[android help] Cannot be resolved to a type: Error

I am getting this error: ShowDialog cannot be resolved to a type

Here is my code:

final CharSequence[] items = {"Low", "Medium", "High"};

            AlertDialog.Builder builder = new AlertDialog.Builder(ShowDialog.this);
            builder.setTitle("Alert Dialog with ListView");
            builder.setIcon(R.drawable.image1);
            builder.setItems(items, new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int item) {
             Toast.makeText(getApplicationContext(), items[item], Toast.LENGTH_SHORT).show();
                }
            });
            AlertDialog alert = builder.create();

            alert.show();

Any ideas why I am getting this annoying error? I have tried to refresh my code and also clean it and still no luck. Thanks

.

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