java.lang.NullPointerException: Versuch

Question

virtuellen Speicher aufzurufen, erhalte ich diesen Fehler, wenn ich meine app versuchen zu laufen ich denke, meine menubutton diesen Fehler verursacht, aber nicht wirklich wissen, wie das Problem

mainactivity

zu beheben

package com.example.vitoriano_vaz.eastbayvapes; 

import android.content.ActivityNotFoundException; 
import android.content.Intent; 
import android.content.pm.PackageManager; 
import android.net.Uri; 
import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.view.View; 
import android.widget.Button; 

import java.util.List; 

/* 
This app is for a local Vape Shop 
it's purpose is to increase customer flow, and provide a menu for Android users 

the array is going to be called = da_menu 
*/ 
public class MainActivity extends AppCompatActivity { 
    private static Intent java; 

    //used this to get rid of red line under intent on line 38 if it causes more problems remove and resolve issue 
    private Intent intent; 

    /* 
    called when the user clicks the send Button 
    */ 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     /* 
     attempting to send user to each individual app with the URI Intent method 
     */ 
     PackageManager packageManager = getPackageManager(); 
     List activites = packageManager.queryIntentActivities(intent, 
       PackageManager.MATCH_DEFAULT_ONLY); 
     boolean isIntentSafe = activites.size() > 0; 

     Uri number = Uri.parse("tel:9259619029"); 
     Intent callIntent = new Intent(Intent.ACTION_DIAL, number); 

     Uri webpage = Uri.parse("http://www.facebook.com/eastbayvapes"); 
     Intent webIntent = new Intent(Intent.ACTION_VIEW, webpage); 

     /*this is to send the user to facebook application 

     try { 

      context.getPackageManager().getPackageInfo("com.facebook.katana", 0); 
      return new Intent(Intent.ACTION_VIEW, Uri.parse("fb://page/eastbay")); 

     } catch (Exception e) { 

      return new Intent(Intent.ACTION_VIEW, Uri.parse("https://www.facebook.com/eastbay")); 

     } 
     */ 


     // intent to send user to instagram 

     Uri uri = Uri.parse("http://instagram.com/_u/eastbayvapes"); 
     Intent likeIng = new Intent(Intent.ACTION_VIEW, uri); 

     likeIng.setPackage("com.instagram.android"); 

     try { 
      startActivity(likeIng); 
     } catch (ActivityNotFoundException e) { 
      startActivity(new Intent(Intent.ACTION_VIEW, 
        Uri.parse("http://instagram.com/eastbayvapes"))); 
     } 

     //Intent to send user to email app 

     Intent intent = new Intent(Intent.ACTION_SEND); 
     intent.setType("plain/text"); 
     intent.putExtra(Intent.EXTRA_EMAIL, new String[]{"eastbayvapes@gmail.com"}); 
     intent.putExtra(Intent.EXTRA_SUBJECT, "subject"); 
     intent.putExtra(Intent.EXTRA_TEXT, ""); 
     startActivity(Intent.createChooser(intent, "")); 

     /*Intent to send user to google maps 

     String uri = "https://maps.google.co.in/maps?q=" + 1549 N Vasco Rd, Livermore, Ca 94551; 
     Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(uri)); 
     context.startActivity(intent); 
     */ 



     /* 
     sends user to about us xml via AboutActivity.class 
     */ 
     Button button = (Button) findViewById(R.id.button); 
     button.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       Intent intent = new Intent(MainActivity.this, AboutActivity.class); 
       startActivity(intent); 
      } 
     }); 




    } 


} 

SecondActivity Hier glaube ich, dass ich die Ursache für meine Störung erhalte, wenn ich die menubutton erklärt aber weiß nicht, was ich falsch tat

package com.example.vitoriano_vaz.eastbayvapes; 

import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.view.View; 
import android.widget.ArrayAdapter; 
import android.widget.Button; 
import android.widget.ListView; 

/** 
* Created by vitoriano-vaz on 5/11/16. 
*/ 
public class SecondActivity extends AppCompatActivity { 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.menuscreen); 

     /* 
     this is the button call that sends user to the menuscreen.xml 
     */ 
     Button mbutton = (Button) findViewById(R.id.menubutton); 
     mbutton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       populateListView(); 
      } 
     }); 

     populateListView(); 

    } 
    private void populateListView() { 
     // Create the list of items 

     String[] juiceMenu= { 
       "#1 BLUEBERRY BOMBSHELL \nThis blueberry dessert will keep your taste buds begging for more", 
       "#2 RICHIE RICH\nShout out to Rich! This was his all day vape. Strawberry cream with a bunch of deliciousness", 
       "#3 CHIQUITA\nCreamy Banana with a bready after taste", 
       "#4 AFTERNOON DELIGHT\nGot that 3 o'clock feeling? Try a little Afternoon delight. Kiwi Strawberry Dessert", 
       "#5 POPPIN OTTERS\nMelt an otterpop put it in your tank and vape it", 
       "#6 VIVA LA SANGRIA\nFruit, with a little bit of fruit, add a teaspoon of fruit mixed with white win and top it off with fruit", 
       "#7 OKOLE MALUNA\nPineapple fruit blend. Bottom up!", 
       "#8 CARMEN MIRANDA\nVanilla custard with a crisp", 
       "#9 POMALADE\nIt's Bombalade! Yuour mother will love it", 
       "#10 IZUAL\nWhirlwind of icy Fruits", 
       "#11 BUTTER STOTCH\nProfessor Chaos will surely get grounded for this one!", 
       "#12 BLUE BULLS\nGrab the bull by the horns", 
       "#13 GRAPE APE\nA grapple a day will keep the doctor away", 
       "#14 BRUCE JUICE\nPerfectly blended old fashioned. This one is for you Bruce", 
       "#15 DOC HOLIDAY\nN.E.T. Tabacco flavor. Limited release", 
       "#16 PEACHY KEEN\nPeach cobbler. Better than what your mama used to make", 
       "#17 HULA\nStrawberry coconut? What in the hula?", 
       "#18 NEW YORK\nPeppermint paddy dipped in chocolate...Amazing really", 
       "#19 AL GORE\nIm super duper cereal right now!", 
       "#20 LUX CHARMS\nHearts, stars, horseshoes, clovers & blue moons, pots of gold % rainbows & me red balloons", 
       "#21 SAILOR JACK\nCant go to the ball game without some cracker jacks", 
       "#22 GET HIM TO THE GREEK\n...Yogurt, peach, delightful", 
       "#23 KEY WE LIE CHI\nFruit lovers will enjoy this lychee vape", 
       "#24 SPRING FLING\nA menage a trois of honeydew and cream on your tongue", 
       "#25 GUMBY\nWatermelon sour gummy", 
       "#26 CHAI\nMILK and Chai Tea", 
       "#27 MR. BBEAN\nCappuccino with cream to start the day off right", 
       "#28 50 SHADES OF ORANGE\nA delightful blend of orange and cream", 
       "#29 BLUE WAFFLES\nBreakfast for dinner with this Blueberry Waffle", 
       "#30 ENIGMA\nEnigma conundrum of mango raspberry with a hint of mystery can you solve the puzzle?", 
       "#31 MR. FREEZE\nPut down the tank and STEP AWAY hardcore mint lovers ONLY! This juice is too coll for most", 
       "#32 CUP OF JOE\nThe best part of waking up is coffee in your vape", 
       "#33 BON JOVI\nVanilla Bourbon ", 
     }; 
     // Build adapter 
     ArrayAdapter<String> adapter = new ArrayAdapter<String>(
       this,    // context for the activity 
       R.layout.da_menu, // Layout to create 
       juiceMenu);   // Items to be displayed 

     //configure list view 
     ListView list = (ListView) findViewById(R.id.listViewMain); 
     list.setAdapter(adapter); 
    } 



} 

AndroidManifest

<application 
     android:allowBackup="true" 
     android:icon="@mipmap/ic_launcher" 
     android:label="@string/app_name" 
     android:supportsRtl="true" 
     android:theme="@style/AppTheme"> 
     <activity android:name=".AboutActivity" 
      android:screenOrientation="portrait"/> 
     <activity android:name=".SecondActivity"/> 
     <activity android:name=".MainActivity"> 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 
       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
    </application> 

</manifest> 

activity_main

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:src="@drawable/ebvbottle" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    tools:context="com.example.vitoriano_vaz.eastbayvapes.MainActivity"> 

    <TextView 
     android:id="@+id/textView" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="East Bay Vapes" 
     android:textAllCaps="true" 
     android:textColor="#FEFEFF" 
     android:textSize="28sp" 
     android:textStyle="bold" 
     android:layout_alignParentTop="true" 
     android:layout_centerHorizontal="true" /> 

    <Button 
     android:id="@+id/button" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:onClick="onClick" 
     android:text="About Us" 
     android:layout_below="@+id/textView" 
     android:layout_alignParentStart="true" /> 

    <Button 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="Menu" 
     android:id="@+id/menubutton" 
     android:layout_alignTop="@+id/button" 
     android:layout_alignParentEnd="true" 
     android:onClick="menubutton" /> 

    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="We are dedicated to helping people get off tabacco! We carry everything from beginner setups, to advanced personalized vaporizers. We pride ourselves in our premuim juices made in shop!" 
     android:id="@+id/textView2" 
     android:layout_centerVertical="true" 
     android:layout_centerHorizontal="true" 
     android:textSize="22dp" 
     android:typeface="serif" /> 

</RelativeLayout> 

MENU-Seite Hier ist, wo ich will se nd meine besiedelten Array

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:scrollIndicators="right"> 

    <ListView 
     android:id="@+id/listViewMain" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_centerHorizontal="true" /> 

</RelativeLayout> 

Hier ist mein Fehler

05-18 16:00:44.619 11983-11983/com.example.vitoriano_vaz.eastbayvapes E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.vitoriano_vaz.eastbayvapes, PID: 11983 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.vitoriano_vaz.eastbayvapes/com.example.vitoriano_vaz.eastbayvapes.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Intent.resolveTypeIfNeeded(android.content.ContentResolver)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2622) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2683) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1440) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:6066) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:770) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:660) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Intent.resolveTypeIfNeeded(android.content.ContentResolver)' on a null object reference at android.app.ApplicationPackageManager.queryIntentActivitiesAsUser(ApplicationPackageManager.java:808) at android.app.ApplicationPackageManager.queryIntentActivities(ApplicationPackageManager.java:797) at com.example.vitoriano_vaz.eastbayvapes.MainActivity.onCreate(MainActivity.java:39) at android.app.Activity.performCreate(Activity.java:6584) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2575) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2683)  at android.app.ActivityThread.-wrap12(ActivityThread.java)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1440)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:148)  at android.app.ActivityThread.main(ActivityThread.java:6066)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:770)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:660) 

Answer 1

Ihre Absicht initialisieren, damit es nicht Null.

List activites = packageManager.queryIntentActivities(intent, 
       PackageManager.MATCH_DEFAULT_ONLY); 

EDIT

Entfernen aus dem Code den folgenden Teil, da sie keine Verwendung im Rest des Codes hat. Und benutze sie nie, bis du den Grund erfährst, warum du sie brauchst.

PackageManager packageManager = getPackageManager(); 
    List activites = packageManager.queryIntentActivities(intent, 
      PackageManager.MATCH_DEFAULT_ONLY); 
    boolean isIntentSafe = activites.size() > 0;