Error: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.XmlResourceParser

Question

I am getting this error.I am new to android studio and i need to create this plugin for unity to install an apk at runtime

Error - Attempt to invoke virtual method 'android.content.Context Android.content.Context.getApplicationContext()' on a null object reference

Plugin Class -

package com.example.unitypluginappinstall;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.support.v4.content.FileProvider;

import java.io.File;

public class PluginClass extends Activity  {
static String errMessage;

public static String InstallApp(String ApkPath){
 try {
     errMessage = "test";
     File toInstall = new File(ApkPath);
     Uri apkUri = FileProvider.getUriForFile(ContextClass.context(), 
ContextClass.context().getApplicationContext().getPackageName() + 
".fileprovider", toInstall);
     Intent intent = new Intent(Intent.ACTION_INSTALL_PACKAGE);
     intent.setData(apkUri);
     intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
     ContextClass.context().startActivity(intent);
 }
 catch (Exception e){
    errMessage = e.getMessage();
 }
    return errMessage;
}

}

ContextClass -

package com.example.unitypluginappinstall;

import android.app.Application;
import android.content.Context;

public class ContextClass extends Application {
private  static ContextClass instance;

public ContextClass(){
    instance = this;
}

public static ContextClass instance(){
    return instance;
}

public static Context context() {
    return instance.getApplicationContext();
}
}

Manifest File -

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="com.example.unitypluginappinstall">

<application android:allowBackup="true" android:label="@string/app_name"
    android:supportsRtl="true">
    <provider
        android:name="android.support.v4.content.FileProvider"
        android:authorities="${applicationId}.fileprovider"
        android:exported="false"
        android:grantUriPermissions="true">
        <meta-data android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/filepaths"></meta-data>
    </provider>
    android:name=".ContextClass">
</application>

PluginWrapper:

public class PluginWrapper : MonoBehaviour {
string savePath;
void Start () {
    savePath = Path.Combine(Application.persistentDataPath, "data");
    savePath = Path.Combine(savePath, "applaunchtest.apk");
    Install();
}

void Install(){
try
    {
        //Install APK
        GameObject.Find("TextDebug").GetComponent<Text().text"Installing...";
        var plugin = new 
   AndroidJavaClass("com.example.unitypluginappinstall.PluginClass");
        GameObject.Find("TextDebug").GetComponent<Text>().text = 
   plugin.CallStatic<string>("InstallApp", savePath);
    }
    catch(Exception e)
    {
        GameObject.Find("TextDebug").GetComponent<Text>().text = e.Message;
    }
}
}

EDIT - Plugin Class

package com.example.unitypluginappinstall;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.support.v4.content.FileProvider;

import java.io.File;

public class PluginClass extends Activity  {
static String errMessage;

public static String InstallApp(Context context, String ApkPath){
 try {
     errMessage = "test";
     File toInstall = new File(ApkPath);
     Uri apkUri = FileProvider.getUriForFile(context,
             context.getApplicationContext().getPackageName() +
                     ".fileprovider", toInstall);
     Intent intent = new Intent(Intent.ACTION_INSTALL_PACKAGE);
     intent.setData(apkUri);
     intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
     context.startActivity(intent);
 }
 catch (Exception e){
    errMessage = e.getMessage();
 }
    return errMessage;
}

}

Plugin Wrapper -

public class PluginWrapper : MonoBehaviour {
string savePath;
void Start () {
    savePath = Path.Combine(Application.persistentDataPath, "data");
    savePath = Path.Combine(savePath, "applaunchtest.apk");
    Install();
}

void Install(){
try
    {
        //Install APK
AndroidJavaClass unityClass = new AndroidJavaClass("com.unity3d.player.UnityPlayer");
        AndroidJavaObject unityActivity = unityClass.GetStatic<AndroidJavaObject>("currentActivity");
        AndroidJavaObject unityContext = unityActivity.Call<AndroidJavaObject>("getApplicationContext");
        GameObject.Find("TextDebug").GetComponent<Text().text"Installing...";
        var plugin = new 
   AndroidJavaClass("com.example.unitypluginappinstall.PluginClass");
        GameObject.Find("TextDebug").GetComponent<Text>().text = 
   plugin.CallStatic<string>("InstallApp",unityContext, savePath);
    }
    catch(Exception e)
    {
        GameObject.Find("TextDebug").GetComponent<Text>().text = e.Message;
    }
}
}

EDIT

Answer 1

The Contect from Java plugin is null. If you need it, you have to send Unity's context to the Java plugin.

Add a another parameter that receives the Context then use that Context from the parameter not the one from Android.content.Context.getApplicationContext().

Java:

public static String InstallApp(Context context, String ApkPath){
 try {
     errMessage = "test";
     File toInstall = new File(ApkPath);
     Uri apkUri = FileProvider.getUriForFile(context, 
context.getPackageName() + 
".fileprovider", toInstall);
     Intent intent = new Intent(Intent.ACTION_INSTALL_PACKAGE);
     intent.setData(apkUri);
     intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
     context.startActivity(intent);
 }
 catch (Exception e){
    errMessage = e.getMessage();
 }
    return errMessage;
}

C#:

Send the Unity Context and the path you want to pass to the function.

void Install()
{
    try
    {
        GameObject.Find("TextDebug").GetComponent<Text>().text = "Installing...";

        //Get Unity Context
        AndroidJavaClass unityClass = new AndroidJavaClass("com.unity3d.player.UnityPlayer");
        AndroidJavaObject unityActivity = unityClass.GetStatic<AndroidJavaObject>("currentActivity");
        AndroidJavaObject unityContext = unityActivity.Call<AndroidJavaObject>("getApplicationContext");


        AndroidJavaClass plugin = new AndroidJavaClass("com.example.unitypluginappinstall.PluginClass");
        string result = plugin.CallStatic<string>("InstallApp", unityContext, savePath);
    }
    catch (Exception e)
    {
        GameObject.Find("TextDebug").GetComponent<Text>().text = e.Message;
    }
}

You may have other unrelated error but the Context null problem should be gone.

EDIT:

If you get the Exception:

Attempt to invoke virtual method 'android.content.res.XmlResourceParser android.content.pm.packageItemInfo.loadXmlMetaData(android.c‌​ontent.pm.PackageMan‌​ager.java.lang.Strin‌​g)'

You have to do few things.

1.Put the ".jar" Plugin your UnityProject/Assets/Plugins/Android directory.

2.Copy "android-support-v4.jar" from your "AndroidSDK/extras/android/support/v4/android-support-v4.jar" directory to your "UnityProject/Assets/Plugins/Android" directory.

3.Create a file called "AndroidManifest.xml" in your UnityProject/Assets/Plugins/Android directory and put the code below into it.

Make sure to replace "com.company.product" with your own package name. There are 2 instances where this appeared. You must replace both of them:

These are found in package="com.company.product" and android:authorities="com.company.product.fileprovider". Don't change or remove the "fileprovider" and don't change anything else.

Here is the "AndroidManifest.xml" file:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.company.product" xmlns:tools="http://schemas.android.com/tools" android:installLocation="preferExternal" android:versionName="1.0" android:versionCode="1">
  <supports-screens android:smallScreens="true" android:normalScreens="true" android:largeScreens="true" android:xlargeScreens="true" android:anyDensity="true" />
  <application android:theme="@style/UnityThemeSelector" android:icon="@drawable/app_icon" android:label="@string/app_name" android:debuggable="true">
    <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>

    <provider
          android:name="android.support.v4.content.FileProvider"
          android:authorities="com.company.product.fileprovider"
          android:exported="false"
          android:grantUriPermissions="true">
      <meta-data
          android:name="android.support.FILE_PROVIDER_PATHS"
          android:resource="@xml/provider_paths"/>
    </provider>

  </application>
  <uses-sdk android:minSdkVersion="16" android:targetSdkVersion="23" />
</manifest>

4.Create a new file called "provider_paths.xml" in your "UnityProject/Assets/Plugins/Android/res/xml" directory and put the code below in it. As you can see, you have to create a res and then an xml folder.

Make sure to replace "com.company.product" with your own package name. It only appeared once.

Here is what you should put into this "provider_paths.xml" file:

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
  <!--<external-path name="external_files" path="."/>-->
  <external-path path="Android/data/com.company.product" name="files_root" />
  <external-path path="." name="external_storage_root" />
</paths>

That's it.