BindService 抛出空指针，即使指向纯字符串

Question

我正在尝试在我的应用程序中创建一个 boundService，但我无法返回任何结果，无论它是什么 returns null。我可以在调试中看到代码在我的服务中运行良好，但我怀疑我的 activity 太快了，所以当它调用服务时，还没有任何东西可以提供。我该如何解决这个问题？

这是我的activity；

import com.example....DownloadPicService.MyBinder;

import java.io.IOException;


public class RecievedSB extends AppCompatActivity {
    public DownloadPicService Dlpic;
    private LoginActivity.UserLoginTask mAuthTask = null;
    private FirebaseAuth mAuth;
    private FirebaseAuth.AuthStateListener mAuthListener;
    private static final String TAG = "Login";
    private DatabaseReference mPostReference;
    private TextView recievedCardTextView;
    private String path1;

    /** Messenger for communicating with the service. */
    DownloadPicService mService;

    /** Flag indicating whether we have called bind on the service. */
    boolean mBound;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_recieved_sb);
        mPostReference = FirebaseDatabase.getInstance().getReference()
                .child("users").child("..");
        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                FirebaseUser user = firebaseAuth.getCurrentUser();
                if (user != null) {
                    // User is signed in
                    Log.d(TAG, "onAuthStateChanged:signed_in:" + user.getUid());
                } else {
                    // User is signed out
                    Log.d(TAG, "onAuthStateChanged:signed_out");
                }
                // ...
            }
        };
        recievedCardTextView = (TextView) findViewById(R.id.recievedCardTextView);


    }
    @Override
    public void onStart(){
        super.onStart();

        if (mAuthTask != null) {
            return;
        }
        ValueEventListener postListener = new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                // Get Post object and use the values to update the UI
                CardService cid = dataSnapshot.getValue(CardService.class);
                recievedCardTextView.setText(cid.email);
                System.out.println(cid.email);
               // if (mBound) {

               // }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                // Getting Post failed, log a message
                Log.w(TAG, "loadPost:onCancelled", databaseError.toException());
                // ...
            }
        };
        mPostReference.addValueEventListener(postListener);

        Intent intent = new Intent(this, DownloadPicService.class);
        // intent.putExtra("FBservice", "DL");
        this.startService(intent);
        this.bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
    }
    @Override
    protected void onStop() {
        super.onStop();
        unbindService(mConnection);
    }
    private ServiceConnection mConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName className, IBinder service) {
            // This is called when the connection with the service has been
            // established, giving us the object we can use to
            // interact with the service.  We are communicating with the
            // service using a Messenger, so here we get a client-side
            // representation of that from the raw IBinder object.
            mBound = true;
            MyBinder myBinder = (MyBinder) service;
            mService = myBinder.getService();


            try {
                path1 = Dlpic.getImagePath2();
                Log.d(TAG, path1);
            }
            catch(IOException e)
            {
                System.out.println(e.getMessage());
            }

        }

        @Override
        public void onServiceDisconnected(ComponentName className) {
            // This is called when the connection with the service has been
            // unexpectedly disconnected -- that is, its process crashed.
            mService = null;
            mBound = false;
        }
    };

}

我的服务：

public class DownloadPicService extends Service {
    FirebaseStorage storage = FirebaseStorage.getInstance();
    StorageReference storageRef = storage.getReferenceFromUrl("gs:/...");

    private static final String TAG = "DLService";
    private FirebaseAuth.AuthStateListener mAuthListener;
    private String path1;
    private IBinder mBinder = new MyBinder();
    private String path2;

    @Override
    public void onCreate() {
        super.onCreate();
    }
    @Override
    public IBinder onBind(Intent intent) {
        Log.v(TAG, "in onBind");
        return mBinder;
    }

    public DownloadPicService() {
        try {
            getImagePath2();
            Log.d(TAG, "Starter DL");

        } catch (IOException e) {
            System.out.println(e.getMessage());
        }
    }

    public String getImagePath2() throws IOException {
        StorageReference islandRef = storageRef.child("/userimages/test@test.dk/test@test.dk");

        File localFile = File.createTempFile("images", "jpg");
        path1 = localFile.getAbsolutePath();

        Log.d(TAG, path1);
        islandRef.getFile(localFile).addOnSuccessListener(new OnSuccessListener<FileDownloadTask.TaskSnapshot>() {
            @Override
            public void onSuccess(FileDownloadTask.TaskSnapshot taskSnapshot) {
                Log.d(TAG, "worked buddy");
                //path2 = path1;
                /*Intent pic = new Intent(DownloadPicService.this, RecievedSB.class);
                pic.putExtra("picpath", path1);
                LocalBroadcastManager.getInstance(DownloadPicService.this).sendBroadcast(pic);*/
              }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception exception) {
                // Handle any errors
            }
        });
        return path1;
    }
    public String getPath(){

        return "hej";
    }

    @Override
    public boolean onUnbind(Intent intent) {
        Log.d(TAG, "in onUnbind");
        return true;
    }

    public class MyBinder extends Binder {
        public DownloadPicService getService() {
            return DownloadPicService.this;
        }
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.v(TAG, "in onDestroy");
    }

    @Override
    public void onRebind(Intent intent) {
        Log.v(TAG, "in onRebind");
        super.onRebind(intent);
    }
}

Answer 1

你还没有初始化Dlpic更新你的代码，

Dlpic.getImagePath2(); to 

mService.getImagePath2();

然后尝试。