trouble associating a listView id with findViewby() in android - android

I am trying to populate a list view, and am trying to select my listview in my main with:
lv = (ListView) findViewById(R.layout.activity_main.xml.id);
My folder structure for XML is:
res>layout>activity_main.xml
and my main_activity.xml file looks like this:
<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" >
<ListView
android:id="#android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true" >
</ListView>
</RelativeLayout>
I think this is a simple mistake of me not fully understanding how the xml id value works in android.


Change the below
In OnCreate
setContentView(R.layout.activity_main);
lv = (ListView) findViewById(R.id.list);
Change listview in xml
<ListView
android:id="#+id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true" >
</ListView>


Try like below:
setContentView(R.layout.activity_main);
lv = (ListView) findViewById(R.id.ist);
and in xml change id of listview like below:
android:id="#+id/list"


Try this in the activity code file (java)
ListView lv = (ListView) findViewById(android.R.id.list);


In onCreate() you will find setContenctView(R.layout.activity_main); If not then you must add it. Make sure it is set to the xml activity you want to work with in the code java file. Then you can easily refer to the listView by using
lv = (ListView) findViewById(R.id.list);
Also the id in xml of a control is defined in the following form
<ListView
android:id="#+id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true" >
</ListView>

Related

Listview dynamically allocate width

I want to allow my ListView to be wrapped to its content on its width and making it aligning to the parent centre.
This is what a normal ListView is giving me
This is almost what i want to achieve, only that i want the ListView to wrap by the longest test in the ListView. Currently this is achieved by declaring the dp which is something I would like to avoid if possible
Some codes for first image:
<ListView
android:id="#+id/lst_test"
android:layout_width="0dip"
android:layout_weight="1"
android:layout_height="wrap_content" >
</ListView>
Some codes for second image:
<ListView
android:id="#+id/lst_test"
android:layout_width="200dp"
android:layout_height="wrap_content" >
</ListView>
Do I have to use custom adapter for this or I can stick with the current one? If I would need to use custom adapter, how do i go about doing this?

You don't need to create custom adapter. Here is an example which can help you.
public class MainActivity extends Activity {
HashMap <String, CheckBox> options = new HashMap<String, CheckBox>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView list_view = (ListView) findViewById(R.id.listView1);
ArrayList<String> str = new ArrayList<String>();
for (int i = 0; i < 10; i++) {
str.add("Example " + i);
}
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.list_layout, R.id.textView1, str);
list_view.setAdapter(adapter);
}
}
Above I have created an activity in which i am getting listview and setting data using ArrayAdapter.
I have created two layouts :
First layout: Contains listview.
Second layout: Contains textview which need to display.
Main logic to align data at center of Listview is you need to set gravity of textview as center.
You can manage second layout according to your needs.
Here is my first XML layout:
<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" >
<ListView
android:id="#+id/listView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true" >
</ListView>
</RelativeLayout>
Here is my second layout:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/RelativeLayout1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:gravity="center"
android:text="TextView" />
</RelativeLayout>
If you are still facing any problem then you can ask. If you need more flexibility then you can create custom adapter by inheriting ArrayAdapter class.
Here is an example of custom adapter: How do I link a checkbox for every contact in populated listview?
Hope it will help you.

Two ListViews in one activity in android 3.0 and above

In Android 2.1 and 2.3 it works fine. But for 3.0 and above findViewById does not find the second ListView. I have already tried cleaning the project, tried not using ListActivity too, nothing helped. Any ideas?
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setListAdapter(List1Adaptor);
list1 = (ListView) findViewById(android.R.id.list);
list2 = (ListView) findViewById(R.id.ListView2);
list2.setAdapter(List2Adapter);//Null Pointer
}
the main.xml
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/linearLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<ListView
android:id="#+id/ListView2"
android:layout_height="wrap_content"
android:layout_width="fill_parent" >
</ListView>
</LinearLayout>
<RelativeLayout
android:id="#+id/listLayout_relativeLayout2"
android:layout_height="320dp"
android:layout_width="fill_parent" >
<ListView
android:id="#android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
</ListView>
</RelativeLayout>

Your xml file is missing a root view. I'm surprised it works on any version of Android. You should surround everything with a linear layout or something like that.

Your layout has android:id="#+id/listView2" (note: lowercase 'l') and your Java code is requesting R.id.ListView2 (note: uppercase 'L'). Try using the same case in both situations.

Android: id list view

I have a list view declared in my xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:background="#F7EFE8">
<ListView android:id="#+id/android:list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
<TextView android:id="#+id/android:empty"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/no_message"/>
</LinearLayout>
But when I try to declare/use it to java, the id is not found. But when i rename the list view to something else and try to use it i can see it "R.id._" but when R.id.list I can't find it. And If I didn't use the android:list there's an error that there should be a list view whose id is android:list. Any help here?

Your ListView object id should be specified either as android:id="#android:id/list"
ListView lv = (ListView) findViewById(android.R.id.list);
or it should have some other id like android:id="#+id/sampleList"
ListView lv = (ListView) findViewById(R.id.sampleList);
Check this : ListActivity
and list
Hope this would help.

In xml layout use,
<ListView
android:id="#+id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
In Java Code:
ListView listview=(ListView)findViewById(R.id.list);// it takes id of listview from xml
if you need to use android id for listview then replace your code as
<ListView
android:id="#+android:id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
It may help you..

Try this: android:id="#+id/list"
Then clean project and rebuild.
In java, just call findViewById like this:
ListView lv = (ListView)findViewById(R.id.list);
Ref: http://developer.android.com/reference/android/view/View.html

List id not found: android:list

Iam trying to find the id for the listview, but it dosen't work just typing like this:
this.view = (ListView) findViewById(R.id.list);
R.id.list -> dosen't work, cause it can't find the id
Iam using my own custom made list.
<ListView
android:id="#+id/android:list"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />

<ListView
android:id="#android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
</ListView>
To obtain it:
findViewById(android.R.id.list);

Showing empty view when ListView is empty

For some reason the empty view, a TextView in this case, always appears even when the ListView is not empty. I thought the ListView would automatically detect when to show the empty view.
<RelativeLayout android:id="#+id/LinearLayoutAR"
android:layout_height="fill_parent"
android:layout_width="fill_parent">
<ListView android:id="#+id/ARListView"
android:layout_width="fill_parent"
android:layout_height="fill_parent"></ListView>
<ProgressBar android:id="#+id/arProgressBar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"></ProgressBar>
<!-- Here is the view to show if the list is emtpy -->
<TextView android:id="#id/android:empty"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="No Results" />
</RelativeLayout>
How can I hook up the empty view properly?

When you extend FragmentActivity or Activity and not ListActivity, you'll want to take a look at:
ListView.setEmptyView()

It should be like this:
<TextView android:id="#android:id/empty"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="No Results" />
Note the id attribute.

As appsthatmatter says, in the layout something like:
<ListView android:id="#+id/listView" ... />
<TextView android:id="#+id/emptyElement" ... />
and in the linked Activity:
this.listView = (ListView) findViewById(R.id.listView);
this.listView.setEmptyView(findViewById(R.id.emptyElement));
Does also work with a GridView...

I tried all the above solutions.I came up solving the issue.Here I am posting the full solution.
The xml file:
<RelativeLayout
android:id="#+id/header_main_page_clist1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="20dp"
android:paddingBottom="10dp"
android:background="#ffffff" >
<ListView
android:id="#+id/lv_msglist"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:divider="#color/divider_color"
android:dividerHeight="1dp" />
<TextView
android:id="#+id/emptyElement"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:text="NO MESSAGES AVAILABLE!"
android:textColor="#525252"
android:textSize="19.0sp"
android:visibility="gone" />
</RelativeLayout>
The textView ("#+id/emptyElement") is the placeholder for the empty listview.
Here is the code for java page:
lvmessage=(ListView)findViewById(R.id.lv_msglist);
lvmessage.setAdapter(adapter);
lvmessage.setEmptyView(findViewById(R.id.emptyElement));
Remember to place the emptyView after binding the adapter to listview.Mine was not working for first time and after I moved the setEmptyView after the setAdapter it is now working.
Output:

I highly recommend you to use ViewStubs like this
<FrameLayout
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1" >
<ListView
android:id="#android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
<ViewStub
android:id="#android:id/empty"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout="#layout/empty" />
</FrameLayout>
See the full example from Cyril Mottier

<ListView android:id="#+id/listView" ... />
<TextView android:id="#+id/empty" ... />
and in the linked Activity:
this.listView = (ListView) findViewById(R.id.listView);
this.listView.setEmptyView(findViewById(R.id.empty));
This works clearly with FragmentActivity if you are using the support library. Tested this by building for API 17 i.e. 4.2.2 image.

Activity code, its important to extend ListActivity.
package com.example.mylistactivity;
import android.app.ListActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import com.example.mylistactivity.R;
// It's important to extend ListActivity rather than Activity
public class MyListActivity extends ListActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mylist);
// shows list view
String[] values = new String[] { "foo", "bar" };
// shows empty view
values = new String[] { };
setListAdapter(new ArrayAdapter<String>(
this,
android.R.layout.simple_list_item_1,
android.R.id.text1,
values));
}
}
Layout xml, the id in both views are important.
<?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">
<!-- the android:id is important -->
<ListView
android:id="#android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
<!-- the android:id is important -->
<TextView
android:id="#android:id/empty"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="i am empty"/>
</LinearLayout>

Just to add that you don't really need to create new IDs, something like the following will work.
In the layout:
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#android:id/list"/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#android:id/empty"
android:text="Empty"/>
Then in the activity:
ListView listView = (ListView) findViewById(android.R.id.list);
listView.setEmptyView(findViewById(android.R.id.empty));

I had this problem. I had to make my class extend ListActivity rather than Activity, and rename my list in the XML to android:id="#android:id/list"

A programmatically solution will be:
TextView textView = new TextView(context);
textView.setId(android.R.id.empty);
textView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
textView.setText("No result found");
listView.setEmptyView(textView);

First check the list contains some values:
if (list.isEmpty()) {
listview.setVisibility(View.GONE);
}
If it is then OK, otherwise use:
else {
listview.setVisibility(View.VISIBLE);
}

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