can someone tell me what I am doing wrong here? I'm getting a null pointer exception for my listview... I am trying to use shared preferences to keep the values in my listview when I come back to it
Apologies if its a silly question but from my view everything is initialised and nothing is empty that shouldnt be, so it would be great if someone else could spot the issue :{)
public class MainActivity3 extends MainActivity{
EditText display;
ListView lv;
ArrayAdapter<String> adapter;
Button addButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
display = (EditText) findViewById(R.id.editText5);
lv = (ListView) findViewById(R.id.listView2);
addButton = (Button) findViewById(R.id.button21);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1);
lv.setAdapter(adapter);
LoadPreferences();
addButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
if (display.getText().toString().equals("")) {
}
else {
String task = display.getText().toString();
adapter.add(task);
adapter.notifyDataSetChanged();
SavePreferences("LISTS", task);
}
}
});
}
protected void SavePreferences(String key, String value) {
// TODO Auto-generated method stub
SharedPreferences data = PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = data.edit();
editor.putString(key, value);
editor.commit();
}
protected void LoadPreferences(){
SharedPreferences data = PreferenceManager.getDefaultSharedPreferences(this);
String dataSet = data.getString("LISTS", "None Available");
adapter.add(dataSet);
adapter.notifyDataSetChanged();
}
}
Apologies if its a silly question but from my view everything is initialised and nothing is empty that shouldnt be, so it would be great if someone else could spot the issue :{)
<ListView
android:layout_width="wrap_content"
android:layout_height="359dp"
android:id="#+id/listView2"
android:layout_alignParentTop="true"
android:layout_toStartOf="#+id/button21"
android:layout_alignRight="#+id/editText6"
android:layout_alignEnd="#+id/editText6" />
Could you put here your layout code?? Because the name of your components are not so good, So, maybe, you can be calling to another listView in another layout.
Could you try to delete your import line when you have android.R ? and then, import the correct.
If this doesn't work, up the code of layout, please :)
I am thinking about another solution. Go to listView and give it this id:
android:id="#android:id/list"
then, Go to MainActivity and write this:
public class YourClass extends ListActivity
So, to access to listView, you just have to use the next method:
getListView();
if you want to know more, see the oficial doc here
I hope It work
Related
I tried making a dynamic list where the user can add elements by writing a text and pushing a button. The user also should be able to delete elements by clicking on them for a longer time.
All of that is working fine, however everytime I close the App the created list is gone. I'm not sure what exactly is failing, either the loading or the saving.
Here is my code:
public class MainActivity extends AppCompatActivity {
private ArrayList<String> ModuleList;
private ArrayAdapter<String> MyAdapter;
private ListView listView;
private Button addButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
loadData();
addButton=findViewById(R.id.btnPlus);
MyAdapter=new ArrayAdapter<>(this, android.R.layout.simple_list_item_1);
listView=findViewById(R.id.listView);
listView.setAdapter(MyAdapter);
addButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
addModule(view);
saveData();
}
});
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener()
{
#Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id)
{
deleteItem(view, position);
saveData();
return true;
}
});
}
private void addModule(View view) {
EditText input =findViewById(R.id.textInput);
String itemText=input.getText().toString();
if(!(itemText.equals("")))
{
ModuleList.add(itemText);
MyAdapter.add(itemText);
MyAdapter.notifyDataSetChanged();
input.setText("");
}
else
{
Toast.makeText(getApplicationContext(),"Please insert Module...",Toast.LENGTH_LONG).show();
}
}
private void deleteItem(View view,int i)
{
Context context = getApplicationContext();
MyAdapter.remove(ModuleList.get(i));
ModuleList.remove(i);
MyAdapter.notifyDataSetChanged();
Toast.makeText(context, "Item Removed", Toast.LENGTH_LONG).show();
}
private void saveData()
{
SharedPreferences sharedPreferences=getSharedPreferences("Shared preferences",MODE_PRIVATE);
SharedPreferences.Editor editor=sharedPreferences.edit();
Gson gson=new Gson();
String json=gson.toJson(ModuleList);
editor.putString("Task List",json);
editor.apply();
}
private void loadData()
{
SharedPreferences sharedPreferences=getSharedPreferences("Shared preferences",MODE_PRIVATE);
Gson gson=new Gson();
String json=sharedPreferences.getString("Task List",null);
Type type= new TypeToken<ArrayList<String>>() {}.getType();
ModuleList=gson.fromJson(json,type);
if(ModuleList==null){
ModuleList=new ArrayList<>();
}
}
}
I can't see my mistake, but I'm new to all of this. So there might be something obvious missing.
Thank you very much.
i once encountered the same problem and the solution was
instead of
SharedPreferences sharedPreferences=getSharedPreferences("Shared preferences",MODE_PRIVATE);
write (remove the space from the name)
SharedPreferences sharedPreferences=getSharedPreferences("Sharedpreferences",MODE_PRIVATE);
similarly with your variable name
editor.putString("TaskList",json);
String json=sharedPreferences.getString("TaskList",null);
i don't know if this is your case or why this happens since the variable is a string and the space shouldn't matter but for me it never allows me to save anything in sharedPrefs if the name has spaces
then check this line
MyAdapter=new ArrayAdapter<>(this, android.R.layout.simple_list_item_1);
update it with this
MyAdapter=new ArrayAdapter<>(this, android.R.layout.simple_list_item_1,ModuleList);
for the issue in saving the item twice the problem is here
if(!(itemText.equals("")))
{
ModuleList.add(itemText);
// MyAdapter.add(itemText); remove this line the itemText is already added to the moduleList
MyAdapter.notifyDataSetChanged();
input.setText("");
}
First: create a static final variable to store "Task List", then add some Log.d("TEST", variable) to show in 'Logcat' the interested variables and then update the question please.
I am trying to make a simple todo list app which will probably store only a few things.
After adding items in the ListView, and closing the app, the only entry that loads is the last one that is entered. How do I make all the entered entries show up after closing the app?
Code:
public class MainActivity extends ActionBarActivity {
EditText display;
ListView lv;
ArrayAdapter<String> adapter;
Button addButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
display = (EditText) findViewById(R.id.editText1);
lv = (ListView) findViewById(R.id.listView1);
addButton = (Button) findViewById(R.id.button1);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1);
lv.setAdapter(adapter);
LoadPreferences();
addButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
String task = display.getText().toString();
adapter.add(task);
adapter.notifyDataSetChanged();
SavePreferences("LISTS", task);
}
});
}
protected void SavePreferences(String key, String value) {
// TODO Auto-generated method stub
SharedPreferences data = PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = data.edit();
editor.putString(key, value);
editor.commit();
}
protected void LoadPreferences(){
SharedPreferences data = PreferenceManager.getDefaultSharedPreferences(this);
String dataSet = data.getString("LISTS", "None Available");
adapter.add(dataSet);
adapter.notifyDataSetChanged();
}}
Thanks in advance.
You should have to keep key different for each item you are adding to SharedPreferences, otherwise last item you added in preference will override the last one.
I won't suggest using SharedPreferences for making an app like a todo list.
Make a SQLite database and store your todos in that. Or you can save the todos in a JSON file which is also very simple to achieve.
Using SharedPreferences won't be efficient in this case as you will need to track the keys of all the todo preferences, which creates another overhead.
Check out this post by Lars Vogel about creating content providers and SQLite Databses:
Android SQLite database and content provider - Tutorial
I have one small problem, after i click on list item, checkbox on item dont change state. Update works perfectly, setChecked maybe, but change will appear after exiting and re-running activity. I read lot of about notifyDataSetChange(), it may work, but not. How can i fix it, like after click on item chechbox value will change.
public class SviatokPridajActivity extends Activity
{
private DatabaseOp mDbHelper;
ListView listview;
String username;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.sviatok_pridaj);
this.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);
listview = (ListView) findViewById(R.id.listSviatok);
showUserSettings();
mDbHelper = new DatabaseOp(this);
mDbHelper.open();
Cursor sviatokCursor = mDbHelper.fetchAllSviatokNastav(username, 3);
if (sviatokCursor.getCount()==0)
{
mDbHelper.naplnSviatky(username);
sviatokCursor = mDbHelper.fetchAllSviatokNastav(username, 3);
}
final SviatokCursorAdapter adapter = new SviatokCursorAdapter(this, sviatokCursor);
listview.setAdapter(adapter);
listview.setOnItemClickListener(new OnItemClickListener()
{
#Override
public void onItemClick(AdapterView<?> arg0, View arg1, int stlpec, long arg3)
{
// TODO Auto-generated method stub
Cursor cur = (Cursor) adapter.getItem(stlpec);
String odosli = cur.getString(cur.getColumnIndex("_id"));
String zobraz = cur.getString(cur.getColumnIndex("dlzka"));
CheckBox check = (CheckBox)findViewById(R.id.checkBox);
if (Integer.parseInt(zobraz)==0)
{
mDbHelper.updateSviatok(odosli, username, 1);
} else {
mDbHelper.updateSviatok(odosli, username, 0);
}
check.setChecked(!check.isChecked());
adapter.notifyDataSetChanged();
}
});
}
#Override
public void onPause()
{
super.onPause();
mDbHelper.close();
}
private void showUserSettings()
{
SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);
username = sharedPrefs.getString("prefUsername", "NULL");
}
}
you have checked your CheckBox in itemclick but it's not reflected to your itemList so before calling adapter.notifyDataSetChanged(); you should have to refresh listItems with new changes.
I ve answered this question in this : https://stackoverflow.com/a/22954806/1332870
can you check it? if it does not solve your problem please let me know
Reload your Cursor and instead of adapter.notifyDataSetChanged(); use adapter.changeCursor(reloadedCursor);
Not sure if this is a strain on the main thread but you could just set the adapter again in the on click method.
I have an activity which is working without operating the shared preference. After adding it, got null pointer error after clicking the button.
I think the way I am using shared preference is not correct. Anyone can help point out what is the issue? Should I new() it before using?
public class BanknameActivity extends Activity {
String [] bank_name;
String selected_bank_config;
SharedPreferences prefs;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bankname);
// Show the Up button in the action bar.
// setupActionBar();
bank_name = getResources().getStringArray(R.array.bankname);
ListView lv1 = (ListView) findViewById(R.id.bankname_listview);
lv1.setChoiceMode(1); // CHOICE_MODE_SINGLE
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, bank_name);
lv1.setAdapter(adapter);
lv1.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapter, View view, int position, long arg) {
//selected_bank_config = "Citi";
prefs.edit().putString(selected_bank_config, "citi").commit();
return_to_config(view);
}
});
}
Below is part of my code:
public void return_to_config(View view){
Intent intent = new Intent(this, ConfigActivity.class);
startActivity(intent);
this.finish();
}
**you need to initialize your shared Preferences. Without initialization it will always be null.**
yo need to do following stuff:
// mPrefs=getSharedPreferences("Preferences Name",mode);
mPrefs=getSharedPreferences("FBPref",0);
Editor edit=mPrefs.edit();
edit.putString("UserName", "");
edit.putString("UserId","");
edit.putString("EmailId","");
edit.commit();
This code is working fine.
I hope you will appreciate it.
i am quite new at coding for android. I tried to use SavePreferences in order to save User Inputted data for a ListView. However this method resulted in only saving the last item that the user inputted, not the entire ListView.(i think this was because i was overwriting the key so that it would only show the last value)
Then it was suggested that i should use a JSONArray but I could not understand what happened.
My Code using JSONArray is below:
Note: there are a bunch of errors on the JSONArray since i dont think i used the correct Key.
public class TaskPage extends SherlockActivity {
EditText display;
ListView lv;
ArrayAdapter<String> adapter;
Button addButton;
ArrayList<String> dataSetarrlist = new ArrayList<String>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
display = (EditText) findViewById(R.id.editText1);
lv = (ListView) findViewById(R.id.listView1);
addButton = (Button) findViewById(R.id.button1);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_multiple_choice);
lv.setAdapter(adapter);
LoadPreferences();
// setChoiceMode places the checkbox next to the listviews
addButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
String task = display.getText().toString();
adapter.add(task);
adapter.notifyDataSetChanged();
SavePreferences("LISTS", task);
}
});
}
protected void SavePreferences(String key, String value) {
// TODO Auto-generated method stub
SharedPreferences data = PreferenceManager.getDefaultSharedPreferences(this);
JSONArray array = new JSONArray(data.getString(key, value));
SharedPreferences.Editor editor = data.edit();
editor.putString(key, value);
editor.commit();
}
protected void LoadPreferences(){
SharedPreferences data = PreferenceManager.getDefaultSharedPreferences(this);
JSONArray dataSet1 = new JSONArray(data.getString("LISTS", "None Available"));
for(int i = 0; i<dataSet1.length(); i++)
adapter.add(dataSet1.getString(i));
adapter.notifyDataSetChanged();
adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_multiple_choice,dataSetarrlist);
lv.setAdapter(adapter);
// setChoiceMode places the checkbox next to the listviews
}
I am quite confused at this point so can someone please show me where Im going wrong and provide some example code. I almost certain it is because I am not using the key and value correctly to save the data but i cant seem to get this correct
Lastly, is there another method where I dont have to use the JSONArray so that it will still show all the user inputs in the listview.
EDITED CODE IS BELOW
addButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
String task = display.getText().toString();
adapter.add(task);
dataSetarrlist.add(task);
adapter.notifyDataSetChanged();
SavePreferences("LISTS", dataSetarrlist.toString());
}
});
}
protected void SavePreferences(String key, String value) {
// TODO Auto-generated method stub
SharedPreferences data = PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = data.edit();
editor.putString("LISTS", dataSetarrlist.toString());
editor.commit();
}
protected void LoadPreferences(){
SharedPreferences data = PreferenceManager.getDefaultSharedPreferences(this);
String dataSet = data.getString("LISTS", dataSetarrlist.toString());
ArrayList<String> dataSetarrlist = new ArrayList<String>();
dataSetarrlist.add(dataSet);
adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_multiple_choice,dataSetarrlist);
lv.setAdapter(adapter);
lv.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
// setChoiceMode places the checkbox next to the listviews
}
Your TextView (display) only contains 1 value. On the OnClickListener of addButton, you should add "task" on your array & pass the array to SavePreferences instead of "task":
addButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
String task = display.getText().toString();
adapter.add(task);
dataSetarrlist.add(task);
adapter.notifyDataSetChanged();
SavePreferences("LISTS", dataSetarrlist);
}
});
}
You should modify SavePreferences to process the ArrayList.