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我應該做一個筆記/提醒類應用程序。我的問題是，當我退出應用程序時，listview（它應該包含添加的註釋）是空的。我要在這裏發佈我的所有代碼。即使在不使用數據庫的情況下退出應用程序後，我仍然如何保留筆記？重新啓動應用程序Android後，Listview再次爲空
MainActivity.java
public class MainActivity extends AppCompatActivity {
private NoteAdapter mNoteAdapter;
private boolean mSound;
private int mAnimOption;
private SharedPreferences mPrefs;
Animation mAnimFlash;
Animation mAnimFadeIn;
int mIDBeep = -1;
SoundPool nsp;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
AudioAttributes audioAttributes = new AudioAttributes.Builder()
.setUsage(AudioAttributes.USAGE_MEDIA)
.setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
.build();
nsp = new SoundPool.Builder().setMaxStreams(5).setAudioAttributes(audioAttributes).build();
}else{
// sp = new SoundPool(5, AudioAttributes.STREAM_MUSIC,0);
}
try{
AssetManager assetManager = this.getAssets();
AssetFileDescriptor descriptor;
//Load our fx
descriptor = assetManager.openFd("fx1.ogg");
mIDBeep = nsp.load(descriptor,0);
} catch (IOException e) {
Log.e("error", "failed to load sound files");
mNoteAdapter = new NoteAdapter();
ListView listNote = (ListView)findViewById(R.id.listView);
listNote.setAdapter(mNoteAdapter);
listNote.setLongClickable(true);
listNote.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
mNoteAdapter.deleteNote(position);
return true;
}
});
listNote.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int whichItem, long id) {
if (mSound){
nsp.play(mIDBeep, 1,1,0,0,1);
}
Note tempNote = mNoteAdapter.getItem(whichItem);
DialogShowNote dialog = new DialogShowNote();
dialog.sendNoteSelected(tempNote);
dialog.show(getFragmentManager(), "");
}
});
}}
public void createNewNote(Note n) {
mNoteAdapter.addNote(n);
}
public void addNote(View view) {
DialogNewNote dialog = new DialogNewNote();
dialog.show(getFragmentManager(), "");
}
public void viewSettings(View view){
Intent intent = new Intent(this, SettingsActivity.class);
startActivity(intent);
}
public class NoteAdapter extends BaseAdapter{
private JSONSerializer mSerializer;
List<Note> noteList = new ArrayList<Note>();
public NoteAdapter(){
mSerializer = new JSONSerializer("NotetoSelf.json",MainActivity.this.getApplicationContext());
try{
noteList= mSerializer.load();
}catch (Exception e){
noteList = new ArrayList<Note>();
Log.e("Error loading notes: ","",e);
}
}
public void saveNote(){
try{
mSerializer.save(noteList);
}catch (Exception e){
Log.e("Error Saving notes: ","",e);
}
}
public int getCount() {
return noteList.size();
}
public Note getItem(int whichItem) {
return noteList.get(whichItem);
}
public long getItemId(int whichItem) {
return whichItem;
}
public View getView(int whichItem, View view, ViewGroup viewGroup){
if(view == null){
LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = inflater.inflate(R.layout.list_item, viewGroup, false);
}
//Grab a referece to all our TextView and ImageView Widgets
TextView txtTitle = (TextView) view.findViewById(R.id.txtTitle);
TextView txtDescription = (TextView) view.findViewById(R.id.txtDescription);
ImageView ivImportant = (ImageView) view.findViewById(R.id.imageViewImportant);
ImageView ivToDo = (ImageView) view.findViewById(R.id.imageTodo);
ImageView ivIdea = (ImageView) view.findViewById(R.id.imageViewIdea);
Note tempNote = noteList.get(whichItem);
if(!tempNote.ismImportant() && mAnimOption != SettingsActivity.NONE){
view.setAnimation(mAnimFlash);
}
else{
view.setAnimation(mAnimFadeIn);
}
if(!tempNote.ismImportant()){
ivImportant.setVisibility(View.GONE);
}
if(!tempNote.ismTodo()){
ivToDo.setVisibility(View.GONE);
}
if(!tempNote.ismIdea()){
ivIdea.setVisibility(View.GONE);
}
txtTitle.setText(tempNote.getmTitle());
txtTitle.setText(tempNote.getmDescription());
return view;
}
public void deleteNote(int n){
noteList.remove(n);
notifyDataSetChanged();
}
public void addNote(Note n){
noteList.add(n);
notifyDataSetChanged();
}
}
protected void onResume(){
super.onResume();
mPrefs = getSharedPreferences("Note to Self", MODE_PRIVATE);
mSound = mPrefs.getBoolean("sound", true);
mAnimOption = mPrefs.getInt("anim option",SettingsActivity.FAST);
mAnimFlash = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.flash);
mAnimFadeIn= AnimationUtils.loadAnimation(getApplicationContext(), R.anim.fade_in);
//set the rate of flash based on settings
if(mAnimOption == SettingsActivity.FAST) {
mAnimFlash.setDuration(100);
Log.i("anime = ", "" + mAnimOption);
}else if(mAnimOption == SettingsActivity.SLOW)
{
mAnimFlash.setDuration(1000);
Log.i("anime = ", "" + mAnimOption);
}
mNoteAdapter.notifyDataSetChanged();;
}
protected void onPause(){
}
}
Note.java
public class Note {
private String mTitle;
private String mDescription;
private boolean mIdea;
private boolean mTodo;
private boolean mImportant;
private static final String JSON_TITLE = "title";
private static final String JSON_DESCRIPTION = "description";
private static final String JSON_IDEA = "idea";
private static final String JSON_TODO= "todo";
private static final String JSON_IMPORTANT = "important";
//constructor
public Note(JSONObject jo) throws JSONException{
mTitle = jo.getString(JSON_TITLE);
mDescription = jo.getString(JSON_DESCRIPTION);
mIdea = jo.getBoolean(JSON_IDEA);
mTodo = jo.getBoolean(JSON_TODO);
mImportant = jo.getBoolean(JSON_IMPORTANT);
}
public Note(){
}
public JSONObject convertToJSON() throws JSONException{
JSONObject jo = new JSONObject();
jo.put(JSON_TITLE,mTitle);
jo.put(JSON_DESCRIPTION,mDescription);
jo.put(JSON_IDEA,mIdea);
jo.put(JSON_TODO,mTodo);
return jo;
}
public String getmTitle() {
return mTitle;
}
public void setmTitle(String mTitle) {
this.mTitle = mTitle;
}
public String getmDescription() {
return mDescription;
}
public void setmDescription(String mDescription) {
this.mDescription = mDescription;
}
public boolean ismIdea() {
return mIdea;
}
public void setmIdea(boolean mIdea) {
this.mIdea = mIdea;
}
public boolean ismTodo() {
return mTodo;
}
public void setmTodo(boolean mTodo) {
this.mTodo = mTodo;
}
public boolean ismImportant() {
return mImportant;
}
public void setmImportant(boolean mImportant) {
this.mImportant = mImportant;
}
}
JSONserializer.java
public class JSONSerializer {
private String mFilename;
private Context mContext;
public JSONSerializer(String fn, Context con){
mFilename = fn;
mContext = con;
}
public void save(List<Note> notes)throws IOException, JSONException{
//Make an array in JSON fomat
JSONArray jArray = new JSONArray();
//And load it with the notes
for(Note n : notes) {
jArray.put(n.convertToJSON());
//Now write it to the private disk space of our app
Writer writer = null;
try{
OutputStream out = mContext.openFileOutput(mFilename,mContext.MODE_PRIVATE);
writer = new OutputStreamWriter(out);
writer.write(jArray.toString());
}finally {
if(writer != null){
writer.close();
}
}
}
}
public ArrayList<Note> load() throws IOException,JSONException{
ArrayList<Note> noteList = new ArrayList<Note>();
BufferedReader reader = null;
try{
InputStream in = mContext.openFileInput(mFilename);
reader = new BufferedReader(new InputStreamReader(in));
StringBuilder jsonString = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null)
jsonString.append(line);
JSONArray jArray = (JSONArray)new JSONTokener(jsonString.toString()).nextValue();
for (int i = 0; i < jArray.length(); i++)
noteList.add(new Note(jArray.getJSONObject(i)));
}catch (FileNotFoundException e){
//we will ignore this one, since it happens
//when we start fresh, You could add a log here.
}finally{
if (reader != null)
reader.close();
}
return noteList;
}
}
DialogNewNote.java
public class DialogNewNote extends DialogFragment {
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
View dialogView = inflater.inflate(R.layout.dialog_new_note, null);
final EditText editTitle = (EditText) dialogView.findViewById(R.id.editTitle);
final EditText editDescription = (EditText) dialogView.findViewById(R.id.editDescription);
final CheckBox checkBoxIdea = (CheckBox) dialogView.findViewById(R.id.checkBoxIdea);
final CheckBox checkBoxToDo = (CheckBox) dialogView.findViewById(R.id.checkBoxToDo);
final CheckBox checkBoxImportant = (CheckBox) dialogView.findViewById(R.id.checkBoxImportant);
Button btnCancel = (Button) dialogView.findViewById(R.id.btnCancel);
Button btnOk = (Button) dialogView.findViewById(R.id.btnOk);
builder.setView(dialogView).setMessage("Add a new note");
btnCancel.setOnClickListener(new View.OnClickListener(){
public void onClick(View view){
dismiss();
}
});
btnOk.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
Note newNote = new Note();
newNote.setmTitle(editTitle.getText().toString());
newNote.setmDescription(editDescription.getText().toString());
newNote.setmIdea(checkBoxIdea.isChecked());
newNote.setmTodo(checkBoxToDo.isChecked());
newNote.setmImportant(checkBoxImportant.isChecked());
MainActivity callingActivity = (MainActivity) getActivity();
callingActivity.createNewNote(newNote);
dismiss();
}
});
return builder.create();
}
}
DialogShowNote.java
public class DialogShowNote extends DialogFragment {
public Note mNote;
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
View dialogView = inflater.inflate(R.layout.dialog_show_note, null);
TextView txtTitle = (TextView)dialogView.findViewById(R.id.txtTitle);
TextView txtDescription = (TextView)dialogView.findViewById(R.id.txtDescription);
ImageView ivImportant = (ImageView)dialogView.findViewById(R.id.imageViewImportant);
ImageView ivtoDo = (ImageView)dialogView.findViewById(R.id.imageViewBlank);
ImageView ivIdea = (ImageView)dialogView.findViewById(R.id.imageViewIdea);
if (!mNote.ismImportant()) {
ivImportant.setVisibility(View.GONE);
}
if (!mNote.ismTodo()) {
ivtoDo.setVisibility(View.GONE);
}
if (!mNote.ismIdea()) {
ivIdea.setVisibility(View.GONE);
}
Button btnOK = (Button)dialogView.findViewById(R.id.btnOk);
builder.setView(dialogView).setMessage("Your Note");
btnOK.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dismiss();
}
});
return builder.create();
}
public void sendNoteSelected(Note noteSelected){
mNote = noteSelected;
}
}
你在哪裏存儲你的筆記？ –
當用戶添加一個筆記時，它會顯示在列表視圖上。我們的老師說使用JSONserializer.java將值保存在一個數組中。 –
如果你真的重新啓動應用程序，那麼信息將消失，除非你持久保存它，你有很多選擇：sqlite，mysql，sharedpreferences，sd卡，如果你只是想保存整個應用程序的數據，你可以使用實現可分類的類並將數據保存爲全局數據，並沿着活動傳遞對象。 – HaroldSer