There's a decent amount of information out there on the Activity lifecycle. But I'm surprised how difficult it is to find a comprehensive description of the rendering lifecycle. By that I mean the order and rules by which a tree of nested activities, views, and drawables get to be sized and drawn to the screen, and the points at which a developer can modify rendering behavior.
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In my application I have several activities, the main screen has 4 buttons that each start a different activity. So one of them is a search activity, once it searches it shows you a result activity. This result activity can be reached from other activities, so in general something like this:
Main activity -> Search activity -> Result activity
Main acitivty -> someother activity -> Result activity
Now, if I have reached this result activity and press back once or twice, and after that press the Home key it will show the Home screen. But if I want to get back to my application by holding the Home button and clicking on my app it will always go back to the Result activity, no matter which activity was the last one I was using. And if I press again back it will take me back to the Home screen.
If I try it again it will take me again to the Result activity. The only way to avoid this is to start the application by clicking on the app's icon. And this takes me to the last activity I was using and it remembers the state so if I press back again it doesn't take me to the Home screen, instead to the activity before it. To illustrate this:
Main activity -> Search activity -> result activity --back--> Search activity --Home Button--> Home Screen --Hold Home and select the app --> Result activity --back--> Home Screen
--Click application icon--> Search activity --back--> Main activity
Another thing that happens is that if I press the Home button while on the Result activity, and start the app by clicking the icon, it will take me to the activity prior the the Result one.
In the Android Application Fundamentals it says that after the call to the onStart()-method of the activity lifecycle either the callback method Resume() or onStop() is called. In case of an "normal" Start of an activity the system calls onCreate(), onStart(), onResume().But does somebody know an example where onStart() - onStop() are executed one after another?
View 2 Replies View RelatedI am having difficulties with the lifecycle of the opengl context. While rendering my scene and the user hits the back button, home button or another application opens in front of my application, my app is still running in the background.
So when my application comes to the foreground later on (user relaunches it or the app that was opened on top of it finishes), my application crashes and leaves me nothing but a GL stack trace which i can't properly decipher.
For rendering i use the GLSurfaceView and therefore delegate the onPause and onResume. The crash happens on the first call to glDrawElements(..).
I have tried to reload my resource (geometry/textures etc.) on onSurfaceChanged but with or without reloading... The problem persists.
This behavior can be observed on all AVD versions of the emulator as well as on the G1.
Here is the gl stacktrace i get.
CODE:.............
I just ran into a situation where it looks like a static variable reference is persisted across activity sessions. I didn't expect that because I thought that when an activity exits, it's de-referenced and garbage collected. I am wondering if anyone can shed some (more) light on when the VM eliminates object references for Activities and Services and in particular when static variables get reset to default values?
View 7 Replies View RelatedI am trying to create a Servicefor my application which will negotiate Bluetooth connections and data. I want this service's lifecycle to start and end with the Application, but still be able to have specific Activities listen for events that occur within this service (in addition an Activty should be able to call specific methods of the Service to write data or query connection state).
I started by creating AIDL interfaces for my callbacks and service, but I can't figure out exactly what I'm doing.
How is the best way to go about this? EDIT: To be clear, I do not specifically need (or want) more than one process for my application. Right now I don't have more than one; I'm just using AIDL because it is the only way I know of for a Service to communicate with an Activity.
I have creating application with 3 activities, where A - list of categories, B - list of items, C - single item. Data displayed in B and C is parsed from online XML. But, if I go trough A -> B1 -> C, then back to A and then back to B1 I would like to have it's data cached somewhere so I wouldn't have to request XML again.I'm new to Android and Java programming, I've googled a lot and still can't find (or simply do not have an idea where to look) a way to do what I want.Would storing all received data in main activity A (HashMaps? ContentProviders?) and then passing to B and C (if they get same request that was before) be a good idea?
View 3 Replies View RelatedI slapped together a simple test application that has a button, and makes a noise when the user clicks on it.
Here are it's method:
CODE:..................
My question is, why is onCreate acting like it's in a while loop? I can click on the button whenever, and it makes the sound. I might think it was just a property of listeners, but the Button object wasn't a member variable. I thought that Android would just go through onCreate onse, and proceed onto the next lifecycle method. Also, I know that my current way of seeing if the sound is playing is crap...I'll get to that later.
http://developer.android.com/reference/android/app/Activity.html
The Activity Lifecycle could have implementation and or design bug: One case is to initialize a big image in onCreate(), try to reuse the image during the whole lifecycle, and then recycle the image in onDestroy(). Test showed that onCreate() is called every time one navigate away from the activity and back again, but onDestroy() is not called at all. This behavour causes memory leaking for the big image (size 960*1920). After 6+ times away and back to activity, the system runs out of memory and has to kill the process.
One workaround is to initialize the big image in onResume() and recycle in onPause(), but that's not so good reuse.
Could it be better to change the process (as shown in the diagram) a little bit such as: Call onDestroy() first when a process is killed?
I have a problem with the activity lifecycle specifically on Nexus One (2.1 running on emulator works fine). If I just create a simple empty Activity with no special launchModes that logs the calls on the onStart and onStop methods, this is what I see: - launch app: onStart called; - home button: onStop NOT called; - launch app: onStart NOT called; - home button: onStop NOT called: and so on. Sometimes if I press the back button then the onStop is not called, but the when i launch the activity again the onStart is called and right after the onStop is called. Similar results with different launchModes. What is going on? Can anyone confirm this?
i found an android issue for the problem here: http://code.google.com/p/android/issues/detail?id=6094 and a similar thread here http://groups.google.com/group/android-developers/browse_thread/threa.
I have a custom view on which I need to call a method from my activity after the view has been measured in onMeasure. I would like to know exactly when onMeasure is called in the View layout process. It looks like onMeasure is called after my activity´s onCreate, onStart, and onResume. I could override onMeasure and maintain a variable that contains whether the view has been measured or not. However it would be nice to know if there is a rule that relates onMeasure to the activity lifecycle?
View 4 Replies View RelatedI'm binding to a local Service (that is, not using IPC and AIDL) from several activities. I want to ensure that I'm not holding references to this service from activities that the user isn't using. My options are: 1.) to bind to the service in onCreate() and unbind in onDestroy(). 2.) bind in onStart() and unbind in onStop(). 3.) bind in onResume() and unbind in `onPause(). Or some combination of these. Which is the best-practice way of binding and unbinding to a local service? Do I not need to be concerned with holding local connections from stopped activities? Additionally, once bound to this particular service I am retrieving a Cursor which is attached to my ListActivity via a CursorAdapter. The data retrieved by the Cursor may have changed while the Activity was out of view so I want to requery it when the Activity is shown again. If I bind in onCreate() I can requery in onRestart(). If I bind in onResume() each time the data will be fresh because I'll query it in the Service's connected callback.
View 1 Replies View RelatedI'm having a couple of problems with an alarm app I am developing.
The first thing that I think is a bit weird is that when an alarm goes of and wakes the phone up. These things happend.
oncreate
onresume
onpause
onresume
Why are they run in that order? The last two should not be called? And this is what's causes me big trouble, because when i press home or back on the phone, onPause is run, which I want to call finish() from. And that part works as it should, but that does not work when the phone wakes upp from sleep bacause of the onPause call...
I've an App which performs a potentially large download in background thread. When the orientation changes or the keyboard is opened the App lifecycle system invokes the start/stop/pause/resume etc calls - is there any strategy available to resume the download rather than just set a flag so the new onCreate() knows it was interrupted and has to start it again?
View 2 Replies View RelatedI wrote a program in Android for setting different kinds of images as my background image, but it is not working with svg files. I am not getting any errors, it is not displaying any image and I'm getting a blank screen in my emulator when using svg files. Can any one suggest how to read and display svg files in Android with some code? Or should I convert xml code?
View 1 Replies View RelatedI'm trying to compare the difference in speed between software and hardware graphics rendering. I have 2 apps right now - one written with only java/android 2D APIs, and one written with openGL calls...
View 6 Replies View RelatedI want to get the size of a view that is in my activity but I am not able to get that information in any of the activity lifecycle callbacks (onCreate, onStart, onResume). I'm assuming this is because the views have not been drawn yet. At what point are views drawn and is there a callback I can put my code so I can get the size of the view?
View 2 Replies View RelatedI'm fairly new in Android/Java programming, so some of the basic stuff is still quite confusing. So, lets say my application gets all data (articles) it requires from external XML files, it parses them to data models (Article class) and those articles will be used (displaying in lists or single article) all over the application for all it's lifecycle.
Where should I keep them? Can I create singleton class with an array containing all the articles I've parsed? Or should I save them to database and then query it on demand? (that sounds like too much work, I don't need to cache them for now) What's the best practice here?
I need to find out how big a view will be after attaching it to its parent.I have overridden this method: Do you think there is a way to get this information before rendering the view itself? Basically I need to know the actually size before attaching it and not attach the view at all if it would take more certain amount of space. Code...
View 2 Replies View RelatedCan anyone help me to understand how WebView decided which content it can render and which it can't? For example I am inside a webview select a link and if the link sends an XML file I want my application to handle to data instead of WebView, Is this possible?
View 4 Replies View RelatedI have an ImageView object that I'm setting the android:src="@drawable/some_xml_file" instead of a standard png and it seems to not always render the drawable, as you can see in the first row here (it also happens intermittently in other rows as well):
I've tried setting the src & the background property but they both have the same effect. the source code from my list view row item is this:
CODE:...............
Then my res/drawable/action_box.xml is this:
CODE:................
I need to render video on android. I got sw decoder which decodes stream to YUV or RGB with very reasonable cpu usage, but so far haven't found a nice way how to render frames.
I have tried 3 methods so far: 1) using opengl from native code: * create a texture of type GL_TEXTURE_2D * set coordinates to fill full opengl rendering area * to render a frame update the texture with glTexSubImage2D or glTexImage2D function (more or less the same method that is used in vlc media player)
With this method the performance is most terrible.. VGA rendering @5..7FPS uses up 100% of nexus one cpu!
2) rendering with canvas function Canvas.drawBitmap(int[] colors, int offset, int stride, int x, int y, int width, int height, boolean hasAlpha, Paint paint)Was hoping to use this via JNI. First i just made a simple perfo test: * colors array was initialized in java code * then I just called mSurfaceHolder.lockCanvas(); canvas.drawBitmap(colors, ... ); mSurfaceHolder.unlockCanvasAndPost(canvas); in sequence
Perfo is better than with opengl - VGA@30FPS uses up 40% of nexus one- s cpu...
3) Rendering with canvas function Canvas.drawBitmap(Bitmap bitmap, float left, float top, Paint paint), while updating bitmap in native code * in java code i do:
CODE:.......
To get native pointer to memory (need to link to native android library libskia.so to get these functions) * copy or decode the video frame to this memory
With this method i get only 10% cpu usage when doing VGA@30fps... but lets face it - its a hack which may break in future. Am I missing something or there really isn't any better way to render video? for example some opengl extension function etc..?
I'm putting together a simple test made up of two tutorials available online for OpenGL ES on Android. This is really just so that I can learn about the basics of OpenGL ES to better understand how I have to design my program.
Right now, when it tries to render, the mouse movement effect works, but I get no square drawn on the screen.
Here are the two source files I'm dealing with:
CODE:.......
The second one is the tile object itself:
CODE:........
When trying to process this png image, webkit displays it blurry.
View 2 Replies View RelatedI have an Android app with a C++ library which uses pthreads to break down rendering tasks. This is for devices running Android 4+.
Lets say I have a 100 x 100 array of elements into which I repetitively do CPU-intensive processing. Currently I'm breaking the array up into four 25 x 100 element chunks and handing it off to four Posix threads (from a pool of stalled, pre-created threads). This gives an almost 4x speed increase on iOS and desktop Mac but slower results than single-threading under Android.
So the same code is used successfully to speed up the app on iOS or desktop Mac but in Android it often makes it even slower. I have done some tests on it and only quite big junks of data speed up when using multi threading. If the whole process (all threads) takes around 2 seconds or more it will speed up in multi threading mode but if it is less (say only takes about 400ms) it will be either the same speed or slower than just calling the rendering function normally. Which could point to thread switching being really slow. The bigger the processing tasks, the more they profit from multithreading. My tasks are usually not as big, but not fast enough in single threading mode.
I have also noticed that on ARM builds the speed difference between slower multi threading and the faster single threading is quite significant (almost twice as fast in multi threading rather than single threading) whereas on x86 builds the multi and single threaded versions will run at about the same speed as single threading on ARM builds. So x86 builds do not get slower on multithreading but also not faster.
My app is made of two activities, A and B. I'm considering this sequence of steps: Activity A is started. A launches B [A is paused, B is running]. B launches a map intent [A and B are both paused now]. Now the user is using the maps application and the system decides it needs more memory. Can the system kill only one of my activities for memory, or will it always kill all activities in a "process" in this situation?
Both activities share some static data like:
class Data {
public static String mName;
public void save() {
// write to file: mName;...................
This is with the 1.6 & 1.5 SDKs, not tried earlier ones. When you switch from portrait to landscape the onSaveInstanceState()/ onRestoreInstanceState() pair are called once, but when going back from landscape to portrait they are called twice, unless I've missed something. To test, see the log after creating a default Hello World app and change the main class like this: code...
View 4 Replies View RelatedI'm currently developing my first android app, and my first game. I've been developing on a netbook with a CliqXT (HVGA). Things are going well, it renders perfectly on the smaller screen. I knew I'd have some issues when rendering on larger screens, but the issues I'm having are not what I was expecting and I'm kind of stuck.
So basically the game consists of a main SurfaceView which I'm rendering the tiled game world on to. I followed this tutorial to get started, and my structure is still pretty similar except that it calculates the boundries based on the player location:
http://www.droidnova.com/create-a-scrollable-map-with-cells-part-i,654.html
The game also has various buildings the player can enter. Upon entering it launches another activity for that particular building. The building activities are just normal Views with Android UI stuff defined in XML (Buttons, TextViews, etc).
What I expected to happen:
So I expected the the building UIs to render correctly on the larger screen. I specified all dimensions in "dp" and fonts in "sp" in hopes that they'd scale correctly. I expected the actual game tilemap to render generally correctly, but maybe be really tiny due to the higher resolution / dpi. I'm using a very similar function to the tutorial linked above (calculateLoopBorders(), my version is pasted below) to calculate how many tiles to render based on screen height and width (getHeight() and getWidth()).
What is actually happening:
The whole game is just being rendered as if it's HVGA. The tilemap, and the building UIs are just scaled down to the smaller screen size, leaving black borders around the left, right, and bottom (see images).
From the adb log of my G1's boot time, it shows "requestGPU returned -1", among other stuff. Does this mean that my OpenGL app is being rendered using software? BTW, I see the same messages on Hero as well.
------------------------------------------ log begin ------------------------------------------
I/SurfaceFlinger( 81): SurfaceFlinger is starting I/SurfaceFlinger( 81): SurfaceFlinger's main thread ready to run. Initializing graphics H/W... D/SurfaceFlinger( 81): pid 81 requesting gpu core (owner = -1) W/SurfaceFlinger( 81): couldn't grant gpu core to pid 81 D/EGL ( 81): requestGPU returned -1 E/libEGL ( 81): h/w accelerated eglGetDisplay() failed (EGL_SUCCESS) I/SurfaceFlinger( 81): EGL informations: I/SurfaceFlinger( 81): # of configs : 6 I/SurfaceFlinger( 81): vendor : Android I/SurfaceFlinger( 81): version : 1.31 Android META-EGL I/SurfaceFlinger( 81): extensions: I/SurfaceFlinger( 81): Client API: OpenGL ES I/EGLDisplaySurface( 81): using (fd=19) I/EGLDisplaySurface( 81): .......
What is a rendering engine? Is there any for Android?
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