Develop Reference

Check if current activity is required activity (same parent)

I have DrawerParent class which is basically a drawer. And, say, two activities inherited from DrawerParent. What I want is to not re-open same activity if it is already running. For such thing I need to somehow check whether this activity is running or not. It works like this in drawer:
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_about) {
startActivity(new Intent(this, AboutActivity.class));
finish();
} else ...
And I don't know how to check it. Thank you.
== Edit ==
Making group in layout and adding selectable="single" not works.

If you are running that code on the activity, you can compare using:
if (!(this instanceof ActivityToBeOpened)) {
startActivity(new Intent(this, ActivityToBeOpened.class));
finish();
}
You can get more info about instanceof here.
Hope it helps!

Start Activity in same intent

i want to know how to start all my activities in same intent. My app have a drawer activity and i want when i select any item, it will start an activity in the same intent, how can i do that ?
Main Acitivy
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
startActivity(new Intent(MainActivity.this, Main2Activity.class));
return true;

I checked Google Drive and I'm guessing you're referring to the behavior that when you click on something only a part of the screen updates. You can easily implement this by using Fragments. I cannot explain it to you in detail but this is a developer.google link that will help you get started. https://developer.android.com/training/basics/fragments/index.html

How to open an activity on click of a DrawerLayout navigationView item in android?

What function should i use to open an activity when a DrawerLayout navigationView item is clicked, and do i need to make object for that activity?
Here is my code so far:
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_profile) {
// Handle the camera action
} else if (id == R.id.nav_cv) {
} else if (id == R.id.nav_subscription) {
} else if (id == R.id.nav_logout) {
}

You can open activity like this.
Intent I=new Intent(MainActivity.this,actvitytoopen.class);
StartActivity(I);

You better use fragments instead of activities and change them using FragmentManager. You can find plenty of tutorials just by searching on Google/Youtube.

You can start new activity by
Intent intent = new Intent(this,NextActivity.class);
intent.putExtra(EXTRA_MESSAGE, message);
startActivity(intent);
for further info refer https://developer.android.com/training/basics/firstapp/starting-activity.html

I spent a lot of time trying to call a new activity by clicking on navigation drawer item . but it is virtually impossible and if it is possible in any other way I tried, then it is sure that on the called activity there will be no drawer navigation drawer then. Fragment is a part of similar activity so calling fragment is the correct way. If you are calling fragment, navigation drawer will still be there on the side pane and you would be able to select between different items of the drawer.

Back button behavior on an Activity

I have a problem in my app. I have a MainActivity with Fragments, each Fragment have a list with a recyclerView. When I click an Item of the list, the app goes to a new DetailActivity.
In the DetailActivity I have the next code line:
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
When I click the back button in the ActionBar I return to the MainActivity in another fragment, not the one I clicked the item.
Thanks!

As stated by #kareem adel make sure you are not ending the previous activity. Dont use Flag_activity_clear_task or flag_activity_new_task
If that doesn't help you could just tell the back button where to go.
With getSupportActionBar().setDisplayHomeAsUpEnabled(true); set you can do this:
#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(id == android.R.id.home){
//Back button was hit so go somewhere.
Intent i= new Intent(this, MainActivity.class);
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK); //Clear previous Activities
startActivity(i);
finish(); //End this activity.
return true;
}
return super.onOptionsItemSelected(item);
}

Action bar on Action back (Navigation Up) to custom activity?

I have many activities in my application
in that I have Given this
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
ActionBar actionBar = getSupportActionBar();
if (actionBar != null) {
actionBar.setDisplayHomeAsUpEnabled(true);
}
to Go back to Home Page from other activities
like Below
If I press those three buttons all menus are working
this is my Option menu
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.abc) {
Intent mypIntent = new Intent(this, abc.class);
startActivity(mypIntent);
return true;
}
else if (id == R.id.web) {
Intent webIntent = new Intent(this, Web.class);
startActivity(webIntent);
return true;
}
else if (id == R.id.about) {
Intent aboutIntent = new Intent(this, About.class);
startActivity(aboutIntent);
return true;
}
.
.
.
..
return super.onOptionsItemSelected(item);
}
Here There is no menu named id == R.id.login or id == R.id.home but its going to login few days back its gone to home activity
but If I press Back.. action back is redirect to Login page Inst-ed of Home
I have added a Login page for my application using shared preferences.. and it is now launcher activity..
Here In my Login activity on if once user is sign in it should it should redirect to Home activity on every time..
and its working fine..
But on action bar when I press arrow button it is redirecting to empty login page..
if I press cancel entire app is working .. my credentials are safe except this action bar..
Update
I have Given Intent also if Login credentials success redirect to Home activity on app start up it will check every time
every thing is as for fine except action back
how to fix this...

Alright make sure u do declare activities as below -
<activity
android:name="com.example.myfirstapp.DisplayMessageActivity"
android:parentActivityName="com.example.myfirstapp.MainActivity" >
<!-- The meta-data element is needed for versions lower than 4.1 -->
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.example.myfirstapp.MainActivity" />
</activity>
Now in every activity add below code block-
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
// Respond to the action bar's Up/Home button
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
Update
add a New class file to check login or not else use home as default.. and replace your new class as launcher in Manifest

Just override this method.
#Override
public boolean onOptionsItemSelected(MenuItem item)
{
switch (item.getItemId())
{
case android.R.id.home:
{
Intent intent = new Intent(mContext, Activity.class);/*your activity name*/
startActivity(intent);
}
default:
return super.onOptionsItemSelected(item);
}
}