java我怎样才能延迟点击按钮的动作，这样我就可以存储一个JSON数组了？

Question

以下代码中的所有内容都可以正常工作，除非用户单击其中一个按钮进行快速操作，而没有时间连接数据库并获取json值

我尝试环绕try-catch块，并尝试检查create-if语句，该语句检查第一个字符=='{'，因为这始终是给定json字符串中的第一个字符

这是一节课

package com.example.allrateform;

import 安卓.app.AlertDialog;
import 安卓.content.Intent;
import 安卓.os.AsyncTask;
import 安卓.support.v7.app.AppCompatActivity;
import 安卓.os.Bundle;
import 安卓.view.View;
import 安卓.widget.Button;
import 安卓.widget.TextView;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import static com.example.allrateform.MainActivity.UsernameText;

public class Categories extends AppCompatActivity {

    public static String Category;
    public static char[] TextList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_categories);

        //CREATING ALL INSTANCES
        final Button ComputersButton=(Button)findViewById(R.id.ComputersButton);
        final Button HobbiesButton=(Button)findViewById(R.id.HobbiesButton);
        final Button BooksButton=(Button)findViewById(R.id.BooksButton);
        final Button TourismButton=(Button)findViewById(R.id.TourismButton);
        final Button GamesButton=(Button)findViewById(R.id.GamesButton);
        final Button FantasyButton=(Button)findViewById(R.id.FantasyButton);
        final Button SportsButton=(Button)findViewById(R.id.SportsButton);

        final TextView TextViewUsername=(TextView)findViewById(R.id.TextViewUsername);
        TextViewUsername.setText(UsernameText);

        getJSON();

        ComputersButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Category="Computers";
                openQuestion();
            }
        });
        HobbiesButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Category="Hobbies";
                openQuestion();
            }
        });
        BooksButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Category="Books";
                openQuestion();
            }
        });
        TourismButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Category="Tourism";
                openQuestion();
            }
        });
        GamesButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Category="Games";
                openQuestion();
            }
        });
        FantasyButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Category="Fantasy";
                openQuestion();
            }
        });
        SportsButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Category="Sports";
                openQuestion();
            }
        });
    }

    public void openQuestion(){
        try {
            Intent intent = new Intent(this, Question.class);
            startActivity(intent);
        }catch(Exception ex) {
            AlertDialog.Builder builder = new AlertDialog.Builder(Categories.this);
            builder.setMessage("Try again later")
                    .setNegativeButton("Ok", null)
                    .create()
                    .show();
        }
    }

    public void getJSON() {
        new Categories.BackgroundTask().execute();
    }

    class BackgroundTask extends AsyncTask<Void, Void, String> {

        String json_url;
        String JSON_STRING;

        @Override
        protected void onPreExecute() {
            json_url = "https://allratejohnnycode.000webhostapp.com/List.php";
        }

        @Override
        protected String doInBackground(Void... voids) {
            try {
                URL url = new URL(json_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                StringBuilder stringBuilder = new StringBuilder();

                while ((JSON_STRING = bufferedReader.readLine()) != null) {
                    stringBuilder.append(JSON_STRING + "\n");
                }

                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();
                return stringBuilder.toString().trim();

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);
        }

        @Override
        protected void onPostExecute(String result) {
            TextList=result.toCharArray();
        }
    }
}

Answer 1

我想提供两种不同的方法

1st就是你想要的，不过我推荐2nd一个：

---

单击按钮会触发循环进度加载程序

您可以维护一个boolean来表示JSON是否已加载， 因此，当用户单击按钮时，首先检查布尔状态。如果加载-继续创建意图。Else——提供一个循环进度加载器，等待JSON加载。（如果您需要帮助，请给我留言，我将为您提供一个代码示例）

---

使用Android View Model架构

这是一个更“繁重”的解决方案，但在研究Android Architecture Components之后，你会发现这是最干净的&；在后台加载数据的有效方法，同时通常保持数据和UI之间的分离。非常有用的知识

---

---

第一种方法——实施示例

第1步：添加一个进度条，开头有visibility="gone"。随心所欲地设计

第二步：试试这个代码。它是有效的（经过测试）

public class Categories extends AppCompatActivity {

    public static String Category;
    public static char[] TextList;
    //4 new variables
    private static volatile boolean isJsonLoaded, isButtonClicked;
    private ProgressBar progressBar;
    private final Object locker = 0; //for concurrent modification & synchronization

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_categories);

        TextView TextViewUsername = findViewById(R.id.TextViewUsername);
        TextViewUsername.setText(UsernameText);

        this.progressBar = findViewById(R.id.progressBar);
        isJsonLoaded = false;
        isButtonClicked = false;

        initButtons();
        getJSON();
    }

    //Slightly beautified your code
    private void initButtons() {
        //Temp array of buttons
        ArrayList<Button> buttons = new ArrayList<>(Arrays.asList(
                (Button) findViewById(R.id.ComputersButton),
                (Button) findViewById(R.id.HobbiesButton),
                (Button) findViewById(R.id.BooksButton),
                (Button) findViewById(R.id.TourismButton),
                (Button) findViewById(R.id.GamesButton),
                (Button) findViewById(R.id.FantasyButton),
                (Button) findViewById(R.id.SportsButton)
        ));

        //Mutual 'onClick' listener for all of them
        View.OnClickListener buttonClick = new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //Get the button's name
                String buttonName = getResources().getResourceEntryName(v.getId());
                //Eliminate the "...Button" part
                Category = buttonName.substring(0, buttonName.indexOf("Button"));
                handleButtonClick();
            }
        };

        for (Button button : buttons)
            button.setOnClickListener(buttonClick);
    }

    public void handleButtonClick() {
        synchronized (locker) {
            if (isJsonLoaded) openQuestion();
            else {
                isButtonClicked = true;

                //Show the progress bar
                progressBar.setVisibility(View.VISIBLE);
            }
        }
    }

    void openQuestion() {
        Intent intent = new Intent(this, Question.class);
        startActivity(intent);
    }

    public void getJSON() {
        new Categories.BackgroundTask().execute();
    }

    class BackgroundTask extends AsyncTask<Void, Void, String> {

        String json_url;
        String JSON_STRING;

        @Override
        protected void onPreExecute() {
            json_url = "https://allratejohnnycode.000webhostapp.com/List.php";
        }

        @Override
        protected String doInBackground(Void... voids) {
            try {
                URL url = new URL(json_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                StringBuilder stringBuilder = new StringBuilder();

                while ((JSON_STRING = bufferedReader.readLine()) != null) {
                    stringBuilder.append(JSON_STRING + "\n");
                }

                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();

                return stringBuilder.toString().trim();

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);
        }

        @Override
        protected void onPostExecute(String result) {
            TextList = result.toCharArray();
            isJsonLoaded = true;
            synchronized (locker) {
                if (isButtonClicked)
                    openQuestion();
            }

            //Hide the progress bar
            progressBar.setVisibility(View.GONE);
        }
    }
}