来自另一个类的AlertDialog

Question

In mainActivity I have

public void showDialog(String title, String message, String accept, String denied){
    AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
    builder.setTitle(title);
    builder.setMessage(message);
    builder.setCancelable(true);

    builder.setPositiveButton(accept, new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.dismiss();
        }
    });

    builder.setNegativeButton(denied, new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.dismiss();
        }
    });

    builder.create().show();
}

It works inside main activity, but I am traing call this from another activity, so I wrote

MainActivity o = new MainActivity();
o.showDialog("t", "t", "t", "t");

And app is crashing. I tried also wrote "this", "getAplicationContext()" instead of "MainActivity.this".

Answer 1

It works inside main activity, but I am traing call this from another activity, so I wrote

MainActivity o = new MainActivity(); o.showDialog("t", "t", "t", "t");

you shouldn't use the new operator on classes that extends Activity . Back to your problem, it looks to me like you want to minimize the repeating code. One way, in your case could be an utility class, which contains your showDialog method. Its signature would be slightly different because you need a Context object to instantiate the builder:

public final class Utility { 

public static void showDialog(Context context, String title, String message, String accept, String denied){
    AlertDialog.Builder builder = new AlertDialog.Builder(context);
    builder.setTitle(title);
    builder.setMessage(message);
    builder.setCancelable(true);

    builder.setPositiveButton(accept, new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.dismiss();
        }
    });

    builder.setNegativeButton(denied, new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.dismiss();
        }
    });

    builder.create().show();
}

 private Utility() {}
}

Note also that the class Utility, has a private default constructor , which means that you can't explicitly instantiate it.

and the you can use like:

  Utility.showDialog(ActivityName.class, "aa", "bb", "cc", "dd");

Answer 2

+1 for Blackbelt's answer.

But just to follow up since OP wants to use it in another activity, you would use it in another activity like this. Say you wanted to use it in an activity called SecondActivity : Utility.showDialog(SecondActivity.class, "aa", "bb", "cc", "dd");