NullPointerException beim Hochladen von Images auf Firebase

Question

Ich entwickle eine grundlegende Android-Chat-Anwendung mit Firebase-Technologie. Ich habe ein Problem beim Hochladen von Bildern in die Firebase-Datenbank. Ich klicke auf ImageButton, um ein Bild aus meiner Galerie auszuwählen. Wenn ich das Bild auswähle, kann mein Bild nicht in die Firebase-Datenbank hochgeladen werden. Stattdessen meine app stürzt

private static final int RC_PHOTO_PICKER = 1;  
ImageButton imageBtn;        
private FirebaseStorage storage;      
private DatabaseReference databaseRef;    
private StorageReference storageRef;     
private FirebaseApp app;        
private FirebaseDatabase database; 

@Override            
protected void onCreate(Bundle savedInstanceState)  
{    


    // image upload code                           

    app = FirebaseApp.getInstance();                       
    database = FirebaseDatabase.getInstance(app);                    
    storage = FirebaseStorage.getInstance(app);                     
    storageRef=storage.getReferenceFromUrl("gs://friendlychat-8a091.appspot.com/");            
    storageRef=storage.getReference("images");                     

    imageBtn = (ImageButton)findViewById(R.id.imageBtn);                  
    imageBtn.setOnClickListener(new View.OnClickListener()                  
    {                               
     public void onClick(View v)                        
     {                              
      Intent intent = new Intent(Intent.ACTION_GET_CONTENT);                
      intent.setType("image/jpeg");                      
      intent.putExtra(Intent.EXTRA_LOCAL_ONLY, true);                  
      startActivityForResult(Intent.createChooser(intent, getString(R.string.complete_action_with)), RC_PHOTO_PICKER); 
     }                              
    });                               


}        

    @Override                   
    protected void onActivityResult(int requestCode, int resultCode, Intent data)  
    { 
      if(requestCode==RC_PHOTO_PICKER && resultCode==RESULT_OK)                
     {                              
      Uri selectedImageUri = data.getData();                    
      final StorageReference PhotoRef=storageRef.child("images/"+selectedImageUri.getLastPathSegment());     

      PhotoRef.putFile(selectedImageUri)                     
       .addOnFailureListener(new OnFailureListener() {                
        @Override                        
        public void onFailure(@NonNull Exception exception)              
        {                          
        Toast.makeText(getApplicationContext(),"error ="+exception.getMessage(),Toast.LENGTH_LONG).show(); 
        }                          
       })                           
       .addOnSuccessListener(this, new OnSuccessListener<UploadTask.TaskSnapshot>() {        
        @Override                        
        public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {           
         Uri downloaduri = taskSnapshot.getDownloadUrl();              
         mMessageEditText.setText(downloaduri.toString());             

        }                          
       });                           

     }                                                
    } 

Dies ist logcat Meldung, wenn ich ein Bild auswählen hat die Galerie bilden

07-30 18:50:00.946 5268-5268/com.google.firebase.codelab.friendlychat D/MainActivity: onActivityResult: requestCode=1, resultCode=-1 
07-30 18:50:00.962 5268-5268/com.google.firebase.codelab.friendlychat D/AndroidRuntime: Shutting down VM 
07-30 18:50:00.962 5268-5268/com.google.firebase.codelab.friendlychat W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x411342a0) 
07-30 18:50:01.188 5268-5268/com.google.firebase.codelab.friendlychat D/FirebaseCrashApiImpl: throwable java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { dat=content://media/external/images/media/757 (has extras) }} to activity {com.google.firebase.codelab.friendlychat/com.google.firebase.codelab.friendlychat.MainActivity}: java.lang.NullPointerException 
07-30 18:50:01.290 5268-5268/com.google.firebase.codelab.friendlychat E/AndroidRuntime: FATAL EXCEPTION: main 
                         java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { dat=content://media/external/images/media/757 (has extras) }} to activity {com.google.firebase.codelab.friendlychat/com.google.firebase.codelab.friendlychat.MainActivity}: java.lang.NullPointerException 
                          at android.app.ActivityThread.deliverResults(ActivityThread.java:3179) 
                          at android.app.ActivityThread.handleSendResult(ActivityThread.java:3222) 
                          at android.app.ActivityThread.access$1100(ActivityThread.java:140) 
                          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1276) 
                          at android.os.Handler.dispatchMessage(Handler.java:99) 
                          at android.os.Looper.loop(Looper.java:137) 
                          at android.app.ActivityThread.main(ActivityThread.java:4895) 
                          at java.lang.reflect.Method.invokeNative(Native Method) 
                          at java.lang.reflect.Method.invoke(Method.java:511) 
                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994) 
                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761) 
                          at dalvik.system.NativeStart.main(Native Method) 
                         Caused by: java.lang.NullPointerException 
                          at com.google.firebase.codelab.friendlychat.MainActivity.onActivityResult(MainActivity.java:329) 
                          at android.app.Activity.dispatchActivityResult(Activity.java:5347) 
                          at android.app.ActivityThread.deliverResults(ActivityThread.java:3175) 
                          at android.app.ActivityThread.handleSendResult(ActivityThread.java:3222)  
                          at android.app.ActivityThread.access$1100(ActivityThread.java:140)  
                          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1276)  
                          at android.os.Handler.dispatchMessage(Handler.java:99)  
                          at android.os.Looper.loop(Looper.java:137)  
                          at android.app.ActivityThread.main(ActivityThread.java:4895)  
                          at java.lang.reflect.Method.invokeNative(Native Method)  
                          at java.lang.reflect.Method.invoke(Method.java:511)  
                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)  
                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)  
                          at dalvik.system.NativeStart.main(Native Method)  

07-30 18:53:01.196 5268-5270/com.google.firebase.codelab.friendlychat D/dalvikvm: GC_CONCURRENT freed 454K, 10% free 10859K/12039K, paused 19ms+7ms, total 76ms 
07-30 18:53:01.259 5268-5276/com.google.firebase.codelab.friendlychat D/AbsListView: [unregisterDoubleTapMotionListener] 
07-30 18:53:01.259 5268-5276/com.google.firebase.codelab.friendlychat I/MotionRecognitionManager: .unregisterListener :/listener count = 0->0, listener=android.widget.AbsListView$4@41b77058 

Answer 1

@Override 
public void onClick(View view) 
{ 
Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT); 
intent.addCategory(Intent.CATEGORY_OPENABLE); 
intent.setType("image/*"); 
startActivityForResult(intent, REQUEST_IMAGE); 
}