Since you're overriding the Main UnityPlayerActivity your AndroidManifest should look like :
<?xml version="1.0" encoding="utf-8"?>
<manifest android:theme="@*android:style/Theme.NoTitleBar" android:versionCode="1" android:versionName="1.0" android:installLocation="auto" package="a.b.c" xmlns:android="http://schemas.android.com/apk/res/android">
<supports-screens android:anyDensity="true" android:smallScreens="true" android:normalScreens="true" android:largeScreens="true" android:xlargeScreens="true" />
<application android:label="@string/app_name" android:icon="@drawable/app_icon" android:debuggable="false">
<activity android:label="@string/app_name" android:name=".UnityBridge" android:launchMode="singleTask" android:screenOrientation="portrait" android:configChanges="mcc|mnc|locale|touchscreen|keyboard|keyboardHidden|navigation|orientation|screenLayout|uiMode|fontScale">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
<category android:name="android.intent.category.LEANBACK_LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-feature android:glEsVersion="0x20000" />
</manifest>
And to successfully call "callSharedIntent" method from Unity you should get the instance of the Activity first and not only its Class as this is not a static call to a static method. Try this :
package a.b.c;
import android.content.Intent;
import android.os.Bundle;
import com.unity3d.player.UnityPlayerActivity;
public class UnityBridge extends UnityPlayerActivity {
public static Context context;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
context = this;
}
public void callShareIntent() {
Intent shareIntent = new Intent (Intent.ACTION_VIEW);
startActivity(shareIntent);
}
}
And from Unity :
using UnityEngine;
using System.Collections;
public class BotonCompartir : MonoBehaviour {
#if !UNITY_EDITOR && UNITY_ANDROID
AndroidJavaClass androidClass;
AndroidJavaObject androidActivity;
// Use this for initialization
void Start () {
AndroidJNI.AttachCurrentThread ();
androidClass = new AndroidJavaClass ("a.b.c.UnityBridge");
androidActivity = androidClass.GetStatic<AndroidJavaObject>("context");
}
// Update is called once per frame
void Update () {
if (Input.GetMouseButtonDown (0)) {
androidActivity.Call("callShareIntent");
}
}
void OnDestroy(){
if (androidClass !=null) androidClass.Dispose();
if (androidActivity !=null) androidActivity.Dispose();
}
#endif
}