Android - SuppressLint cannot be resolved to a type

After upgrading my Android SDK 20 and ADT-23.0.2, some projects got error "SuppressLint cannot be resolved to a type"

I fixed this by

1. In project property -> Android, change to another API level and change back.
2. change the order in project property ->Java build path -> Order and Export.
3. also please try refresh and clean the project.

Hope it can help and save some hours.

Fix Android cannot show Logcat, "Invalid Argument"

Fix problem: Android cannot show Logcat, "Invalid Argument"

• Unplug and plug your device
• Switch ON/OFF the developer option – USB debugging
• Clicking at the device on DDMS-Device tab
• Use command "adb logcat -c" followed by unplug/plug device.
• On DDMS-Device tab, click the down triangle, choose “Reset adb”
• Huawei device: *#*#2846579#*#*  Go ProjectMenu / Background Setting / Log setting
• Use app to show logcat, such as CatLog (play.google.com/store/apps/details?id=com.nolanlawson.logcat
• Run “echo 1 > /sys/kernel/logger/log_main/enable” in “adb shell”

Reference :
[1] http://stackoverflow.com/questions/2250112/why-doesnt-logcat-show-anything-in-my-android/2945333#2945333
[2] http://stackoverflow.com/questions/3823934/android-the-ddms-shows-the-message-logcat-read-invalid-argument

Galaxy Note 2 screen specifications, size, density, aspect

Samsung Galaxy Note I/II screen specifications
--situee's blog

It's important to know the specification the device classifies itself for Android developers.

Galaxy Note 1 calculated ppi is 285; density is xhdpi.
After the ICS update, the device classification changed to "large" and "not long".

Galaxy Note 2 calculated ppi is 267; density is xhdpi.

	Resolution	Size	Density	Aspect
Galaxy Note 2.3	1280x800	Large	xhdpi	Not Long *
Galaxy Note 4.x	1280x800	Normal	xhdpi	Not long
Galaxy Note II	1280x720	Normal	xhdpi	Long

Resolution Qualifier of Layout Drawable for Android

It's hard to differentiate 800x480 854x480 resolutions. 

Most mobile phones are of these two resolution and goes to qualifier "-normal-hdpi". Both are "-long"

There is resolution qualifier, thougth it's deprecated and recommended to not be used.
something like "-800x400"  "-854x480" (situee's blog)

GalaxyTab, Motorola Xoom Screen Desity and Size

Galaxy Tab (7") is 170dpi, it is close to 160dpi, and should be mdpi . However, it is declared as "hdpi" and "large" by Samsung, because it's look better with a hdpi configuration. The new GalaxyTab 10.1 is the same size and resolution as Motorola Xoom, it should be mdpi and xlarge.(situee's blog)

-->

(situee's blog)	Density	Screen Size	Resolution
Samsung GalaxyTab 7	hdpi	7" large	1024 x 600
Motorola Xoom	mdpi	10.1" xlarge	1280 x 800

Pre-scaling, Auto-Scaling and Screen Density

Designing android layout for multiple screens is really confusing.

Pre-scaling

Pre-scaling resource is an important concept.
If resources are not available in the correct density, the system loads the default resources and scales them up or down as needed to match the current screen's density.

Examples:
for an hdpi device, when there is only mdpi image 100x100, then the image will be pre-scaled to 150x150;
for an mdpi device, when there is only hdpi image 150x150, then the image will be pre-scaled to 100x100;

ERROR: Unknown command 'crunch'

I upgraded the Android ADT to version 15. Everything seems fine until I tried to run an app.

ERROR: Unknown command 'crunch'

Now, use the new Android SDK Manager to upgrade the Android SDK Tools. Then we can forget about the "crunch" problem.

dex2jar Decompile APK file

When I find difficult to do something on Android, I will decompile the APK file and try to learn from the messy java code. But anyway, you may really find something useful that help you out.

Let's see how to decompile. We need some tools to decompile. That is dex2jar. You can find it here. And jd-gui to view the jar as java files.

1. uncompress the apk. On Windows, use winrar to open the apk and extract.
2. run command "dex2jar.bat classes.dex", "classes.dex.dex2jar.jar" is generated.
3. use jd-gui.exe to open jar file and view the java code.

C2DM Implementation Checklist Step by Step

Android C2DM helps your app server push message to your app. It's a mechanism that the server ask the mobile app to fetch new data from server and update itself. C2DM is still in beta version, or Labs version. To use C2DM with your Android applications, you must first signup to request access.

The official doc has a lot of content.
To make it clear, I make the following checklist:

C2DM: Get ClientLogin Authentication Token

To send C2DM messages, you should create a new google account as an app-based sender ID and get the ClientLogin Authentication Token.
The most convenient way is using Curl:

curl https://www.google.com/accounts/ClientLogin -d Email=$1 -d Passwd=$2 -d accountType=GOOGLE -d source=companyName-applicationName-versionID -d service=ac2dm

Android Push Notification Service and C2DM

Apple has support push notification since iOS 3.0
But what about Android??
Android can do this using a long-polling service or keep connected to server.
There are implementations of Android push notification.

1. Cloud to Device Messaging (C2DM) official service by Google
2. AndriodPN at http://sourceforge.net/projects/androidpn/files/
3. Urban Airship Service
4. IBM's MQTT

Sharp SH7218U Android folding mobile phone

Recently a new cellphone attracts my eyes.  Sharp SH7218U, really makes a difference. It's the first large-screen/ Android / folding mobile phone I have ever seen.

You can turn the lid clockwise 180 degrees.
Then it becomes a pure touch screen, cell phone. In this mode, here are four virtual Android phone buttons at the bottom of the screen.

Unparsed aapt error, main.out.xml

click Run button in Eclipse when I am working in a resource file such as main.xml.
I got error running the project.
a blank xml file "main.out.xml" showed up in editor with message "The document is empty".
In console, "No embedded stylesheet instruction for file".

Create Android sample project, Invalid project description

I found that android sample codes are not Eclipse projects. You have to create Eclipse projects from the sample codes by choosing "Create project from existing sample."

DO NOT set the sample code directory as your workspace, otherwise an error dialog will popup saying something like "Invalid project description, NotePad overlaps the location of another project: 'NotePad'"

Let's build the sample codes and run as Android application.