android studio实验之SQLite
数据库存储是 Android 数据存储中非常重要的内容，Android 提供一个轻量级的嵌入式数据库 SQLite，本次试验将学习如何通过代码建立数据库，并实现添加、删除、查找和更新等基本操作。
建立一个数据库并完成增删查改操作。
activity_main.xml
People.java
package com.example.sqliteexperiment;
public class People {
public int ID = -1;
public String Name;
public String Sex;
public String Department;
public String Monney;
@Override
public String toString() {
String result = "";
result += "ID:" + this.ID + ",";
result += "姓名" + this.Name + ",";
result += "性别" + this.Sex + ",";
result += "部门" + this.Department + ",";
result += "工资" + this.Monney ;
return result;
}
}
DBADapter.java
package com.example.sqliteexperiment;
import android.annotation.SuppressLint;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;
import androidx.annotation.Nullable;
public class DBAdapter {
private static final String DB_NAME="People.db";
private static final String DB_TABLE="peopleinfo";
private static final int DB_VERSION=1;
public static final String KEY_ID="_id";
public static final String KEY_NAME="name";
public static final String KEY_SEX="sex";
public static final String KEY_DEPARTMENT="department";
public static final String KEY_MONNEY="monney";
private SQLiteDatabase db;
private final Context context;
private DBOpenHelper dbOpenHelper;
private static final String DB_CREATE="create table "+
DB_TABLE+" ("+KEY_ID+" integer primary key autoincrement, "+
KEY_NAME+" text not null, "+KEY_SEX+" text not null, "+KEY_DEPARTMENT+
" text not null, "+KEY_MONNEY+" text not null);";
public DBAdapter(Context _context){
context=_context;
// Toast.makeText(context.getApplicationContext(),"nihao",Toast.LENGTH_SHORT).show();
}
public void close(){
if(db!=null){
db.close();
db=null;
}
}
public void open()throws SQLiteException{
dbOpenHelper=new DBOpenHelper(context,DB_NAME,null,DB_VERSION);
try{
db=dbOpenHelper.getWritableDatabase();
}catch(SQLiteException ex){
db=dbOpenHelper.getReadableDatabase();
}
}
private static class DBOpenHelper extends SQLiteOpenHelper{
public DBOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory,int version){
super(context,name,factory,version);
}
private static final String DB_CREATE="create table "+
DB_TABLE+" ("+KEY_ID+" integer primary key autoincrement, "+
KEY_NAME+" text not null, "+KEY_SEX+" text not null, "+KEY_DEPARTMENT+
" text not null, "+KEY_MONNEY+" text not null);";
@Override
public void onCreate(SQLiteDatabase _db){
_db.execSQL(DB_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase _db,int _oldVersion,int _newVersion){
_db.execSQL("DROP TABLE IF EXISTS "+DB_TABLE);
onCreate(_db);
}
};
/*
public long insert(People people){}
public long deleteAllData(){ }
public long deleteOneData(long id){ }
public People[] queryAllData(){ }
public People[] queryOneData(){ }
public long updateOneData(long id,People people){ }
private People[] ConvertTopeople(Cursor cursor){ }
*/
public long insert(People people){
ContentValues newValues=new ContentValues();
newValues.put(KEY_NAME,people.Name);
newValues.put(KEY_SEX,people.Sex);
newValues.put(KEY_DEPARTMENT,people.Department);
newValues.put(KEY_MONNEY,people.Monney);
return db.insert(DB_TABLE,null,newValues);
}
public People[] getOneData(long id){
Cursor results=db.query(DB_TABLE,new String[]{KEY_ID,KEY_NAME,KEY_SEX,KEY_DEPARTMENT,KEY_MONNEY},KEY_ID+"="+id,null,null,null,null);
return ConvertToPeople(results);
}
public People[] getAllData(){
Cursor results=db.query(DB_TABLE,new String[]{KEY_ID,KEY_NAME,KEY_SEX,KEY_DEPARTMENT,KEY_MONNEY},null,null,null,null,null);
return ConvertToPeople(results);
}
@SuppressLint("Range")
private People[] ConvertToPeople(Cursor cursor){//返回数据库全部数据
int resultCounts=cursor.getCount();
cursor.moveToFirst();
People[] peoples=new People[resultCounts];
for(int i=0;iMainActivity.java
package com.example.sqliteexperiment;
import androidx.appcompat.app.AppCompatActivity;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
EditText ED_name,ED_sex,ED_department,ED_monney,ED_id;
Button BT_add,BT_show,BT_clear_show,BT_clearall,BT_id_clear,BT_select,BT_id_update;
DBAdapter dbAdapter;
SQLiteDatabase db;
TextView lable;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DBAdapter dbadapter=new DBAdapter(MainActivity.this);
ED_name=findViewById(R.id.name);
ED_sex=findViewById(R.id.sex);
ED_department=findViewById(R.id.department);
ED_monney=findViewById(R.id.monney);
ED_id=findViewById(R.id.id);
BT_add=findViewById(R.id.bt_add);
BT_show=findViewById(R.id.bt_show);
BT_clear_show=findViewById(R.id.bt_clear_show);
BT_clearall=findViewById(R.id.bt_clearall);
BT_id_clear=findViewById(R.id.bt_id_clear);
BT_select=findViewById(R.id.bt_id_select);
BT_id_update=findViewById(R.id.bt_id_update);
lable=findViewById(R.id.lable);
dbAdapter=new DBAdapter(this);
dbAdapter.open();
BT_add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
People t=new People();
t.Name=ED_name.getText().toString();
t.Sex=ED_sex.getText().toString();
t.Department=ED_department.getText().toString();
t.Monney=ED_monney.getText().toString();
long colunm=dbAdapter.insert(t);
if(colunm==-1){
lable.setText("添加过程出错误");
}else{
lable.setText("成功添加数据,ID:"+String.valueOf(colunm));
}
}
});
BT_show.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
People[] peoples=dbAdapter.getAllData();
if(peoples.length==0){
lable.setText("数据库中没有数据");
}
String t="数据库：\n";
for(int i =0;i0?"成功":"失败");
lable.setText(msg);
}
});
BT_select.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
int id=Integer.parseInt(ED_id.getText().toString());
People people[]=dbAdapter.getOneData(id);
if(people==null){
lable.setText("ID为"+id+"的数据不存在");
}else{
lable.setText("查询成功：\n"+people[0].toString());
}
}
});
BT_id_update.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String s=ED_id.getText().toString();
if(s.equals("")){
lable.setText("未输入ID");
return;
}
int id=Integer.parseInt(ED_id.getText().toString());
People t=new People();
t.Name=ED_name.getText().toString();
t.Sex=ED_sex.getText().toString();
t.Department=ED_department.getText().toString();
t.Monney=ED_monney.getText().toString();
long n=dbAdapter.updateOneData(id,t);
if(n<0){
lable.setText("更新过程错误");
}else{
lable.setText("成功更新数据"+String.valueOf(n)+"条");
}
}
});
}
@Override
protected void onStop(){
super.onStop();
dbAdapter.close();
}
}