AlertDialog.setButton崩溃我的应用程序

Question

正如标题所说，当我将.setButton放入警报对话框时，我的应用程序崩溃了。 有什么问题，我应该如何解决？

button_fs = (Button) findViewById(R.id.button_fs);
    final AlertDialog adfs = new AlertDialog.Builder(this).create();
    button_fs.setOnClickListener(new OnClickListener() {
        @Override
            public void onClick(View view) {
            adfs.setTitle("Meraxes");
            adfs.setMessage("What would you like to do?");
            adfs.setButton(1, "OK", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    Toast.makeText(getApplicationContext(), "Aww yiss", Toast.LENGTH_SHORT).show();
                }
            });
            adfs.setButton(2, "cancel", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    Toast.makeText(getApplicationContext(), "you have pressed cancel", Toast.LENGTH_SHORT).show();
                }
            });
            adfs.show();
        }
    });