Develop Reference

How to use getClassLoader() correctly?

Here I try to use getClassLoader().getResources() to get my .model file, however it returns null. I'm not sure where goes wrong!
And when I try to print out the urls, it gives me java.lang.TwoEnumerationsInOne#5fd1900, what does this means?
public Activity(MainActivity activity) {
MainActivity activity = new MainActivity();
try {
// Open stream to read trained model from file
InputStream is = null;
// this .model file is save under my /project/app/src/main/res/
Enumeration<URL> urls = Activity.class.getClassLoader().getResources("file.model");
// System.out.println("url:"+urls);
if (urls.hasMoreElements()) {
URL element = urls.nextElement();
is = element.openStream();
}
// deserialize the model
classifier = (J48) SerializationHelper.read(is);
is.close();
} catch (Exception e) {
e.printStackTrace();
}
}

In Android, resources put under src/main/res are not visible in the class path and can only be accessed via the android resources API. Try to put the file into src/main/resources.

Android - where can I see the request url that is generated when setDataSource(..) is called?

I am trying to add headers to my setDataSource() method. Is there any way I could see the request itself that is sent ? I need to do this because I'd like to confirm if the url generated by setDataSource method is correctly formed. I don't however see any apis in the MediaPlayer class that can help me do this. Any direction or a solution would be most appreciated.

For non-file media source, the framework handle it by MediaHTTPConnection which is a hide API. You can change its field VERBOSE to true to see the printed log.
Since it's not exported, we can't use it directly. The following code might helpful, but I am not sure if it works. Run it before setDataSource().
try {
Class mediaServiceClass = Class.forName("android.media.MediaHTTPConnection");
Field field = mediaServiceClass.getDeclaredField("VERBOSE");
field.setAccessible(true);
Field modifiersField = Field.class.getDeclaredField("modifiers");
modifiersField.setAccessible(true);
modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
field.setBoolean(null, true);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
You can refer here to see the detail implementation of MediaHTTPConnection.

How to invoke a GUI Class from external apk in android

I have loaded a external apk through DexClassLoader.
in a method will be invoked has a GUI load from .xml layout.
But i can not view this GUI (from external apk) through invoke method !!
In conclusion, I want to load a GUI from an external APK file through invoke method.
Please help me !!
p/s: sorry about my english!
final File _optimizedDexOutputPath = getDir("outdex", Context.MODE_PRIVATE);
String _className;
String _methodToInvoke;
String _apkfilePath;
HashMap<String, String> hmData;
//Prepare
hmData = preWorkflow();
_className = hmData.get("className");
_apkfilePath = hmData.get("apkfilePath");
_methodToInvoke = hmData.get("methodToInvoke");
DexClassLoader dLoader = new DexClassLoader(_apkfilePath,
_optimizedDexOutputPath.getAbsolutePath(),
null, ClassLoader.getSystemClassLoader().getParent());
try {
Class<?> loadedClass = dLoader.loadClass(_className);
Object obj = (Object) loadedClass.newInstance();
Method m = loadedClass.getDeclaredMethod(_methodToInvoke);
m.invoke(obj);
} catch (IllegalAccessException e) {
e.getCause().printStackTrace();
} catch (InvocationTargetException e) {
e.getCause().printStackTrace();
}catch (NullPointerException e){
e.getCause().printStackTrace();
} catch(Exception ex) {
ex.printStackTrace();
}

In Android you don't have a unit 'GUI'. You are probably talking about an Activity. If you want to launch an Activity of another package there is no need for reflection. Simply send an Intent. http://developer.android.com/training/basics/intents/index.html

DexClassLoader, reload Code fails with Signal 7

I'm trying to build a plugin-System, where DexClassLoader is fetching code from other installed apks containing fragments(my plugins), and showing them in my host. This is working quite nice.
I also like to make the plugins hotswappable, this means I can change the code from a plugin, install it new and the host will notice and will load the new code. This also works, if I'm changing the code for the first time. (Although I thought it shouldn't, it seems I've got a wrong understanding of this code:
try {
requiredClass = Class.forName(fullName);
} catch(ClassNotFoundException e) {
isLoaded = false;
}
)
If i'm trying it a second time with the same plugin, the host shuts down at requiredClass = classLoader.loadClass(fullName); with something like
libc Fatal signal 7 (SIGBUS) at 0x596ed4d6 (code=2), thread 28814
(ctivityapp.host)
Does anybody has a deeper insight in the functionality of DexClassLoader and may tell me, what is happening here? I'm quite stuck at this.
Heres the full code of the method loading the foreign code:
/**
* takes the name of a package as String, and tries to load the code from the corresponding akp using DexclassLaoder.
* Checking if a package is a valid plugin must be done before calling this.
* The Plugin must contain a public class UI that extends Fragment and implements plugin as a starting point for loading
* #param packageName The full name of the package, as String
* #return the plugins object if loaded, null otherwise
*/
private Plugin attachPluginToHost(String packageName) {
try {
Class<?> requiredClass = null;
final ApplicationInfo info = context.getPackageManager().getApplicationInfo(packageName,0);
final String apkPath = info.sourceDir;
final File dexTemp = context.getDir("temp_folder", 0);
final String fullName = packageName + ".UI";
boolean isLoaded = true;
// Check if class loaded
try {
requiredClass = Class.forName(fullName);
} catch(ClassNotFoundException e) {
isLoaded = false;
}
if (!isLoaded) {
final DexClassLoader classLoader = new DexClassLoader(apkPath, dexTemp.getAbsolutePath(), null, context.getApplicationContext().getClassLoader());
requiredClass = classLoader.loadClass(fullName);
}
if (null != requiredClass) {
// Try to cast to required interface to ensure that it's can be cast
final Plugin plugin = Plugin.class.cast(requiredClass.newInstance());
installedPlugins.put(plugin.getName(), plugin);
return plugin;
}
} catch (PackageManager.NameNotFoundException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
return null;
}
Many thanks in advance!

Not that it really matters (As nobody is actually viewing this), or that I even understand what's going on, but deleting the corresponding file of the plugin in dexTemp.getAbsolutePath() before reloading it solves the problem.
PS: Tumbleweed-Badge, YAY!

Android- Using DexClassLoader to load apk file

I've hit a bit of a wall. Any help would be appreciated. I have an app that I want to use DexClassLoader to load another apk file.
Here is my code:
DexClassLoader dLoader = new DexClassLoader("/sdcard/download/test.apk","/sdcard/download",null,ClassLoader.getSystemClassLoader().getParent());
Class calledClass = dLoader.loadClass("com.test.classname");
Intent it=new Intent(this, calledClass);
it.setClassName("com.test", "com.test.classname");
startActivity(it);
Now I had already installed test.apk so when I ran the above code it
worked fine and launched the application. However I want to be able to
run this without test.apk being installed already (as that would
defeat the entire point of the application) . So I uninstalled it and
when I ran the my app again I get this error:
android.content.ActivityNotFoundException: Unable to find explicit
activity class {com.test/com.test.classname}; have you declared this
activity in your AndroidManifest.xml.
So I'm a bit stumped here. This activity is declared in the Manifest
of the apk I am trying to run. I can't declare it in my applications
Manifest. Any ideas?
Thanks,
Craig

Try using Android's PathClassLoader:
String packagePath = "com.mypackage";
String classPath = "com.mypackage.ExternalClass";
String apkName = null;
try {
apkName = getPackageManager().getApplicationInfo(packagePath,0).sourceDir;
} catch (PackageManager.NameNotFoundException e) {
// catch this
}
// add path to apk that contains classes you wish to load
String extraApkPath = apkName + ":/path/to/extraLib.apk"
PathClassLoader pathClassLoader = new dalvik.system.PathClassLoader(
apkName,
ClassLoader.getSystemClassLoader());
try {
Class<?> handler = Class.forName(classPath, true, pathClassLoader);
} catch (ClassNotFoundException e) {
// catch this
}

Although the question is old, I will answer because I struggled a bit to find a clear answer for your same question for myself. First, I would like to highlight that a clear requirement in your question is to load a class from an .apk that is not already installed on the device. Therefore, calling the package manager using getPackageManager() and providing it with the package path will clearly lead to NameNotFoundException because the .apk that has the package is not installed on the device.
So, the way to go about loading classes from an .apk file that is not installed on the device (i.e. you only have the .apk stored in a directory on your SDCARD) is by using DexClassLoader as follows:
1- Make sure you have the .apk file in a directory on your SDCARD. I've mine Offloadme.apk in the Download folder on my SDCARD.
2- Add read permission in your AndroidManifest.xml to allow your app to read from the manifest.
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
3- Use the following definitions to define the path of the .apk, the class name inside the apk, and method name in that class that you would like to invoke:
final String apkFile =Environment.getExternalStorageDirectory().getAbsolutePath()+"/Download/Offloadme.apk";
String className = "com.khaledalanezi.offloadme.SimpleCalculator";
String methodToInvoke = "add";
4- Use the DexClassLoader to load the .apk and call the add method in the SimpleCalculator class using reflection as follows:
final File optimizedDexOutputPath = getDir("outdex", 0);
DexClassLoader dLoader = new DexClassLoader(apkFile,optimizedDexOutputPath.getAbsolutePath(),
null,ClassLoader.getSystemClassLoader().getParent());
try {
Class<?> loadedClass = dLoader.loadClass(className);
Object obj = (Object)loadedClass.newInstance();
int x =5;
int y=6;
Method m = loadedClass.getMethod(methodToInvoke, int.class, int.class);
int z = (Integer) m.invoke(obj, y, x);
System.out.println("The sum of "+x+" and "+"y="+z);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Note that in my simple example, I added two numbers using the add method available in the SimpleCalculator class loaded from the Offloadme.apk file stored on my SDCARD and I was able to print the correct answer which is 11.

You can't do that. Even if you're able to access classes from external file, Android still does not know them. And you don't run activities directly, but by requesting Android to run them, so they have to be registered/installed into system.