AlertDialog将不会显示

Question

I'm trying to show an alert dialog in my code. It needs a Context when it is building as its parameter. I want it to pop up in my LoginActivity :

    public class LoginActivity extends ActionBarActivity
    { 
            // Methods inside         
    }

But my function which generates the alertDialog is in a separate class. So in order to get the appropriate Context I tried an extra class which gives me the ApplicationContext , which I then use as the required parameter.

Here is my function which generates the alertDialog :

    public static void alertFailure(String errorTitle, String errorMessage){
            Log.d("Alert Failure", "alerting failure");
            AlertDialog.Builder builder = new AlertDialog.Builder(MyApplication.getAppContext()); // Needs context of loginactivity
            builder.setTitle(errorTitle);
            builder.setMessage(errorMessage);
            builder.setPositiveButton("OK", new DialogInterface.OnClickListener(){
                @Override
                public void onClick(DialogInterface dialog, int which){

                }
            });
            AlertDialog alertDialog = builder.create();
            alertDialog.show();
    }

And here is my class which I use for getting the ApplicationContext :

    public class MyApplication extends Application{
        private static Context context;

        public void onCreate(){
            super.onCreate();
            MyApplication.context = getApplicationContext();
        }

        public static Context getAppContext(){
            return context;
        }
    }

When I log my program I can see that my function is running fine, but the alertDialog doesn't pop up. How can I pass the Context of my LoginActivity as the parameter?

Answer 1

Try replacing this..

AlertDialog alertDialog = builder.create();
        alertDialog.show();

with this..

builder.show();

Answer 2

You need an activity context for dialogs. The application context won't do.

You can pass it as a parameter to the method, eg

public static void alertFailure(Activity context, String errorTitle, String errorMessage){

And calling from an activity:

AnotherClass.alertFailure(this, ...);

Answer 3

add another parameter as ActivityContext in the alertFailure(), then call the alertFailure("Alert Failure", "alerting failure", LoginActivity.this); from LoginActivity class.

Answer 4

you can overload the method

public static void alertFailure(Context context, String errorTitle, String errorMessage) {
 Log.d("Alert Failure", "alerting failure");
        AlertDialog.Builder builder = new AlertDialog.Builder(context); // Needs context of loginactivity
        builder.setTitle(errorTitle);
        builder.setMessage(errorMessage);
        builder.setPositiveButton("OK", new DialogInterface.OnClickListener(){
            @Override
            public void onClick(DialogInterface dialog, int which){

            }
        });
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
}

and call it like NomeClass.alertFailure(LoginActivity.this, "title", "message");

and you can keep the version without context:

public static void alertFailure(String errorTitle, String errorMessage){
      alertFailure(MyApplication.getContext(), erroTitle, errorMessage);
 }

Answer 5

I don't think its a problem with Context .

Call alertFailure like this:

new Handler().post(new Runnable() {
    @Override
    public void run() {
        alertFailure("Title", "Message");
    }
});