Question

我想评估我在java类中的位置，并使用if语句运行一些代码。

这是我在Android Studio中的代码的一部分

public class UsefulGUI extends Application {

    @Override
    public void start(Stage primaryStage) {
        Button button = new Button();
        button.setText("Enter your info");
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                dialogBox();
            }
        });

        StackPane pane = new StackPane();
        pane.getChildren().add(button);

        Scene scene = new Scene(pane, 500, 300);

        primaryStage.setTitle("Useful GUI");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
    public class User {
        private String name;
        private String email;
        private String phone;

        public User(String n, String e, String p) {
            this.name = n;
            this.email = e;
            this.phone = p;
        }
        @Override
        public String toString() {
            return "Name: " + name + " Email: " + email + " Phone: " + phone;
        }
    }
    public void dialogBox() {
        Dialog<User> dialog = new Dialog<>();
        ArrayList<User>list = new ArrayList<User>();


        dialog.setTitle("User info");

        Label name = new Label("Name: ");
        Label email = new Label("Email: ");
        Label phone = new Label("Phone: ");
        TextField textName = new TextField();
        TextField textEmail = new TextField();
        TextField textPhone = new TextField();

        GridPane grid = new GridPane();
        grid.add(name, 1, 1);
        grid.add(textName, 2, 1);
        grid.add(email, 1, 2);
        grid.add(textEmail, 2, 2);
        grid.add(phone, 1, 3);
        grid.add(textPhone, 2, 3);
        dialog.getDialogPane().setContent(grid);

        ButtonType buttonType = new ButtonType("Ok", ButtonData.OK_DONE);
        dialog.getDialogPane().getButtonTypes().addAll(buttonType, ButtonType.CANCEL);

        dialog.setResultConverter(new Callback<ButtonType, User>() {
            @Override
            public User call(ButtonType b) {
                if (b == buttonType) {
                    return new User(textName.getText(), textEmail.getText(), textPhone.getText());
                }
                return null;
            }
        });
        Optional<User>info = dialog.showAndWait();

        // Adds user to list
        list.add(new User(textName.getText(), textEmail.getText(), textPhone.getText()));
        System.out.print("Info Added.\n NEWUSER ");
        System.out.println(new User(textName.getText(), textEmail.getText(), textPhone.getText()));

        //Collections.sort(list);
        for (int i = 0; i < list.size(); i++) {
            System.out.println(i + ". " + list.get(i));
        }

        //if (info.isPresent()) {
        //  System.out.println(info.get());
        //}
    }
    public void quitApplication() {
        Platform.exit();
    }
    public static void main(String[] args) {
        launch(args);
    }
}

`

正如你所看到我放置if（PizzaActivity .class！= null）{}但是我知道这是错误的。

它是一个Android项目。

我希望你能帮助我，提前谢谢你。

问候。

Answer 1

像这样更改onBindViewHolder方法：

  .....
 holder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                     // no neeed this condition
                    //if (PizzaActivity.class != null){
                    if(position == 0){
                        Intent intent = new Intent(activity, Pizza1Activity.class);
                        activity.startActivity(intent);
                    }
                    if(position == 1){
                        Intent intent = new Intent(activity, Pizza2Activity.class);
                        activity.startActivity(intent);
                    }
                    if(position == 2){
                        Intent intent = new Intent(activity, Pizza3Activity.class);
                        activity.startActivity(intent);
                    }
                }
        });

希望它能解决你的问题。

Answer 2

尝试将位置设置为holder.itemView中的标记并在onClick()方法中，使用view.getTag()检索相同的位置并采取相应的行动。

Answer 3

班级不要检查空。如果要检查存在类，可以参考：

public boolean isClass(String className) {
    try  {
        Class.forName(className);
        return true;
    }  catch (ClassNotFoundException e) {
        return false;
    }
}

和

if (isClass("android.app.ActionBar")) {
    Toast.makeText(getApplicationContext(), "YES",     Toast.LENGTH_SHORT).show();
}

我希望它可以帮助你解决问题！

如何在if语句中指出类中的位置？

3 个答案: