This is my code:
public class MainActivity extends AppCompatActivity {
ListView listView ;
ArrayList<String> StoreContacts, id;
Bundle bundle;
ArrayAdapter<String> arrayAdapter ;
Cursor cursor;
Intent intent;
String name, phonenumber ;
public static final int RequestPermissionCode = 1 ;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView)findViewById(R.id.listview1);
StoreContacts = new ArrayList<String>();
id = new ArrayList<String>();
EnableRuntimePermission();
GetContactsIntoArrayList();
arrayAdapter = new ArrayAdapter<String>(
MainActivity.this,
R.layout.contact_items_listview,
R.id.textView, StoreContacts
);
listView.setAdapter(arrayAdapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
bundle =new Bundle();
/*SharedPreferences.Editor editor=getSharedPreferences("Suyash",MODE_PRIVATE).edit();
editor.putString("ID",id.get(i));
editor.apply();*/
intent = new Intent(MainActivity.this, SingleContact.class);
bundle.putString("ID",id.get(i));
intent.putExtra("ID",id.get(i));
startActivity(intent);
}
});
}
public void GetContactsIntoArrayList(){
cursor = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null,null, null, null);
while (cursor.moveToNext()) {
id.add(cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone._ID)));;
name = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
phonenumber = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
StoreContacts.add(name + " " + ":" + " " + phonenumber);
}
cursor.close();
}
public void EnableRuntimePermission(){
if (ActivityCompat.shouldShowRequestPermissionRationale(
MainActivity.this,
Manifest.permission.READ_CONTACTS))
{
Toast.makeText(MainActivity.this,"CONTACTS permission allows us to Access CONTACTS app", Toast.LENGTH_LONG).show();
} else {
ActivityCompat.requestPermissions(MainActivity.this,new String[]{
Manifest.permission.READ_CONTACTS}, RequestPermissionCode);
}
}
#Override
public void onRequestPermissionsResult(int RC, String per[], int[] PResult) {
switch (RC) {
case RequestPermissionCode:
if (PResult.length > 0 && PResult[0] == PackageManager.PERMISSION_GRANTED) {
Toast.makeText(MainActivity.this,"Permission Granted, Now your application can access CONTACTS.", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(MainActivity.this,"Permission Canceled, Now your application cannot access CONTACTS.", Toast.LENGTH_LONG).show();
}
break;
}
}
}
on receiving end:
public class SingleContact extends AppCompatActivity {
Bundle bundle=getIntent().getExtras();
//SharedPreferences preferences=getSharedPreferences("Suyash",MODE_PRIVATE);
0String string = bundle.getString("ID",null);
Button button;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_single_contact);
button= (Button) findViewById(R.id.button);
//string= bundle.getString("ID");
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Toast.makeText(SingleContact.this, string, Toast.LENGTH_SHORT).show();
}
});
}
}
the crashes when I click the item.
i have tried sharedpreference too, it does the same thing. im using android studio 2.3.3.
anyone suggest what i should do.
please help
You can not get the bundle before onCreate(). Write your code something like below and it will resolve your error.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_single_contact);
// Your bundle code.
Bundle bundle=getIntent().getExtras();
String string = bundle.getString("ID",null);
}
Probably wrong initialization of bundle data in SingleContact Activity, you should initialise inside of onCreate method
public class SingleContact extends AppCompatActivity {
Bundle bundle;
String string;
Button button;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_single_contact);
bundle = getIntent().getExtras()
button= (Button) findViewById(R.id.button);
string= bundle.getString("ID");
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Toast.makeText(SingleContact.this, string, Toast.LENGTH_SHORT).show();
}
});
}
}
Related
I'm making an Android app and in my app, I add the feature of storing the login state.
My Splash screen:
public class Splash extends AppCompatActivity {
private SharedPreferences preferences;
public int a = 0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_splash);
final ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressbar);
new CountDownTimer(5000, 1000) {
#Override
public void onTick(long millisUntilFinished) {
a = a + 1;
progressBar.setProgress(a);
}
#Override
public void onFinish() {
SharedPreferences preferences = getSharedPreferences("login", MODE_PRIVATE);
String check = preferences.getString("login", "off");
if (check.equals("on")) {
startActivity(new Intent(Splash.this, Menu.class));
} else {
startActivity(new Intent(Splash.this, LoginPage.class));
}
}
}.start();
} }
My Login screen:
public class LoginPage extends AppCompatActivity {
private SharedPreferences preferences;
Context context;
Button login, register, database;
EditText username;
EditText password;
TextView msg;
MyDBManager db;
static final int REGISTRATION_REQUEST = 1; // The request code
#Override
protected void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.loginpage);
db = new MyDBManager(this);
msg = (TextView) findViewById(R.id.msg);
login = (Button) findViewById(R.id.button);
register = (Button) findViewById(R.id.button2);
database = (Button) findViewById(R.id.button3);
username = (EditText) findViewById(R.id.user);
password = (EditText) findViewById(R.id.pass);
// Click and move to the next activity
login.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
db.open();
Cursor c = db.getUser(username.getText().toString(), password.getText().toString());
if (c.moveToFirst()) {
db.close();
context.startActivity(new Intent(context,Menu.class));
// Intent i=new Intent(getApplicationContext(),Menu.class); //
i.putExtra("Username", username.getText().toString()); //
startActivity(i); // call Login Activity
Store();
}
else
{
db.close();
// set error message when the username and/or password is not valid
msg.setText("Unable to login: wrong username or password!");
// Stay at the current activity.
}
}
private void Store() {
SharedPreferences preferences=context.getSharedPreferences("login",Context.MODE_PRIVATE);
SharedPreferences.Editor editor=preferences.edit();
editor.putString("login_status","on");
editor.commit();
}
});
// Click and move to the next activity
register.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(LoginPage.this, Registration.class);
startActivityForResult(intent, REGISTRATION_REQUEST);
}
});
// Click and move to the next activity
database.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(LoginPage.this, Database.class);
startActivity(intent);
}
});
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == REGISTRATION_REQUEST) {
//if(resultCode == Registration.RESULT_OK){
Log.d("Pikatchu", "User successfully registered!");
Bundle res = data.getExtras();
String result = res.getString("result");
System.out.println(result);
msg.setText(result);
}
}
}
My Menu screen:
public class Menu extends AppCompatActivity {
private SharedPreferences preferences;
Button startJourney, displayJourneys;
TextView msg; // where to display the name of the user
Button buttonLogout ;
/* the string is where to store data when we select something */
String db_username;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.menu);
buttonLogout = (Button) findViewById(R.id.btn_logout);
msg = (TextView) findViewById(R.id.msg);
startJourney = (Button) findViewById(R.id.recordingmode);
// Bundle bundle = getIntent().getExtras(); //
db_username = (bundle.getString("Username")); //// //// // Set
Welcome message to the user who logged in //
msg.setText("Welcome "+db_username);
// Click and move to the next activity // startJourney.setOnClickListener(new View.OnClickListener() { //
#Override // public void onClick(View v) { //
Intent intent = new Intent(Menu.this, Recordingmode.class); //
intent.putExtra("Username", db_username); //
startActivity(intent); // } // });
// Click and move to the next activity buttonLogout.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
SharedPreferences preferences=getSharedPreferences("login", Context.MODE_PRIVATE);
SharedPreferences.Editor editor=preferences.edit();
editor.putString("login_status","off");
editor.commit();
finish();
moveTaskToBack(true);
} });
}
}
But if I login in the app, the error is thrown:
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null
object reference
I am creating a simple tasklist app in Android Studios.
I have two activities as following (removed imports and package specifications):
MainActivity.java
public class MainActivity extends AppCompatActivity implements View.OnClickListener, AdapterView.OnItemClickListener {
EditText taskAdd;
Button add;
public ListView tasks;
public Integer pos = 0;
public ArrayList<String> taskArray;
public ArrayAdapter<String> adapter;
#Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
taskAdd = findViewById(R.id.taskAdd);
add = findViewById(R.id.add);
tasks = findViewById(R.id.tasks);
taskArray = FileHelper.readData(this);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, taskArray);
tasks.setAdapter(adapter);
add.setOnClickListener(this);
tasks.setOnItemClickListener(this);
}
#Override
public void onClick(View v) {
switch(v.getId()){
case R.id.add:
String entered = taskAdd.getText().toString();
if (entered != "" || entered != null || entered != "null") {
adapter.add(entered);
taskAdd.setText("");
FileHelper.writeData(taskArray, this);
Toast.makeText(this, "Task Added!", Toast.LENGTH_SHORT).show();
}
break;
}
}
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
pos = position;
Intent intent = new Intent(MainActivity.this, Pop.class);
startActivity(intent);
}
#Override
protected void onNewIntent(Intent intent) {
super.onNewIntent(intent);
setIntent(intent);
processExtraData();
}
private void processExtraData(){
Bundle extras = getIntent().getExtras();
if (extras != null) {
int value = extras.getInt("Value");
if (value == 1) {
taskArray.remove(pos);
adapter.notifyDataSetChanged();
Toast.makeText(this, "Task Removed!", Toast.LENGTH_SHORT).show();
}
}
}
}
Pop.java (a popup)
public class Pop extends Activity implements View.OnClickListener {
Button deleteButton;
Button finishedButton;
Button timerButton;
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.popwindow);
deleteButton = findViewById(R.id.deleteButton);
DisplayMetrics dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);
int width = dm.widthPixels;
int height = dm.heightPixels;
getWindow().setLayout((int)(width*0.5),(int)(height*0.5));
deleteButton.setOnClickListener(this);
}
#Override
public void onClick(View v) {
Intent i = new Intent(this, MainActivity.class);
i.putExtra("Value", 1);
startActivity(i);
}
}
After I click deleteButton in Pop.java, processExtraData in MainActivity.java is supposed to run. The Toast does appear, but the selected object in the ListView is not deleted. No errors are thrown either. In addition, using Log.d to check the size of taskArray confirmed that this is not just a graphical issue. Why is this the case, and how should I go about fixing it?
Thank you for replying in advance.
The issue is that you are using an object reference instead of a primitive data type, and so when you are calling taskArray.remove(pos), it is looking for pos the object rather than its denoted integer value.
Instead of:
taskArray.remove(pos);
try:
taskArray.remove(pos.intValue());
Excuse my noobness. I just don't understand how to implement it to work with my code. What I'm doing is editing a name that's in a list view. When editing the name in "EditDeleteList" and get back to the previous activity (ListView) to see the name updated within the list view, nothing happens. I have to go out of the activity completely to see the change reflected. How do I get this to update? I implement an onActivityReult() method but then get this error message "java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference" so I removed it completely. How I could get the list view to update without getting that error message?
ListView.Java
public class ListView extends AppCompatActivity {
private static final String TAG = "ListView";
DatabaseHelper mDatabaseHelper;
Button btnAdd;
private EditText editText;
private android.widget.ListView listView;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list_view);
mDatabaseHelper = new DatabaseHelper(this);
btnAdd = (Button) findViewById(R.id.btnAdd);
editText = (EditText) findViewById(R.id.editText);
listView = (android.widget.ListView) findViewById(R.id.lv);
ArrayList<String> list = getIntent().getStringArrayListExtra("myList");
android.widget.ListView lv = (android.widget.ListView) findViewById(R.id.lv);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, list);
lv.setAdapter(adapter);
//Takes user back to the main activity
ImageView ivBack = (ImageView) findViewById(R.id.ivBackArrow);
ivBack.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.d(TAG, "onClick: pressed back arrow");
Intent intent = new Intent(ListView.this, MainActivity.class);
startActivity(intent);
}
});
btnAdd.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String newEntry = editText.getText().toString();
if (editText.length() != 0) {
addData(newEntry);
editText.setText("");
} else {
toastMessage("you must put something in the text field");
}
}
});
populateListView();
}
public void addData(String newEntry) {
boolean insertData = mDatabaseHelper.addData(newEntry);
if (insertData) {
toastMessage("Successfully inserted");
recreate();
} else {
toastMessage("Whoops, something went wrong");
}
}
private void toastMessage(String message) {
Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
}
private void populateListView() {
Log.d(TAG, "populateListView: displaying data in the listview");
//get data and append to list
Cursor data = mDatabaseHelper.getData();
ArrayList<String> listData = new ArrayList<>();
while(data.moveToNext()) {
//get the value from the database in column 1
//set it to the arraylist
listData.add(data.getString(1));
}
//create arraylist and set it to the adapter
ListAdapter adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, listData);
listView.setAdapter(adapter);
//set onclick listen to edit activity
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
String name = adapterView.getItemAtPosition(position).toString();
Log.d(TAG, "onItemClick: you clicked on " + name);
Cursor data = mDatabaseHelper.getItemID(name); //get the id associated with that name
int itemID = -1;
while (data.moveToNext()) {
itemID = data.getInt(0);
}
if (itemID > -1) {
Log.d(TAG, "onItemID: the ID is: " + itemID);
Intent editScreenIntent = new Intent(ListView.this, EditDeleteList.class);
editScreenIntent.putExtra("id",itemID);
editScreenIntent.putExtra("name",name);
startActivity(editScreenIntent);
} else {
toastMessage("No ID found");
}
}
});
}
}
EditDeleteList.java
public class EditDeleteList extends AppCompatActivity {
private static final String TAG = "EditDeleteList";
DatabaseHelper mDatabaseHelper;
private ImageView ivDelete;
private ImageView ivApprove;
private EditText editHashtag;
private String selectedName;
private int selectedID;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_edit_delete);
mDatabaseHelper = new DatabaseHelper(this);
editHashtag = (EditText) findViewById(R.id.editHashtag);
ivDelete = (ImageView) findViewById(R.id.ivDelete);
ivApprove = (ImageView) findViewById(R.id.ivApprove);
//get the intent extra from the ListView activity
final Intent receivedIntent = getIntent();
//get item ID passed as an extra
selectedID = receivedIntent.getIntExtra("id", -1);
//get name passed as an extra
selectedName = receivedIntent.getStringExtra("name");
//set text field to selected item text
editHashtag.setText(selectedName);
ivApprove.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String item = editHashtag.getText().toString();
if (!item.equals(null)) {
mDatabaseHelper.updateName(item, selectedID, selectedName);
} else {
toastMessage("you must enter a #hashtag");
}
finish();
}
});
}
private void toastMessage(String message) {
Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
}
}
In the EditDeleteList.java I have an onClickListener that saves the changes and goes back to the previous activity by using finish();
ivApprove.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String item = editHashtag.getText().toString();
if (!item.equals(null)) {
mDatabaseHelper.updateName(item, selectedID, selectedName);
} else {
toastMessage("you must enter a #hashtag");
}
finish();
}
});
Notify the adapter in some part of the activity lifecycle.
OnCreate() should not run when you go back (this is the reason you have to completely recreate the activity to see the list updated) so you should use OnRestart/OnStart/OnResume to notify the adapter to check for new items.
Check this image
The code below is intended to pass the data, using bundle, collected on signing up in Signup.java to ViewProfile.java which displays the data. On checking for a key in the bundle, it returns true, however, the bundle is null when checked in ViewProfile.java. Help will b appreciated.
Signup.java
public class Signup extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_signup);
final EditText n=(EditText)findViewById(R.id.editText3);
final EditText u=(EditText)findViewById(R.id.editText4);
final EditText p=(EditText)findViewById(R.id.editText5);
final EditText c=(EditText)findViewById(R.id.editText6);
Button s=(Button)findViewById(R.id.button4);
final Userdatabase udb=new Userdatabase(this);
s.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
String name=n.getText().toString();
String email=u.getText().toString();
String password=p.getText().toString();
String phone=c.getText().toString();
boolean b=udb.insertuser(name,email,password);
if(b==true) {
Intent i = new Intent(Signup.this, MainActivity.class);
Bundle bundle=new Bundle();
bundle.putString("NAME",name);
bundle.putString("ID",email);
bundle.putString("PHONE",phone);
i.putExtras(bundle);
startActivity(i);
}
else
Toast.makeText(getApplicationContext(),"Please try again",Toast.LENGTH_SHORT).show();
}
});
}
}
ViewProfile.java
public class ViewProfile extends AppCompatActivity {
String name,username,contact,profession;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_profile);
Intent intent=getIntent();
Bundle b=intent.getExtras();
if(b!=null) {
name = b.getString("NAME");
username = b.getString("ID");
contact = b.getString("PHONE");
TextView tv1=(TextView)findViewById(R.id.textView17);
TextView tv2=(TextView)findViewById(R.id.textView18);
TextView tv3=(TextView)findViewById(R.id.textView19);
tv1.setText(name);
tv2.setText(username);
tv3.setText(contact);
}
ImageView img=(ImageView)findViewById(R.id.imageView4);
img.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
Intent i=new Intent(ViewProfile.this,Profile.class);
startActivity(i);
}
});
}
}
You are calling the wrong activity in the SignUp activity:
if(b==true) {
Intent i = new Intent(Signup.this, MainActivity.class);//problem here
You have set the intent as MainActivity.class and sending data to MainActivity and not to ViewProfile activity.
Change to this in SignUp activity:
if(b==true) {
Intent i = new Intent(Signup.this, ViewProfile.class);
For some reason my android application will not execute when a the ADD button is clicked.
I am using fragments Can you please help me and lead me in the right direction. When I click the
ADD button, nothing happens, not even the first Toast statement when the fields are empty
public class AthleteCreation extends Fragment implements View.OnClickListener{
Communicator communicator;
Button btnAdd;
EditText editFirstName, editLastName, editAge, editTier;
public AthleteCreation() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_athlete_creation, container, false);
final List<String> genderList=new ArrayList<String>();
genderList.add("Male");
genderList.add("Female");
Spinner s = (Spinner) view.findViewById(R.id.spinnerGender);
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(getActivity(), R.layout.support_simple_spinner_dropdown_item, genderList);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
s.setAdapter(dataAdapter);
return view;
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
}
public void initializeVariables(){
btnAdd = (Button) getActivity().findViewById(R.id.btnAdd);
editFirstName = (EditText) getActivity().findViewById(R.id.editFirstName);
editLastName = (EditText) getActivity().findViewById(R.id.editLastName);
editAge = (EditText) getActivity().findViewById(R.id.editAge);
editTier = (EditText) getActivity().findViewById(R.id.editTier);
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
initializeVariables();
btnAdd.setOnClickListener(this);
}
#Override
public void onDetach() {
super.onDetach();
}
#Override
public void onClick(View v) {
switch(v.getId()){
case R.id.btnAdd:
Athlete athlete = new Athlete();
if(editFirstName.getText().length() == 0 || editLastName.getText().length() == 0
|| editAge.getText().length() == 0 || editTier.getText().length() == 0) {
Toast.makeText(getActivity(), "Fill in all fields!", Toast.LENGTH_SHORT).show();
}
else{
athlete.setFirstName(editFirstName.getText().toString());
athlete.setLastName(editLastName.getText().toString());
athlete.setAge(Integer.parseInt(editAge.getText().toString()));
athlete.setGender("");
athlete.setEvent("");
athlete.setTier(Integer.parseInt(editTier.getText().toString()));
Toast.makeText(getActivity(), athlete.toString(), Toast.LENGTH_LONG).show();
communicator = (Communicator) getActivity();
communicator.send(athlete);
}
break;
}
}
}
In initializeVariables() you are using getActivity().findViewById(R.id.foo) instead of using the Fragment's root view, that's probably the reason that you don't get a matching case in the switch statement.
Try:
getView().findViewById(R.id.foo);
In your initializeVariables() method, replace getActivity() by getView().
btnAdd = (Button) getView().findViewById(R.id.btnAdd);
Then btnAdd.setOnClickListener(this) will work.