MainActivity
package com.example.admin.myapplication; import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.graphics.Color; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.EditText; import android.widget.LinearLayout; import android.widget.ListView; import android.widget.TextView; import android.widget.Toast; import java.util.ArrayList; import java.util.List; import java.util.Random; public class MainActivity extends AppCompatActivity { StudentHelper helper; EditText extext; LinearLayout ll; ListView lv; List<Person> personinfos; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.adbdemo); helper=new StudentHelper(this); extext=(EditText)findViewById(R.id.extext); ll=(LinearLayout)findViewById(R.id.ll); lv=(ListView)findViewById(R.id.lv); } class Myad extends BaseAdapter{ @Override public int getCount() { return personinfos.size(); } @Override public Object getItem(int position) { return null; } @Override public long getItemId(int position) { return 0; } @Override public View getView(int position, View convertView, ViewGroup parent) { TextView tv=new TextView(MainActivity.this); tv.setText(personinfos.get(position).toString()); tv.setTextSize(25); return null; } } public void Insert(View v){ SQLiteDatabase db=helper.getWritableDatabase(); //db.execSQL("insert into info(name,phone) values(\"zhangsan\",\"110\")"); Random rm=new Random(); ContentValues values=new ContentValues(); values.put("name","lisi"+rm.nextInt(20)); values.put("phone","130"+rm.nextInt(200)); long l=db.insert("info",null,values); if(l==-1){ Toast.makeText(this, "insert--error", Toast.LENGTH_SHORT).show(); } else Toast.makeText(this, "insert--"+l, Toast.LENGTH_SHORT).show(); db.close(); } public void Update(View v){ SQLiteDatabase db=helper.getWritableDatabase(); // String sql="update info set name='lisi' where name=?"; ContentValues values=new ContentValues(); values.put("name","wangwu"); values.put("phone","130"); int i=db.update("info",values,"name=?",new String[]{"lisi7"}); Toast.makeText(this, "update--"+i, Toast.LENGTH_SHORT).show(); db.close(); } public void Delete(View v){ SQLiteDatabase db=helper.getWritableDatabase(); int i=db.delete("info","name=?",new String[]{"wangwu"}); if(i==0){ Toast.makeText(this, "数据库没有信息", Toast.LENGTH_SHORT).show(); } else Toast.makeText(this, "Delete--"+i, Toast.LENGTH_SHORT).show(); db.close(); } public void Select(View v){ SQLiteDatabase db=helper.getReadableDatabase(); personinfos=new ArrayList<Person>(); Cursor cr=db.query("info",null,null,null,null,null,null); while(cr.moveToNext()){ Person person=new Person(); person.setId(cr.getInt(0)); person.setName(cr.getString(1)); person.setPhone(cr.getString(cr.getColumnIndex("phone"))); personinfos.add(person); person=null; } cr.close(); // extext.setText(""); for(Person p:personinfos){ Log.e("abc",p.toString()); // extext.setText(extext.getText()+p.getName()+" "); TextView tv=new TextView(this); tv.setText(p.toString()); tv.setTextColor(Color.RED); tv.setTextSize(20); ll.addView(tv); } Toast.makeText(this, "Select--ok", Toast.LENGTH_SHORT).show(); db.close(); lv.setAdapter(new Myad()); } }Person
package com.example.admin.myapplication; /** * Created by admin on 2020/10/13. */ public class Person { private int id; private String name; private String phone; public String getPhone() { return phone; } public void setPhone(String phone) { this.phone = phone; } 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; } @Override public String toString() { return "Person{" + "id=" + id + ", name='" + name + '\'' + ", phone='" + phone + '\'' + '}'; } }StudentHelper
package com.example.admin.myapplication; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.util.Log; /** * Created by admin on 2020/10/13. */ public class StudentHelper extends SQLiteOpenHelper { public StudentHelper(Context context) { super(context, "person.db", null, 1); //版本号从1开始，只增不减 } @Override public void onCreate(SQLiteDatabase db) { Log.e("abc", "onCreate: " ); db.execSQL("create table info(_id integer primary key autoincrement,name varchar(20),phone varchar(20))"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.e("abc", "onUpgrade: " ); } }