Develop Reference

Can I limit findViewById() to within the scope of an individual fragment?

In my application, I have multiple instances of the same fragment, Activity_Fragment, displayed in a LinearLayout. In each fragment, there is an activity_text textview and an edit_button. When the button is pressed in a fragment, it should change the text of the textview in the same fragment. However, when multiple instances of the fragment are added, any edit_button pressed in any fragment will only change the activity_text textview in the first fragment added to the LinearLayout. This is because all fragments are identical, and their child views share the same id's. Each fragment should act independently of one other; any edit_button pressed in a fragment should only affect that fragment.
Is it possible to have the findViewById() method limited to the scope of an individual fragment so that one fragment won't be affected by an event in another fragment, or will I have to somehow change the id of each view in a fragment upon creation?
Here is the Activity Fragment xml:
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/activity_fragment">
<CheckBox
android:id="#+id/checkbox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="32dp"
android:layout_marginTop="16dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/activity_text"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginEnd="5dp"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:text="Edit Activity"
android:textSize="18sp"
app:layout_constraintBaseline_toBaselineOf="#+id/checkbox"
app:layout_constraintLeft_toRightOf="#+id/checkbox"
app:layout_constraintRight_toLeftOf="#+id/edit_button"/>
<Button
android:id="#+id/edit_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="16dp"
android:layout_marginEnd="16dp"
android:layout_marginTop="16dp"
android:onClick="editActivity"
android:text="Edit Activity"
app:layout_constraintBaseline_toBaselineOf="#+id/checkbox"
app:layout_constraintRight_toRightOf="parent"/>
Here is my MainActivity.java with the ActivityFragment class. The onClick method for the edit_button is at the very bottom:
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public static class ActivityFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup
container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.activity_fragment, container,
false);
}
}
public void addActivity(View view) {
ActivityFragment fragment1 = new ActivityFragment();
getSupportFragmentManager().beginTransaction()
.add(R.id.fragment_container, fragment1).commit();
}
//This is the editButton method
public void editActivity(View view) {
TextView activityText = (TextView) findViewById(R.id.activity_text);
activityText.setText("success");
}
}

Your problem can be solved by limiting the scope that findViewById() scans. If you want to look within a particular fragment, you'll probably want to call myFragment.getView().findViewById() (rather than just using findViewById() from your activity).
So how can you do this? Well, it's not easy with the way you have things set up. Since you're using the android:onClick attribute to set your click listener, you have to handle things from inside the activity.
So don't use android:onClick.
Instead, inside your Fragment's onCreateView() method, write something like this:
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.your_fragment, container, false);
Button button = (Button) root.findViewById(R.id.edit_button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
TextView activityText = (TextView) getView().findViewById(R.id.activity_text);
activityText.setText("success");
}
});
return root;
}

you can use view.findViewById(R.id.activity_text) instead of the method from the activity.

Fragment Add not work

I have tried to load a fragment dynamically by adding a fragment(AnotherFragment) to a layout(sample_content_fragment) in mainactivity .But it doesn't work when i click button1.The code below have run so the error isn't the Button.
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
AnotherFragment fragment = new AnotherFragment();
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction transaction = fragmentManager.beginTransaction();
transaction.add(R.id.sample_content_fragment, fragment);
transaction.commit();
break;
}
And here you can see mainactivity's layout:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<fragment
android:id="#+id/fregment_test"
android:name="com.example.henucmapus.TestFragment"
android:layout_width="match_parent"
android:layout_height="112dp" />
<FrameLayout
android:id="#+id/sample_content_fragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
Here is the fragment i want to load.
import android.app.Fragment;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class AnotherFragment extends Fragment{
public View OnCreateView(LayoutInflater inflater,ViewGroup container,
Bundle savedInstanceState){
View view =inflater.inflate(R.layout.anotherfragment,container, false);
return view;
}
}
Here is the fragment layout:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="#+id/t1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="11111111111"
/>
</LinearLayout>

OnCreateView means nothing in Android terms (at least in Java, Xamarin does have it capitalized).
The correct method you want is onCreateView. (lowercase on)
If you used annotations, you could see that.
For example.
public class AnotherFragment extends Fragment{
#Override
public View onCreateView(LayoutInflater inflater,ViewGroup container,
Bundle savedInstanceState){
View view = inflater.inflate(R.layout.anotherfragment,container, false);
return view;
}
}
And if that doesn't work, you seem to have no R.id.button1 in your main layout, so there's no fragment transaction being done anyway

Android Textview doesn't show text in a Fragment

I'm trying to add a Fragment to my FrameLayout, it seems that it is added correctly, but then i can't see the text of the TextView.
Fragment Layout:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
>
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/text1"
android:text="Hello"
android:background="#34f5d6"/>
</LinearLayout>
The FragmentClass:
import android.app.Fragment;
import android.content.Context;
import android.graphics.Color;
import android.os.Bundle;
import android.text.method.CharacterPickerDialog;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
public class TimerClass extends Fragment {
public static Fragment newInstance(Context context) {
TimerClass fragment = new TimerClass();
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstance){
ViewGroup root=(ViewGroup)inflater.inflate(R.layout.mylayout,container,false);
return root;
}
}
And the code i use to add the fragment to the FrameLayout
FragmentTransaction tx= getFragmentManager().beginTransaction();
Fragment fragment= TimerClass.newInstance(getApplicationContext());
tx.replace(R.id.fl, fragment);
tx.commit();
I don't undestand why it doesn't show the text, I tryed to change the color of the text but it doesn't work.
If I change the background of the TextView, it works; also if I add an OnClockListener on the TextView, it works. Only it doesn't show the text.
Can you help me?
EDIT:
I found the solution: the problem was with the FrameLayout; it's top part was covered by the action bar.
By fixing the layout of the FrameLayout the problem disappeared.

First simply change this
ViewGroup root=(ViewGroup)inflater.inflate(R.layout.mylayout,container,false);
return root;
to
View root = inflater.inflate(R.layout.mylayout,container,false);
return root;
Also this one
public static Fragment newInstance(Context context) {
TimerClass fragment = new TimerClass();
return fragment;
}
to
public static TimerClass getInstance() {
TimerClass fragment = new TimerClass();
return fragment;
}

I think issue is only with height and width of your TextView because you have sated them as match_parent
so try to replace
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/text1"
android:text="Hello"
android:background="#34f5d6"/>
with
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/text1"
android:text="Hello"
android:background="#34f5d6"/>

Android fragment not created after runtime

I'm trying to add a fragment to an activity after the content view in the activity has been set. I'm not using the compatibility package and have my target API set to 16. I'm expecting the activity to be set to the fragments layout after the setContentView method in the main activity but on runtime, the fragment is never added and the screen in blank. The callbacks for the life cycle events in the fragment are never called thus the System.outs don't output. Logcat doesn't output any errors relating to fragments either. If a fragment element is made in the activity_main.xml, the fragment works fine but adding it to the RelativeLayout in the class doesn't work. Can someone please help me? Thanks!
Edit: Tried using a FrameLayout as the fragment_container but no difference.
This is my main activity:
package com.example.derp;
import android.os.Bundle;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Fragment frag = new Fragment();
FragmentManager fManager = getFragmentManager();
fManager.beginTransaction().add(R.id.fragment_container, frag).commit();
}
}
This is my fragment:
package com.example.derp;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class Frag extends Fragment{
public Frag(){
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
System.out.println("onAttach");
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
System.out.println("onCreate");
}
#Override
public void onStart() {
super.onStart();
System.out.println("onStart");
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
System.out.println("onCreateView");
return inflater.inflate(R.layout.fragment_frag, container, false);//
}
}
This is the fragment_frag.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="Button" />
<EditText
android:id="#+id/editText1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/button1"
android:layout_centerHorizontal="true"
android:layout_marginBottom="64dp"
android:ems="10"
android:inputType="textPersonName" >
<requestFocus />
</EditText>
</RelativeLayout>
The activity_main.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<RelativeLayout
android:id="#+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent">
</RelativeLayout>
</RelativeLayout>

You are not creating the instance of your fragment class. Rather you are creating the base fragment class's object.
Change...
Fragment frag = new Fragment();
To...
Fragment frag = new Frag();

Fragment doesn't work

I have main layout like this
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal" >
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<Button
android:id="#+id/btn_showdetails"
android:layout_width="100dip"
android:layout_height="wrap_content"
android:layout_marginLeft="110dip"
android:layout_marginTop="15dip"
android:text="Show Details" />
</LinearLayout>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal"
android:id="#+id/my_parent_layout"
>
</LinearLayout>
</LinearLayout>
am trying to call another activity in the my_parent_layout using this class
package com.appnetics;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.View;
import android.widget.Button;
public class FragmenttestActivity extends FragmentActivity {
Button LogIn = null ;
final FragmentManager fragmentManager = getSupportFragmentManager() ;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
LogIn = (Button) findViewById(R.id.btn_showdetails);
LogInEvent() ;
}
public void LogInEvent(){
LogIn.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
details fragment = new details();
fragmentTransaction.add(R.id.my_parent_layout, fragment);
fragmentTransaction.commit();
}
});
}
}
the details layout is :
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="#+id/date_time_label"
android:layout_centerVertical="true"
android:layout_marginLeft="200dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="32dp"
android:textStyle="bold"
android:text="time_label"
/>
<TextView
android:id="#+id/last_view_time"
android:layout_toRightOf="#+id/date_time_label"
android:layout_alignBaseline="#+id/date_time_label"
android:layout_marginLeft="8dip"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="32dp"
/>
</LinearLayout>
and the layout code is
/* $Id: $
*/
package com.appnetics;
import java.text.SimpleDateFormat;
import java.util.Date;
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.TextView;
/**
* DateTime
*/
public class details extends Fragment {
private static String getDateTimeString(Date time) {
return new SimpleDateFormat("d MMM yyyy HH:mm:ss")
.format(time);
}
private final String time = getDateTimeString(new Date());
/** #see android.app.Fragment#onCreateView(android.view.LayoutInflater, android.view.ViewGroup, android.os.Bundle) */
#Override
public View onCreateView(
LayoutInflater inflater,
ViewGroup container,
Bundle b)
{
View view = inflater.inflate(
R.layout.details,
container,
false); //!!! this is important
((TextView) view.findViewById(R.id.last_view_time))
.setText(time);
return view;
}
}
the problem is that when click the button, nothing appear , any idea what's wrong in my code

Lets start!
On your details XML:
android:layout_toRightOf="#+id/date_time_label"
android:layout_alignBaseline="#+id/date_time_label"
this two tags are for relative layouts, the parent of the layouts must be of relative type in order to work.
android:layout_centerVertical="true"
This tag is also incorrect, if you want to center the text in the textview you can use two ways or wrap content in textView and set center in its parent or use:
android:gravity="right"
android:width="fill_parent"
This will be the detail_fragment.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="#+id/date_time_label"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="32dp"
android:textStyle="bold"
android:text="time_label"
/>
<TextView
android:id="#+id/last_view_time"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="right"
android:text="view time"
android:textSize="32dp" />
</LinearLayout>
On your main.xml you declare the schema lots of times! should be declared once on your root layout.
LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
So the main.xml will be...
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center_horizontal"
android:orientation="vertical" >
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/hello" />
<Button
android:id="#+id/add_fragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<LinearLayout
android:id="#+id/fragment_holder"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
</LinearLayout>
</LinearLayout>
The fragment is an element that is declared in its class and apply its xml.
public class DetailsFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment, container, false);
}
}
And in the main activity add it to the holder layout:
public class FragmentSimpleTestActivity extends FragmentActivity {
private Button addFragment;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final FragmentManager fragmentManager = getSupportFragmentManager();
addFragment = (Button) findViewById(R.id.add_fragment);
addFragment.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
DetailsFragment fragment = new DetailsFragment();
fragmentTransaction.add(R.id.fragment_holder,fragment, "MY_FRAG");
fragmentTransaction.commit();
}
});
}
}
Its important that fragmentTransaction.add has parameters
1: the id of the view to hold the fragment.
2: the fragment object.
3: a tag that is used to find the fragments in the stack.
and thats all :)
Enjoy your fragments! you can also set animations when adding or removing it.

onCreateView()
The system calls this when it's time for the fragment to draw its user interface for the first time. To draw a UI for your fragment, you
must return a View from this method that is the root of your
fragment's layout. You can return null if the fragment does not
provide a UI.
Call OnCreateView in your fragment class
return inflater.inflate(R.layout.fragmentlayout, container, false);

I had a similar problem, when fragment wasn't showing up. The problem was that I removed AndroidAnnotations, but forgot to move the code from onViewCreated and onCreate methods to the onCreateView. I found this mistake by comparing the code of two fragments - one, that was showing up and the other that wasn't. So, if you have similar problems, try to check the code of fragments. It may not show any errors at first glance, but will not still work or show up because of those errors.
Particularly, check that you have this method and that you inflate a view:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.your_fragment_layout, container, false);
return v;
}