Develop Reference

Navigation Bar Inside Tabbed Activity Android

I Create a tabbed activity from android studio from the options. Then i tried to add Navigation Bar. Now its giving me error on
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
The error is
Android Error [Attempt to invoke virtual method 'void android.app.ActionBar' on a null object reference]
Code:
MainActivity.java
package com.example.android.myves;
import android.support.annotation.NonNull;
import android.support.design.widget.NavigationView;
import android.support.design.widget.TabLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity
{
private DrawerLayout dl;
private ActionBarDrawerToggle t;
private NavigationView nv;
/**
* The {#link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {#link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {#link android.support.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {#link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dl = (DrawerLayout)findViewById(R.id.d1);
t = new ActionBarDrawerToggle(this, dl,R.string.Open, R.string.Close);
t.setDrawerIndicatorEnabled(true);
dl.addDrawerListener(t);
t.syncState();
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
nv = (NavigationView)findViewById(R.id.nv);
nv.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
int id = item.getItemId();
switch(id)
{
case R.id.lib:
Toast.makeText(MainActivity.this, "My Account",Toast.LENGTH_SHORT).show();
case R.id.evt:
Toast.makeText(MainActivity.this, "Settings",Toast.LENGTH_SHORT).show();
case R.id.que:
Toast.makeText(MainActivity.this, "My Cart",Toast.LENGTH_SHORT).show();
default:
return true;
}
}
});
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
else if(t.onOptionsItemSelected(item))
{
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
public PlaceholderFragment() {
}
/**
* Returns a new instance of this fragment for the given section
* number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_t1comps, container, false);
return rootView;
}
}
/**
* A {#link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return PlaceholderFragment.newInstance(position + 1);
}
#Override
public int getCount() {
// Show 3 total pages.
return 3;
}
}
}
What can I do to make the error go away?

First you have to set your SupportActionBar.
Just add the following lines to your code:
Toolbar toolbar = (Toolbar)findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
It's important to declare the SupportActionBar before setting it DisplayHomeAsUpEnabled.

I need help working with fragments in Android Studio: need to change content on each fragment

I have just started working with android studio and developing with tabbed fragments. I am trying to build a simple app with three fragments, each fragment is going to have its own required input. I know this requires working with the content of each fragment, I am not sure how to do that. I want the first fragment to have one button, the second one two, the third one, three. And I want to design each of these as an activity and have them started by tabbing/swiping thru. Rightnow this is my code:
package com.example.riskcalculator;
import android.support.design.widget.TabLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
/**
* The {#link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {#link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {#link android.support.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {#link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
public PlaceholderFragment() {
}
/**
* Returns a new instance of this fragment for the given section
* number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
TextView textView = (TextView) rootView.findViewById(R.id.section_label);
textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
/**
* A {#link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return PlaceholderFragment.newInstance(position + 1);
}
#Override
public int getCount() {
// Show 3 total pages.
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "SYSTEM A";
case 1:
return "SYSTEM B";
case 2:
return "SYSTEM C";
}
return null;
}
}
}

If you have three different classes for each fragments, then you can add, button in the fragment layout as per your requirements.
If you are using just one fragment instance class.
Then, one approach would be to tag the fragment, with some id and get it by tag id and create button from program.
or
If you have just 3 or 4 tabs, then you can just check it in the getItem() callback, by checking position and pass a variable or something to the fragment, and based on passed value you can create buttons as per your need.

How to pass value to viewpager fragment from other activity?

Here let me explain my requirement i have two tabs of viewpager namely task and calls . There is one button in task fragment when user clicks that it will go to new activity from there users will enter the values in edittext then the values from this activity need to populate listview in task fragment of that viewpager how can i do this. So far what i have tried is:
THis is my Main activity:
package servicefiirst.precision.activitiestabs;
import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends AppCompatActivity {
/**
* The {#link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {#link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {#link android.support.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {#link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
// Bundle bundle=getIntent().getExtras();
// Intent intent=getIntent();
// ActivityView activityView=(ActivityView)intent.getSerializableExtra("yog");
// intent.putExtra("yogs",activityView);
// Bundle bundle=new Bundle();
// bundle.putSerializable("yogs",activityView);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
Bundle bundle = getIntent().getExtras();
if (bundle != null) {
String yogan = bundle.getString("yog");
String yogans = bundle.getString("yogs");
Bundle bundle1 = new Bundle();
bundle.putString("yoges", yogan);
bundle.putString("yogesh", yogans);
Task task = new Task();
task.setArguments(bundle1);
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
/**
* A {#link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
switch (position){
case 0:
Task task=new Task();
return task;
case 1:
Calls calls=new Calls();
return calls;
}
return null;
}
#Override
public int getCount() {
// Show 3 total pages.
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position){
case 0:
return "Task";
case 1:
return "Call";
}
return null;
}
}
}
This is Task fragment in viewpager where listview is there:
package servicefiirst.precision.activitiestabs;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.List;
public class Task extends Fragment
{
List<ActivityView>activityViews;
ActivityView activityView=new ActivityView();
ActivityListAdapter activityListAdapter;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootview= inflater.inflate(R.layout.yog,container,false);
ListView listview=(ListView)rootview.findViewById(R.id.listView);
if (activityViews == null)
{
activityViews = new ArrayList<ActivityView>();
}
if(getArguments()!=null) {
getArguments().getSerializable("yog");
}
activityViews.add(activityView);
activityListAdapter = new ActivityListAdapter(getActivity(), R.id.listView, activityViews);
listview.setAdapter(activityListAdapter);
activityListAdapter.notifyDataSetChanged();
Button btn=(Button)rootview.findViewById(R.id.button2);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v)
{
Intent intent = new Intent(getActivity(), DetailActivity.class);
startActivity(intent);
}
});
return rootview;
}
}
This is detail activity where data go to populate listview in task fragment:
package servicefiirst.precision.activitiestabs;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
public class DetailActivity extends AppCompatActivity {
ActivityView activityView = new ActivityView();
// public static String endpoint;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
final EditText editText = (EditText) findViewById(R.id.editText);
final Spinner spinner = (Spinner) findViewById(R.id.spinner);
final ArrayAdapter<CharSequence> arrayAdapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.yog, R.layout.support_simple_spinner_dropdown_item);
spinner.setAdapter(arrayAdapter);
final Button btn = (Button) findViewById(R.id.button);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
activityView.setDescription(editText.getText().toString());
activityView.setStatus(spinner.getSelectedItem().toString());
// Bundle bundle=new Bundle();
// bundle.putSerializable("yog", activityView);
Task task=new Task();
//task.setArguments(bundle);
android.support.v4.app. FragmentManager fm=getSupportFragmentManager();
android.support.v4.app. FragmentTransaction ft=fm.beginTransaction();
ft.add(R.id.container,task,"");
ft.commit();
}
});
}
}
how to navigate data from other activity to fragment of viewpager of other acitivity? can anybody help me

Please use static variable to save the value from your activity and then resuse it in task fragment by calling the task fragment of viewpager activity , i guess it would helps you..!!

Start the activity from task fragment using
startActivityForResult(Intent intent, int requestCode)
method, it will let fragment to receive result data from the activity. In new Activity when button is pressed to populate values save the values to a intent so you can send that intent to fragment by using
setResult(intent) // setResult has other overloaded methods pick them to your requirement
method of Activity class in your button onClickListener onClick() method.
Ex : onClick() {
intent.putString("name", editText.getText());
setResult(intent); // setting the intent as result to receive at fragment
this.finish(); // To finish the activity
}
When activity gets finished(when you call finish() or press back button)
onActivityResult(intent)
method of Fragment which started the activity will be automatically called. you can use this method to retrieve the intent which contained the populated data.

How to pass value between activity and viewpager fragment? [duplicate]

This question already has answers here:
Send data from activity to fragment in Android
(22 answers)
Closed 7 years ago.
It may be dumb question but am struggling with this how to pass value between activity and viewpager. Now let me explain my requirement i have two tabs namely task and calls . Having one button in task when user press that it will go to new activity from there will be two forms one is edittext and spinner need to populate listview in task fragment from that activity data so far what i have tried is:
This is my Main activity:
import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends AppCompatActivity {
/**
* The {#link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {#link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {#link android.support.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {#link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
// Bundle bundle=getIntent().getExtras();
// Intent intent=getIntent();
// ActivityView activityView=(ActivityView)intent.getSerializableExtra("yog");
// intent.putExtra("yogs",activityView);
// Bundle bundle=new Bundle();
// bundle.putSerializable("yogs",activityView);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
Bundle bundle = getIntent().getExtras();
if (bundle != null) {
String yogan = bundle.getString("yog");
String yogans = bundle.getString("yogs");
Bundle bundle1 = new Bundle();
bundle.putString("yoges", yogan);
bundle.putString("yogesh", yogans);
Task task = new Task();
task.setArguments(bundle1);
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
/**
* A {#link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
switch (position){
case 0:
Task task=new Task();
return task;
case 1:
Calls calls=new Calls();
return calls;
}
return null;
}
#Override
public int getCount() {
// Show 3 total pages.
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position){
case 0:
return "Task";
case 1:
return "Call";
}
return null;
}
}
}
This is my task fragment(where listview is gets populated)
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.List;
public class Task extends Fragment
{
List<ActivityView>activityViews;
ActivityView activityView=new ActivityView();
ActivityListAdapter activityListAdapter;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootview= inflater.inflate(R.layout.yog,container,false);
ListView listview=(ListView)rootview.findViewById(R.id.listView);
if (activityViews == null)
{
activityViews = new ArrayList<ActivityView>();
}
if(getArguments()!=null) {
getArguments().getSerializable("yog");
}
activityViews.add(activityView);
activityListAdapter = new ActivityListAdapter(getActivity(), R.id.listView, activityViews);
listview.setAdapter(activityListAdapter);
activityListAdapter.notifyDataSetChanged();
Button btn=(Button)rootview.findViewById(R.id.button2);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v)
{
Intent intent = new Intent(getActivity(), DetailActivity.class);
startActivity(intent);
}
});
return rootview;
}
}
This is the activity where data go to populate listview in task fragment:
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
public class DetailActivity extends AppCompatActivity {
ActivityView activityView = new ActivityView();
// public static String endpoint;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
final EditText editText = (EditText) findViewById(R.id.editText);
final Spinner spinner = (Spinner) findViewById(R.id.spinner);
final ArrayAdapter<CharSequence> arrayAdapter = ArrayAdapter.createFromResource(getApplicationContext(), R.array.yog, R.layout.support_simple_spinner_dropdown_item);
spinner.setAdapter(arrayAdapter);
final Button btn = (Button) findViewById(R.id.button);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
activityView.setDescription(editText.getText().toString());
activityView.setStatus(spinner.getSelectedItem().toString());
// Bundle bundle=new Bundle();
// bundle.putSerializable("yog", activityView);
Task task=new Task();
//task.setArguments(bundle);
android.support.v4.app. FragmentManager fm=getSupportFragmentManager();
android.support.v4.app. FragmentTransaction ft=fm.beginTransaction();
ft.add(R.id.container,task,"");
ft.commit();
}
});
}
}
Here how to pass data between activity and fragment of viewpager can anybody help me out? Thanks in advance!

You can use a Bundle to pass datas from an Activity to a Fragment:
In the Activity, create your Bundle and add it to the Fragment
Bundle myBundle = new Bundle();
myBundle .putLong( "exampleId", mExampleId);
myBundle .putString("exampleName", mName);
...
myFragment.setArguments( myBundle );
Then, when the Fragment is created, get the values in your Bundle using the function getArguments() like:
Long exampleId = getArguments().getLong("exampleId");
And even set a default value if you don't find the key in your Bundle
String exampleName = getArguments().getString( "exampleName", "None"));

You should create a NewInstance method inside your fragment. In short, it could look like this:
public class MyFragment {
private int value;
private static final String ARG_VALUE = "argValue";
public static MyFragment NewInstance(int value) {
Bundle args = new Bundle();
args.putInt(ARG_VALUE, value);
MyFragment fragment = new MyFragment();
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate() {
Bundle args = getArguments();
this.value = args.getInt(ARG_VALUE, 0); // Default 0 if key not found.
}
}
And you just pass in that value anytime you create the fragment:
MyFragment tenFragment = MyFragment.newInstance(10);
Then it can be used in a fragment transaction or inserted into a FragmentStatePagerAdapter however you need it. The same principle applies to any data type, so you can do this if you need to pass in Strings, or your own serializable object, etc.

Populate 3 ListViews from a Database in three Fragments

I'm working on an app that allows the user to add an item to a list (todo list). The user has the choise of which list the item will go into. The app uses Tabbed Views (Simular to Skype), and I need to be able to populate the lists from the Database (SQLite).
My MainActivity.java :
import android.content.ContentValues;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.speech.RecognizerIntent;
import android.support.design.widget.TabLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import static com.example.todo.Constants.*;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;
import android.text.Editable;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private static String[] FROM = { _ID, TODO_TEXT, LOCATION, };
private static int[] TO = { R.id.todoTextView };
private static String ORDER_BY = ORDER + " DESC";
ListView taskListView;
/**
* The {#link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {#link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {#link android.support.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
public Button speakButton;
/**
* The {#link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
Context context = this;
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab2);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
showAlert();
}
});
Cursor cursor = getEvents();
showEvents(cursor);
}
private void addEvent(String string) {
// Insert a new record into the Events data source.
// You would do something similar for delete and update.
ContentValues values = new ContentValues();
values.put(ORDER, System.currentTimeMillis());
values.put(REMINDER_TEXT, string);
getContentResolver().insert(CONTENT_URI, values);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
void showAlert(){
final EditText reminderinput = (EditText) findViewById(R.id.reminderText);
AlertDialog.Builder adb = new AlertDialog.Builder(MainActivity.this);
LayoutInflater inflater = MainActivity.this.getLayoutInflater();
adb.setView(inflater.inflate(R.layout.dialog_new_reminder, null))
.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener(){
#Override
public void onClick(DialogInterface dialog, int id) {
// save reminder here
Editable reminderText = reminderinput.getText();
String reminderTextString = String.valueOf(reminderText);
addEvent(reminderTextString);
}
})
.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
//it already cancels
}
});
adb.setTitle("Set a reminder");
AlertDialog ad = adb.create();
ad.show();
}
private Cursor getEvents() {
// Perform a managed query. The Activity will handle closing
// and re-querying the cursor when needed.
return managedQuery(CONTENT_URI, FROM, null, null, ORDER_BY);
}
private void showEvents(Cursor cursor) {
// Set up data binding
ListView mListView = (ListView) findViewById(R.id.listview);
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
R.layout.task_item, cursor, FROM, TO);
mListView.setAdapter(adapter);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
Intent intent = new Intent(this, AppSettings.class);
startActivity(intent);
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
public PlaceholderFragment() {
}
/**
* Returns a new instance of this fragment for the given section
* number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
return rootView;
}
}
/**
* A {#link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return PlaceholderFragment.newInstance(position + 1);
}
#Override
public int getCount() {
// Show 3 total pages.
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Important";
case 1:
return "Kinda Important";
case 2:
return "Not very Important";
}
return null;
}
}
}
Obviously, i have a Constants.java and also some layout files in the project.
Unfortunately, the app throws an error saying:
Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
HELP!

So you have the listviews in your fragment and you are doing
ListView mListView = (ListView) findViewById(R.id.listview);
This finds the listview in activity_main and not the fragment.
You should populate the listviews in the fragment.
Call this in the fragment.
ListView mListView = rootview.findViewById(R.id.listview);
Cursor cursor = getEvents();
showEvents(cursor);