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错误：java.lang.NullPointerException：尝试调用虚拟方法’android.content.res.XmlResourceParser

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我收到此错误.我是android studio的新手,我需要创建此插件以统一在运行时安装apk

错误-尝试在空对象引用上调用虚拟方法’android.content.Context Android.content.Context.getApplicationContext()’

插件类-

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();
}
}

清单文件-

<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;
    }
}
}

编辑-
插件类

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;
}

}

插件包装器-

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;
    }
}
}

编辑

Plugins/Android

解决方法:

来自Java的Contect插件为null.如果需要,您必须将Unity的上下文发送到Java插件.

添加另一个接收上下文的参数,然后使用该参数中的该上下文而不是Android.content.Context.getApplicationContext()中的那个.

Java的：

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#：

发送Unity上下文和要传递给函数的路径.

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;
    }
}

您可能有其他不相关的错误,但是Context null问题应该消失了.

编辑：

如果收到异常：

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

您只需要做几件事.

1.将“ .jar”插件插入UnityProject / Assets / Plugins / Android目录.

2.从“ AndroidSDK / extras / android / support / v4 / android-support-v4.jar”中复制“ android-support-v4.jar”
 目录到您的“ UnityProject / Assets / Plugins / Android”目录.

3.在UnityProject / Assets / Plugins / Android目录中创建一个名为“ AndroidManifest.xml”的文件,并将下面的代码放入其中.

确保用您自己的包名称替换“ com.company.product”.有2种情况出现.您必须同时替换它们：

这些可以在package =“ com.company.product”和android：authorities =“ com.company.product.fileprovider”中找到.不要更改或删除“文件提供程序”,也不要更改其他任何内容.

这是“ AndroidManifest.xml”文件：

<?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.在“ UnityProject / Assets / Plugins / Android / res / xml”目录中创建一个名为“ provider_paths.xml”的新文件,并将代码放在下面.如您所见,您必须创建一个res,然后创建一个xml文件夹.

确保用您自己的包名称替换“ com.company.product”.
它只出现一次.

这是您应该放入此“ provider_paths.xml”文件的内容：

<?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>

而已.

标签：android,android-fileprovider,unity3d,android-context,c-2
来源： https://codeday.me/bug/20191011/1892397.html