Android :: Passing Around Object References In Java?
Jun 25, 2010
I'm writing some stuff in java and i ran into some problems lately. cut short, i need to compare an object i created to another instance of this very class i instantiazed before with different data.
looks like this:
CODE:........
with a class a:
CODE:..........
The problem is, that i end up finding out that the values from newA are always equal to those from oldA. so i guess sth went wrong with passing the references of the objects in the last line of the loop...i thought java always passes references of objects unless an explicit copy() is called? if this does matter: this code is running on android - don't know if the dalvik vm messes aroung with this...
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Sep 29, 2010
I thought when you passed objects to methods in Java, they were supposed to be by value.
public class MyClass{
int mRows;
int mCols;
Tile mTiles[][]; //Custom class
//Constructor
public MyClass(Tile[][] tiles, int rows, int cols) {..........
At this point, any changes to the mTiles object are reflected back to the tiles object.
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Dec 8, 2009
I'm working on an application that requires non-serializable objects to be passed between Activities. The following page suggests using a HashMap of WeakReferences to accomplish this:
http://developer.android.com/guide/appendix/faq/framework.html
Is this solution safe? I know Activities are completely destroyed and recreated when the screen orientation changes. Couldn't those weakly referenced objects get GCed in the split second when the screen is rotated, since they wouldn't be referenced elsewhere at that point?
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Jun 16, 2010
I'm writing an Android app. I have a main method, which creates and runs a new Thread using an anonymous inner Runnable class. The run() method, when it's done, calls a method on it's parent class (in the main thread) that calls notifyDataSetChanged() so that the main thread can redraw the new data. This is causing all kinds of trouble (ViewRoot$CalledFromWrongThreadException). The thing is, this method being called from the worker thread is on the class that's created in the UI thread. Shouldn't that be running on the UI thread? Or am I missing something.
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Feb 18, 2009
I am trying to get a FileInputStream object on an image that the user selects from the picture gallery.
This is the android URI returned by android.provider.MediaStore.Images.Media.INTERNAL_CONTENT_URI content://media/external/images/media/3
When I try to construct a java URI object from this object, I get an IllegalArgumentException with the exception description Expected file scheme in URI: content://media/external/images/media/3 whereas the android URI shows the scheme as content
Never found a solution for the original question. But if you want the byte stream of an image in the pictures gallery, this piece of code will do that.
CODE:...................
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Jun 23, 2010
I am trying to display a dialog box in a simple Java class that is called from my main Activity but not successful. Please help me to figure it out.
I am passing the required values as parametrs.
I have two class: class MainActivity extends Activity :: Main *starting point *of Application class ShowMyDialog :: a simple java program In which I *generate an URl* and *display a dialog with WebView*.
I am passing the Acitivity from my MainActivity to this class as a parameter in function.
But I am *unable to call* the onCreateDialog method that I have *defined in the simple java class.
However, If I define the *onCreateDialog method in MainActivity, I am able to display it successfully.
What Should I pass as Parameter to the non Activity class from MainActivity class so that I am able to display the dialog as defined by showdialog method in JAVA class ???*
My steps of source code is as follow:
code:.........................
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Jan 9, 2010
I am creating an application which retrieves images from the web. In case the image cannot be retrieved another local image should be used.
While trying to execute the following lines:
CODE:................
The line if(drawable.equals(null)) throws an exception if drawable is null.
Does anyone know how should the value of drawable be checked in order not to throw an exception in case it is null and retrieve the local image (execute drawable = getRandomDrawable())?
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Apr 14, 2009
I have constructed a Bitmap object in Java. Can you please tell me how can I scale it (x, y with a different ratio) on android?
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Dec 2, 2009
(Code is for Android Actually, I need code to be portable between Android and Java SE.)
I want to have a "settings" class with various game settings, like
public int map_size;
public String server_name;
etc.
The data needs to be accessed fairly frequently (so members, not a key-value map), and from time to time de/serialized in some standard way (mainly to send it through network).
I want to be able to
Serialize and deserialize the object into XML or JSON, without having to explicitly write the code for every member (but still having some degree of control over the format).
Define some (constant) meta-data about every member (default value, GUI name, XML identifier, ...), in a way that allows for easy modification in the source code (I want to be able to add a new meta-property, define a default value for it, and not have to specify it everywhere else).
1 is achievable by using reflection. I thought Java annotations for class members would be perfect for 2:
CODE:.............
But it looks like (user-defined) annotations don't work in Android yet - code using them crashes the compiler...
What would be the easiest way to store the meta-data about the settings (or another way to approach all this)?
Store information about settings in some external XML file? Store it in a Java data structure, with content defined in the code? Defining the data in this way somehow seems very unwieldy, especially compared to keyword arguments of annotations?
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Oct 29, 2010
From my android client i am sending a json to string object.but the .net client is getting it as empty string. here is my code...
is this header format correct?
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Jun 21, 2010
I have created a class with 3 sub classes in Java. The 3 sub classes contain variables to store information from my XML document. I am able to store in the first two for there are only single instances of the data in the XML. The third class contains variables that repeat multiple times. I want to store an object of "third class" objects. I also have a SAX parser class. I am doing this within an Android environment (1.6).
Does this make enough sense without displaying any code?
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Jul 28, 2010
I have 2 String Operations I would need relevant in Object C // Get the newstring from mystring start at counter Java: newstring = mystring.substring(counter) OBJ-C: ? // Get the position from searchstring in mystring Java: startpos = mystring.indexOf(searchstring) ObJ-C: ?
I had two other questions and found now the solution (here als for others)
CODE:.................................
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May 23, 2010
I was wondering what the simplest program for sending an object from my Android phone to my computer wirelessly (via LAN) would be. I have created Java RMI programs with a server and multiple clients, so I have a grasp of the concept. However with android I'm just not sure where to start.
What I am aiming to do is send some sort of information (could simply be text) to my computer and my computer will do an action. I have the GUI interface's and the actions to be carried out all worked out, just the sending of some sort of information is getting me.
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Apr 19, 2010
I'm building an android application, which has a list view, and in the list view, a click listener, containing an onItemClick method. So I have something like this:
public class myList extends ListActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
getListView().setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
/* Do something*/
}
}
}
Normally, this works fine. However, many times I find myself needing too preform an application using the outer class as a context. thusfar, I've used: parent.getContext(); to do this, but I would like to know, is that a bad idea? I can't really call: because it's not really a subclass, just an embedded one. So is there any better way, or is that considered cosure? Also, if it is the right way, what should I do if the embedded method doesn't have a parameter to get the outside class?
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Mar 2, 2010
I'm writing an Android application. One problem is your app cannot contain a file whose uncompressed size is bigger than about 1Mb. I have a serialized object that I want to load that totals about 2Mb. My plan was to split this file into two smaller files, then load the object by combining both files at runtime.
However, I cannot work out how to use e.g. InputStream and ObjectInputStream to specify that I want to read the data from two input streams. How can I do this?
For example, say my object was split between file O1 and O2. How can I say "Load the object by reading the data from O1 then from O2"?
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Jun 22, 2010
So I ran into a problem today while working on my Android program. I have a class that turns that an XML string into a Java object (third party) and it works fine in as a regular java project but on Android I get this weird error:
CODE:.......
I hide my application name and my package for obvious reasons but I was wondering if anyone has ever encountered problems like this. Class is in the correct package, which is a library I have added. Other classes that I reference before are there and those can be made. Are there any other reasons a ClassNotFound Exception is thrown?
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Aug 25, 2010
In my Android client I want to receive JSON objects from a server. By googling I found a lot of different possibilities how to best parse the InputStream from the Server, but most of them wrote their own parser. Isn't there a library which does this parsing for me? Or how should I best implement it by myself?
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Sep 9, 2009
I want to do some automated testcase with Instrumentation . Suggest that my AUT has 2 Activity. After clicking the button in ther first Activity, the second one will be shown with new content base on what we enter in the first Activity.) Instrumentation provides us the function called startActivitySync() and return the Activity object for processing. My question is how we can get the pointer of the second Activity after the it is shown by clicking the button on the first activity.?
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Jun 8, 2009
I would like to convert a Picture object to Bitmap object in memory, without writing data to disk.
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Sep 21, 2009
I have an Activity that running on system. I can get the Intent that is used to start the activity. But i don't know how to get the Activity object from the Intent object or something else. Can anyone tell me how to do this??? Note that, I don't use Instrumentation object.
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Apr 20, 2010
I have a static Preferences class that hold some application preferences and stuff like that. Is it ok to store reference to ApplicationContext there? I need that reference so i can get cache folder and stuff like that in classes that don't inherit Activity.
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Aug 11, 2010
There's a bug in my network code so that when the server's not available the Android client tries over and over to connect. On 1.5 (emulator) this results, within a minute, in an "Excessive JNI global references" error where the leaked object is a small (20 byte) boolean array. The same code on emulated 2.1 runs for as long as my patience lasts. Is there any possibility the leak is in my code and not an Android bug that's been fixed since 1.5?
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Nov 5, 2010
I wonder if it's possible to reference a XML string value in another XML String resource.But in case of an concated resource string, I found no solution yet,I would like to keep the string references in the string.xml file itself.
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Jul 21, 2010
I would like to add an HTML resource to my Android project with references to other resources (mainly drawables).
Where should I put it and how do I reference other resources from it?
Is there a particular way to pass the HTML resource to a WebView?
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Jul 27, 2010
I've read that it is a mistake and a source of memory leaks in Android application to keep a long-lived references to a Context.
But I don't understand if it is ok to create an class that looks like this one:
CODE:..........
And call it from an Activity:
CODE:.................
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May 11, 2010
I'm currently working on Android NDK, porting my libs, and I'm using SWIG (Simplified Wrapper and Interface Generator) that is a great tool to generate JNI code around my C/C++ headers for Java.
However, there is a big issue using it on Android, 'cause of incomplete JNI support : 'Weak Global References' are missing. Unfortunatly, SWIG is waiting for a full compatible Oracle/Sun JVM, and use this feature with its 'director' option (for proxy class creation).
For now, I comment each time, in a (kind of) bad way, the use of weak global references in my generated C/C++ wrapper files (4 lines in my case). I think it is really a shame that we can't use (one of) the best wrapper with Android NDK just for one missing feature.
I read that Google Team will add it in future release : "NewWeakGlobalRef and DeleteWeakGlobalRef are not implemented. The VM supports weak references, but not JNI "weak global" references. These will be supported in a future release." (http://android.git.kernel.org/?p=platform/ dalvik.git;a=blob_plain;f=docs/jni-tips.html;hb=HEAD)
So my question is, does anybody know when 'Weak Global References' will appear in Android NDK ?
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Nov 24, 2010
I am working on a system on which currently Linux kernel and microwindows windowing system is running. Code of current Linux system drivers is available to me. I want to port android on it, just as a hobby project.
can you please tell me what all understanding of linux-kernel is required to port it?
Please give me references (Books, Tutorials) to build-up understandings.
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Oct 27, 2010
I'm in the middle of implementing themes for my application right now, and everything's been going really smooth until as of late. I've been using the android:background="?thin_border" tag to provide a background for linearlayouts with items that I want visually grouped together. The problem I'm running into is when I try to use this tag in an xml with a custom class as one of the elements, and try to add this background tag.
I've got an xml file that looks generally like so:
CODE:.................
and the custom class has two constructors:
CODE:........
with some other functions that store values, manipulate the data, etc. The custom layout class is only ever called directly in the xml, and the xml is inflated like so:
CODE:...........
The problem I'm running into is that I'm getting these error messages:
CODE:.................
The error seems to be caused by the android:background="?thin_border" tag. If I remove it from the layout, it inflates fine, and the program continues on. As soon as I add it back in, I get these errors and the program stops.
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Mar 14, 2010
I need to create paused analog clock. Since I have never done any graphics/drawing before I am customizing Analogue widget defined in the core/java/android/widget.
The problem is when I create the class in my project following are the unresolved references: mContext com.android.internal.R mRight mLeft mTop mBottom
I know the most likely cause is com.android.internal is private and I need to use public but the problem I do not know what the public equivalent is. I have tried substituing it with android.R but that doesn't seem work either.
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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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