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SQLite简介
SQLite是一个实现了自给自足的、无服务器的、零配置的、事务性的SQL数据库引擎，并且是一个开源项目。
Android上自带SQLite，因此是Android项目上常用的数据库。
一个简单的demo通过SQLiteOpenHelper类实现了SQLite的增删改查操作
Person.java
public class Person implements Serializable {
//序列化的版本号
private static final long serialVersionUID = 1L;
private int id;
private String name;
private int age;
private String sex;
public Person() {
}
public Person(String name, int age, String sex) {
this.name = name;
this.age = age;
this.sex = sex;
}
public Person(int id, String name, int age, String sex) {
this.id = id;
this.name = name;
this.age = age;
this.sex = sex;
}
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
}
SQLiteHelper.java
public class SQLiteHelper extends SQLiteOpenHelper {
private static final String TAG = "SQLiteHelper";
//数据库名
private static final String DATABASE_NAME = "mydb.db";
//数据库 表名
public static final String PERSON_TABLE_NAME = "person";
public static final String USER_TABLE_NAME = "user";
public SQLiteHelper(Context context, int version) {
super(context, DATABASE_NAME, null, version);
}
//创建数据库
@Override
public void onCreate(SQLiteDatabase db) {
Log.e(TAG, "数据库创建");
String sql1 = "create table if not exists " + PERSON_TABLE_NAME +
"(id integer Primary Key autoincrement," +
"name varchar(20)," +
"age integer," +
"sex varchar(20))";
String sql2 = "create table if not exists " + USER_TABLE_NAME +
"(id integer Primary Key autoincrement," +
"name varchar(20)," +
"age integer," +
"sex varchar(20))";
//执行sql语句
db.execSQL(sql1);
db.execSQL(sql2);
}
//更新数据库
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.e(TAG, "数据库更新");
}
//以下 增删改查函数可以放到Activity中
//插入
public void insertPerson(Person person) {
Log.e(TAG, "插入");
SQLiteDatabase db = getWritableDatabase();
String sql = "insert into " + PERSON_TABLE_NAME + "(name,age,sex) values("
+ String.format("'%s'", person.getName()) + ","
+ person.getAge() + ","
+ String.format("'%s'", person.getSex()) +
");";
//插入数据库
db.execSQL(sql);
db.close();
}
//更新
public void updatePerson(Person person) {
Log.e(TAG, "更新");
SQLiteDatabase db = getWritableDatabase();
String sql = "update " + PERSON_TABLE_NAME + " set name = "
+ String.format("'%s'", person.getName())
+ ",age = " + person.getAge()
+ ",sex = " + String.format("'%s'", person.getSex())
+ "where id = " + person.getId();
db.execSQL(sql);
db.close();
}
//删除
public void deletePersonById(int id) {
Log.e(TAG, "删除");
SQLiteDatabase db = getWritableDatabase();
String sql = "id = ?";
String wheres[] = {String.valueOf(id)};
db.delete(PERSON_TABLE_NAME, sql, wheres);
db.close();
}
//查询所有
public List<Person> queryAllPerson() {
List<Person> list = new ArrayList<>();
SQLiteDatabase db = getReadableDatabase();
String sql = "select * from " + PERSON_TABLE_NAME;
Cursor cursor = db.rawQuery(sql, null);
while (cursor.moveToNext()) {
int id = cursor.getInt(cursor.getColumnIndex("id"));
String name = cursor.getString(cursor.getColumnIndex("name"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
String sex = cursor.getString(cursor.getColumnIndex("sex"));
Person person = new Person();
person.setId(id);
person.setName(name);
person.setAge(age);
person.setSex(sex);
list.add(person);
}
cursor.close();
db.close();
return list;
}
//根据id查询
public Person queryPersonById(int id) {
Person person = null;
SQLiteDatabase db = getReadableDatabase();
String[] columns = {"id", "name", "age", "sex"};
String selection = "id = ?";
String[] selectionArgs = {String.valueOf(id)};
Cursor cursor = db.query(PERSON_TABLE_NAME, columns, selection, selectionArgs, null, null, null);
if (cursor.moveToNext()) {
person = new Person();
person.setId(cursor.getInt(cursor.getColumnIndex("id")));
person.setAge(cursor.getInt(cursor.getColumnIndex("age")));
person.setName(cursor.getString(cursor.getColumnIndex("name")));
person.setSex(cursor.getString(cursor.getColumnIndex("sex")));
}
cursor.close();
db.close();
return person;
}
}
InsertDialog.java
public class InsertDialog extends Activity implements View.OnClickListener {
//插入请求代码 大于0
private static final int INSERT_RESULTCODE = 11;
//姓名控件
private EditText nameView;
//年龄控件
private EditText ageView;
//性别控件
private EditText sexView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//去掉标题栏
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_insert_dialog);
nameView = (EditText) findViewById(R.id.insert_edit_name);
ageView = (EditText) findViewById(R.id.insert_edit_age);
sexView = (EditText) findViewById(R.id.insert_edit_sex);
Button confirmBtn = (Button) findViewById(R.id.insert_confirm);
Button cancelBtn = (Button) findViewById(R.id.insert_cancel);
confirmBtn.setOnClickListener(this);
cancelBtn.setOnClickListener(this);
}
private void confirm() {
String name = String.valueOf(nameView.getText());
int age = Integer.valueOf(String.valueOf(ageView.getText()));
String sex = String.valueOf(sexView.getText());
Person person = new Person(name, age, sex);
Intent intent = new Intent();
intent.putExtra("person", person);
setResult(INSERT_RESULTCODE, intent);
finish();
}
private void cancel() {
setResult(INSERT_RESULTCODE);
finish();
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.insert_confirm:
confirm();
break;
case R.id.insert_cancel:
cancel();
break;
default:
break;
}
}
}
DeleteDialog.java
public class DeleteDialog extends Activity implements View.OnClickListener {
//插入请求代码
private static final int DELETE_RESULTCODE = 22;
//id控件
private EditText idView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_delete_dialog);
idView = (EditText) findViewById(R.id.delete_edit_id);
Button confirmBtn = (Button) findViewById(R.id.delete_confirm);
Button cancelBtn = (Button) findViewById(R.id.delete_cancel);
confirmBtn.setOnClickListener(this);
cancelBtn.setOnClickListener(this);
}
private void confirm() {
int id = Integer.valueOf(String.valueOf(idView.getText()));
Intent intent = new Intent();
intent.putExtra("id", id);
setResult(DELETE_RESULTCODE, intent);
finish();
}
private void cancel() {
setResult(DELETE_RESULTCODE);
finish();
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.delete_confirm:
confirm();
break;
case R.id.delete_cancel:
cancel();
break;
default:
break;
}
}
}
UpdateDialog.java
public class UpdateDialog extends Activity implements View.OnClickListener {
//修改请求代码
private static final int UPDATE_RESULTCODE = 33;
//id控件
private EditText idView;
//姓名控件
private EditText nameView;
//年龄控件
private EditText ageView;
//性别控件
private EditText sexView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_update_dialog);
idView = (EditText) findViewById(R.id.update_edit_id);
nameView = (EditText) findViewById(R.id.update_edit_name);
ageView = (EditText) findViewById(R.id.update_edit_age);
sexView = (EditText) findViewById(R.id.update_edit_sex);
Button confirmBtn = (Button) findViewById(R.id.update_confirm);
Button cancelBtn = (Button) findViewById(R.id.update_cancel);
confirmBtn.setOnClickListener(this);
cancelBtn.setOnClickListener(this);
}
private void confirm() {
int id = Integer.valueOf(String.valueOf(idView.getText()));
String name = String.valueOf(nameView.getText());
int age = Integer.valueOf(String.valueOf(ageView.getText()));
String sex = String.valueOf(sexView.getText());
Person person = new Person(id, name, age, sex);
Intent intent = new Intent();
intent.putExtra("person", person);
setResult(UPDATE_RESULTCODE, intent);
finish();
}
private void cancel() {
setResult(UPDATE_RESULTCODE);
finish();
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.update_confirm:
confirm();
break;
case R.id.update_cancel:
cancel();
break;
default:
break;
}
}
}
ListAdapter.java
public class ListAdapter extends BaseAdapter {
private List<Person> list;
private LayoutInflater inflater;
public ListAdapter(List<Person> list, Context context) {
this.list = list;
this.inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public void setList(List<Person> list) {
this.list = list;
}
@Override
public int getCount() {
return list.size();
}
@Override
public Person getItem(int position) {
return list.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null)
convertView = inflater.inflate(R.layout.activity_main_list1, null);
TextView idView = (TextView) convertView.findViewById(R.id.text_id);
TextView nameView = (TextView) convertView.findViewById(R.id.text_name);
TextView ageView = (TextView) convertView.findViewById(R.id.text_age);
TextView sexView = (TextView) convertView.findViewById(R.id.text_sex);
Person person = list.get(position);
idView.setText(String.valueOf(person.getId()));
nameView.setText(person.getName());
ageView.setText(String.valueOf(person.getAge()));
sexView.setText(String.valueOf(person.getSex()));
return convertView;
}
}
MainActivity.java
/**
* SQLite 数据库操作 增删改查
*/
public class DBMainActivity extends AppCompatActivity implements View.OnClickListener {
private SQLiteHelper db;
private ListAdapter listAdapter;
private static final int INSERT_REQUESTCODE = 1;
private static final int INSERT_RESULTCODE = 11;
private static final int DELETE_REQUESTCODE = 2;
private static final int DELETE_RESULTCODE = 22;
private static final int UPDATE_REQUESTCODE = 3;
private static final int UPDATE_RESULTCODE = 33;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_dbmain);
db = new SQLiteHelper(this, 1);
Button insertBtn = (Button) findViewById(R.id.btn_insert);
Button deleteBtn = (Button) findViewById(R.id.btn_delete);
Button updateBtn = (Button) findViewById(R.id.btn_update);
Button queryBtn = (Button) findViewById(R.id.btn_query);
insertBtn.setOnClickListener(this);
deleteBtn.setOnClickListener(this);
updateBtn.setOnClickListener(this);
queryBtn.setOnClickListener(this);
listAdapter = new ListAdapter(new ArrayList<Person>(), this);
ListView listView = (ListView) findViewById(R.id.list_data);
listView.setAdapter(listAdapter);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btn_insert:
insert();
break;
case R.id.btn_delete:
delete();
break;
case R.id.btn_update:
update();
break;
case R.id.btn_query:
query();
break;
default:
break;
}
}
private void insert() {
Intent intent = new Intent(this, InsertDialog.class);
startActivityForResult(intent, INSERT_REQUESTCODE);
}
private void delete() {
Intent intent = new Intent(this, DeleteDialog.class);
startActivityForResult(intent, DELETE_REQUESTCODE);
}
private void update() {
Intent intent = new Intent(this, UpdateDialog.class);
startActivityForResult(intent, UPDATE_REQUESTCODE);
}
private void query() {
List<Person> list = db.queryAllPerson();
loadData(list);
}
private void loadData(List<Person> list) {
listAdapter.setList(list);
listAdapter.notifyDataSetChanged();
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
switch (requestCode) {
case INSERT_REQUESTCODE:
if (resultCode == INSERT_RESULTCODE) {
if (data != null) {
db.insertPerson((Person) data.getSerializableExtra("person"));
Toast.makeText(this, "Insert Success!", Toast.LENGTH_SHORT).show();
query();
} else {
Toast.makeText(this, "Insert Cancel!", Toast.LENGTH_SHORT).show();
}
}
break;
case DELETE_REQUESTCODE:
if (resultCode == DELETE_RESULTCODE) {
if (data != null) {
int id = data.getIntExtra("id", -1);
if (id != -1) {
if (db.queryPersonById(id) != null) {
db.deletePersonById(id);
Toast.makeText(this, "Delete Success!", Toast.LENGTH_SHORT).show();
query();
} else {
Toast.makeText(this, "Delete Fail! id" + id + "not exist", Toast.LENGTH_SHORT).show();
}
} else {
Toast.makeText(this, "Delete Fail!", Toast.LENGTH_SHORT).show();
}
} else {
Toast.makeText(this, "Delete Cancel!", Toast.LENGTH_SHORT).show();
}
}
break;
case UPDATE_REQUESTCODE:
if (resultCode == UPDATE_RESULTCODE) {
if (data != null) {
Person person = (Person) data.getSerializableExtra("person");
int id = person.getId();
if (db.queryPersonById(person.getId()) != null) {
db.updatePerson(person);
Toast.makeText(this, "Update Success!", Toast.LENGTH_SHORT).show();
query();
} else {
Toast.makeText(this, "Update Fail! id" + id + "not exist", Toast.LENGTH_SHORT).show();
}
} else {
Toast.makeText(this, "Update Cancel!", Toast.LENGTH_SHORT).show();
}
}
break;
default:
break;
}
}
}