Develop Reference

FrameLayout.LayoutParams doesn't work

I am trying to avoid the following situation in the activity( screen shot of the activity). When I add the margins using setMargins it does not work. I have tried adding margins via xml code and the end result is achieved but it very time consuming and it can't be guaranteed that it will work for all devices. How can i do it in code?
Here is the code.
package com.example.android.tourguide;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.design.widget.NavigationView;
import android.support.design.widget.TabLayout;
import android.support.v4.content.ContextCompat;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;
import android.widget.FrameLayout;
public class TouristAttractions extends AppCompatActivity {
private DrawerLayout mDrawerLayout;
private NavigationView mNavigationView;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.menu_item);
/*
Finding the Toolbar that is defined in activity_main.xml via the id toolbar.
Note:The following three lines should be repeated for all the activities that are opened from the MainActivity. Also the toolbar should have an orientation
which is not zero.
*/
android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar_for_menu_items);
/*
Setting the action bar as the toolbar defined in the above code line
*/
setSupportActionBar(toolbar);
/*
Setting the title text color of the app bar.
*/
toolbar.setTitleTextColor(ContextCompat.getColor(this, R.color.color_of_text_of_app_bar));
mNavigationView = (NavigationView) findViewById(R.id.navigation_view);
/*
Finding the drawerLayout so that when the user clicks on the menu item of the navigation drawer it should close as we invoke the method closeDrawers()
*/
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem menuItem) {
if (menuItem.getItemId() == R.id.home_menu) {
/*
Opening the home class that is the MainActivity when the Tourist Home menu button is clicked.
*/
Intent intentToOpenHomeClass = new Intent(TouristAttractions.this, MainActivity.class);
startActivity(intentToOpenHomeClass);
} else if (menuItem.getItemId() == R.id.entertainment_menu) {
Intent intentToOpenEntertainmentClass = new Intent(TouristAttractions.this, Entertainment.class);
startActivity(intentToOpenEntertainmentClass);
} else if (menuItem.getItemId() == R.id.gardens_menu) {
Intent intentToOpenGardenClass = new Intent(TouristAttractions.this, Garden.class);
startActivity(intentToOpenGardenClass);
} else {
mDrawerLayout.closeDrawers();
}
return true;
}
});
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout_for_menu_items);
ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager_for_menu_items);
AdapterForFragmentOfTouristAttraction adapterForFragmentOfTouristAttraction = new AdapterForFragmentOfTouristAttraction(this, getSupportFragmentManager());
viewPager.setAdapter(adapterForFragmentOfTouristAttraction);
tabLayout.setupWithViewPager(viewPager);
FrameLayout.LayoutParams params = (FrameLayout.LayoutParams) toolbar.getLayoutParams();
params.setMargins(0, toolbar.getHeight(), 0, 0);
ActionBar actionbar = getSupportActionBar();
/*
actionBar.setDisplayHomeAsUpEnabled(true) will make the icon clickable and add the < at the left of the icon.
*/
actionbar.setDisplayHomeAsUpEnabled(true);
/*
Enabling the menu icon of the navigation.However note we are simply adding the menu icon however clicking on the icon does absolutely nothing.
*/
actionbar.setHomeAsUpIndicator(R.drawable.baseline_menu_white_24);
}
}

First of all, it might be a better idea to use a LinearLayout with a vertical orientation, a RelativeLayout, or a ConstraintLayout to position views below one another. In more exotic use cases even a CoordinatorLayout might be better suited.
FrameLayouts are mostly used to simply overlay views on one another, without depdendencies between them.
This said, the issue you are facing occurs because you use toolbar.getHeight() right after adding the view, which will always be 0. Try attaching a debugger and see for yourself!
The reason is that Android needs a bit of time to measure -> layout -> draw its views, and if you call getHeight right after adding the layout it will not have done either of those steps, leaving the values uninitialized, at 0.
There are ways around that, but again, you would be better off using a different layout alltogether. If you insist on using a FrameLayout the cleanest approach would be to extend it and create your own, where you can measure and layout the view yourself. The hacky, hard to maintain, and confusing approach would be to use ViewTreeObserver to listen for the changes and react to them. This is bad because you have to wait for a full layout pass before you trigger yet another one.
Don't use a FrameLayout here.

You havn't Done
yourView.setLayoutParams(params);

cannot resolve symbol fragmentcontainer

So I've decide to go back into android developing after dropping it for a bit. I Restarted making an old project in android studio I ran into a issue where I'm getting "cannot resolve symbol fragmentcontainer" and I'm sure it was working last time.
import android.support.v4.app.FragmentManager;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
public class MainActivity extends FragmentActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// add fragment to the activity
FragmentManager fm = getSupportFragmentManager();
// give fragment to manage
Fragment fragment = fm.findFragmentById(R.id.fragmentContainer);
if (fragment == null) {
fragment = new HomeFragment();
fm.beginTransaction().add(R.id.fragmentContainer, fragment)
.commit();
}
}
}

It looks like your Activity layout R.layout.activity_main does not contain a view with id fragmentContainer. If that's not the issue, check this related question: Android Studio cannot resolve symbol but code executes correctly.

just using "fragment_container" not "android.R.id.fragment_container" works for me...here is the detail
getFragmentManager().beginTransaction()
.replace(fragment_container, new SettingsFragment())
.commit();

I think you can use
getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment).commitNow(); instead of using R.id.fragmentContainer to create fragment in an activity.

Get rid of fragments

I decided to not use fragments for now, although Android wants developers to now use it.
But I don't find it useful at the beginning. Unfortunately my IDE prepares everything to use fragments, so my question basically is, how to I get rid of everything, thats necessary for fragments? Is there a way to create a project without fragments? Thats what I did:
package com.pthuermer.juraquiz;
import java.io.IOException;
// import com.pthuermer.juraquiz.QuizActivity.PlaceholderFragment; // only necessary for Fragments
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.os.Build;
public class AppLaunch extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_app_launch);
/* FRAGMENTS
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
END FRAGMENTS */
// code goes here...
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.app_launch, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
* Useredit: not going to use fragments for now.
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_app_launch,
container, false);
return rootView;
}
}
*/
}

I think many people in the Android community will agree that fragments are not easy to handle and even draw new problems, some of them without even a decent proper solution.
Nevertheless, trying to remove all fragments from an app is not an easy task and might require good Android programming skills. You will have to convert your fragments either to views or activities, and that is not so easy to do, especially for activities containing multiple fragments.
The best option so far is to use mortar from Square, but this alternative is not totally ready and mature yet and using it requires, TMHO, advanced Android skills.
So, if I were a relatively new programmer in the Android world, I would keep fragments, get used to them, understand how they can be used to create reusable components and make apps that work on both phones and tablets.
After a while, when you will master them, you will find their drawbacks, and be able to look for alternatives.

I tried to study mortar from Square three times and still I haven't the slightest idea how to use it. So I went ahead and used Kotlin+Anko, switched all Fragments to Views and I'm more than happy - the code base is three times smaller, no dirty Fragment hacks, no NPEs that view has not been created for unknown reason, etc. Just implement views as follows:
class QuestionnaireView(ctx: Context, questions: List<Question>): _LinearLayout {
init {
orientation = LinearLayout.VERTICAL
for (question in questions) {
verticalLayout {
textView {
text = question.title
}.lparams(matchParent, wrapContent)
... etc - generate answer fields as necessary
}.lparams(matchParent, wrapContent)
}
}
}
Advantages:
Pass parameters using constructors like a human being, not via retarded arguments Bundle
No longer worry about the Fragment lifecycle and whether onCreateView() has yet been called or not.
Gets rid of exceptions thrown in Android's moveToState() mammoth method
Get rid of thousands layout.xml files stored in a single directory
Get rid of that styles.xml horrible mess
No need to define multiple layouts just to show a list+details on 720dp devices: just add if(screenWidthDp>=720) { detailView {} } to your init block.
Disadvantages:
No layout previews
Android Studio will become so slow it's almost useless.
You'll need to generate IDs for those views, otherwise their state will be lost on rotate

Having errors with R variables

I am getting errors on the R variables. The variables are R.id.drawer_layout, R.id.layout, and R.id.main. There is a red squiggly line under the words after id. These are all errors from R. Is there something wrong with my layout? I'm just beginning android programming and this is coming from github.
http://manishkpr.webheavens.com/android-navigation-drawer-example-using-fragments/
^This is where the tutorial and code is from.
package com.anshikka.datagushalpha;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.widget.DrawerLayout;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class MainActivity extends FragmentActivity {
final String[] data ={"one","two","three"};
final String[] fragments ={
"com.anshikka.datagushalpha.FragmentOne",
"com.anshikka.datagushalpha.FragmentTwo",
"com.anshikka.datagushalpha.FragmentThree"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
#SuppressWarnings({ "unchecked", "rawtypes" })
ArrayAdapter adapter = new ArrayAdapter(getActionBar().getThemedContext(), android.R.layout.simple_list_item_1, data);
final DrawerLayout drawer = (DrawerLayout)findViewById(R.id.drawer_layout);
final ListView navList = (ListView) findViewById(R.id.drawer);
navList.setAdapter(adapter);
navList.setOnItemClickListener(new OnItemClickListener(){
#Override
public void onItemClick(AdapterView<?> parent, View view, final int pos,long id){
drawer.setDrawerListener( new DrawerLayout.SimpleDrawerListener(){
#Override
public void onDrawerClosed(View drawerView){
super.onDrawerClosed(drawerView);
FragmentTransaction tx = getSupportFragmentManager().beginTransaction();
tx.replace(R.id.main, Fragment.instantiate(MainActivity.this, fragments[pos]));
tx.commit();
}
});
drawer.closeDrawer(navList);
}
});
FragmentTransaction tx = getSupportFragmentManager().beginTransaction();
tx.replace(R.id.main,Fragment.instantiate(MainActivity.this, fragments[0]));
tx.commit();
}
}

Import your R,
is something like
import com.yourproject.R;

Look into you imports and if you find "android.R" delete it. Finally, press Ctrl + Shift + O to import your project's R (using Eclipse as IDE) or just manually add it:
import com.anshikka.R
After that you should see com.anshikka.R on your imports at the top of the file.

Check if you have two main.java classes. I had this problem a couple of days ago when I imported a project into a current project. I had two main classes and after I deleted one the R error disappeared. Also make sure you imported the right R class. If after you imported the R class you get a redline under .activity_main you imported the wrong R class

I suppose those variables don't exist, since the red line only appears under the words after "id".
If you haven't copied the file activity_main.xml provided in the link you mentioned, which defines "#+id/drawer_layout", "#+id/"main" and "#+id/drawer", into your project's res/layout folder, the corresponding variables weren't generated.

Fragments: Remove all fragments in a view

The scenario I am faced with, is in my application I have a single pane and dual pane style layout. Rather than individually handle every single navigation operation possible between the screens, for every different style of layout, I am using a function which sets up the layout correctly when given the desired screen.
It is basically a switch statement for each screen in the app, with a nested switch statement in each screen to handle each layout style. This is what I'm talking about in code:
protected void setupScreen() {
switch(currentScreen) {
case SCREEN_ONE:
switch(currentLayout) {
case SINGLE_PANE:
// Perform actions to setup the screen
break;
case DUAL_PANE:
// Perform actions to setup the screen
break;
}
break;
case SCREEN_TWO:
switch(currentLayout) {
case SINGLE_PANE:
// Perform actions to setup the screen
break;
case DUAL_PANE:
// Perform actions to setup the screen
break;
}
break
// ... etc ....
}
}
In the section where I want to perform the actions to setup the screen, this consists of the following basic three operations:
// Create the fragments if necessary
if (screenFragment == null) {
screenFragment = new myFragment();
}
// Remove the existing fragments from the layout views
// HOW???
// Add the fragments for this screen to the view
getSupportFragmentManager().beginTransaction().add(pane1.getId(), myFragment, "myFragment").commit();
As you can see, what I am struggling with is how to do the second step. How do you remove all Fragments from a given View without knowing exactly which ones you are wanting to remove? The closest I have found is FragmentTransaction.replace() which does successfully do this for every case but when it turns out you are replacing a Fragment with the same fragment. In this case, it does not remove all, then add (like the documentation suggests), it just seems to remove. Is this an issue with using the compatibility libraries or is it not the way FragmentTransaction.replace() should be used?
In any case, how should I go about doing this? Do I have to code a removeAllFragments() function to go through every fragment and detach it or is there a way to do the first half of what the 'two in one' FragmentTransaction.replace() function claims to do?

None of the other answers were really working for me. Here's what I did:
List<Fragment> al = getSupportFragmentManager().getFragments();
if (al == null) {
// code that handles no existing fragments
return;
}
for (Fragment frag : al)
{
// To save any of the fragments, add this check.
// A tag can be added as a third parameter to the fragment when you commit it
if (frag == null || frag.getTag().equals("<tag-name>")) {
continue;
}
getSupportFragmentManager().beginTransaction().remove(frag).commit();
}
or, if you're forced to use it (but not recommended):
.commitAllowingStateLoss();
Also, if you're removing all fragments from the view multiple times, you might consider checking if the current frag is null or isDetached() or isRemoving() or you might get NullPointerExceptions.
Update: The documentation for getSupportFragmentManger().getFragments() is apparently hidden now, but still works just fine in my code. Here's the screenshot of the documentation:
Having said that, since it is hidden, they no longer want this method used, so see my update below.
Update 8-4-15: If you're not using the support library for fragments, there is unfortunately no getFragments() available, but there are still a couple, more inconvenient, options.
Give each fragment a tag or id upon creation, and iterate through them to process each fragment as desired.
Create a listener using onAttachListener so each time a new fragment is attached to the activity, you can store that fragment, and then iterate through that data structure to process each fragment as desired.
When not using the getSupportFragmentManager(), to process a transaction you will need to use getFragmentManager() instead.

The typical mechanism is to use FragmentManager.findFragmentByTag() . You use this and add tags to your fragments (or the alternative for id's). This way you can determine what fragments are currently being managed. Then, once you have a handle to a present fragment (findFragmentByTag returns non-null), you can use FragmentManager.beginTransaction() to start a FragmentTransaction and remove / add the necessary fragments. Working in this way will allow you to avoid the 're-adding' process for the fragment you want to keep.
What I'd probably do is have code like so: (warning psuedo code)
Fragment pane1 = FragmentManager.findFragmentByTag("myFragmentPane1");
Fragment pane2 = FragmentManager.findFragmentByTag("myFragmentPane2");
setupScreen(pane1, pane2);
You should also consider sub-classes of your class instead of having 'everything in one class'. You have a fairly obvious case of Martin Fowler's Replace Conditional with Subclass. Otherwise, I fear this is going to be incredibly hard to manager when you add another screen.

If you use android.support.v4.app.Fragment you can do this:
List<Fragment> fragments = getSupportFragmentManager().getFragments();
if (fragments != null) {
for (Fragment fragment : fragments) {
getSupportFragmentManager().beginTransaction().remove(fragment).commit();
}
}

Turns out FragmentTransaction.replace() is the correct operation and should work correctly. It only does not work when using ActionBarSherlock and SherlockFragmentActivity so I can only assume it is a bug in this compatibility library.
I have confirmed this through using the code below to implement the desired behaviour through Android on API11+, the android compatibility library, and ActionBarSherlock. It only breaks in the last instance.
package com.test.test;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import android.os.Bundle;
import android.content.Context;
import android.graphics.Color;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
import android.widget.LinearLayout.LayoutParams;
import android.widget.TextView;
public class MainActivity extends SherlockFragmentActivity {
// Consistent fragment instance
myFragment myFrag = null;
// Views
FrameLayout fl = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LinearLayout ll = new LinearLayout(this);
ll.setOrientation(LinearLayout.VERTICAL);
Button b = new Button(this);
b.setText("Repeat");
b.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// Reattach the same fragment
getSupportFragmentManager().beginTransaction().replace(fl.getId(), myFrag).commit();
}
});
fl = new FrameLayout(this);
fl.setId(200);
fl.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
myFrag = new myFragment();
getSupportFragmentManager().beginTransaction().add(fl.getId(), myFrag).commit();
ll.addView(b);
ll.addView(fl);
setContentView(ll);
}
public static class myFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
TextView tv = new TextView(getActivity());
tv.setText("My fragment");
tv.setGravity(Gravity.CENTER);
tv.setBackgroundColor(Color.RED);
return tv;
}
}
}

This is more or less how I have handled this. Have all your fragments implement an interface something like:
public interface NamedFragment{
public FragmentName getFragmentName();
}
Make an enum corresponding to your fragments:
public enum FragmentName{
SOME_FRAGMENT,
SOME_OTHER_FRAGMENT;
}
Then in your fragment switching activity:
// Get the manager and transaction separately so you can use both:
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction ft = fragmentManager.beginTransaction();
// Get a reference to the fragment(s) currently in the container(s)
Fragment currentFragment = fragmentManager.findFragmentById(position);
FragmentName cFragmentName =
((NamedFragment) currentFragment).getFragmentName();
Fragment nextFragment =
Fragment.instantiate(this, some_new_fragment_string);
FragmentName nFragmentName =
((NamedFragment) nextFragment).getFragmentName();
// Compare the "names"
if(cFragmentName != nFragmentName){
ft.replace(position, nextFragment);
}
You'll have to change things around a little to fit your particulars.