I'm porting an SDK from Android to plain Java and have run into an AutoParcel annotation that I don't understand.
Here's the original class and a snippet below:
#AutoParcel.Builder
public abstract static class Builder {
public abstract Builder id(String id);
...
public abstract SimpleFeature build();
}
public static Builder builder() {
return new AutoParcel_SimpleFeature.Builder();
}
I am able to pretty much port everything to AutoValue without incident, except that last function, as I don't understand what it is or it's equivalent in AutoValue.
Can someone explain what this is, and what its equivalent is in AutoValue?
The build annotation allows you to construct the immutable POJOs using the builder pattern i.e. something like
SimpleFeature.builder().id("test").build()
The equivalent annotation (not surprisingly since AutoParcel is a port of Autovalue with android specific features i.e. Parcelable)
#AutoValue.Builder
You should be able to find much more comprehensive documentation at https://github.com/google/auto/tree/master/value#builders
As JohnWowUs' comment suggests, this was largely an Eclipse issue.
The link he mentioned was only part of the solution, but I didn't need to drop more JARs into the project. With the help of an issue in the AutoValue repo and specifically configuring the maven-compiler-plugin, setting JDK1.7 as a target, with the following section added to the pom.xml:
<annotationProcessors>
<annotationProcessor>com.google.auto.value.processor.AutoValueProcessor</annotationProcessor>
</annotationProcessors>
Say I need (its required) to use fizz-1.0.jar and buzz-2.3.2.jar in my Java project. Now, fizz-1.0.jar depends on foo-0.1.35.jar, and buzz-2.3.2.jar depends on foo-4.2.17.jar.
foo-0.1.35.jar contains a Widget class like so:
public class Widget {
public int doSomething(int x) {
return x++;
}
}
foo-4.2.17.jar contains a heavily modifed version of Widget:
public class Widget {
public Meh makeStuff() {
return new Meh();
}
}
Unfortunately, both fizz-1.0.jar and buzz-2.3.2.jar make heavy use of both versions of Widget.
I can't just blindly add both versions of foo-x.y.z.jar to the classpath, because whichever Widget gets loaded first will only work for either fizz-1.0.jar or buzz-2.3.2.jar.
What are my options here? Remember I must have both fizz-1.0.jar and buzz-2.3.2.jar, and must satisfy all of their transitive dependencies.
I would recommend that you use a framework which distinguishes class loads.
E.g. OSGi framework. Then you can create 2 bundles - one with the fizz implementation and one with the buzz implementation. They both can contain their dependent libraries which do not conflict anymore because they are loaded from 2 different classs loaders.
Example osgi containers or "Eclipse Equinox" and "Apache Felix" but there are more.
Hope that helps.
We're using an Android Library Project to share core classes and resources across different builds (targets) of our Android application. The Android projects for each specific target reference the Core library project (behind the scenes, Eclipse creates and references a jar from the referenced library project).
Overriding resources such as images and XML layouts is easy. Resource files placed in the target project, such as the app icon or an XML layout, automatically override the core library's resources with the same name when the app is built. However, sometimes a class needs to be overridden to enable target-specific behavior. For example, the Amazon target preferences screen cannot contain a link to the Google Play app page, requiring a change in the Amazon project's preferences.xml and preferences Activity class.
The goal is to reduce the amount of duplicate code among target projects while removing as much target-specific code from the Core library as possible. We've come up with a couple of approaches to implement logic specific to different targets:
Write the target-specific functions within Core library classes and use if/switch blocks to select behavior based on product SKU. This approach is not very modular and bloats the Core library codebase.
Extend the particular Core class in a target project and override the base (Core) class functions as needed. Then keep a reference to the base-class object in the Core library and instantiate it with an extended class object (from How to override a class within an Android library project?)
Are there other strategies to override or extend an Android library project class? What are some of the best practices for sharing and extending common classes among Android app targets?
Library project is referenced as a raw project dependency (source-based mechanism), not as a compiled jar dependency (compiled-code based library mechanism).
#yorkw this is not true for the latest versions of ADT Plugin for Eclipse
http://developer.android.com/sdk/eclipse-adt.html
From version 17 Change log
New build features
Added feature to automatically setup JAR dependencies. Any .jar files in the /libs folder are added to the build configuration (similar to how the Ant build system works). Also, .jar files needed by library projects are also automatically added to projects that depend on those library projects. (more info)
More info http://tools.android.com/recent/dealingwithdependenciesinandroidprojects
Before that, update overwriting of the Activity from Library project was easy, just exclude the class. Now the library is included as jar file, and there is no way to exclude class file from jar dependency.
EDIT:
My solution to overwrete/extend Activity from library jar:
I created a simple util class:
public class ActivityUtil {
private static Class getActivityClass(Class clazz) {
// Check for extended activity
String extClassName = clazz.getName() + "Extended";
try {
Class extClass = Class.forName(extClassName);
return extClass;
} catch (ClassNotFoundException e) {
e.printStackTrace();
// Extended class is not found return base
return clazz;
}
}
public static Intent createIntent(Context context, Class clazz) {
Class activityClass = getActivityClass(clazz);
return new Intent(context, activityClass);
}
}
In order to overwrite a library's "SampleActivity" class it a the project which depends on that library, create a new class with the name SampleActivityExtended in the project in the same package and add the new activity to your AndroidManifest.xml.
IMPORTANT: all intents referencing overwritten activities should be created through the util class in the following manner:
Intent intent = ActivityUtil.createIntent(MainActivity.this, SampleActivity.class);
...
startActivity(intent);
behind the scenes, Eclipse creates and references a jar from the referenced library project.
This is not quite accurate. Library project is referenced as a raw project dependency (source-based mechanism), not as a compiled jar dependency (compiled-code based library mechanism). Currently Android SDK does not support exporting a library project to a self-contained JAR file. The library project must always be compiled/built indirectly, by referencing the library in the dependent application and building that application. When build dependent project, the compiled source and raw resources that need to be filtered/merged from Library project are copied and properly included in the final apk file. Note that Android team had started revamping the whole Library Project design (move it from ource-based mechanism to compiled-code based library mechanism) since r14, as mentioned in this earlier blog post.
What are some of the best practices for sharing and extending common classes among Android app targets?
The solution given by Android is Library Project.
The solution given by Java is Inheritance and Polymorphism.
Come together, the best practice IMO is the second option you mentioned in the question:
2.Extend the particular Core class in a target project and override the base (Core) class functions as needed. Then keep a reference to the base-class object in the Core library and instantiate it with an extended class object (from Android library project - How to overwrite a class?)
From my personal experience, I always use Android Library Project (Sometimes with Regular Java Project, for implementing/building common-lib.jar that contains only POJO) manage common code, for instance SuperActivity or SuperService, and extends/implements proper classes/interfaces in the dependent project for Polymorphism.
Solution based on PoisoneR's solution and Turbo's solution.
public static Class<?> getExtendedClass(Context context, String clsName) {
// Check for extended activity
String pkgName = context.getPackageName();
Logger.log("pkgName", pkgName);
String extClassName = pkgName + "." + clsName + "Extended";
Logger.log("extClassName", extClassName);
try {
Class<?> extClass = Class.forName(extClassName);
return extClass;
} catch (ClassNotFoundException e) {
e.printStackTrace();
// Extended class is not found return base
return null;
}
}
The benefits of this is that
The extended class can be in the project's package, not the library's package. Thanks to Turbo for this part.
By taking a String as an argument instead of a Class object, this method is able to be used even with ProGuard. getName() is where the problem is with ProGuard, as that will return something like "a" instead of the name of the original class. So in the original solution instead of looking for ClassExtended it will look for aExtended instead, something which does not exist.
What about using a callback approach here? (Okay, callback is a little bit misleading but I currently have no other word for it:
You could declare an interface in every Activity which should/may be expanded by the user. This interface will have methods like List<Preference> getPreferences(Activity activity) (pass whatever parameters you need here, I would use an Activity or at least a Context to be futureproof).
This approach could give you what you want when I have understood it correctly. While I haven't done this before and don't know how other people handle this I would give it a try and see if it works.
Could you, please, clarify what is different in Kindle and regular Android?
I think - they are the same.
What you need is different resources for Kindle and other devices. Then use appropriate resource.
For example I use 2 links to store:
<string name="appStore"><a href=http://market.android.com/details?id=com.puzzle.jigsaw>Android Market</a> or <a href=http://www.amazon.com/gp/mas/dl/android?p=com.puzzle.jigsaw>Amazon Appstore</a> <br>http://market.android.com/details?id=com.puzzle.jigsaw <br>href=http://www.amazon.com/gp/mas/dl/android?p=com.puzzle.jigsaw</string>
<string name="appStore_amazon"><a href=http://www.amazon.com/gp/mas/dl/android?p=com.puzzle.jigsaw>Amazon Appstore</a> <br>href=http://www.amazon.com/gp/mas/dl/android?p=com.puzzle.jigsaw</string>
and use appStore for all none Amazone product and appStore_amazon for Kindle.
How to determine where are you on run time - that would be another question which was answered here many times.
I was inspired by PoinsoneR's answer to create a Utility class to do the same thing for Fragments - override a fragment in an android Library. The steps are similar to his answer so I won't go into great detail, but here is the class:
package com.mysweetapp.utilities;
import android.support.v4.app.Fragment;
public class FragmentUtilities
{
private static Class getFragmentClass(Class clazz)
{
// Check for extended fragment
String extClassName = clazz.getName() + "Extended";
try
{
Class extClass = Class.forName(extClassName);
return extClass;
}
catch (ClassNotFoundException e)
{
e.printStackTrace();
// Extended class is not found return base
return clazz;
}
}
public static Fragment getFragment(Class clazz)
{
Class fragmentClass = getFragmentClass(clazz);
Fragment toRet = null;
try
{
toRet = (Fragment)fragmentClass.newInstance();
return toRet;
}
catch (InstantiationException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (IllegalAccessException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
return toRet;
}
}
Usage:
FragmentUtilities.getFragment(MySpecialFragment.class)
You can also use an Activity factory if you need to provide extended activitys for differnt build variants and have your library deal with the abstract factory alone. This can be set in your build variants Application file.
By running System.loadLibrary("myAPI"), I verified that the DLL file "myAPI.dll" can be successfully loaded into my Eclipse Java project. Now I need to call methods specified inside this DLL file from my Java code. To do this, I added JNA to my Java project. Then I wrote the below-given code snippet that should be able to get instances of classes IProject and ProjectFactory (specified in the DLL file).
I still don't understand how to properly implement this with JNA. I checked different threads, e.g. this one, but the ones I checked don't provide an answer. Any help is highly appreciated. Thanks.
import com.sun.jna.Library;
import com.sun.jna.Native;
public class MyClass {
public interface myAPI extends Library {
//...
}
void LoadProj() {
myAPI api = (myAPI) Native.loadLibrary("myAPI",myAPI.class);
String fileName = "xxx.sp";
IProject project; // this is wrong but shows what I am trying to do
try {
project = ProjectFactory.LoadProject(fileName);
}
catch (Exception ex) {
MessageBox.Show(this, ex.Message, "Load failure");
}
}
}
Not sure what problem you are facing but as a practice your myAPI interface should declare all the methods verbatim with appropriate parameter mapping. I don't see any methods inside your interface.
Please checkout the this link as well as the link mentioned above by #Perception
If there are no Java classes or Java source hidden inside this DLL (which would be ... strange), then it will never work this way. You can't instantiate C# classes or use C# interfaces. MessageBox.Show( isn't Java either, it is Windows Forms code.
I'm developing a java application that has 20 plugins, each plugin's have some similar GUI menu item's and menu event's but they store data in different table's in a database. Currently I'm creating separate GUI, event and model classes for each plugin by copying and pasting in diffrent class files.
Is it wise to develop separate GUI, event and model classes for each plugin's and duplicate similar methods to other plugin's?
I need your advice on how to create a generic GUI, event and model interface for all the plugin's without making my application uneasy to maintain.
Thank you.
We have a plug-in system in our product, and ran into the same issue. Many of the plug-ins share a lot of code. We ultimately decided on the following:
Define clean Interfaces (PluginABC implements MyProductInterface). These interfaces don't require a specific implementation but...
We provided a AbstractPlugin that Plugins can extend. This AbstractPlugin provides a ton of standard functionality that is useful for most plug-ins.
Example:
public interface MyProductInterface {
public void doIt();
}
public class MyPlugin implements MyProductInterface extends AbtractPlugin {
public doIt() {
// ...
usefulMethodForMostPlugins();
/// ...
}
}
public abstract class AbstractPlugin {
public usefulMethodForMostPlugins() ...
}