[Xposed Framework Development] looxonline:
Hi,

First, a disclaimer.

I am a Java and xposed noob. My background is in embedded C development so I can get by with some simple Java code and thanks to the great tutorials online I have been able to put together an xposed module but I'm struggling with a problem that is beyond my abilities now and am reaching out to the community for help.

Next, the background.

I have an Android head unit in my car. There is an app that provides me with CarPlay functionality but none of the controls on the steering wheel work with the app. When I analysed the code I found that they handle all of their button inputs using proprietary methods that do not inject an event into any input streams. I wrote an xposed module to hook the button press methods and then inject a proper input into one of the event streams.

Initially I tried to use the command line 'input' command to do this but since it is a Java app and takes about 1s to load it was too slow. My only other option was to create a virtual device on an input stream that I could then use to inject keypresses through the hooked method. To create a virtual device I needed to write C code that my xposed module would be able to access through the JNI. Long story short, after some pain I was able to get the native library integrated into the project and compiling using the NDK.

Finally, the problem.

When I was using the module without the native library it worked but just with a large delay because of the time it takes to load the 'input' java app. I was able to see logs from the module in the logcat as I hooked the method and as I went through the various actions within the hook.

As soon as I introduce the native library though the entire xposed module just stops running completely. I do not get any logs from the module even though I have installed, activated and rebooted. It shows up in the xposed installer but it just does nothing. The funny thing is that this happens even if I make no reference whatsoever to any native functions within the library. All I need to do to kill the module is to build it with the System.loadlibrary line in the Main.java uncommented. As soon as I comment that piece of code out the module starts to hook the function and output logs again. Below is the code from the Main.Java that I am referring to. I am happy to make any manifest, C and gradle files available too. Looking for any ideas as to why the module dies completely as soon as I include this...

package projects.labs.spike.zlink_xposed_swc;

import de.robv.android.xposed.XposedBridge;
import static de.robv.android.xposed.XposedHelpers.findAndHookMethod;
import de.robv.android.xposed.IXposedHookLoadPackage;
import de.robv.android.xposed.IXposedHookZygoteInit;
import de.robv.android.xposed.XSharedPreferences;
import de.robv.android.xposed.XC_MethodHook;
import de.robv.android.xposed.callbacks.XC_LoadPackage;
import de.robv.android.xposed.XposedHelpers;

import android.app.AndroidAppHelper;
import android.content.Intent;
import android.os.Bundle;
import android.content.Context;

/* shellExec and rootExec methods */
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ByteArrayOutputStream;
import android.view.KeyEvent;

import android.media.AudioManager;

public class Main implements IXposedHookLoadPackage {

public static final String TAG = "ZLINK_XPOSED ";

public static void log(String message) {
XposedBridge.log("[" + TAG + "] " + message);
}

//public native int CreateVirtualDevice();

//public native int SendPrev();

@Override
public void handleLoadPackage(final XC_LoadPackage.LoadPackageParam lpparam) throws Throwable {
log("handleLoadPackage: Loaded app: " + lpparam.packageName);

if (lpparam.packageName.equals("com.syu.ms")) {

findAndHookMethod("module.main.HandlerMain", lpparam.classLoader, "mcuKeyRollLeft", new XC_MethodHook() {
@Override
protected void afterHookedMethod(XC_MethodHook.MethodHookParam param) throws Throwable {
// previous
log("PREVKEYHIT");

//rootExec("input keyevent 88");
log("EVENTSENT");
//Below was trying to use media keys which zlink never responded to...
/* Context context = (Context) AndroidAppHelper.currentApplication();
AudioManager mAudioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);

KeyEvent event = new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_MEDIA_PREVIOUS);
mAudioManager.dispatchMediaKeyEvent(event);
KeyEvent event2 = new KeyEvent(KeyEvent.ACTION_UP, KeyEvent.KEYCODE_MEDIA_PREVIOUS);
mAudioManager.dispatchMediaKeyEvent(event2);*/

//Below is the failed broadcast intent method...
/*Context mcontext = (Context) AndroidAppHelper.currentApplication();
Intent i = new Intent("com.android.music.musicservicecommand");
i.putExtra("command", "pause");
mcontext.sendBroadcast(i);*/
}
});

}
}

public static String rootExec(String... strings) {
String res = "";
DataOutputStream outputStream = null;
InputStream response = null;
try {
Process su = Runtime.getRuntime().exec("su");
outputStream = new DataOutputStream(su.getOutputStream());
response = su.getInputStream();

for (String s : strings) {
s = s.trim();
outputStream.writeBytes(s + "\n");
outputStream.flush();
}

outputStream.writeBytes("exit\n");
outputStream.flush();
try {
su.waitFor();
} catch (InterruptedException e) {
e.printStackTrace();
}
res = readFully(response);
} catch (IOException e) {
e.printStackTrace();
} finally {
Closer.closeSilently(outputStream, response);
}
return res;
}

public static String readFully(InputStream is) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int length = 0;
while ((length = is.read(buffer)) != -1) {
baos.write(buffer, 0, length);
}
return baos.toString("UTF-8");
}

static {
System.loadLibrary("native-lib");
}
}