We have a shared library that contains version info and is referenced by all our projects in our Visual Studio Solution.
For the most part, we can reference the version string from every project and the dll reflect the info accordingly.
My issue here is, with our Android application (xamarin based). It has a manifest file which contains the versionName and versionCode.
How can we make those values in our android manifest file read from our shared project?
My understanding is that, it is not possible. Because
The manifest file presents essential information about your app to the Android system, information the system must have before it can run any of the app's code.
From Google's documentation
So this is a file that is required before the App builds.
C# Code in Shared Project (SAP/PCL) is ready to be used only after successful Compilation. So logically setting the Version Code and Version Name in Android Manifest File from Shared logic is not possible.
Another standard approach would be to set it from String Resource (XML) file in Android. You may have to copy and paste the value from Shared Project to strings.xml file and refer it in manifest, like
#string/versionCode
Note: I do not know anything about xamarin.
In java you can get the versioninfo from the manifest like this
public static String getAppVersionName(final Context context) {
try {
final String versionName = context.getPackageManager()
.getPackageInfo(context.getPackageName(), 0).versionName;
return versionName;
} catch (final NameNotFoundException e) {
}
return null;
}
I assume that xamarin has some mechanism to call PackageManager to get Packageinfo, too
You could do this by using a Dependency Service. Here's a great article on them: https://developer.xamarin.com/guides/xamarin-forms/dependency-service/
The idea would be your Dependency Service would expose the Android specific information to the shared code library.
For instance you might have an interface in your common code declared such as:
public interface IPlatformVersionInfo
{
string GetOSVersion ();
}
Now, in your Android library you would implement it:
public class PlatformVersionInfo : IPlatformVersionInfo
{
public string GetOSVersion () {
return Android.OS.Build.VERSION.SdkInt.ToString ();
}
}
Finally, in your common code you would use your dependency service of choice to invoke an instance of it:
var osVersion = DependencyService.Get<IPlatformVersionInfo>().GetOSVersion ();
Of course this is somewhat pseudo-code and depending what dependency service you choose the code may look a bit different.
I am using this code for saving database, using BackupAgent class
public class MyBackupAgent extends BackupAgentHelper {
String DATABASE_NAME = "mydb";
String DATABASE_FILE_NAME = "mydb.db";
#Override
public void onCreate() {
SharedPreferencesBackupHelper helper = new SharedPreferencesBackupHelper(this, PREFS);
addHelper(PREFS_BACKUP_KEY, helper);
FileBackupHelper dbs = new FileBackupHelper(this, DATABASE_FILE_NAME);
addHelper("dbs", dbs);
}
#Override
public File getFilesDir() {
File path = getDatabasePath(DATABASE_FILE_NAME);
return path.getParentFile();
}
}
Now after that i want to know how to restore database?
Please help me about this, Thanks in advance
In theory only with that code and changes on AndroidManifest the backup should work as per Android Google page inform.
Please take a look on this page: http://developer.android.com/guide/topics/data/backup.html
For summary from this above page:
To implement a backup agent, you must:
1 - Declare your backup agent in your manifest file with the android:backupAgent attribute.
2 - Register your application with a backup service. Google offers Android Backup Service as a backup service for most Android-powered devices, which requires that you register your application in order for it to work. Any other backup services available might also require you to register in order to store your data on their servers.
3 - Define a backup agent by either: Extending BackupAgent or Extending BackupAgentHelper;
My app was working great until I got it ready for deployment. I have a portion of my app that checks to see if a checkmark is checked in the preferences. Well since I added as a library and am running through another application (created a free version of the app and trying to keep my code as a library) it always returns false.
SharedPreferences appPrefs = context.getSharedPreferences("com.company.widget_preferences", Context.MODE_PRIVATE);
boolean blNotifications;
blNotifications = appPrefs.getBoolean("notifications_new_message", false);
if (blNotifications)
{
//always returns false
}
Thanks for your help.
Figured it out guys. For some reason using SharedPreferences appPrefs = context.getSharedPreferences worked in dev, but as soon as I made it into a Library it didn't like it anymore. The correct way to call a default sharepreference is the following.
SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(this);
String value = pref.getString("name_of_my_pref", "default_value");
Thanks again.
I've researched and followed how to get my android app to backup the data to google backup so if user loses phone or upgrades to a new phone, they don't lose their data. However, when I test it out (by using the app myself, then uninstalling and reinstalling), no data is restored. Here's what I've done. Perhaps someone can figure out what is wrong.
Applied for a backup key from google
Placed following code in Manifest File (in place of key I did add the key value and for packageName I used my app package name)
android:backupAgent="packageName.MyPrefsBackup">
<meta-data android:name="com.google.android.backup.api_key" android:value="key" />
Created class MyPrefsBackup with following code. The name of the sharedpreference file I want to backup is called UserDB. As far as the PREFS_BACKIP_KEY, I just called it prefs. From what I understand, this is not the same key as the one that goes in the manifest file.
Code:
package packageName;
import android.app.backup.BackupAgentHelper;
import android.app.backup.SharedPreferencesBackupHelper;
public class MyPrefsBackup extends BackupAgentHelper {
// The name of the SharedPreferences file
static final String PREFS = "UserDB";
// A key to uniquely identify the set of backup data
static final String PREFS_BACKUP_KEY = "prefs";
// Allocate a helper and add it to the backup agent
public void onCreate() {
SharedPreferencesBackupHelper helper = new SharedPreferencesBackupHelper(this, PREFS);
addHelper(PREFS_BACKUP_KEY, helper);
}
}
Added BackupManager mBackupManager = new BackupManager(this); in my main class where I call the backup manager in next step
Lastly, in my main program I call the backupHelper when data is changed by the following line:
mBackupManager.dataChanged();
Any help is much appreciated.
try new BackupManager(this).dataChanged()
If you are testing this from AVD - you'll need to enable backups - AVD are disabled for backups by default.
adb shell bmgr enable true
Then you can actually debug it to see if the onCreate is called after running
adb shell bmgr run
Is there any way to make an Android application to download and use a Java library at runtime?
Here is an example:
Imagine that the application needs to make some calculations depending on the input values. The application asks for these input values and then checks if the required Classes or Methods are available.
If not, it connects to a server, downloads the needed library, and loads it at runtime to calls the required methods using reflection techniques. The implementation could change depending on various criteria such as the user who is downloading the library.
Sorry, I'm late and the question has already an accepted answer, but yes, you can download and execute external libraries. Here is the way I did:
I was wondering whether this was feasible so I wrote the following class:
package org.shlublu.android.sandbox;
import android.util.Log;
public class MyClass {
public MyClass() {
Log.d(MyClass.class.getName(), "MyClass: constructor called.");
}
public void doSomething() {
Log.d(MyClass.class.getName(), "MyClass: doSomething() called.");
}
}
And I packaged it in a DEX file that I saved on my device's SD card as /sdcard/shlublu.jar.
Then I wrote the "stupid program" below, after having removed MyClass from my Eclipse project and cleaned it:
public class Main extends Activity {
#SuppressWarnings("unchecked")
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
try {
final String libPath = Environment.getExternalStorageDirectory() + "/shlublu.jar";
final File tmpDir = getDir("dex", 0);
final DexClassLoader classloader = new DexClassLoader(libPath, tmpDir.getAbsolutePath(), null, this.getClass().getClassLoader());
final Class<Object> classToLoad = (Class<Object>) classloader.loadClass("org.shlublu.android.sandbox.MyClass");
final Object myInstance = classToLoad.newInstance();
final Method doSomething = classToLoad.getMethod("doSomething");
doSomething.invoke(myInstance);
} catch (Exception e) {
e.printStackTrace();
}
}
}
It basically loads the class MyClass that way:
create a DexClassLoader
use it to extract the class MyClass from "/sdcard/shlublu.jar"
and store this class to the application's "dex" private directory (internal storage of the phone).
Then, it creates an instance of MyClass and invokes doSomething() on the created instance.
And it works... I see the traces defined in MyClass in my LogCat:
I've tried on both an emulator 2.1 and on my physical HTC cellphone (which is running Android 2.2 and which is NOT rooted).
This means you can create external DEX files for the application to download and execute them. Here it was made the hard way (ugly Object casts, Method.invoke() ugly calls...), but it must be possible to play with Interfaces to make something cleaner.
Wow. I'm the first surprised. I was expecting a SecurityException.
Some facts to help investigating more:
My DEX shlublu.jar was signed, but not my app
My app was executed from Eclipse / USB connection. So this is an unsigned APK compiled in DEBUG mode
Shlublu's anwser is really nice. Some small things though that would help a beginner:
for library file "MyClass" make a separate Android Application project which has the MyClass file as only file in the src folder (other stuff, like project.properties, manifest, res, etc. should also be there)
in library project manifest make sure you have:
<application android:icon="#drawable/icon"
android:label="#string/app_name">
<activity android:name=".NotExecutable"
android:label="#string/app_name">
</activity>
</application>
(".NotExecutable" is not a reserved word. It is just that I had to put something here)
For making the .dex file, just run the library project as android application (for the compiling) and locate .apk file from the bin folder of the project.
Copy the .apk file to your phone and rename it as shlublu.jar file (an APK is actually a specialization of a jar, though)
Other steps are the same as described by Shlublu.
Big thanks to Shlublu for cooperation.
Technically should work but what about Google rules?
From: play.google.com/intl/en-GB/about/developer-content-policy-print
An app distributed via Google Play may not modify, replace or update
itself using any method other than Google Play’s update mechanism.
Likewise, an app may not download executable code (e.g. dex, JAR, .so
files) from a source other than Google Play. This restriction does not
apply to code that runs in a virtual machine and has limited access to
Android APIs (such as JavaScript in a WebView or browser).
I am not sure if you can achieve this by dynamically loading java code. May be you can try embedding a script engine your code like rhino which can execute java scripts which can be dynamically downloaded and updated.
sure, it is possible. apk which is not installed can be invoked by host android application.generally,resolve resource and activity's lifecircle,then,can load jar or apk dynamically.
detail,please refer to my open source research on github: https://github.com/singwhatiwanna/dynamic-load-apk/blob/master/README-en.md
also,DexClassLoader and reflection is needed, now look at some key code:
/**
* Load a apk. Before start a plugin Activity, we should do this first.<br/>
* NOTE : will only be called by host apk.
* #param dexPath
*/
public DLPluginPackage loadApk(String dexPath) {
// when loadApk is called by host apk, we assume that plugin is invoked by host.
mFrom = DLConstants.FROM_EXTERNAL;
PackageInfo packageInfo = mContext.getPackageManager().
getPackageArchiveInfo(dexPath, PackageManager.GET_ACTIVITIES);
if (packageInfo == null)
return null;
final String packageName = packageInfo.packageName;
DLPluginPackage pluginPackage = mPackagesHolder.get(packageName);
if (pluginPackage == null) {
DexClassLoader dexClassLoader = createDexClassLoader(dexPath);
AssetManager assetManager = createAssetManager(dexPath);
Resources resources = createResources(assetManager);
pluginPackage = new DLPluginPackage(packageName, dexPath, dexClassLoader, assetManager,
resources, packageInfo);
mPackagesHolder.put(packageName, pluginPackage);
}
return pluginPackage;
}
your demands is only partly of function in the open source project mentioned at the begining.
If you're keeping your .DEX files in external memory on the phone, such as the SD card (not recommended! Any app with the same permissions can easily overwrite your class and perform a code injection attack) make sure you've given the app permission to read external memory. The exception that gets thrown if this is the case is 'ClassNotFound' which is quite misleading, put something like the following in your manifest (consult Google for most up to date version).
<manifest ...>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
android:maxSdkVersion="18" />
...
</manifest>
I think #Shlublu answer is correct but i just want to highlight some key points.
We can load any classes from external jar and apk file.
In Any way, we can load Activity from external jar but we can not start it because of the context concept.
To load the UI from external jar we can use fragment. Create the instance of the fragment and embedded it in the Activity. But make sure fragment creates the UI dynamically
as given below.
public class MyFragment extends Fragment {
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup
container, #Nullable Bundle savedInstanceState)
{
super.onCreateView(inflater, container, savedInstanceState);
LinearLayout layout = new LinearLayout(getActivity());
layout.setLayoutParams(new
LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.MATCH_PARENT));
Button button = new Button(getActivity());
button.setText("Invoke host method");
layout.addView(button, LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.WRAP_CONTENT);
return layout;
}
}