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LayoutInflater doesnt work

Im building like an chat app, so I want to add elements (user picture and message) on the go to my current view. The problem is in the showMessage function, nothings happens but no error too.
Here's my code:
ChatActivity -> showMessage:
RelativeLayout rly = new RelativeLayout(ChatActivity.this);
rly.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT));
LayoutInflater inflater = getLayoutInflater();
View viewToAppend = inflater.inflate(R.layout.messages,null);
rly.addView(viewToAppend);
messages XML:
<ImageView
android:id="#+id/imageView1"
android:layout_width="40dp"
android:layout_height="40dp"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:src="#drawable/fede" />
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_marginLeft="10dp"
android:layout_toRightOf="#+id/imageView1"
android:text="messagetext" />
</RelativeLayout>
UPDATE
Adding setContentView(rly); works, but replace all the content with the "xml loaded", i want to append it, not replace all.

if you want to add a layout to the inflater you can just use the inflate method with the layout id as the parameter.
View v = ((LayoutInflater) context.getSystemService( Context.LAYOUT_INFLATER_SERVICE )).inflate(R.layout.info_window_adapter_layout, null);
Where context the the reference to the activity context

You may be try like codes. such as
LayoutInflater inflater = (LayoutInflater) this
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
May be work successfully. Best of luck!

You create a new RelativeLayout and add the messages view to it, but you never attach the RelativeLayout to the content view. Assign your main layout an id (such as 'main_layout') in your layout xml, then add this:
RelativeLayout mainLayout = (RelativeLayout) findViewById(R.id.main_layout);
mainLayout.addView(rly);

added footer view to list activity listview but it doesn't show

i have a xml file for footer view with a textview inside it, i have inflated the footer view and extracted textview from it, then i added it to list activity's list view as footer view but it doesn't show when i run it. here is the code:
LayoutInflater inflater=(LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View view = inflater.inflate(R.layout.footer_view, null);
TextView footer=(TextView) view.findViewById(R.id.footer);
getListView().addFooterView(footer);
and here is the xml file content:
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/footer"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="#string/footer_text"
android:textColor="#0000FF"
android:textSize="20sp" />
what's wrong?

Try adding your footer view like this:
LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
TextView footer = (TextView) inflater.inflate(R.layout.footer_view, getListView(), false);
getListView().addFooterView(footer);
Update: Just looked up how I did it in one of my projects, so this should work as well:
TextView footer = (TextView) getLayoutInflater().inflate(R.layout.footer_view, getListView(), false);
getListView().addFooterView(footer);

Why do I keep getting a null reference to my LinearLayout?

I have a layout called view.xml which contains a View called view_related. Basically, in my dictionary app, if there are related words to an entry, I will replace view_related with a LinearLayout that contains a header "Related entries" and a bunch of TextViews representing every related word.
I keep getting a NullPointerException everytime I'm adding a TextView to the LinearLayout in my Activity's onCreate() method, and I don't understand why though my code looks pretty straightforward.
view.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView android:id="#+id/view_header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="12pt"
android:textColor="#fff"
android:textStyle="bold"
android:background="#990011"
android:padding="10dp"
android:text="lalala word"
/>
<ScrollView android:id="#+id/view_description"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#id/view_header">
<LinearLayout android:id="#+id/view_description_content"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="20dp"
android:text="#string/demo_definition"
/>
<!-- THIS WILL BE REPLACED -->
<View android:id="#+id/view_related"
android:layout_width="match_parent"
android:layout_height="wrap_content"></View>
</LinearLayout>
</ScrollView>
</RelativeLayout>
view_related.xml, the LinearLayout that will replace the View element in view.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/view_related_entries"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView android:id="#+id/view_related_header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="5dp"
android:textColor="#fff"
android:textStyle="bold"
android:textSize="7pt"
android:background="#000"
android:text="Related entries"
/>
<LinearLayout android:id="#+id/view_related_list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
>
</LinearLayout>
</LinearLayout>
And finally, the onCreate method, which for now assumes the related entries are "Hello" and "Goodbye:"
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view);
LinearLayout ll = (LinearLayout) findViewById(R.id.view_related_list);
TextView tv = new TextView(this);
tv.setText("Hello");
ll.addView(tv); // NULL POINTER EXCEPTION
tv = new TextView(this);
tv.setText("Goodbye");
ll.addView(tv);
LayoutInflater li = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
View view = findViewById(R.id.view_related);
ViewGroup parent = (ViewGroup) view.getParent();
int index = parent.indexOfChild(view);
parent.removeView(view);
View llview = li.inflate(R.id.view_related_entries, parent, false);
parent.addView(llview, index);
}

setContentView(R.layout.view);
LinearLayout ll = (LinearLayout) findViewById(R.id.view_related_list);
The function findViewById only finds views that are actually set. Your current setContentView does not set an xml that has the id you are looking for in it, so the first line I quoted will not result in anything.
You should either load the correct XML, or inflate the view you are looking for with an inflater

the line (LinearLayout ll = (LinearLayout) findViewById(R.id.view_related_list);) will search for view_related_list in view.xml, as in the line before that is the view you are using..
You need to inflate view_related.xml first and then get the view from it..

You're doing a lot of wrong things in your code. First you search for a LinearLayout that isn't in the current layout and also isn't in any inflated layout at that moment. Second, you try to inflate an id reference instead of a layout reference. Last, you should use another approach for what you're trying to do. Your code should be(from what I understood):
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view);
LayoutInflater li = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
View view = findViewById(R.id.view_related);
ViewGroup parent = (ViewGroup) view.getParent();
int index = parent.indexOfChild(view);
parent.removeView(view);
View llview = li.inflate(R.layout.view_related, parent, false); // is view_related the name of the extra layout file?
parent.addView(llview, index);
LinearLayout ll = (LinearLayout) findViewById(R.id.view_related_list); // or search for it in llview, llview.findViewById(R.id.view_related_list);
TextView tv = new TextView(this);
tv.setText("Hello");
ll.addView(tv); // NULL POINTER EXCEPTION
tv = new TextView(this);
tv.setText("Goodbye");
ll.addView(tv);
}
This is a situation when you should use a ViewStub to add the new layout file. Although, I don't understand why don't you add the new layout file directly in the view.xml if you're going to add the layout's content in the onCreate method.

i think you need to use setContentView(R.layout.view_related); instead of setContentView(R.layout.view);
or another simple thing you can do is take the linear layout in the same layout "view" and make it invisible when not required and visible when required

You may forgetting to declare your Activity in manifest.xml

Inflater inflate but height is small ( looks like wrap_content and need fill_parent)

I have layout and I want to inflate that
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<EditText
android:id="#+id/editText1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
</EditText>
</LinearLayout>
like
LinearLayout ll=(LinearLayout)findViewById(R.id.llContainer);
View view;
LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = inflater.inflate(R.layout.question_free_text, null);
ll.addView(view);
where ll is
<LinearLayout
android:id="#+id/llContainer"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_marginTop="20dp"
android:layout_marginBottom="20dp"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
>
</LinearLayout>
in other xml, but problem is when it inflate it shows but height is big (fill_parent, it looks like wrap_content, but there is no wrap_content in layout). Can anybody help me ?

As Yashwanth Kumar correctly mentioned in the comments, the second parameter of the inflate-method should be the root view in which the new view will be inserted:
LinearLayout ll = (LinearLayout) findViewById(R.id.llContainer);
View view;
LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = inflater.inflate(R.layout.question_free_text, ll);
If a root view is provided in the inflate-call, the LayoutInflator calls the generateLayoutParams(ViewGroup.LayoutParams p) method of this root view to get some LayoutParams (basically containing information about how big a view can/should be) which will be passed to the new view.
Note that if you provide a root view, the inflated view will be automatically added to the root view via root.addView(View child, LayoutParams params).
You can also pass a third parameter to the inflate-method (boolean attachToRoot), if this value is false, the new view will not be added automatically to the root view, but the LayoutParams are still set with setLayoutParams(params). You can use this if you wand to add you view manually to the root view (e.g. at a specific position/index):
LinearLayout ll = (LinearLayout) findViewById(R.id.llContainer);
View view;
LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = inflater.inflate(R.layout.question_free_text, ll, false); // the LayoutParams of view are set here
ll.addView(view, 2);

Android - Dynamically Add Views into View

I have a layout for a view -
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="0px"
android:orientation="vertical">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="#+id/items_header"
style="#style/Home.ListHeader" />
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="#+id/items_none"
android:visibility="gone"
style="#style/TextBlock"
android:paddingLeft="6px" />
<ListView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="#+id/items_list" />
</LinearLayout>
What I want to do, is in my main activity with a layout like this
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="0px"
android:id="#+id/item_wrapper">
</LinearLayout>
I want to loop through my data model and inject multiple views consisting of the first layout into the main layout. I know I can do this by building the controls completely within the code, but I was wondering if there was a way to dynamically build the views so that I can continue using a layout instead of putting everything in code.

Use the LayoutInflater to create a view based on your layout template, and then inject it into the view where you need it.
LayoutInflater vi = (LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v = vi.inflate(R.layout.your_layout, null);
// fill in any details dynamically here
TextView textView = (TextView) v.findViewById(R.id.a_text_view);
textView.setText("your text");
// insert into main view
ViewGroup insertPoint = (ViewGroup) findViewById(R.id.insert_point);
insertPoint.addView(v, 0, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT));
You may have to adjust the index where you want to insert the view.
Additionally, set the LayoutParams according to how you would like it to fit in the parent view. e.g. with FILL_PARENT, or MATCH_PARENT, etc.

See the LayoutInflater class.
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
ViewGroup parent = (ViewGroup)findViewById(R.id.where_you_want_to_insert);
inflater.inflate(R.layout.the_child_view, parent);

It looks like what you really want a ListView with a custom adapter to inflate the specified layout. Using an ArrayAdapter and the method notifyDataSetChanged() you have full control of the Views generation and rendering.
Take a look at these tutorials
http://www.softwarepassion.com/android-series-custom-listview-items-and-adapters/
http://developerlife.com/tutorials/?p=327
http://www.androidguys.com/2008/07/14/fancy-listviews-part-one/

To make #Mark Fisher's answer more clear, the inserted view being inflated should be a xml file under layout folder but without a layout (ViewGroup) like LinearLayout etc. inside. My example:
res/layout/my_view.xml
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/i_am_id"
android:text="my name"
android:textSize="17sp"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"/>
Then, the insertion point should be a layout like LinearLayout:
res/layout/activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/aaa"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:id="#+id/insert_point"
android:layout_width="match_parent"
android:layout_height="match_parent">
</LinearLayout>
</RelativeLayout>
Then the code should be
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_shopping_cart);
LayoutInflater inflater = getLayoutInflater();
View view = inflater.inflate(R.layout.my_view, null);
ViewGroup main = (ViewGroup) findViewById(R.id.insert_point);
main.addView(view, 0);
}
The reason I post this very similar answer is that when I tried to implement Mark's solution, I got stuck on what xml file should I use for insert_point and the child view. I used layout in the child view firstly and it was totally not working, which took me several hours to figure out. So hope my exploration can save others' time.

// Parent layout
LinearLayout parentLayout = (LinearLayout)findViewById(R.id.layout);
// Layout inflater
LayoutInflater layoutInflater = getLayoutInflater();
View view;
for (int i = 1; i < 101; i++){
// Add the text layout to the parent layout
view = layoutInflater.inflate(R.layout.text_layout, parentLayout, false);
// In order to get the view we have to use the new view with text_layout in it
TextView textView = (TextView)view.findViewById(R.id.text);
textView.setText("Row " + i);
// Add the text view to the parent layout
parentLayout.addView(textView);
}