Develop Reference

How to fix error on android webview

So here are my codes :
public class AboutActivity extends Activity{
WebView aboutwebview;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.edit_profile_settings);
aboutwebview = (WebView) findViewById(R.id.aboutwebview);
aboutwebview.setHorizontalScrollBarEnabled(false);
aboutwebview.loadUrl("file:///android_asset/pickld.html");
}
}
and here is the xml file :
<?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" >
<LinearLayout
android:id="#+id/header"
android:layout_width="match_parent"
android:layout_height="45dp"
android:background="#7fad33"
android:gravity="center"
android:orientation="horizontal" >
<TextView
android:id="#+id/tv0"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:text="Our Team"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textColor="#fff" />
</LinearLayout>
<WebView
android:id="#+id/aboutwebview"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
and im pretty sure that the html file is on the assets folder, i also put a permission on the manifest file, but when i run the application, im getting a force close error its says that the problem is on this line :
aboutwebview.loadUrl("file:///android_asset/pickld.html");
im wondering what could be the problem.
here's the logcat error :

If this line causes NPE
aboutwebview.loadUrl("file:///android_asset/pickld.html");
means your aboutwebview is null. Either you refer to the wrong id or you set the wrong layout to your activity with setContentView(R.layout.edit_profile_settings);. Make sure you do that right to avod NPE.

Sidebar in each activity

For an application I am designing we have to deal with some "special" needs of our users. One of these is to create a navigation sidebar that has to appear in almost all the activities.
This navigation bar has to contain always the same three buttons that links to three activities: HOME, INFO, CONFIGURATION.
Each of these three activities can also load others activities that can (or cannot) contain this navigation bar.
Each of these buttons has to reset the current activity-stack status bringing to the top the corresponding activity selected by the user.
The navigation bar has to be customisable (made visible/invisible) and I would like also to deactivate some of the buttons.
EDIT: It has to be similar to a Drawer, but the buttons have to be highly customisable (in size and appearance) and it has to be always on (no sliding functions).
What is the best way to achieve that without manually including those buttons in each of my layouts?

You can create this layout manually but only once - in your ActivityBase class. Other activities can extend this base class.
EDIT:
As I said, I'm improving my answer.
So my idea is to create an Activity with menu. And if other Activity needs to have the same menu it can extend this ActivityBase and add it's own layout.
Let's look on a simple example.
ActivityBase 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"
tools:context=".MainActivity" >
<RelativeLayout
android:id="#+id/menu"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:background="#android:color/black" >
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:text="Button" />
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="#+id/button1"
android:layout_centerHorizontal="true"
android:text="Button" />
<Button
android:id="#+id/button3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="#+id/button2"
android:layout_alignBottom="#+id/button2"
android:layout_alignParentRight="true"
android:text="Button" />
</RelativeLayout>
<RelativeLayout
android:id="#+id/container"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_below="#+id/menu" >
</RelativeLayout>
</RelativeLayout>
As you can see I created a simple layout that contains menu bar and a container for layout from Activities that will be extending AcivityBase.
Now ActivityBase:
public class ActivityBase extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_base);
}
}
It's a simple Activity, but if you want, you can also place here menu events handling if they are the same for all Activities that will be extending this.
And now let's see at SecondActivity's 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/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<EditText
android:id="#+id/editText1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10" >
<requestFocus />
</EditText>
</LinearLayout>
It's a normal layout, nothing special. I put some controls in there just for purpose of this example.
And SecondActivity class:
public class SecondActivity extends MainActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LayoutInflater inflater = getLayoutInflater();
inflater.inflate(R.layout.second_activity, (ViewGroup) findViewById(R.id.container));
}
}
It extends ActivityBase and what is important - it does not call setContentView. Instead we are creating LayoutInflater and we are inflating second_activity layout in the container that we created in activity_base layout.

Fragment does not show after inflating [Fixed, but...]

I'm trying to create a music player that will be visible in all my activities. To do this, I'm going to use a Fragment as some of you advised me earlier.
Since I have no experience with Fragments whatsoever, I decided to implement a fragment in a "filler" activity first.
I created a simple fragment containing only a button and some text, and try to inflate that in my filler activity.
However, after inflating this fragment does not show up. A message does get printed to LogCat telling me that the fragment has been inflating.
I'm pretty sure I'm missing something, but since I have no experience with this and I couldn't find a tutorial that quite explained how to do this, I don't know what it is that I'm missing.
Music player Fragment
public class AppMusicPlayer extends Fragment{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
System.out.println("fragment added");
return inflater.inflate(R.layout.musicplayer_main, container, false);
}
}
Music Player layout
<?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="wrap_content"
android:orientation="vertical" >
<Button
android:id="#+id/button1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Button" />
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="This is the fragment you're looking for" />
</LinearLayout>
Filler Activity
public class Filler extends FragmentActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.filler);
Button b = (Button) findViewById(R.id.terug);
b.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {
Intent intent = new Intent();
setResult(RESULT_OK, intent);
finish();
}
});
}
}
Filler 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" >
<!-- Title bar -->
<RelativeLayout
android:id="#+id/linearLayout1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:background="#drawable/title_bar" >
<TextView
android:id="#+id/fillertitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="Work In Progress"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textStyle="bold" >
</TextView>
<Button
android:id="#+id/terug"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_centerVertical="true"
android:background="#drawable/button_back"
android:text="Back"
android:textColor="#FFFFFFFF"
android:textStyle="bold" >
</Button>
</RelativeLayout>
<!-- End of title bar -->
<TextView
android:id="#+id/wip"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="This section of the app has not been made yet. Work in progress." >
</TextView>
<fragment
android:id="#+id/musicPlayerFragment"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:name="com.mobowski.app.player.AppMusicPlayer" />
</LinearLayout>
Obviously I'm doing something wrong, but what?
Note: I'm using Android 2.3 with the Compatibility library.
Any help is appreciated
The problem has been fixed with the help of Yashwanth Kumar and blessenm. One gave an XML solution, the other a programmatic solution. Now I'm just wondering which solution is the most desirable one. Are there any concessions to be made with either of the solutions, or does it all boil down to the programmer's preferred solution?

I haven't tried adding fragments directly to xml. But what I normally do is add a framelayout or linearlayout to the filler layout.
Suppose its id is 'fragment_holder'. I use the following code in the fragment activity right after setContentView. Try this
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(R.id.fragment_holder,new AppMusicPlayer(),"musicplayer");
ft.commit();

you should mention layout_height as 0dip, not the width in vertical linear layout.
change that it should work.
<fragment
android:id="#+id/musicPlayerFragment"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_weight="1"
android:name="com.mobowski.app.player.AppMusicPlayer" />

ImageView xml being returned as TextView

I declared a ImageView on my layout (XML) but when I try to grab it by the ID I'm getting a TextField!?! Then my code throw a ClassCastException.
Here is my layout code (splash.xml):
<?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"
style="#android:style/Theme.Light" android:layout_height="wrap_content" android:background="#drawable/bg">
<ImageView android:layout_height="wrap_content" android:layout_width="match_parent" android:src="#drawable/splash" android:layout_marginTop="20pt" android:id="#+id/splashLogo"></ImageView>
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="#string/app_name" android:id="#+id/splashTitle" android:textStyle="bold" android:textSize="#dimen/title_size" android:layout_gravity="center" android:lineSpacingExtra="#dimen/spacer" android:gravity="center"></TextView>
<TextView android:id="#+id/splashCopyleft" android:textSize="#dimen/version_size" android:lineSpacingExtra="#dimen/version_spacing" android:layout_width="wrap_content" android:gravity="center" android:layout_height="wrap_content" android:text="#string/app_version_info" android:layout_gravity="center" android:textColor="#color/version"></TextView>
</LinearLayout>
Here is my Java (Activity) code:
// imports
public class SplashActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.splash);
// Grab a ClassCastException here
ImageView logo = (ImageView) findViewById(R.id.splashLogo);
// Never get here :'(
Log.i("GOT", logo.toString());
}
}

Sometimes Eclipse shifts resource ids. Try cleaning your project and building it again.

First, clean your project and then build it.
If the problem persists, close Eclipse and re-open it.

Add ExpandableListView to a tab with other elements

I am developing an app with tabs. On one of the tabs,
I have two EditText fields and a couple of buttons. I want to add an ExpandableListView
to the tab, below the rest of the elements.
My problem is that the current class extends Activity. All the example I've found extend ExpandableListActivity, but I can't extend both for the same class.
How can I add this list to the tab? I've added an ExpandableListView element in the XML file, but whenever I run it, it doesn't show up. I understand that I need to bind the view to some data, but how do I go about doing this?
Thank you.
Here is my class code:
public class DirectionsTab extends Activity
{
private Button clear_btn;
private Button go_btn;
private EditText origin_txt;
private EditText dest_txt;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.directions_tab);
// initialize views and onClick event handler
origin_txt = (EditText)findViewById(R.id.origin_txt);
dest_txt = (EditText)findViewById(R.id.dest_txt);
clear_btn = (Button)findViewById(R.id.clear_btn);
// clear all text fields and return focus to dest_txt
clear_btn.setOnClickListener(new OnClickListener(){
#Override
public void onClick(View v)
{
origin_txt.setText("");
dest_txt.setText("");
origin_txt.requestFocus();
}
});
} // end public void onCreate(Bundle savedInstanceState)
} // end public class DirectionsTab extends Activity
and XML:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:id="#+id/origin_lbl"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Origin"/>
<EditText
android:id="#+id/origin_txt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="#android:drawable/editbox_background"
android:layout_below="#id/origin_lbl"/>
<TextView
android:id="#+id/dest_lbl"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="#id/origin_txt"
android:text="Destination" />
<EditText
android:id="#+id/dest_txt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="#android:drawable/editbox_background"
android:layout_below="#id/dest_lbl" />
<ExpandableListView
android:id="#+id/listView"
android:layout_below="#+id/dest_txt"
android:layout_height="wrap_content"
android:layout_width="wrap_content" /><!--android:id="#android:id/list"-->
<Button style="?android:attr/buttonStyleSmall"
android:id="#+id/clear_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#id/dest_txt"
android:layout_alignParentRight="true"
android:layout_marginLeft="10dip"
android:layout_marginTop="10dip"
android:text="Clear" />
<Button style="?android:attr/buttonStyleSmall"
android:id="#+id/go_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toLeftOf="#id/clear_btn"
android:layout_alignTop="#id/clear_btn"
android:text="Go!" />
</RelativeLayout>

I got this!, If anyone is having problems with this, make sure you follow these steps:
Copy and paste ExpandableList3 example (located in ApiDemos project from Samples folder in your Android SDK). This is just a good example of how to set up a list.
Make your class inherit from ExpandableListActivity
Create the following in your XML layout file:
<ExpandableListView
android:id="#android:id/list"
android:layout_below="#+id/go_btn"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"/>
It is VERY important that the ID property matches what you see above, otherwise, nothing will work. This little detail wasted plenty of hours for me and was discovered seating neatly as a small detail in the android docs.