CODEWITHSUNDEEP
javaandroidandroid-dialogfragment
Manny265
Manny265

Reputation: 1709

Cannot create a default constructor from a class that extends DialogFragment and I have created my own custom constructor

I'm abit confused on an error message about default constructors.

I have 2classes MainActivity and ResultDialog. Some methods in MainActivity create a new dialog and pass 2strings to a custom constructor in ResultDialog.

ResultDialog extends DialogFragment. So I defined my own constructor but then when that error came up I just created a no arguments constructor and still that is not allowed.

I've searched abit on SO but the answers kind of explain that screen rotation may destroy and recreate the screen using the default constructor but still doesnt answer how I can solve that.

The error is Avoid non-default constructors in fragments:use a default constructor plus Fragment#setArguments(Bundle) instead

Someone please help me on this i'am a bit confused. Part of my ResultDialog class:

  public class ResultDialog extends DialogFragment {

private String message;//to hold the message to be displayed
private String title;//for alert dialog title

//constructor for the dialog passing along message to be displayed in the alert dialog
public ResultDialog(String message,String title){
    this.message = message;
    this.title = title;

}

public ResultDialog(){
    //default constructor
}

Upvotes: 4

Views: 5453

Answers (3)

Raghunandan
Raghunandan

Reputation: 133560

You can use newInstance. Check the docs

http://developer.android.com/reference/android/app/Fragment.html

Also check this

Why do I want to avoid non-default constructors in fragments?

 ResultDialog rd = ResultDialog.newInstance("message","title");

Then

  public static ResultDialog newInstance(String message,String title) {
    ResultDialog f = new ResultDialog();
    Bundle args = new Bundle();
    args.putString("message", message);
    args.putString("title", title);
    f.setArguments(args);
    return f;
}

And use getArguments() to retrieve values.

String message = getArguments().getString("message");
String title = getArguments().getString("title");

getArguments()

public final Bundle getArguments ()

Added in API level 11
Return the arguments supplied when the fragment was instantiated, if any.

Upvotes: 6

Dave
Dave

Reputation: 4291

Instead of defining the separate constructor, you are recommended to only have a parameter-less constructor and use the setArguments(Bundle) method to pass data into the Fragment. According to the documentation:

All subclasses of Fragment must include a public empty constructor. The framework will often re-instantiate a fragment class when needed, in particular during state restore, and needs to be able to find this constructor to instantiate it. If the empty constructor is not available, a runtime exception will occur in some cases during state restore.

Once you use setArguments(Bundle), you can call getArguments() from inside the Fragment to retrieve the data.

Upvotes: 1

A.S.
A.S.

Reputation: 4574

Same works for Dialogs. Link You can not declare your own constructor. Just generate a new instance of your dialog and pass the Strings by Arguments. In your onCreate just fetcjph them with getArguments().getString("key")

Hope this helps you

Upvotes: 1

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