals(note.getSelection(), "very important")) {
impTextView.setText(note.getSelection());
impTextView.setBackgroundColor(Color.rgb(255, 0, 0));
}
if (Objects.equals(note.getSelection(), "important")) {
impTextView.setText(note.getSelection());
impTextView.setBackgroundColor(Color.rgb(255, 255, 153));
}
if (Objects.equals(note.getSelection(), "not very important")) {
impTextView.setText(note.getSelection());
impTextView.setBackgroundColor(Color.rgb(240, 248, 255));
}
return convertView;
}
}
AddFragment.java
public class AddFragment extends Fragment {
private EditText titleEditText, descEditText;
private Note selectedNote;
private ImageView newImg;
private FloatingActionButton addImg;
private ConstraintLayout imgContainer;
private final int PICK_IMAGE_CODE = 123;
private String tempUri = "empty";
private String[] importancy = {"very important", "important", "not very important"};
private Spinner spinner;
private String selectedItem;
private View view;
private Button saveNote;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_add, container, false);
SQLiteManager sqLiteManager = new SQLiteManager(getActivity());
spinner = view.findViewById(R.id.importancy);
titleEditText = view.findViewById(R.id.titleEditText);
descEditText = view.findViewById(R.id.descriptionEditText);
addImg = view.findViewById(R.id.addImg);
imgContainer = view.findViewById(R.id.imgContainer);
newImg = view.findViewById(R.id.newImg);
spinner = view.findViewById(R.id.importancy);
saveNote = view.findViewById(R.id.saveNote);
saveNote.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
saveNote(view);
}
});
ArrayAdapter<String> importancyAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_spinner_item, importancy);
importancyAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(importancyAdapter);
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
selectedItem = adapterView.getSelectedItem().toString();
for (int u = 0; u < importancy.length; u ) {
if (importancy[i] == "very important")
view.setBackgroundColor(Color.rgb(255, 0, 0));
if (importancy[i] == "important")
view.setBackgroundColor(Color.rgb(255, 255, 153));
if (importancy[i] == "not very important")
view.setBackgroundColor(Color.rgb(240, 248, 255));
}
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
return view;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
public void saveNote(View view) {
SQLiteManager sqLiteManager = new SQLiteManager(getActivity());
String title = String.valueOf(titleEditText.getText());
String desc = String.valueOf(descEditText.getText());
long realTime = System.currentTimeMillis();
String uri = String.valueOf(tempUri);
String selection = String.valueOf(selectedItem);
if(selectedNote == null){
int id = Note.noteArrayList.size();
Note newNote = new Note(id, title, desc, realTime, uri, selection);
Note.noteArrayList.add(newNote);
System.out.println(Note.noteArrayList);
sqLiteManager.addNoteToDatabase(newNote);
Toast.makeText(getActivity().getApplicationContext(), "Note saved", Toast.LENGTH_SHORT).show();
}
else {
selectedNote.setTitle(title);
selectedNote.setDescription(desc);
selectedNote.setRealTime(realTime);
selectedNote.setUri(uri);
selectedNote.setSelection(selection);
sqLiteManager.updateNoteInDB(selectedNote);
}
}
}
Note.java
public class Note {
public static ArrayList<Note> noteArrayList = new ArrayList<>();
public static String NOTE_EDIT_EXTRA = "noteEdit";
private int id;
private String title;
private String description;
private long realTime;
private String uri = "empty";
private String selection;
private Date deleted;
public Note(int id, String title, String description, long realTime, String uri, String selection, Date deleted) {
this.id = id;
this.title = title;
this.description = description;
this.realTime = realTime;
this.uri = uri;
this.selection = selection;
this.deleted = deleted;
}
public Note(int id, String title, String description, long realTime, String uri, String selection) {
this.id = id;
this.title = title;
this.description = description;
this.realTime = realTime;
this.uri = uri;
this.selection = selection;
deleted = null;
}
public static Note getNoteForID(int passedNoteID) {
for(Note note : noteArrayList){
if(note.getId() == passedNoteID){
return note;
}
}
return null;
}
public static ArrayList<Note> nonDeletedNotes(){
ArrayList<Note> nonDeleted = new ArrayList<>();
for(Note note : noteArrayList){
if(note.getDeleted() == null){
nonDeleted.add(note);
}
}
return nonDeleted;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public long getRealTime() {return realTime; }
public void setRealTime(long realTime) {this.realTime = realTime;}
public String getUri (){return uri;}
public void setUri(String uri) {this.uri = uri;}
public String getSelection(){return selection;}
public void setSelection(String selection) {this.selection = selection;}
public Date getDeleted() {
return deleted;
}
public void setDeleted(Date deleted) {
this.deleted = deleted;
}
}
** SQLiteManager.java **
public class SQLiteManager extends SQLiteOpenHelper {
private static SQLiteManager sqLiteManager;
private static final String DATABASE_NAME = "NoteDB";
private static final int DATABASE_VERSION = 3;
private static final String TABLE_NAME = "Note";
private static final String COUNTER = "Counter";
private static final String ID_FIELD = "id";
private static final String TITLE_FIELD = "title";
private static final String DESC_FIELD = "desc";
private static final String REAL_TIME = "realtime";
private static final String IMAGE_URI = "uri";
private static final String SELECTED_ITEM = "selection";
private static final String DELETED_FIELD = "deleted";
@SuppressLint("SimpleDateFormat")
private static final DateFormat dateFormat = new SimpleDateFormat("MM-dd-yyyy HH:mm:ss");
public SQLiteManager(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public static SQLiteManager instanceOfDatabase(Context context) {
if (sqLiteManager == null) {
sqLiteManager = new SQLiteManager(context);
}
return sqLiteManager;
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
StringBuilder sql;
sql = new StringBuilder()
.append(" CREATE TABLE ")
.append(TABLE_NAME)
.append("(")
.append(COUNTER)
.append(" INTEGER PRIMARY KEY AUTOINCREMENT, ")
.append(ID_FIELD)
.append(" INT, ")
.append(TITLE_FIELD)
.append(" TEXT, ")
.append(DESC_FIELD)
.append(" TEXT, ")
.append(REAL_TIME)
.append(" TEXT, ")
.append(IMAGE_URI)
.append(" TEXT, ")
.append(SELECTED_ITEM)
.append(" TEXT, ")
.append(DELETED_FIELD)
.append(" TEXT)");
sqLiteDatabase.execSQL(sql.toString());
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
//if(newVersion ==2)
sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " TABLE_NAME );
onCreate(sqLiteDatabase);
//sqLiteDatabase.execSQL("ALTER TABLE " "Note" " ADD COLUMN " REAL_TIME " TEXT");
}
public void addNoteToDatabase(Note note) {
SQLiteDatabase sqLiteDatabase = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(ID_FIELD, note.getId());
contentValues.put(TITLE_FIELD, note.getTitle());
contentValues.put(DESC_FIELD, note.getDescription());
contentValues.put(REAL_TIME, String.valueOf(note.getRealTime()));
contentValues.put(IMAGE_URI, note.getUri());
contentValues.put(SELECTED_ITEM, note.getSelection());
contentValues.put(DELETED_FIELD, getStringFromDate(note.getDeleted()));
sqLiteDatabase.insert(TABLE_NAME, null, contentValues);
}
public void populateNoteListArray(String title_field) {
SQLiteDatabase sqLiteDatabase = this.getReadableDatabase();
String Selection = "title" " like ?";
Cursor result = sqLiteDatabase.query(TABLE_NAME, null, Selection, new String[]{"%" title_field "%"}, null, null, null);
while (result.moveToNext()) {
int id = result.getInt(1);
String title = result.getString(2);
String desc = result.getString(3);
String time = result.getString(4);
long realtime = Long.parseLong(time);
String imgUri = result.getString(5);
String selection = result.getString(6);
String stringDeleted = result.getString(7);
Date deleted = getDatefromString(stringDeleted);
Note note = new Note(id, title, desc, realtime, imgUri, selection, deleted);
Note.noteArrayList.add(note);
}
}
public void updateNoteInDB(Note note){
SQLiteDatabase sqLiteDatabase = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(ID_FIELD, note.getId());
contentValues.put(TITLE_FIELD, note.getTitle());
contentValues.put(DESC_FIELD, note.getDescription());
contentValues.put(SELECTED_ITEM, note.getSelection());
contentValues.put(DELETED_FIELD, getStringFromDate(note.getDeleted()));
sqLiteDatabase.update(TABLE_NAME, contentValues, ID_FIELD " =?", new String[]{String.valueOf(note.getId())});
}
private String getStringFromDate(Date date) {
if(date == null){
return null;
}
return dateFormat.format(date);
}
private Date getDatefromString(String string){
try
{
return dateFormat.parse(string);
}
catch (ParseException | NullPointerException e)
{
return null;
}
}
問題：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: andrii.sosnytskyi.nure.mynote_v2, PID: 16771
java.lang.RuntimeException: Unable to start activity ComponentInfo{andrii.sosnytskyi.nure.mynote_v2/andrii.sosnytskyi.nure.mynote_v2.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at andrii.sosnytskyi.nure.mynote_v2.NoteFragment.setNoteAdapter(NoteFragment.java:55)
at andrii.sosnytskyi.nure.mynote_v2.NoteFragment.onCreateView(NoteFragment.java:37)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2963)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:518)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:282)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2189)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2100)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:2002)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3138)
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:3072)
at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:251)
at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:502)
at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:248)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1334)
at android.app.Activity.performStart(Activity.java:7029)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2741)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
請解釋我如何解決它。
uj5u.com熱心網友回復：
根據堆疊跟蹤，在此方法noteListView中為空：
private void setNoteAdapter() {
NoteAdapter noteAdapter = new NoteAdapter(getContext().getApplicationContext(), Note.nonDeletedNotes());
noteListView.setAdapter(noteAdapter);
}
轉載請註明出處，本文鏈接：https://www.uj5u.com/gongcheng/531995.html
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