Check if extras are set or not

问题:

Is there any way to check if an extra has been passed when starting an Activity?

I would like to do something like (on the onCreate() in the Activity):

    Bundle extras = getIntent().getExtras();
    String extraStr = extras.getString("extra");

    if (extraStr == null) {
        extraStr = "extra not set";
    }

But this is throwing a java.lang.NullPointerException.

Thank you.

回答1:

Use the Intent.hasExtra(String name) to check if an extra with name was passed in the intent.

Example:

Intent intent = getIntent();

if (intent.hasExtra("bookUrl")) {
    bookUrl = b.getString("bookUrl");
} else {
   // Do something else
}

Also, use Intent.getStringExtra(String name) directly on the intent to handle the NullPointerException if no extras were passed.

回答2:

Well, I had similiar problem. in my case the null point exception was happen when I checked if my bundle.getString() was equall to null.

here is how IN MY CASE I solved it:

Intent intent = getIntent();        
    if(intent.hasExtra("nomeUsuario")){
        bd = getIntent().getExtras();
        if(!bd.getString("nomeUsuario").equals(null)){
            nomeUsuario = bd.getString("nomeUsuario");
        }
    }

回答3:

if (this.getIntent().getExtras() != null && this.getIntent().getExtras().containsKey("yourKey")) {
   // intent is not null and your key is not null
}

回答4:

I would use this solution in your case.

String extraStr;
    try {
        extraStr = getIntent().getExtras().getString("extra");
    } catch (NullPointerException e ) {
        extraStr = "something_else";
    }

回答5:

I think you need to check when extras != null

Bundle extras = getIntent().getExtras();
   if (extras != null) {
        String extraStr = extras.getString("extra");
    }else {
        extraStr = "extra not set";
    }