error when calling build.create

I have customized a dialog, but since the AlertDialog.Builder does not have dismiss () I removed the builder and now it does not accept the create call due to a vesrion error.

public AlertDialog DespachoAct() {
    final AlertDialog builder = new AlertDialog.Builder(DespachoDActivity.this).show();
    LayoutInflater inflater = DespachoDActivity.this.getLayoutInflater();
    View v = inflater.inflate(R.layout.update_despacho, null);
    builder.setView(v);
    builder.show();
    cb1 = (CheckBox) v.findViewById(R.id.cb1) ;
    txtsoles = (EditText) v.findViewById(R.id.txtsoles);
    txtobs2 = (EditText) v.findViewById(R.id.txtobs2);
    act = (Button) v.findViewById(R.id.btnactualizar2);
    can = (Button) v.findViewById(R.id.btncancelar);
    act.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    DownloadTask2 up = new DownloadTask2();
                    up.execute();
                    new DownloadTask().execute("");
                    builder.dismiss();
                }
            }
    );
    can.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    builder.dismiss();
                }
            }
    );
    /////////// sale : call requires api level 21 (current min is 19)android.app.Dialog#create return builder.create();
     return builder.create();
}

.........................

after making several attempts I solved it. to see if it's useful:)

public AlertDialog DespachoAct(){
    final AlertDialog builder = new AlertDialog.Builder(DespachoDActivity.this).create();
    LayoutInflater inflater = DespachoDActivity.this.getLayoutInflater();
    View v = inflater.inflate(R.layout.update_despacho, null);
    builder.setView(v);
    builder.show();
    cb1 = (CheckBox) v.findViewById(R.id.cb1) ;
    cb1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            boolean isChecked = cb1.isChecked();
            if(isChecked){
                b="1";
            }
            else
            {
                b="";
            }
        }
    });
    txtsoles = (EditText) v.findViewById(R.id.txtsoles);
    txtobs2 = (EditText) v.findViewById(R.id.txtobs2);
    txtrecibo = (EditText) v.findViewById(R.id.txtrecibo);
    act = (Button) v.findViewById(R.id.btnactualizar2);
    can = (Button) v.findViewById(R.id.btncancelar);
    act.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {

                    if (b=="1" && txtsoles.getText().toString().length()>0 && txtobs2.getText().toString().length()>0
                            && txtrecibo.getText().toString().length()>0){


                        DownloadTask2 up = new DownloadTask2();
                        up.execute();
                        new DownloadTask().execute("");
                        builder.dismiss();

                    }

                    else{
                        Toast.makeText(context, "Se encontraron datos vacios ",Toast.LENGTH_SHORT).show();
                    }

                }
            }
    );
    can.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    builder.dismiss();
                }
            }
    );
    return builder;
}