Sqlite数一种轻量级的关系型数据库，android里面可以用来持久化存储一些用户数据。
一、SQLiteOpenHelper方式
SQLiteOpenHelper是原生的数据库帮助类，继承这个类，用来创建，更新数据库的操作
public class MySqliteOpenHelper extends SQLiteOpenHelper {
private static final String TAG = MySqliteOpenHelper.class.getSimpleName();
private static final String DBNAME = "test_sqlite.db";
private static final int DBVERSION = 1;
/**
* @param context 上下文
* name 数据库名称
* factory 游标工厂
* version 版本号
*/
public MySqliteOpenHelper(@Nullable Context context) {
super(context, DBNAME, null, DBVERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
Log.i(TAG, "创建数据库时的回调");
String sql = "create table student(_id integer,name varchar,age integer,salary integer)";
db.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.i(TAG, "升级数据库时的回调");
String updateSql = "";
switch (oldVersion) {
case 1:
updateSql = "alter table student add sex integer";
break;
case 2:
updateSql= "alter table student add address varchar";
break;
case 3:
break;
}
db.execSQL(updateSql);
}
}创建一个DAO,封装操作具体数据表操作，插入，删除等等
public class Dao {
private static final String TAG = Dao.class.getSimpleName();
private MySqliteOpenHelper mHelper;
public Dao(Context context) {
mHelper = new MySqliteOpenHelper(context);
}
public void insert() {
SQLiteDatabase db = mHelper.getWritableDatabase();
String sql = "insert into student(_id,name,age,salary) values(?,?,?,?)";
db.execSQL(sql, new Object[]{1, "Tony", 17, 100000});
db.close();
}
public void delete() {
SQLiteDatabase db = mHelper.getWritableDatabase();
String sql = "delete from student where _id = 1";
db.execSQL(sql);
db.close();
}
public void update() {
SQLiteDatabase db = mHelper.getWritableDatabase();
String sql = "update student set age = 23 where _id = 1";
db.execSQL(sql);
db.close();
}
public void query() {
SQLiteDatabase db = mHelper.getWritableDatabase();
String sql = "select * from student ";
Cursor cursor = db.rawQuery(sql, null);
while (cursor.moveToNext()) {
Log.e(TAG, "_id :" + cursor.getString((int) cursor.getColumnIndex("_id")) +
", name : " + cursor.getString((int) cursor.getColumnIndex("name")) +
", age :" + cursor.getString((int) cursor.getColumnIndex("age")) +
", salary :" + cursor.getString((int) cursor.getColumnIndex("salary")));
}
db.close();
}
}最后在界面上添加几个按钮，用来测试添加删除等等操作
public class SqliteActivity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = SqliteActivity.class.getSimpleName();
private Button mButtonCreateDb;
private MySqliteOpenHelper mMySqliteOpenHelper;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.sqlite_test);
initView();
}
private void initView() {
mButtonCreateDb = findViewById(R.id.create_db_id);
mButtonCreateDb.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.create_db_id:
createDb();
}
}
// 创建数据库
private void createDb() {
mMySqliteOpenHelper = new MySqliteOpenHelper(this);
mMySqliteOpenHelper.getWritableDatabase();
}
}layout.xml页面
<?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">
<Button
android:id="@+id/create_db_id"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="创建数据库"/>
<Button
android:id="@+id/add_db_id"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="增"/>
<Button
android:id="@+id/delete_db_id"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="删"/>
<Button
android:id="@+id/update_db_id"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="改"/>
<Button
android:id="@+id/query_db_id"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="查"/>
</LinearLayout> 
创建数据库以后，在 /data/com.example（你的应用包名）下面就会出现创建的数据库了
二、Android : Room方式
Android Room 是 Android 官方提供的一个持久性库，用于在 Android 应用程序中管理数据库。它提供了一个简单的 API 层，使得使用 SQLite 数据库变得更加容易和方便。
比起上面OpenHelper的方式，操作数据库更加的便捷。我们只需要根据自己的需要定义接口并且加上对应的注解，就可以实现对应的功能啦，接口的实现在build的时候room会帮我们实现。
引入依赖,app的build.gradle文件下面
//Room
def room_version = "2.5.0"
implementation "androidx.room:room-runtime:$room_version"
annotationProcessor "androidx.room:room-compiler:$room_version"新建一个用户实体类
@Entity(tableName = "user")
public class User {
@PrimaryKey(autoGenerate = true)
private Integer id;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
@ColumnInfo(name = "name")
private String name;
@ColumnInfo(name = "age")
private Integer age;
@ColumnInfo(name = "sex")
private String sex;
public User() {
}
public User(String name, Integer age, String sex) {
this.name = name;
this.age = age;
this.sex = sex;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
}新建一个DAO
@Dao
public interface UserDao {
@Insert
void insert(User... users);
@Delete
int delete(User... users);
@Update
int update(User... users);
@Query("SELECT * FROM user ORDER BY ID DESC")
List<User> query();
@Query("SELECT * FROM user where ID = :id ")
User queryById(Integer id);
@Query("DELETE FROM user")
void deleteTableData();
}新建database类
@Database(entities = {User.class}, version = 1, exportSchema = false)
public abstract class UserDatabase extends RoomDatabase {
public abstract UserDao getUserDao();
}接下来就是创建页面和activity了
public class RoomActivity extends AppCompatActivity {
private static final String TAG = "RoomActivity";
private Button btnInsert, btnDelete, btnUpdate, btnSelect, btnDeleteData;
private TextView textContent;
private EditText etName, etAge, etSex, etSelect, etDelete, etUpdate;
private UserDatabase mUserDatabase;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
init();
}
private void init(){
setContentView(R.layout.room_layout);
textContent = findViewById(R.id.tvcontent);
etName = findViewById(R.id.etName);
etAge = findViewById(R.id.etAge);
etSex = findViewById(R.id.etSex);
etSelect = findViewById(R.id.etSelect);
etDelete = findViewById(R.id.etDelete);
etUpdate = findViewById(R.id.etUpdate);
btnInsert = findViewById(R.id.btnSave);
btnDelete = findViewById(R.id.btnDelete);
btnUpdate = findViewById(R.id.btnUpdate);
btnSelect = findViewById(R.id.btnselect);
btnDeleteData = findViewById(R.id.btnDeleteTB);
mUserDatabase = Room.databaseBuilder(this,UserDatabase.class,"user")
//默认不允许在主线程中连接数据库，强制允许
.allowMainThreadQueries()
.build();
selectData(null);
//按钮事件 插入数据
btnInsert.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//插入数据 防止空
String name = etName.getText().toString().equals("") ? "张三" : etName.getText().toString();
int age = etAge.getText().toString().equals("") ? 20 : Integer.parseInt(etAge.getText().toString());
String sex = etSex.getText().toString().equals("") ? "男" : etSex.getText().toString();
User people = new User(name, age, sex);
mUserDatabase.getUserDao().insert(people);
//查询数据
selectData(null);
}
});
//修改数据
btnUpdate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//修改
int id = etUpdate.getText().toString().equals("") ? 0 : Integer.parseInt(etUpdate.getText().toString());
if (id != 0) {
String name = etName.getText().toString();
int age = Integer.parseInt(etAge.getText().toString());
String sex = etSex.getText().toString();
User people = new User(name, age, sex);
people.setId(id);
mUserDatabase.getUserDao().update(people);
//查询
selectData(null);
}
}
});
//删除
btnDelete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int id = etDelete.getText().toString().equals("") ? 0 : Integer.parseInt(etDelete.getText().toString());
if (id != 0) {
User people = new User();
people.setId(id);
mUserDatabase.getUserDao().delete(people);
//查询
selectData(null);
}
}
});
//根据id 查数据
btnSelect.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int id = etSelect.getText().toString().equals("") ? 0 : Integer.parseInt(etSelect.getText().toString());
if (id != 0) {
selectData(id);
}
}
});
//删除全部数据
btnDeleteData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mUserDatabase.getUserDao().deleteTableData();
}
});
}
/**
* 查询数据的方法
*/
public void selectData(Integer id) {
try {
StringBuilder text = new StringBuilder();
if (id == null || id == 0) {
List<User> peopleList = mUserDatabase.getUserDao().query();
if (peopleList.size() != 0) {
for (int i = 0; i < peopleList.size(); i++) {
User people = peopleList.get(i);
text.append("id:")
.append(people.getId())
.append("---name:")
.append(people.getName())
.append("---age:")
.append(people.getAge())
.append("---sex:")
.append(people.getSex())
.append("\n");
}
} else {
text.append("没有可用的数据");
}
} else {
User people = mUserDatabase.getUserDao().queryById(id);
text.append("id:")
.append(people.getId())
.append("---name:")
.append(people.getName())
.append("---age:")
.append(people.getAge())
.append("---sex:")
.append(people.getSex());
}
textContent.setText(text.toString());
} catch (Exception e) {
Log.e("TAG", "----查询失败------------" + e.getMessage());
}
}
}layout.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="@+id/btnUpdate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="修改"
app:layout_constraintBottom_toBottomOf="@+id/etUpdate"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/etUpdate"
app:layout_constraintTop_toTopOf="@+id/etUpdate"
app:layout_constraintVertical_bias="0.0" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.05" />
<TextView
android:id="@+id/textView"
android:layout_width="match_parent"
android:layout_height="0dp"
android:text="Room简单应用："
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/guideline2"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/btnSave"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="4dp"
android:text="保存"
app:layout_constraintBottom_toTopOf="@+id/guideline9"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.203"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/guideline4" />
<Button
android:id="@+id/btnDelete"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="删除"
app:layout_constraintBottom_toBottomOf="@+id/etDelete"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/etDelete"
app:layout_constraintTop_toTopOf="@+id/etDelete" />
<Button
android:id="@+id/btnselect"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="查询"
app:layout_constraintBottom_toBottomOf="@+id/etSelect"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/etSelect"
app:layout_constraintTop_toTopOf="@+id/etSelect" />
<Button
android:id="@+id/btnDeleteTB"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="4dp"
android:text="删除表数据"
app:layout_constraintBottom_toTopOf="@+id/guideline9"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.873"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/guideline4" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.13" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.29548565" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="姓名："
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/guideline3"
app:layout_constraintEnd_toStartOf="@+id/etName"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5" />
<EditText
android:id="@+id/etName"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入"
android:inputType="text"
app:layout_constraintBottom_toBottomOf="@+id/textView2"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/textView2"
app:layout_constraintTop_toTopOf="@+id/textView2" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.05352798" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.21" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline8"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.6" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline9"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.37" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="性别："
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/guideline6"
app:layout_constraintEnd_toStartOf="@+id/etSex"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5" />
<EditText
android:id="@+id/etSex"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入"
android:inputType="text"
app:layout_constraintBottom_toBottomOf="@+id/textView3"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/textView3"
app:layout_constraintTop_toTopOf="@+id/textView3" />
<EditText
android:id="@+id/etAge"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入"
android:inputType="number"
app:layout_constraintBottom_toBottomOf="@+id/textView4"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/textView4"
app:layout_constraintTop_toTopOf="@+id/textView4" />
<TextView
android:id="@+id/textView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="年龄："
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/guideline4"
app:layout_constraintEnd_toStartOf="@+id/etAge"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline10"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.9" />
<EditText
android:id="@+id/etSelect"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入id"
android:inputType="number"
app:layout_constraintBottom_toTopOf="@+id/guideline8"
app:layout_constraintEnd_toStartOf="@+id/btnselect"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/guideline9"
app:layout_constraintVertical_bias="0.0" />
<EditText
android:id="@+id/etDelete"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入id"
android:inputType="number"
app:layout_constraintBottom_toTopOf="@+id/guideline8"
app:layout_constraintEnd_toStartOf="@+id/btnDelete"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/guideline9"
app:layout_constraintVertical_bias="0.451" />
<EditText
android:id="@+id/etUpdate"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入id"
android:inputType="number"
app:layout_constraintBottom_toTopOf="@+id/guideline8"
app:layout_constraintEnd_toStartOf="@+id/btnUpdate"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/etSelect"
app:layout_constraintVertical_bias="1.0" />
<TextView
android:id="@+id/tvcontent"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/guideline8"
tools:hint="这里显示数据" />
</androidx.constraintlayout.widget.ConstraintLayout>运行以后，会创建数据库和对应的表，可以在设备的 /data/包名/database下看到自己的数据库
