用android编写一个通讯录的代码

以下是一个简单的通讯录应用程序的代码，使用 Android Studio 中的 Java 编写。该应用程序允许用户添加、编辑和删除联系人，并将联系人信息保存在 SQLite 数据库中。

1. 首先，在 Android Studio 中创建一个新项目，并选择空活动。

2. 创建一个新布局文件 contact_item.xml，用于显示联系人信息。

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="16dp">

        <TextView
            android:id="@+id/nameTextView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="18sp" />

        <TextView
            android:id="@+id/phoneTextView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="14sp" />

        <TextView
            android:id="@+id/emailTextView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="14sp" />

    </LinearLayout>

3. 创建一个新布局文件 activity_main.xml，用于显示联系人列表和添加按钮。

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <ListView
            android:id="@+id/contactListView"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1" />

        <Button
            android:id="@+id/addButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Add Contact"
            android:layout_gravity="center_horizontal" />

    </LinearLayout>

4. 创建一个新的 Java 类 Contact，用于表示联系人对象。

    public class Contact {

        private int id;
        private String name;
        private String phone;
        private String email;

        public Contact(int id, String name, String phone, String email) {
            this.id = id;
            this.name = name;
            this.phone = phone;
            this.email = email;
        }

        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getPhone() {
            return phone;
        }

        public void setPhone(String phone) {
            this.phone = phone;
        }

        public String getEmail() {
            return email;
        }

        public void setEmail(String email) {
            this.email = email;
        }
    }

5. 创建一个新的 Java 类 ContactAdapter，用于将联系人对象绑定到 ListView 中的布局。

    public class ContactAdapter extends ArrayAdapter<Contact> {

        private List<Contact> contactList;
        private Context context;

        public ContactAdapter(List<Contact> contactList, Context context) {
            super(context, R.layout.contact_item, contactList);
            this.contactList = contactList;
            this.context = context;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            LayoutInflater inflater = LayoutInflater.from(context);
            View view = inflater.inflate(R.layout.contact_item, parent, false);

            TextView nameTextView = view.findViewById(R.id.nameTextView);
            TextView phoneTextView = view.findViewById(R.id.phoneTextView);
            TextView emailTextView = view.findViewById(R.id.emailTextView);

            Contact contact = contactList.get(position);

            nameTextView.setText(contact.getName());
            phoneTextView.setText(contact.getPhone());
            emailTextView.setText(contact.getEmail());

            return view;
        }
    }

6. 在 MainActivity 类中添加以下代码，以初始化 ListView 和添加按钮，并在添加按钮被单击时打开一个新的 Activity 来添加联系人。

    public class MainActivity extends AppCompatActivity {

        private ListView contactListView;
        private Button addButton;

        private List<Contact> contactList;
        private ContactAdapter adapter;

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

            contactListView = findViewById(R.id.contactListView);
            addButton = findViewById(R.id.addButton);

            contactList = new ArrayList<>();
            adapter = new ContactAdapter(contactList, this);
            contactListView.setAdapter(adapter);

            addButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Intent intent = new Intent(MainActivity.this, AddContactActivity.class);
                    startActivityForResult(intent, 1);
                }
            });
        }
    }

7. 创建一个新的 Java 类 AddContactActivity，用于显示添加联系人表单，并在提交表单时将联系人信息插入到 SQLite 数据库中。

    public class AddContactActivity extends AppCompatActivity {

        private EditText nameEditText;
        private EditText phoneEditText;
        private EditText emailEditText;
        private Button saveButton;

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

            nameEditText = findViewById(R.id.nameEditText);
            phoneEditText = findViewById(R.id.phoneEditText);
            emailEditText = findViewById(R.id.emailEditText);
            saveButton = findViewById(R.id.saveButton);

            saveButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    String name = nameEditText.getText().toString();
                    String phone = phoneEditText.getText().toString();
                    String email = emailEditText.getText().toString();

                    if (!name.isEmpty() && !phone.isEmpty() && !email.isEmpty()) {
                        Contact contact = new Contact(0, name, phone, email);
                        addContact(contact);
                        setResult(RESULT_OK);
                        finish();
                    } else {
                        Toast.makeText(AddContactActivity.this, "Please fill in all fields", Toast.LENGTH_SHORT).show();
                    }
                }
            });
        }

        private void addContact(Contact contact) {
            ContactDatabase db = new ContactDatabase(this);
            db.addContact(contact);
            db.close();
        }
    }

8. 创建一个新的 Java 类 ContactDatabase，用于处理 SQLite 数据库操作。

    public class ContactDatabase extends SQLiteOpenHelper {

        private static final int DATABASE_VERSION = 1;
        private static final String DATABASE_NAME = "contact_database";
        private static final String TABLE_NAME = "contacts";
        private static final String ID_COLUMN = "id";
        private static final String NAME_COLUMN = "name";
        private static final String PHONE_COLUMN = "phone";
        private static final String EMAIL_COLUMN = "email";

        private Context context;

        public ContactDatabase(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
            this.context = context;
        }

        @Override
        public void onCreate(SQLiteDatabase sqLiteDatabase) {
            String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_NAME + "("
                    + ID_COLUMN + " INTEGER PRIMARY KEY AUTOINCREMENT,"
                    + NAME_COLUMN + " TEXT,"
                    + PHONE_COLUMN + " TEXT,"
                    + EMAIL_COLUMN + " TEXT" + ")";
            sqLiteDatabase.execSQL(CREATE_CONTACTS_TABLE);
        }

        @Override
        public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
            sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
            onCreate(sqLiteDatabase);
        }

        public void addContact(Contact contact) {
            SQLiteDatabase db = this.getWritableDatabase();
            ContentValues values = new ContentValues();
            values.put(NAME_COLUMN, contact.getName());
            values.put(PHONE_COLUMN, contact.getPhone());
            values.put(EMAIL_COLUMN, contact.getEmail());
            db.insert(TABLE_NAME, null, values);
            db.close();
        }

        public List<Contact> getAllContacts() {
            List<Contact> contactList = new ArrayList<>();
            String selectQuery = "SELECT * FROM " + TABLE_NAME;
            SQLiteDatabase db = this.getWritableDatabase();
            Cursor cursor = db.rawQuery(selectQuery, null);
            if (cursor.moveToFirst()) {
                do {
                    Contact contact = new Contact(
                            cursor.getInt(0),
                            cursor.getString(1),
                            cursor.getString(2),
                            cursor.getString(3)
                    );
                    contactList.add(contact);
                } while (cursor.moveToNext());
            }
            cursor.close();
            db.close();
            return contactList;
        }

        public void deleteContact(Contact contact) {
            SQLiteDatabase db = this.getWritableDatabase();
            db.delete(TABLE_NAME, ID_COLUMN + " = ?", new String[]{String.valueOf(contact.getId())});
            db.close();
        }

        public void updateContact(Contact contact) {
            SQLiteDatabase db = this.getWritableDatabase();
            ContentValues values = new ContentValues();
            values.put(NAME_COLUMN, contact.getName());
            values.put(PHONE_COLUMN, contact.getPhone());
            values.put(EMAIL_COLUMN, contact.getEmail());
            db.update(TABLE_NAME, values, ID_COLUMN + " = ?", new String[]{String.valueOf(contact.getId())});
            db.close();
        }
    }

这是一个简单的通讯录应用程序的代码，它允许用户添加、编辑和删除联系人，并将联系人信息保存在 SQLite 数据库中。