Develop Reference

How to use high resolution images in a way that application don't lag?

High/medium resolution photo takes time to load from drawable and affects application performance, whereas low resolution photo looks blurred; I want to use high resolution images but not compromise with the performance, How to do that?
I am trying to set a high resolution background image of layout login from drawable, so when switching between components of the same activity lagging occurs.
For instance: switching between field email to password, keyboard appears/disappear in slow motion.

If I were you , I would use the Glide library. Its faster than Picasso and ideal when you want to load large images.
From the github documentation :
Glide's primary focus is on making scrolling any kind of a list of images as smooth and fast as possible, but Glide is also effective for almost any case where you need to fetch, resize, and display a remote image

Yes, use Piccaso. It will adjust and load a correct image size depending on your device and size of imageview.

Hard to know what you need, but you can use a FrameLayout to download multiple pictures in the background and set them invisible till you need it with android:visibility attribute.This solution is for one activity. Asynchronous work and cache can be the answer.
You should consider resize your pic anyway, users prefer see the pic than wait and quit, they know the limitations of their devices (so does android ;-).

Thread assistance

I need some help,
I am creating an app, and want it to run faster I mean when the app is started first it shows a blank white screen for o 1-2 seconds and then loads images. I have a layout background image, and 4 imageviews which are clickable and take you to the next activity. I read somewhere i should use threads to load images and it will load them on a separate thread faster, but i have some problem using it.
So here are the problems and android studio explanations:
Thread thread=new Thread(
public void run(){
ImageView tipka=(ImageView)findViewById(R.id.tipkaproba);
tipka.setImageResource(R.drawable.instructions);
LinearLayout asd=(LinearLayout)findViewById(R.id.layoutproba);
asd.setBackgroundResource(R.drawable.backfround123);
}
).start();
Now the android studio says: 
After
"Thread(" )expected
Before
"public void run(){"
; expected
On ").start();"
Invalid method declaration; return type required, Missing method body, or declare abstract.
Now i would like to know:
Does this speed up loading images, ( if not how to do it then)
How to fix my errors.
Thanks anyway !

Do all images fit in the screen?! If users need to scroll to view other images why load all of them at once? Use a grid view with adapter to load the image. In this way when the app start only images on the screen will be loaded and then when the user scrolls other images show up!
another thing you can do is to have 2 version of each image. one low quality with small size that loads first and one for high quality image. that will load latter. You can also calculate the base color for each image (use open source code or do it manually). then set the background image of iamgeview to this color. So when the image finally loads on the screen. The difference is not as dramatic as it was before.
If you want to use thread try AsyncTask first. Using AsyncTask is simpler than defining thread yourself.
Try to decrease the size of your images! If you be able to do this. it works better than any other trick! It's mobile, you don't have to show supper high quality images. users don't even notice most of the time
You probably took care of this but it worth mentioning that you need to provide different images for different screen densities and it's critical for performance as well as quality.

How do I load a blurred image first, in imageview, and then make it sharp, in order to enhance user experience, for android?

I'm working on an application in which I need to download lots of images. The images are to be seen in the fullscreen mode. Therefore, I wanted to know how to load an image, speedily, to make the application more responsive and enhance user experience. I would like to, atleast, show a blurred image first and than make it sharp. Thanks.

use BitmapFactory.Options.inSamleSize to load a downsampled version of the image. Then load the bigger image and do a fade transition using a TransitionDrawable

You're looking for "progressive image rendering", which can be done in a variety of different image formats, including png, jpeg, gif, etc. The next time you're going to save an image in a good graphics program, select one of those formats and take a look at your save options. You should have an option to save an "interlaced" image.
Jeff Atwood of Coding Horror has a nice write up here: http://www.codinghorror.com/blog/2005/12/progressive-image-rendering.html

Cropping large background image

I have two situations/projects where I have to use a large bitmap as background activity.
The first project ports a WP7 application to Android! The WP7 app is using a panorama control with a bitmap as large as 3 screens. I would like to reuse the large bitmap similar in a way that I use the left part for the first activity, the middle part for the second activity and the right part for the third activity. In other words I would like to define which part to crop.
In the second project we try to develop an app which should run on various screen sizes (including tablet), the app should also use a background image. Is it a good idea to provide only one picture with a quadratic size (as long as the largest screen width) and use this picture through every resolution and just crop the background image depending on the actual size of the display?
Is it possible to crop pictures on Android?
Is it possible to define the part of the picture which is kept?
Is it possible to use this croped pictures as background image or may I encounter performance penalties?
What do you think of this technique? Is it a good idea?
Thanks for your help!

answering your questions:
yes it is possible to crop pictures in Android (I've done so)
you can define wich part of the picture is shown in each activity
with a canvas and only drawing the rect that corresponds to the part
of the image that you want to display (eventough I wouldnt suggest
the approach of having diferent activities with the "same" content)
yes, you can use cropped pictures as background image for whatever
you want. Once you cropped the image use that bitmap and save it in
the device and then you might use it as you wish, and eventought is not recommended to have the whole image as background you can do so.
I suggest that you use a SurfaceView since you will be able to move it (the image) all around the screen without having to create a new activity. Here is a good tutorial to SurfaceView Playing with graphics in Android – Part I and this approach will also work with Tablets.

Giant online image gallery - How do I avoid OutOfMemoryError?

For anyone who's wondering, the gallery is http://www.spore.com/sporepedia.
My app uses the Spore API to get the 100 newest creations, then displays them in a GridView. The text data about the creations is easy to store, but the images present a problem.
As far as I know, I can either keep the images in a Hashtable or grab them every time they are viewed. Neither of these will work - the Hashtable quickly presents an OutOfMemoryError, and the constant reloading causes a lot of load on the server and a lot of lag on the client.
Is there a better way to store the images?

First Don't get 100 at a time, there is no way your displaying 100 images in a gridview and having them be a usefully visible size. Retrieve the images asynchronously and get a screen full or a screen and a half at a time. I'm guessing you can display 6 to 9 images of a decent size per screen with supporting text/UI elements, you may even want to choose how many to display based on the handsets screensize/resolution. So you should probably be getting 9 to 12 images at a time.
Second, i don't know what resolution these images are coming in at, but it sounds like 'big'. If the API supports it receive only a thumbnail version for you grid view. If not, what i would probably do is: when you receive an image from the API, first create a new image scaled down to the size needed for your thumbnail that goes into the grid view, keep this in memory. Then create a new image scaled down to the size you would need for your 'detail' screen (if you have one) and cache this to the SD card and free it from ram as well as the original source image, this scaling should probably occur in a separate thread to avoid it impacting the responsiveness of your UI thread. Depending on the usage pattern, I would probably also cache the thumbnails to the SD card so it would be cheap to free the ram they use in onStop/onPause and reload them in onStart/onResume. IT also sounds like you downloading a 'top 100' or something of the sort. Since i wouldn't expect an entires new top 100 on every application use you could save a lot of network traffic by caching the images and information to the SD card and only downloading new entries each time the program runs.
Alternatively a process like:
Receive Image -> Scale in place to detail size -> cache detail size -> scale detail size to thumbnail size in place -> display thumbnail in gridview while caching thumbnail asynchronously
Would use even less memory since there is only ever 1 copy of the image in memory, but it would slow the response of the gridview as the image has to be scaled twice before it gets displayed. It may be fast enough to not matter or you may be able to play tricks with the grid view by having it display the large image (scaled internally) while the thumbnail is generated in the background, switching the gridview to the thumbnail when its ready. You'll just have to try it to determine if its fast enough.