android studio数据存储建立SQLite数据库实现增删查改

package com.example.shiyan6_sqlite;

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.database.sqlite.SQLiteDatabase.CursorFactory;

public class DBAdapter {

 private static final String DB_NAME = "student.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_BANJI = "banji";
 public static final String KEY_XUEHAO = "xuehao";

 private SQLiteDatabase db;
 private final Context context;
 private DBOpenHelper dbOpenHelper;

 public DBAdapter(Context _context) {
  context = _context;
 }

 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();
  }
 }


 public long insert(People people) {
  ContentValues newValues = new ContentValues();
  newValues.put(KEY_NAME, people.Name);
  newValues.put(KEY_BANJI, people.Banji);
  newValues.put(KEY_XUEHAO, people.Xuehao);

  return db.insert(DB_TABLE, null, newValues);
 }


 public People[] queryAllData() {
  Cursor results =  db.query(DB_TABLE, new String[] { KEY_ID, KEY_NAME, KEY_BANJI, KEY_XUEHAO},
    null, null, null, null, null);
  return ConvertToPeople(results);
 }

 public People[] queryOneData(long id) {
  Cursor results =  db.query(DB_TABLE, new String[] { KEY_ID, KEY_NAME, KEY_BANJI, KEY_XUEHAO},
    KEY_ID   "="   id, null, null, null, null);
  return ConvertToPeople(results);
 }

 @SuppressLint("Range")
 private People[] ConvertToPeople(Cursor cursor){
  int resultCounts = cursor.getCount();
  if (resultCounts == 0 || !cursor.moveToFirst()){
   return null;
  }
  People[] peoples = new People[resultCounts];
  for (int i = 0 ; i<resultCounts; i  ){
   peoples[i] = new People();
   peoples[i].ID = cursor.getInt(0);
   peoples[i].Name = cursor.getString(cursor.getColumnIndex(KEY_NAME));
   peoples[i].Banji = cursor.getString(cursor.getColumnIndex(KEY_BANJI));
   peoples[i].Xuehao = cursor.getString(cursor.getColumnIndex(KEY_XUEHAO));
   cursor.moveToNext();
  }
  return peoples;
 }

 public long deleteAllData() {
  return db.delete(DB_TABLE, null, null);
 }

 public long deleteOneData(long id) {
  return db.delete(DB_TABLE,  KEY_ID   "="   id, null);
 }

 public long updateOneData(long id , People people){
  ContentValues updateValues = new ContentValues();
  updateValues.put(KEY_NAME, people.Name);
  updateValues.put(KEY_BANJI, people.Banji);
  updateValues.put(KEY_XUEHAO, people.Xuehao);

  return db.update(DB_TABLE, updateValues,  KEY_ID   "="   id, null);
 }

 private static class DBOpenHelper extends SQLiteOpenHelper {

  public DBOpenHelper(Context context, String name, 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_BANJI  " text not null,"   KEY_XUEHAO   " 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);
  }
 }
}

package com.example.shiyan6_sqlite;

public class People {
 public int ID = -1;
 public String Name;
 public String Banji;
 public String Xuehao;

 @Override
 public String toString(){
  String result = "";
  result  = "ID："   this.ID   "，";
  result  = "姓名："   this.Name   "，";
  result  = "班级："   this.Banji   "， ";
  result  = "学号："   this.Xuehao;
  return result;
 }
}


MainActivity.java

package com.example.shiyan6_sqlite;

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 e_xm,e_nl,e_sg,e_id;
    TextView t_1;
    Button b_add,b_allsee,b_clearsee,b_alldel,b_delid,b_seeid,b_updid;
    DBAdapter dbAdapter;
    SQLiteDatabase db;

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

        e_xm=findViewById(R.id.e_xm);
        e_nl=findViewById(R.id.e_nl);
        e_sg=findViewById(R.id.e_sg);
        b_add=findViewById(R.id.b_add);
        b_allsee=findViewById(R.id.b_allsee);
        b_clearsee=findViewById(R.id.b_clearall);
        b_alldel=findViewById(R.id.b_delall);
        b_delid=findViewById(R.id.b_delid);
        b_seeid=findViewById(R.id.b_seeid);
        b_updid=findViewById(R.id.b_updid);
        e_id=findViewById(R.id.e_id);
        t_1=findViewById(R.id.t_1);
        dbAdapter=new DBAdapter(this);
        dbAdapter.open();


        b_add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                People t=new People();
                t.Name=e_xm.getText().toString();
                t.Banji=e_nl.getText().toString();
                t.Xuehao=e_sg.getText().toString();
                long colunm=dbAdapter.insert(t);
                if (colunm == -1 ){
                    t_1.setText("添加过程错误！");
                } else {
                    t_1.setText("成功添加数据，ID：" String.valueOf(colunm));
                }
            }
        });

        b_allsee.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                People [] peoples =dbAdapter.queryAllData();
                if (peoples == null){
                    t_1.setText("数据库中没有数据");
                    return;
                }
                String t="数据库:\n";
                for(int i=0;i<peoples.length;  i){
                    t =peoples[i].toString() "\n";
                }
                t_1.setText(t);
            }
        });

        b_clearsee.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                t_1.setText("");
            }
        });

        b_alldel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                dbAdapter.deleteAllData();
                t_1.setText("已删除所有数据！");
            }
        });

        b_delid.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int id=Integer.parseInt(e_id.getText().toString());
                long result=dbAdapter.deleteOneData(id);
                String msg = "删除ID为" e_id.getText().toString() "的数据"   (result>0?"成功":"失败");
                t_1.setText(msg);
            }
        });

        b_seeid.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int id=Integer.parseInt(e_id.getText().toString());
                People people[]=dbAdapter.queryOneData(id);
                if(people==null){
                    t_1.setText("Id为" id "的记录不存在！");
                }
                else{
                    t_1.setText("查询成功：\n" people[0].toString());
                }
            }
        });

        b_updid.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int id=Integer.parseInt(e_id.getText().toString());
                People t=new People();
                t.Name=e_xm.getText().toString();
                t.Banji=e_nl.getText().toString();
                t.Xuehao=e_sg.getText().toString();
                long n=dbAdapter.updateOneData(id,t);
                if (n<0){
                    t_1.setText("更新过程错误！");
                } else {
                    t_1.setText("成功更新数据，" String.valueOf(n) "条");
                }
            }
        });
    }

    @Override
    protected void onStop() {
        super.onStop();
        dbAdapter.close();
    }
}