Just wondering if anyone has tried using new Java 7 language features with Android? I know that Android reads the bytecode that Java spits out and turns it to dex.
If you are using Android Studio, the Java 7 language should be enabled automatically without any patches. Try-with-resource requires API Level 19+, and NIO 2.0 stuff are missing. If you can't use Java 7 features, see 's answer on how to edit your build.gradle. The following is for historical interest only. A small part of Java 7 can certainly be used with Android (note: I have only tested on 4.1). First of all, you could not use Eclipse's ADT because that only Java compiler 1.5 and 1.6 are compliant.
You could recompile ADT but I find there is no simple way to do that aside from recompiling the whole Android together. But you don't need to use Eclipse. For instance, and other javac-based IDEs supports compiling to Android and you could set the compliance even up to Java 8 with:. File → Project Structure → Modules → (pick the module at the 2nd pane) → Language level → (choose '7.0 - Diamonds, ARM, multi-catch, etc.'
) This only allows Java 7 language features, and you can hardly benefit from anything since a half of improvement also comes from the library. Features you could use are those which do not depend on the library:. Diamond operator ( ). String switch. Multiple-catch ( catch (Exc1 Exc2 e)).
Underscore in number literals ( 1234567). Binary literals ( 0b1110111) And these features cannot be used yet:. The try-with-resources statement — because it requires the non-existing interface 'java.lang.AutoCloseable' (this can be used publicly in 4.4+). The @SafeVarargs annotation — because 'java.lang.SafeVarargs' does not exist. 'yet':) It turns out that, although Android's library is targeting for 1.6, the Android source does contain interfaces like and traditional interfaces like does inherit from AutoCloseable (SafeVarargs is really missing, though). We could confirm its existence via reflection. They are hidden simply because the Javadoc has the @hide tag, which caused the 'android.jar' not to include them.
There is already as existing question on how to get those methods back. You just need to replace the existing 'android.jar' reference of the current Platform with our customized one, then many of the Java 7 APIs will become available (the procedure is similar to that in Eclipse. Check Project Structure → SDKs.) In additional to AutoCloseable, (only) the following Java 7 library features are also revealed:. Exception chaining constructors in ConcurrentModificationException, LinkageError and AssertionError.
The static.compare methods for primitives: Boolean.compare, Byte.compare, Short.compare, Character.compare, Integer.compare, Long.compare. EDIT: At the time this was written, the latest release was Android 9 and Eclipse Indigo. Thing have changed since then. Practical answer Yes, I have tried. But this is not a great test as the compatibility was limited to level 6 with no way (no simple way at least) to really use java 7:. First I installed a JDK7 on a machine that had no other JDK installed - Eclipse and Android are not installed either:.
Then I installed a brand new Eclipse Indigo and checked it was actually using the JDK 7 (well, as this is the only one and as this is the one I've selected I would have been surprised). Then I installed the latest version of the Android SDK (EDIT: Honeycomb, API13, at the time this post was written).
It found my JDK 7 and installed properly. The same for ADT.
But I had a surprise when trying to compile and run a Hello Word Android app. The compatibility was set to Java 6 with no way to force it to Java 7:. I tried with a non-Android project, a regular Java one, and I had the explanation. The compatibility level seems to be limited by Eclipse (see the message at bottom of the following image): So I had Hello World working, and also other apps, more complicated and using SQLite, Listview, Sensor and Camera, but this only proves that the compatibility handling of Java 7 seems to be well done and working with Android. So, did someone try with the good old Ant, to bypass the Eclipse limitation seen above?. Theroetical answer Anyway, the SDK is designed to be used with Java 5 or 6, as explained.
We may have something working with Java 7, but it would be working 'by accident'. The building of the DEX may work properly or not, and once the DEX built, it may work or not. This because using a non-qualified JDK gives unpredictable results by definition.
Even if someone has succesfully built an Android app under plain Java 7, this does not qualify the JDK. The same process applied to another application may fail, or the resulting application may have bugs tied to the use of that JDK. Not recommended. For those who are involved on webapps development, this exactly the same as deploying a web application built under Java 5 or 6 under an application server qualified for Java 4 only (let's say Weblogic 8 for example). This may work, but this is not something that can be recommended for other purposes than trying. Quote from dalvikvm.com: dx, included in the Android SDK, transforms the Java Class files of Java classes compiled by a regular Java compiler into another class file format (the.dex format) That means, the.java source file does not matter, it's only the.class bytecode.
As far as I know, only invokedynamic was added to the JVM bytecode in Java 7, the rest is compatible to Java 6. The Java language itself does not use invokedynamic. Other new features, like the switch statement using Strings or the multi- catch are just syntatic sugar and did not require byte code changes. For example, the multi- catch just copies the catch-block for each possible exception. The only problem should be that the new classes introduced in Java 7 are missing in Android, like AutoCloseable, so I'm not sure if you can use the try-with-resources feature (somebody tried it?). Any comments on that?
Am I missing something?
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Getting Started with Android Java If you are new to writing code for Phidgets, we recommend starting by running, then modifying existing examples. This will allow you to:. Make sure your libraries are properly linked. Go from source code to a test application as quickly as possible. Ensure your Phidget is hooked up properly Android Studio Use Our Examples In order to run the examples in Android Studio, all you need to do is download the the relevant example project for your device from:. Next, open Android Studio on your development machine. Import the project using File-New-Import Project.
When you are ready, the next step is configuring your project and writing your own code! Important Note The examples provided are designed to be incredibly simplistic in order to highlight the base requirements to run Phidgets on Android. To this end, we opted to open and close the Phidgets in the onCreate and onDestroy handlers of the main activity respectively. This is likely a bad idea for implementing apps for any practical use, as the activity is prone to being destroyed and re-created for a wide variety of reasons, from closing the app, to rotating the screen. In order to ensure your Phidget remains attached through these events, we recommend running your Phidgets in a secondary service. Check the section for more information. Creating a New Project When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget Java libraries for Android Java.
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To start, create a new project in Android Studio. Import com.phidget22.; The project now has access to Phidgets. Next, view the section located below. Write Code By following the instructions for your operating system and compiler above, you now have working examples and a project that is configured.
This teaching section will help you understand how the examples were written so you can start writing your own code. Remember: your main reference for writing Android Java code will be the Manual and the. Step One: Initialize and Open You will need to declare your Phidget object in your code. For example, we can declare a digital input object like this. //Disable USB connection to Phidgets com. Uninitialize ; Further Reading - Here you can find the basic concepts to help you get started with making your own programs that use Phidgets. Learn about these two properties that control how much data comes in from your sensors.
It can be difficult to figure out how to use more than one Phidget in your program. This page will guide you through the steps.
Your program can gather data in either a polling-driven or event-driven manner. Learn the difference to determine which is best for your application.
Learn about all the tools you can use to debug your program. Phidgets can be controlled and communicated with over your network- either wirelessly or over ethernet.
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Common Problems, Solutions and Workarounds Issue: My Phidget detached when I rotated my phone You are likely using one of our examples, or handling the opening and closing of Phidgets in a similar way. In either case, chances are you are opening and closing Phidgets in your main activity. This is not recommended for practical applications, as the entire activity can be destroyed and re-created many times through its lifecycle due to configuration changes such as rotating the screen. This is a reality of the Android operating system, and must be addressed in whatever way best suits your application.
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A good option to keep your Phidgets connected would be to implement a or a, depending on your application, and open your Phidgets there.