Android Plugin not working in unity with class not found exception?

Question

I tried creating a plugin but not working in unity.I do not have much idea about Android studio but watched this video to create an android plugin.I created a new android project without any activity.So I have written two classes UnityBinder.java and Gallery.java.They are given below

UnityBinder.java

package com.techripples.unityplugin;

import android.app.Activity;
import android.content.Intent;

public class UnityBinder {
public static void OpenGallery(Activity activity)
{

    Intent intent =new Intent(activity,Gallery.class);
    activity.startActivity(intent);

}

}

Gallery.java class given below

package com.techripples.unityplugin;


import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.provider.MediaStore;
import android.net.Uri;
import android.database.*;
import com.unity3d.player.*;



public class Gallery extends Activity {


int PHOTO_GALLERY=1;

@Override
protected void onCreate(Bundle bundle)
{
    super.onCreate(bundle);
    Intent intent=new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
    startActivityForResult(intent,PHOTO_GALLERY);
}

//it will run when user picks a photo from the gallery
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if(resultCode==RESULT_OK && requestCode==PHOTO_GALLERY && data!=null)
    {

        Uri uri=data.getData();
        String[] fileColumn={MediaStore.Images.Media.DATA};
        Cursor cursor=getContentResolver().query(uri,fileColumn,null,null,null);
        cursor.moveToFirst();
        int columnIndex=cursor.getColumnIndex(fileColumn[0]);
        String photoPath=cursor.getString(columnIndex);


        //Send path to unity to get photo
                                        //GamObject Name,method name,argument
        UnityPlayer.UnitySendMessage("Gallery","OnPhotoPick",photoPath);
        Gallery.this.finish();//close activity

    }
}
}

Next I have build and copied the jar file into Unity.The c# code written is as follows

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ShowPicture : MonoBehaviour
{

Texture2D galleryImage;
bool isGalleryImageLoaded = false;

WWW www;

// Start is called before the first frame update
void Start()
{
    
}

// Update is called once per frame
void Update()
{
    
}

void OnGUI()
{

    if(isGalleryImageLoaded)
    {
        GUI.DrawTexture(new Rect(0, 0, Screen.width, Screen.height), galleryImage);

    }
    if(GUI.Button(new Rect(50,50,100,100),"Open"))
    {

        isGalleryImageLoaded = false;
        AndroidJavaClass ajc = new AndroidJavaClass("com.unity.player.UnityPlayer");
        //While asking question used AndroidJavaClass instead of AndroidJavaObject
        AndroidJavaObject ajo = new AndroidJavaObject("com.techripples.unityplugin.UnityBinder");
        ajo.CallStatic("OpenGallery", ajc.GetStatic<AndroidJavaObject>("currentActivity"));
    }

    if(www!=null && www.isDone)
    {
        galleryImage = new Texture2D(www.texture.width, www.texture.height);
        galleryImage.SetPixels32(www.texture.GetPixels32());
        galleryImage.Apply();
        www = null;

        isGalleryImageLoaded = true;

    }

}


public void OnPhotoPick(string filePath)
{
    Debug.Log(filePath);

    www = new WWW("file://" + filePath);
}


 }

The manifest file which I copied into the Unity folder.Assets>Plugins>Android. is as follows.

<?xml version="1.0" encoding="utf-8"?>
<manifest
xmlns:android="http://schemas.android.com/apk/res/android"
package="com.unity3d.player"
xmlns:tools="http://schemas.android.com/tools"
android:installLocation="preferExternal">
<supports-screens
    android:smallScreens="true"
    android:normalScreens="true"
    android:largeScreens="true"
    android:xlargeScreens="true"
    android:anyDensity="true"/>

<application
    android:theme="@style/UnityThemeSelector"
    android:icon="@mipmap/app_icon"
    android:label="@string/app_name">
    <activity android:name="com.unity3d.player.UnityPlayerActivity"
              android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
        <meta-data android:name="unityplayer.UnityActivity" android:value="true" />
    </activity>
  <activity android:name="com.techripples.unityplugin.Gallery"></activity>
    
</application>

The error I got from terminal is as follows

01-28 13:25:06.305 27032 27061 E Unity : java.lang.ClassNotFoundException: Didn't find class "com/unity/player/UnityPlayer" on path: DexPathList[[zip file "/data/app/com.testing.androidplugin-Aq1j3vpTxsomWMvd4kK7NQ==/base.apk"],nativeLibraryDirectories=[/data/app/com.testing.androidplugin-Aq1j3vpTxsomWMvd4kK7NQ==/lib/arm, /data/app/com.testing.androidplugin-Aq1j3vpTxsomWMvd4kK7NQ==/base.apk!/lib/armeabi-v7a, /system/lib, /system/vendor/lib]]

Video of plugin done.What I am doing wrong here. Making Of Android plugin

I dont know how the calls are being made or what should I write in the manifest for the activity to run.

Answer 1

If you open UnityPlayerActivity, you can see, that its package name is "com.unity3d.player" and class name is "UnityPlayer"

So you should change you unity player class name in C# script to "com.unity3d.player.UnityPlayer".

Another solution is add to your android plugin Unity classes and extend your activity from UnityPlayerActivity and you can call your methods directly from your plugin