Android :: How To Avoid NullPointerException When Using Custom Views Or SurfaceViews

Jun 12, 2009

I created a custom SurfaceView called CaptureView and tried to add it into main.xml file.The application seems to work fine but if I switch from main.xml tab to Layout in Eclipse the text NullPointerException appears instead of layout preview.Does anyone know how this issue could be solved?

Android :: How to avoid NullPointerException when using custom Views or SurfaceViews


Android :: Views And Their Child Views - How To Avoid The Ugly - Boxes - When Child Views In A View Has Another Color Than Background

Jan 6, 2010

I have a simple ListView and on that ListView I have placed a number of custom defined Views. The CustomView has ImageView and two TextViews.

The CustomView also has a "stateful drawable" as background, so that the background image (a 9-patch) changes if you press the Row in the ListView. When pressing the Row, the background image changes to a Red-ish thing.

The problem is that when the background changes from the default greyish, all the Views in the CustomView (ImageView and TextViews) still have their greyish background and thus creates very ugly greay boxes on top of the now redish background.

What is the best way to solve that problem? I hoped that such things were handled automatically (as it is done in for example .NET), but I was wrong it seems.

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Android : Avoid Re-drawing All Views In An ArrayAdapter?

Mar 25, 2010

I have an ArrayAdapter powering a ListView. I would like to change the data behind the ArrayAdapter and update the ListView's. Sounds like notifyDataSetChanged(); would be exactly what I am looking for, but it updates the entire ListView, and I would prefer to update on a row-by-row basis.

Is there a way to do this with ArrayAdapter, or do I need to manage my data some other way if I want this functionality?

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Android :: How To Cache Views And Avoid Calling OnCreate Everytime

Apr 27, 2009

With Android, I've got an application that seems calling "onCreate" every time on a new instance of an activity, because this activity is the son of an another and it finishes itself while it ends its role for one piece of data.

The calling of "onCreate" everytime seems to be re-parsing the xml to create the views and re-attaching/re-creating the listners to the code and so on. So Is there a way to "cache" an activity to be recalled everytime, without seeing it if we click on "back" in the mobile devie? it's like having it really hidden (not accessible with the back button) and destroyed only if it's necessary.

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Android :: Cannot Understand NullPointerException With Custom Adapter

Apr 28, 2010

I am trying to create a list view which as TextView that can display html content , an WebView and other basic TextViews.I tried to extend SimpleAdapter but i struck with the problem ,I will be glad if someone can point out the mistake i am doing.

In onCreate method:

CODE:.............

And my row.xml file looks like:

CODE:.............

The error i was getting was:

CODE:..................................

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Samsung Epic 4G : Avoid Getting Mobile Views (page) On Web Sites In Browser?

Sep 20, 2010

Does anyone know how to avoid getting mobile views (page) on web sites in the browser? I can't figure it out. My old HTC Hero had a way to not get the mobile versions..

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Android :: Android Custom Dialog NullPointerException

Jun 8, 2010

I cannot for the life of me figure out why I'm getting a NullPointerException.

When a user clicks on a particular image, a dialog window is supposed to pop-up and display a larger version of said image:

CODE:..............

The associated onCreateDialog looks like this:

CODE:.........

For reference, this is cover_dialog.xml:

CODE:....................

Now, when the image previously described is clicked, the application immediately crashes and throws the following error through LogCat:

CODE:......................

The line in question refers to this line inside of onCreateDialog:

coverLarge.setImageBitmap(book.getCover());

I don't get why coverLarge is null at that point.

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Android :: Using Custom Views In XML

Aug 16, 2010

im having a problem getting a custom view that i created on the xml layout file. i have a class named DrawingLayout which extends FrameLayout. it is found in the package Drawing

as stated on this page http://developer.android.com/guide/topics/ui/custom-components.html i used the following decleration in xml

<Drawing.DrawingLayout ... />

but whenever i run the program with that decleration i get a runtime exception error on SetContentView( ... )

is there something im not doing well? If you need any more details please tell me because i cant seem to figure this one out.

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Android :: Nest One Custom Views Within Another?

Nov 10, 2010

Is it possible to nest one custom views within another Custom view?

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Android :: DrawHeaderpanel Does Not Work In Custom Views

Aug 13, 2009

*I have used three custom views... playpanel works fine.. but drawHeaderpanel does not workk..*

public class MainPanel extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);...................

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Android :: How To Extend Resources Xml With Custom Views?

Aug 30, 2009

Does anybody knows if (and how ) I can write a custom view/widget and then use it in resources in layout defintions?

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Android :: Create Custom Text Views?

Oct 2, 2010

I am parsing the url to display the contents in it, my requirement i have to display the each content in separate textviews.

For Instance: Let us assume the contents in that url are FootBall, Carom , chess, VolleyBall and so on . I want to display FootBall as a individual textview similarly others. so i cannot declare the textviews in xml what i usually do.

CODE:................

So i planned to create textview via java code

This is my parsing code which parse the url contents and store the result in a string array namely san_tagname; depending upon the length of this variable i want to create number of textviews.

CODE:..................

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Android :: Views In Custom Compound Component Not Inflated

Jun 12, 2010

I have made a Custom Component in XML, consisting of a button with an imageview stacked on top of it:

<myapp.widget.ClearableCaptionedButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<Button
android:id="@+id/ccbutton_button"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical|left"
android:textAppearance="?android:attr/textAppearanceMedium"
android:background="@android:drawable/edit_text"/>
<ImageView
android:id="@+id/ccbutton_clear"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="5dip"
android:layout_alignRight="@id/ccbutton_button"
android:layout_alignTop="@id/ccbutton_button"
android:layout_alignBottom="@id/ccbutton_button"/>
</myapp.widget.ClearableCaptionedButton>

Extract of java source code:
public class ClearableCaptionedButton extends RelativeLayout implements OnClickListener {
...
public ClearableCaptionedButton(Context context, AttributeSet attrs) { super(context, attrs);
// some stuff that works fine
} ..
protected void onFinishInflate() { super.onFinishInflate();
mButton = (Button) findViewById(R.id.ccbutton_button);
mClear = (ImageView) findViewById(R.id.ccbutton_clear);
mButton.setText(""); // error here: mButton == null
}

My problem is similar to this one. When I try to find the views inside the custom compound, findViewById returns null. But, as you can see, i already added super(context, attrs); to the constructor. I am using the custom component directly in xml layout, like this:

<LinearLayout>
<!-- some stuff -->
<myapp.widget.ClearableCaptionedButton
android:layout_width="fill_parent"
android:layout_height="wrap_content"
app:caption="to"/>
</LinearLayout>

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Android :: Add Custom Views To Linear Layout Object

May 31, 2010

I have a set of custom views that I would like to add to a LinearLayout object. However, the first object I add to the layout (I do this dynamically, during runtime) has a OnMeasure method that tries to get as much space as possible resulting in that it get's all the space LinearLayout object. This is correct behavior, but when I then add more objects following that I want the allocated area for the first object to decrease so the others will fit. As it is now, each following object will get zero space, and hence won't be visible.

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Android :: Custom Control Or Make Views Inline?

Dec 22, 2009

I have a requirement to create a control similar to UITabBar in iPhone, which is to be present on every activity of my application. UITabBar essentially is a battery of buttons exhibiting a TAB like behavior: every button maps to an activity. I have two solutions for this: 1. In the layout XML for every activity, I insert a <LinearLayout><Button/><Button/><Button/></LinearLayout> element. And then have a common listener class that will handle the button clicks. So, every activity will have an instance of this listener. 2. To create a custom Widget extending LinearLayout class, put all the buttons as its static members and let it handle the button clicks. Include this custom control in every screen.

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Android :: Support Clone Of A View In Custom Views / Api To Use It?

May 14, 2009

Is it possible to clone a view. If no, how to support clone of a view in custom views. If yes.. which api should we use. clone method seems to be protected for view.

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Android : Put Custom View Above Built In Views In Droid?

Mar 11, 2010

I am developing a small app for Android. I am creating my own view.

I am planning to design the layout to be:

<LinearLayout>
<MyView>
<Button><Button>
</LinearLayout>

But when I run my program, my custom view will cover the whole screen. Is there anyway to avoid this?

I have already tried to add android:layout_width, layout_height to be wrap_content, fill_partent, but no luck.

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Android :: Keeping References To Inflated Custom Views

Apr 26, 2010

While researching how to create custom compound views in Android, I have come across this pattern a lot (example comes from the Jteam blog)I mostly understand how this is working, except for the part where inflate() is called. The documentation says that this method returns a View object, but in this example the author does not store the result anywhere. After inflation, how is the new View created fromt eh XML associated with this class? I thought about assigning it to "this", but that seems very wrong.

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Android :: Two SurfaceViews In FrameLayout

Jul 27, 2009

I have two SurfaceViews in one FrameLayout. So they are stacked upon another. What I want to achieve is to use the lower SurfaceView as kind of background that is changing heavily, and the upper SurfaceView as annotation overlay. So the upper SurfaceView has a (small) number of quickly changing elements that I will draw. Somehow, I can always only see one of the SurfaceViews, depending on which one is top. I thought that SurfaceViews are always transparent, but it seems I am missing something here.Any thoughts on why I can't overlay two SurfaceViews?

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Android :: ACTION_UP And ACTION_MOVE Touch Events Passed Through To Custom Views?

Jan 20, 2010

I have an activity defined as:

CODE:...................

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Android :: Prevent Custom Views From Losing State Across Screen Orientation Changes

Aug 22, 2010

I've successfully implemented onRetainNonConfigurationInstance() for my main activity to save and restore certain critical components across screen orientation changes.

But it seems, my custom views are being re-created from scratch when the orientation changes. This makes sense, although in my case it's inconvenient because the custom view in question is an X/Y plot and the plotted points are stored in the custom view.

Is there a crafty way to implement something similar to onRetainNonConfigurationInstance() for a custom view, or do I need to just implement methods in the custom view which allow me to get and set its "state"?

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Android :: Multiple Resolution Support And SurfaceViews

Aug 7, 2010

I am having an issue understanding how to get Bitmaps from resources in density specific directories to scale properly when drawing them to a Surface View.If I have a resource in folder "drawable" I expect it to be scaled up when run on hdpi screens and scaled down on ldpi screens and left as is on mdpi or 1.5 screens.Likewise I expect anything found in hdpi when run on an hdpi screen to remain unscaled. However, there is some combination of settings that I am not getting right to do this seemingly simple thing.I am not running compatibility mode so my manifest supports all screen sizes with anydensity=true.I do not understand the BitmapFactory.Options fields of inScaled, inTargetDensity, and inDensity that I am thinking have to be set appropriately and slightly different for each resource decoded depending on which directory they were found in and what screen they are currently run on.

All I have been able to find is that if either inTargetDensity and inDensity are 0, no scaling occurs, but if not, scaling occurs such that inDensity matches inTargetDensity. Is this correct?I have no idea what valid settings are for these fields from the documentation other than ints.What are the integer values for LDPI, MDPI, and HDPI? And how do I determine the density of a resource in order to set this before I decode it? Am I way off base in my approach for drawing bitmaps from various resource directories on various screen sizes?

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Android :: SurfaceViews Handling / Thread And General Game Design

Jul 14, 2009

I'm a new Android developer. I would like to make a simple game using the SurfaceView (Canvas drawing).the game has a a custom Object name Box. Box can draw itself and need to get an event when it is clicked. when it does, there is an animation sequence coming out of the box like a "jumping clown". I have several Boxes on the screen when each of them can be activated. Several Boxes animation can also be presented simultaneously.Here it gets tricky: Since I have a "complicated" animation sequence, each Box extends SurfaceView. The problem is I haven't figured it out how can I handle several SurfaceView's drawing using only one Thread (in order to present an animation I need to use one) and also how can I get the onClick/ onThouch event from my Activity to each of my Boxes.

The LunarLanding example in the SDK uses only one Thread but also uses only one SurfaceView which manage the animation of the game components (there are no several game components SurfaceViews). Also, there is no need to get onTouch event, so this example doesn't match to my case. I have several questions about what is the right approach do code this:

1. Should I use Box extends SurfaceView?

2. Can SurfaceView gets user events like onTouch/onClick?

3. Is there a way to add to the "main" SurfaceView another SurfaceView (Box)?

4. If none of the above questions is positive, should I use one SurfaceView (and one Thread) and try to map the other Boxes on the screen for user event handling. I mean Box only paints itself but the user event is being handled by me (not by the OS).

5. Should each Box (SurfaceView) should handle it's own Thread in case of animation (it is not good design but it is also an option)?

6. do you have any other proposal?

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Android :: How Can Update The All The Views Inside A TabHost When Pressing On A ContextMenu Item From Within One Of The Views

Nov 16, 2010

I am implementing a music player application in Android. My play list selection screen is implemented as a tab selector widget which contains a ListActivity inside each of the tabs: Artist, Albums, Songs.
I want to update the ListView in each of the ListActivity when I delete an item from any of the lists.

i.e. When I long press an item in the Artists list a context menu is drawn with "Delete Artist"
And it should delete all the songs from this artist in the Songs ListView, delete all the albums by this artist in the Albums ListView, and finally delete the entry for the artist in the Artist ListView.

Each of the ListActivity has its own fillData() method, which updates the ListView when the button in the context menu is pressed.

How can I call the fillData() method of the Albums ListActivity after I update the ListView inside of the Artists ListActivity?

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Android :: How To Make Use Of Views Defined In Layout XML File As Template To Create Views Programmatic Way

Feb 28, 2010

I want to populate a table, defined in layout xml file through the programmatic way. I have define Table with a single row defining its header, with all the attributes set. Now i want to know a way so that i can just replicate that header row in the table with new content.

I tried using inflator inflate(int,view) method, but at runtime it showed up with error.

Here is the XML code for the layout file defining the table

CODE:.................

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Android :: Switching Views With RadioButton And Saving Views In Bundle

Mar 6, 2010

I have the following XML code:.................

The idea is to change the views, whenever I press one of the radio buttons. When I press a button the first time everything works out fine, but the second time I press a button, I get an IllegalStateException, and I can't quite see why I'm getting this.

Also, the Activity seems to set all my global variables to null, which is why I have to create them every time I switch from portrait to landscape or vice versa. So I would like to know if there is a way I can save my views in the Bundle, or any other way in which I can permanently save my views, so I don't have to add or create them every time, I flip the phone. And whenever I flip the phone, it seems that it rereads the main XML file, causing the RadioGroup to be set to 2D even if the 3D button is checked. This is because I've said the 2D button to be checked from when the app is first created, but I would like to also save the state of that RadioGroup.

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Android :: How To Align Views In The Middle Of Another Views Baseline

Jun 16, 2010

How do you align views relative to the "middle" part of another view? I think it is best explained with a pic of the UI I'm trying to create in android.

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Android :: Do Root Views Of An Activity In Android Have Any Prior Knowledge Of The Child Views That Will Be Loaded Into Them

Jan 25, 2010

Is there any way to query a root view of an activity for all of its child views even before the root view or its children have been inflated? I guess what I'm looking for is whether a view knows ahead of time what children it will have before it gets inflated, and can I get that list in some way. Bizarre I realize, but I think it will help me with some unconventional automation testing I'm working on. I haven't found anything in the API like this.

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Android :: Programmatically Add Views To Views

Mar 7, 2010

Let's say I have a LinearLayout, and I want to add a View to it, in my program from the Java code. What method is used for this? I'm not asking how it's done in XML, which I do know, but rather, how can I do something along the lines of (One View).add(Another View) Like one can do in Swing.

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Android :: NullPointerException ItemizedOverlay?

Nov 15, 2010

This does not refer to anywhere in my code at all.

How do I go about getting to the bottom of it?

CODE:..........................

Here is the draw method of the ItemizedOverlay

CODE:..........................

I now print out the stacktrace and no difference!

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