三、简答题 1、简述如何使用 SharedPreferences 读写数据。 2、简述 Handler 消息机制的工作原理。 3、简述使用HttpURConnection访问网络的步骤。 四、编程题 1、现有两个Activity，分别为UserinfoActivity和ShowActivity，现在要从UserinfoActivity中通过一个“查看”按钮切换界面到ShowActivity，并传递如下三个参数 id=1:username="eric”;state=True，且ShowActivity使用 Toast 显示接收到的参数，请写出两个Activity中的核心代码 2、在网络接口 http://192.168.1.100:8080/news/getnewslist中提供了如下所示的JSON数组格式的返回数据:[f"id":1001,"title”:“"程序员因写代码太乱被杀害"，"detail”:"凶手是死者同事，维护死者代码时完全看不懂而痛下杀手":"comment" 16359,"image”:"http://192.168.1.100:8080/news/images/6.jpg) 请编写程序，访问该接口获取数据，解析后将数据显示到界面的控件上，同时将数据保存到本地的SQLite 数据库中。

三、简答题 1、使用SharedPreferences读写数据的步骤： ① 获取SharedPreferences对象：SharedPreferences sharedPreferences = getSharedPreferences("name", Context.MODE_PRIVATE); ② 获取SharedPreferences.Editor对象：SharedPreferences.Editor editor = sharedPreferences.edit(); ③ 写入数据：editor.putString("key", value); ④ 提交数据：editor.commit(); ⑤ 读取数据：sharedPreferences.getString("key", defaultValue); 2、Handler消息机制的工作原理： Handler是Android中消息机制的基础，它可以实现不同线程之间的通信。Handler包括两个主要部分：消息队列和消息处理器。消息队列是一个存储消息的FIFO队列，消息处理器则是用来处理消息的对象。当Handler创建时，它会自动与当前线程的消息队列关联起来。当调用Handler的sendMessage()方法，会向消息队列中添加一条消息。当Handler处理消息时，会从消息队列中取出一条消息，交给消息处理器处理，如果消息处理器处理完消息后需要更新UI，可以使用Handler的post()或者postDelayed()方法将消息发送到UI线程中执行。 3、使用HttpURLConnection访问网络的步骤： ① 创建URL对象：URL url = new URL("http://www.example.com"); ② 打开URLConnection连接：HttpURLConnection connection = (HttpURLConnection) url.openConnection(); ③ 设置请求方式：connection.setRequestMethod("GET"); ④ 设置连接超时时间：connection.setConnectTimeout(5000); ⑤ 设置读取超时时间：connection.setReadTimeout(5000); ⑥ 发送请求：connection.connect(); ⑦ 获取响应码：int responseCode = connection.getResponseCode(); ⑧ 获取输入流：InputStream inputStream = connection.getInputStream(); ⑨ 读取数据：BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)); StringBuilder stringBuilder = new StringBuilder(); String line; while ((line = reader.readLine()) != null) { stringBuilder.append(line); } String result = stringBuilder.toString(); ⑩ 关闭连接：connection.disconnect(); 四、编程题 1、UserinfoActivity中的代码： ``` public void onClick(View view) { Intent intent = new Intent(UserinfoActivity.this, ShowActivity.class); intent.putExtra("id", 1); intent.putExtra("username", "eric"); intent.putExtra("state", true); startActivity(intent); } ``` ShowActivity中的代码： ``` Intent intent = getIntent(); int id = intent.getIntExtra("id", 0); String username = intent.getStringExtra("username"); boolean state = intent.getBooleanExtra("state", false); Toast.makeText(ShowActivity.this, "id=" + id + " username=" + username + " state=" + state, Toast.LENGTH_SHORT).show(); ``` 2、代码如下： ``` public void getData() { new Thread(new Runnable() { @Override public void run() { try { URL url = new URL("http://192.168.1.100:8080/news/getnewslist"); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); connection.setRequestMethod("GET"); connection.setConnectTimeout(5000); connection.setReadTimeout(5000); connection.connect(); int responseCode = connection.getResponseCode(); if (responseCode == HttpURLConnection.HTTP_OK) { InputStream inputStream = connection.getInputStream(); BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)); StringBuilder stringBuilder = new StringBuilder(); String line; while ((line = reader.readLine()) != null) { stringBuilder.append(line); } String result = stringBuilder.toString(); Gson gson = new Gson(); List<News> newsList = gson.fromJson(result, new TypeToken<List<News>>(){}.getType()); for (News news : newsList) { // 将数据保存到SQLite数据库中 dbHelper.insertNews(news.getId(), news.getTitle(), news.getDetail(), news.getComment(), news.getImage()); } // 更新UI Message message = Message.obtain(); message.what = UPDATE_UI; message.obj = newsList; handler.sendMessage(message); reader.close(); inputStream.close(); } connection.disconnect(); } catch (Exception e) { e.printStackTrace(); } } }).start(); } private void updateUI(List<News> newsList) { // 将数据显示到界面的控件上 } // News类 public class News { private int id; private String title; private String detail; private int comment; private String image; public News(int id, String title, String detail, int comment, String image) { this.id = id; this.title = title; this.detail = detail; this.comment = comment; this.image = image; } public int getId() { return id; } public String getTitle() { return title; } public String getDetail() { return detail; } public int getComment() { return comment; } public String getImage() { return image; } } // DBHelper类 public class DBHelper extends SQLiteOpenHelper { private static final String DB_NAME = "news.db"; private static final int DB_VERSION = 1; private static final String TABLE_NAME = "news"; private static final String COLUMN_ID = "id"; private static final String COLUMN_TITLE = "title"; private static final String COLUMN_DETAIL = "detail"; private static final String COLUMN_COMMENT = "comment"; private static final String COLUMN_IMAGE = "image"; private static final String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + " (" + COLUMN_ID + " INTEGER PRIMARY KEY, " + COLUMN_TITLE + " TEXT, " + COLUMN_DETAIL + " TEXT, " + COLUMN_COMMENT + " INTEGER, " + COLUMN_IMAGE + " TEXT)"; public DBHelper(Context context) { super(context, DB_NAME, null, DB_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(CREATE_TABLE); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME); onCreate(db); } public void insertNews(int id, String title, String detail, int comment, String image) { SQLiteDatabase db = getWritableDatabase(); ContentValues values = new ContentValues(); values.put(COLUMN_ID, id); values.put(COLUMN_TITLE, title); values.put(COLUMN_DETAIL, detail); values.put(COLUMN_COMMENT, comment); values.put(COLUMN_IMAGE, image); db.insert(TABLE_NAME, null, values); db.close(); } public List<News> getNewsList() { List<News> newsList = new ArrayList<>(); SQLiteDatabase db = getReadableDatabase(); Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_NAME, null); if (cursor.moveToFirst()) { do { int id = cursor.getInt(cursor.getColumnIndex(COLUMN_ID)); String title = cursor.getString(cursor.getColumnIndex(COLUMN_TITLE)); String detail = cursor.getString(cursor.getColumnIndex(COLUMN_DETAIL)); int comment = cursor.getInt(cursor.getColumnIndex(COLUMN_COMMENT)); String image = cursor.getString(cursor.getColumnIndex(COLUMN_IMAGE)); News news = new News(id, title, detail, comment, image); newsList.add(news); } while (cursor.moveToNext()); } cursor.close(); db.close(); return newsList; } } // Handler类 private static final int UPDATE_UI = 1; private Handler handler = new Handler(new Handler.Callback() { @Override public boolean handleMessage(@NonNull Message message) { switch (message.what) { case UPDATE_UI: List<News> newsList = (List<News>) message.obj; updateUI(newsList); break; } return false; } });