【达内课程】SQLite（三）项目之增加和显示联系人列表

最后一节，来做一个关于SQLite的项目
先做出以下界面

第一个页面MainActivity对应的布局activity_main

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.example.xx.sqliteproject.MainActivity" android:orientation="vertical">

    <Button  android:id="@+id/btn_add" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="添加联系人"/>

    <ListView  android:id="@+id/lv_contacts" android:layout_width="match_parent" android:layout_height="match_parent"/>

</LinearLayout>

第二个ContactFormActivity对应的布局activity_contact_form

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.example.xx.sqliteproject.ContactFormActivity" android:orientation="vertical">

    <TextView  android:layout_width="match_parent" android:layout_height="wrap_content" android:text="请输入联系人信息"/>

    <EditText  android:id="@+id/et_username" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="text" android:hint="请输入联系人姓名"/>
    <EditText  android:id="@+id/et_age" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="number" android:hint="请输入联系人年龄"/>
    <EditText  android:id="@+id/et_phone" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="number" android:hint="请输入联系人电话"/>
    <EditText  android:id="@+id/et_email" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="text" android:hint="请输入联系人Email"/>

    <Button  android:id="@+id/btn_save" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="保存"/>
    <Button  android:id="@+id/btn_back" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="返回"/>

</LinearLayout>

我们可以用一个DBOpenHelper来帮助我们管理数据库，以免反复执行出错

public class DBOpenHelper extends SQLiteOpenHelper{

    //修改原来的构造方法
   /* public DBOpenHelper(Context context,String name,SQLiteDatabase.CursorFactory factory,int version) { super(context,name,factory,version); }*/
    public DBOpenHelper(Context context) {
        super(context,"test.db",null,1);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        //当创建数据库时，直接创建数据表
        String sql = "CREATE TABLE users ("+
                "_id INTEGER PRIMARY KEY AUTOINCREMENT,"+
                "_name VARCHAR(10) UNIQUE NOT NULL,"+
                "_age INTEGER,"+
                "_phone CHAR(11),"+
                "_email VARCHAR(31) UNIQUE"+
                ")";
        sqLiteDatabase.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase,int oldVersion,int newVersion) {
        //当升级时
    }
}

DBOpenHelper的onCreate()方法确保创建数据库的时候执行，不创建的时候不反复执行

MainActivity

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private Button btn_add;
    private ListView lv_contacts;

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

        initView();

        DBOpenHelper dbOpenHelper = new DBOpenHelper(this);
        //必须调用以下其中一个方法才能执行创建数据库
        //dbOpenHelper.getReadableDatabase();
        SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
    }

    private void initView() {
        btn_add = findViewById(R.id.btn_add);
        lv_contacts = findViewById(R.id.lv_contacts);

        btn_add.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        Intent  intent = new Intent(this,ContactFormActivity.class);
        startActivity(intent);
    }
}

项目结构如下图

创建一个Person类

public class Person {
    private String name;
    private int age;
    private String phone;
    private String email;

    public Person() {
    }

    public Person(String name,int age,String phone,String email) {
        this.name = name;
        this.age = age;
        this.phone = phone;
        this.email = email;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    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;
    }
}

创建接口IDao，实现相关功能

public interface IDao<T> {
    long insert(T t);
}

创建PersonDao

public class PersonDao implements IDao<Person> {
    private Context context;

    public PersonDao(Context context) {
        setContext(context);
    }

    private void setContext(Context context) {
        if(context == null){
            throw new IllegalArgumentException("参数context不能为空");
        }
        this.context = context;
    }

    @Override
    public long insert(Person person) {
        //获取SQLiteDatabase对象
        DBOpenHelper dbOpenHelper = new DBOpenHelper(context);
        SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
        //执行业务，增加数据
        String table = "users";
        String nullColumnHack = "_id";
        ContentValues values = new ContentValues();
        values.put("_name",person.getName());
        values.put("_age",person.getAge());
        values.put("_phone",person.getPhone());
        values.put("_email",person.getEmail());
        long id = db.insert(table,nullColumnHack,values);

        //释放资源
        db.close();
        db = null;

        //返回
        return id;
    }
}

ContractFormActivity

public class ContactFormActivity extends AppCompatActivity implements View.OnClickListener{
    private EditText etUsername;
    private EditText etAge;
    private EditText etPhone;
    private EditText etEmail;
    private Button btnSave;
    private Button btnBack;

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

        initViews();
        setListeners();
    }

    private void setListeners() {
        btnSave.setOnClickListener(this);
        btnBack.setOnClickListener(this);
    }

    private void initViews() {
        etUsername = findViewById(R.id.et_username);
        etAge = findViewById(R.id.et_age);
        etPhone = findViewById(R.id.et_phone);
        etEmail = findViewById(R.id.et_email);
        btnSave = findViewById(R.id.btn_save);
        btnBack = findViewById(R.id.btn_back);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.btn_save:
                //获取表单中的数据
                String name = etUsername.getText().toString().trim();
                String phone = etPhone.getText().toString().trim();
                String email = etEmail.getText().toString().trim();
                int age = Integer.parseInt(etAge.getText().toString());

                Person person = new Person(name,age,phone,email);
                PersonDao personDao = new PersonDao(this);
                long id = personDao.insert(person);
                if(id == -1){
                    Toast.makeText(this,"姓名或电子邮件可能冲突！",Toast.LENGTH_SHORT).show();
                }else {
                    Toast.makeText(this,"数据增加成功",Toast.LENGTH_SHORT).show();
                    etUsername.setText(null);
                    etPhone.setText(null);
                    etEmail.setText(null);
                    etAge.setText(null);
                }
                break;
            case R.id.btn_back:
                finish();
                break;
        }
    }
}

运行程序

可以在添加联系人的列表增加返回按钮

添加点击监听，点击时，finish()当前页面返回上一页面

在上一页中显示联系人列表

IDao中增加查询方法

public interface IDao<T> {
    long insert(T t);

    List<T> query(String whereClause,String[] whereArgs,String orderBy);
}

PersonDao中完善query方法

@Override
    public List<Person> query(String whereClause,String[] whereArgs,String orderBy) {
        //声明返回值
        List<Person> persons = new ArrayList<Person>();
        //获取SQLiteDatabase对象
        DBOpenHelper dbOpenHelper = new DBOpenHelper(context);
        SQLiteDatabase db = dbOpenHelper.getWritableDatabase();

        //执行业务：查询数据
        String table = "users";
        String[] columns = {"_id","_name","_age","_phone","_email"};
        Cursor c = db.query(table,columns,whereClause,whereArgs,null,orderBy);
        //将数据封装到返回值中
        for(c.moveToFirst();!c.isAfterLast();c.moveToNext()){
            Person p = new Person();
            p.setId(c.getInt(0));
            p.setName(c.getString(1));
            p.setAge(c.getInt(2));
            p.setPhone(c.getString(3));
            p.setEmail(c.getString(4));
            persons.add(p);
        }
        //释放资源
        db.close();
        db = null;
        //返回
        return persons;
    }

因为查询字段中有id字段，所以Person类中增加id字段

public class Person {
    private int id;
    private String name;
    private int age;
    private String phone;
    private String email;

    public Person() {
    }

    public Person(String name,String email) {
        this.name = name;
        this.age = age;
        this.phone = phone;
        this.email = email;
    }

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

    public int getId() {
        return id;
    }

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

    ......
}

MainActivity中准备显示列表的Adaper，把之前写好的BaseAdapter拿过来用
BaseAdapter的源码在达内课程-音乐播放器3.0(上)中

新建PersonAdapter

public class PersonAdapter extends BaseAdapter{
    public PersonAdapter(Context context,List data) {
        super(context,data);
    }

    @Override
    public View getView(int i,View view,ViewGroup viewGroup) {
        //2.声明ViewHolder对象
        ViewHolder viewHolder = null;
        //3.判断view
        if(view == null){
            viewHolder = new ViewHolder();
            view = getInflater().inflate(R.layout.item_contact,null);
            viewHolder.tvName = view.findViewById(R.id.tv_name);
            viewHolder.tvAge = view.findViewById(R.id.tv_age);
            viewHolder.tvPhone = view.findViewById(R.id.tv_phone);
            viewHolder.tvEmail = view.findViewById(R.id.tv_email);

            view.setTag(viewHolder);
        }else{
            viewHolder = (ViewHolder) view.getTag();
        }
        //4.根据参数position确定需要显示的数据
        Person p = (Person) getData().get(i);

        //5.向控件中填充数据
        viewHolder.tvName.setText(p.getName());
        viewHolder.tvAge.setText(p.getAge()+"");
        viewHolder.tvPhone.setText(p.getPhone());
        viewHolder.tvEmail.setText(p.getEmail());
        return view;
    }

    //1.声明ViewHolder类
    class ViewHolder{
        TextView tvName;
        TextView tvAge;
        TextView tvPhone;
        TextView tvEmail;
    }
}

MainActivity

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    private Button btn_add;
    private ListView lv_contacts;
    private List<Person> persons;
    private PersonAdapter adapter;

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

        btn_add = findViewById(R.id.btn_add);
        lv_contacts = findViewById(R.id.lv_contacts);

        btn_add.setOnClickListener(this);

        //获取数据源
        PersonDao personDao = new PersonDao(this);
        persons = personDao.query(null,"_name ASC");
        adapter = new PersonAdapter(this,persons);
        lv_contacts.setAdapter(adapter);
    }


    @Override
    public void onClick(View view) {
        Intent intent = new Intent(this,ContactFormActivity.class);
        startActivity(intent);
    }

    @Override
    protected void onRestart() {
        super.onRestart();
        //获取新的数据，刷新列表
        PersonDao personDao = new PersonDao(this);
        persons.clear();
        persons.addAll(personDao.query(null,"_name ASC"));
        adapter.notifyDataSetChanged();
    }
}

（编辑：李大同）

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