我有ArrayList<String>我在共享偏好中保存在活动A 中。我从第二个活动（ ListActivity ）访问该列表。 活动A 为结果启动 ListActivity 。单击某个项目时， ListActivity 会将该位置的字符串发送到活动A 以供使用。长按可让您删除。
当我从列表中删除时，我想在sharedpreferences中保存新的（最新的）列表。请！我怎样才能做到这一点？我只需要弹出列表，你做你的事情，并在保存最新列表后消失。
我尝试了很多方法（此时代码拼凑而成）但删除项目后，当我再次打开 ListActivity 时，删除的项目仍然存在。
我的代码如下......
活动A：
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_write);
...
lyricTitle = (AutoCompleteTextView) findViewById(R.id.lyricTitle);
...
lyricTitle.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
// load in song when selected from auto-complete list
lyricHolder.setText(openSongFile(lyricTitle.getText().toString()));
}
});
lyricHolder = (EditText) findViewById(R.id.lyricHolder);
newSongBtn = (ImageView) findViewById(R.id.newSongBtn);
newSongBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (areFieldsNull(lyricTitle.getText().toString(),
lyricHolder.getText().toString()))
alertEmpty.show();
else {
/** There is some redundancy within performSave() here */
performSave();
lyricTitle.setText("");
lyricHolder.setText("");
}
}
});
...
findBtn = (Button) findViewById(R.id.findBtn);
findBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent showListIntent = new Intent(getApplicationContext(), pickActivity.class);
startActivityForResult(showListIntent, GET_SONG_CODE);
Log.i("TAG1", "Starting pickActivity.class for result");
}
});
saveBtn = (Button) findViewById(R.id.saveBtn);
saveBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
performSave();
}
});
...
// init sharedPreferences
colorPref = getSharedPreferences(COLOR_PREF, MODE_PRIVATE);
titlePref = getSharedPreferences(TITLE_PREF, MODE_PRIVATE);
externalSDPref = getSharedPreferences(EXTERNAL_SD_PREF, MODE_PRIVATE);
// load defaults of sharedPreferences
titleList = new ArrayList<>();
try {
titleList = (ArrayList<String>) ObjectSerializer
.deserialize(titlePref.getString(TITLE_PREF, ObjectSerializer.serialize(new ArrayList<String>())));
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
mSetTitleListAdapter(titleList);
...
} //end onCreate
private void mSetTitleListAdapter(ArrayList<String> List) {
autoCompleteAdapter = new ArrayAdapter<>(
this,
android.R.layout.simple_list_item_1,
List
);
lyricTitle.setAdapter(autoCompleteAdapter);
}
...
private boolean areFieldsNull(String title, String song) {
// check if the text fields are empty
return (
title.isEmpty()||
title.equals(" ")||
title.equals(" ")||
song.isEmpty()||
song.equals(" ")||
song.equals(" ")
);
}
private void performSave() {
String title = lyricTitle.getText().toString();
String song = lyricHolder.getText().toString();
if(!areFieldsNull(title, song)) {
saveSongFile(title, song);
alertSave.show();
}
else
alertEmpty.show();
}
private void saveTitleArray() {
// save string array list in shared prefs
try {
prefEditor = titlePref.edit();
prefEditor.putString(TITLE_PREF, ObjectSerializer.serialize(titleList));
} catch (IOException e) {
e.printStackTrace();
}
prefEditor.apply();
}
private void saveSongFile(String title, String song) {
BufferedWriter bufferWriter = null;
try {
FileOutputStream fos = openFileOutput(title, Context.MODE_PRIVATE);
bufferWriter = new BufferedWriter(new OutputStreamWriter(fos));
bufferWriter.write(song);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
bufferWriter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(isExternalStoragePresent()&&externalSD_box.isChecked()){
// save to the SD card IF SD is found AND enableSD_box is checked
File path = Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
File songFile = new File (path, title + ".txt");
try {
OutputStream os = new FileOutputStream(songFile);
byte[] data = song.getBytes();
os.write(data);
} catch (IOException e) {
e.printStackTrace();
}
}
// new songs (but not updated songs) go to top
if (!titleList.contains(title))
titleList.add(0, title);
mSetTitleListAdapter(titleList);
saveTitleArray();
}
private String openSongFile(String title){
BufferedReader bufferReader = null;
StringBuilder builder = new StringBuilder();
try {
FileInputStream fis = openFileInput(title);
bufferReader = new BufferedReader(new InputStreamReader(fis));
String line;
while ((line = bufferReader.readLine()) != null) {
builder.append(line + "\r\n");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
bufferReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return builder.toString();
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// when pickActivity ListView returns result
Log.i("TAG1", "Activity data returned from pickActivity.class");
if (requestCode == GET_SONG_CODE && resultCode == RESULT_OK) {
String title = data.getData().toString();
lyricTitle.setText(title);
lyricHolder.setText(openSongFile(title));
Log.i("TAG1", "Result success\nSong loaded into edittext");
Toast.makeText(this, "\""+title+"\""+" selected", Toast.LENGTH_SHORT).show();
}
}
ListActivity：
public class pickActivity extends ListActivity {
ArrayList<String> songListArray;
SharedPreferences titlePref;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_pick_song);
Log.i("TAG2", "pickActivity.class created");
// init string array from blank list or sharedPref saved data
titlePref = getSharedPreferences(writeActivity.TITLE_PREF, MODE_PRIVATE);
songListArray = new ArrayList<>();
try {
songListArray = (ArrayList<String>) ObjectSerializer
.deserialize(titlePref.getString(writeActivity.TITLE_PREF, ObjectSerializer.serialize(new ArrayList<String>())));
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
mSetListAdapter(songListArray);
Log.i("TAG2", "Extra received and set");
mSetListAdapter(songListArray);
getListView().setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
Log.i("TAG2", "onItemLongClick()");
final AlertDialog.Builder confirmDel = new AlertDialog.Builder(pickActivity.this);
confirmDel.setTitle("Delete Song")
.setIcon(R.mipmap.ic_keeper)
.setMessage("Are you sure you want " +
"\"" + songListArray.get(position) +
"\"" + " gone?")
.setPositiveButton("CANCEL", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// system default is dismiss()
}
})
.setNegativeButton("YES", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// delete song, title, then update title list
getApplicationContext().deleteFile(songListArray.get(position));
songListArray.remove(position);
Log.i("TAG2", "Item deleted from list");
updateSharedPref(titlePref, writeActivity.TITLE_PREF, songListArray);
mSetListAdapter(songListArray);
Toast.makeText(
getApplicationContext(),
"Deleted",
Toast.LENGTH_SHORT).show();
}
});
confirmDel.create().show();
return true;
}
});
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
Log.i("TAG2", "onListItemClick()");
Intent resultIntent = new Intent(EXTRA_NAME, Uri.parse(songListArray.get(position)));
setResult(RESULT_OK, resultIntent);
finish();
}
private void mSetListAdapter(ArrayList<String> list) {
final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<>(
this,
android.R.layout.simple_list_item_1,
list
);
setListAdapter(arrayAdapter);
Log.i("TAG2", "ArrayList adapter set");
}
private void updateSharedPref(SharedPreferences sharedPref,
String prefFileName,
ArrayList<String> list) {
SharedPreferences.Editor editor = sharedPref.edit();
try {
editor.putString(prefFileName, ObjectSerializer.serialize(list));
} catch (IOException e) {
e.printStackTrace();
}
editor.commit();
Log.i("TAG2", "SharedPref updated!");
}
}
答案 0 :(得分：0)
老实说，在这种情况下，源代码会有很多帮助......
我最好的猜测（没有任何代码），请确保你打电话
editor.apply();
而不是
editor.commit();