安卓增删改查

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="hhh.com.can">

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="点餐管理系统"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">

    </activity>

    <activity android:name=".find">

    </activity>

    <activity android:name=".login">
        <intent-filter>
            <action android:name="android.intent.action.MAIN"/>

            <category android:name="android.intent.category.LAUNCHER"/>
        </intent-filter>
    </activity>

    <activity android:name=".register">

    </activity>

    <activity android:name=".add">

    </activity>

    <activity android:name=".alt">

    </activity>
</application>

</manifest>

import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class add extends AppCompatActivity implements View.OnClickListener {
    private EditText et_name,et_price;
    private String name,price;
    private SharedPreferences sp;
    private SharedPreferences.Editor editor;
    private int num = 0;
    private RelativeLayout back_layout;
    private SQLiteDatabase db;
    private static String TABLE_NAME = "cais";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add);
        initView();
    }

    private void initView(){
        et_price = (EditText) findViewById(R.id.et_price);
        et_name = (EditText) findViewById(R.id.et_name);

        Button bt_submit = (Button) findViewById(R.id.bt_submit);
        bt_submit.setOnClickListener(this);
        sp = getSharedPreferences("user",MODE_PRIVATE);
        editor = sp.edit();
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.bt_submit:
                price = et_price.getText().toString().trim();
                name = et_name.getText().toString().trim();

                if(price.equals("")||name.equals("")){
                    Toast.makeText(this,"信息不完整！",Toast.LENGTH_SHORT).show();
                    return;
                }else{
                        MySqlite mySQLite = new MySqlite(this, 1);
                        db= mySQLite.getWritableDatabase();
                        //使用ContentValues添加数据
                        ContentValues values=new ContentValues();
                        values.put("name",name);
                        values.put("price",price);

                        db.insert(TABLE_NAME, null, values);
                        db.close();
                        Toast.makeText(this,"添加成功",Toast.LENGTH_SHORT).show();
                        finish();
                }
                break;

        }
    }
}

package hhh.com.can;

import android.content.ContentValues;
import android.content.SharedPreferences;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RelativeLayout;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class alt extends AppCompatActivity implements View.OnClickListener {
    EditText et_name,et_price;
    Button bt_alt;
    SharedPreferences sp;
    SharedPreferences.Editor editor;
    String name,price,id;
    RelativeLayout back_layout;
    private static String TABLE_NAME="cais";
    private MySqlite mySqlite;
    private SQLiteDatabase db;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_alt);

        sp = getSharedPreferences("user",MODE_PRIVATE);
        editor = sp.edit();
        et_name = (EditText) findViewById(R.id.et_name);
        et_price = (EditText) findViewById(R.id.et_price);

        name = sp.getString("name","");
        id = sp.getString("id","");
        price = sp.getString("price","");

        et_name.setText(name);
        et_price.setText(price);

        bt_alt = (Button) findViewById(R.id.bt_alt);
        bt_alt.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.bt_alt:
                price = et_price.getText().toString().trim();
                name = et_name.getText().toString().trim();
                if(price.equals("")||name.equals("")){
                    Toast.makeText(this,"信息不完整！",Toast.LENGTH_SHORT).show();
                    return;
                }
                mySqlite=new MySqlite(this,1);
                db=mySqlite.getWritableDatabase();
                ContentValues values=new ContentValues();
                values.put("name",name);
                values.put("price",price);

                db.update(TABLE_NAME,values,"id=?",new String[]{id});
                Toast.makeText(this,"修改成功",Toast.LENGTH_SHORT).show();
                finish();
                break;
        }
    }
package hhh.com.can;

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class find extends AppCompatActivity {
    private SharedPreferences sp;
    private TextView tv_name,tv_price;
    private List<Map<String,String>> list;
    private MyAdapter adapter;
    private SharedPreferences.Editor editor;
    private ListView lv_user;
    private static String TABLE_NAME = "cais";
    private MySqlite mySqlite;
    private SQLiteDatabase db;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_find);
        sp = getSharedPreferences("user",MODE_PRIVATE);
        editor = sp.edit();

        lv_user = (ListView) findViewById(R.id.lv_user);
        list = new ArrayList<>();
        getData();
        adapter = new MyAdapter(
                find.this,
                list,
                R.layout.item,
                new String[]{"name","price"},
                new int[]{R.id.tv_name,R.id.tv_price}
        );

        lv_user.setAdapter(adapter);

        lv_user.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
                deleteStudent(list.get(i).get("id"));
                Toast.makeText(find.this, "删除成功", Toast.LENGTH_SHORT).show();
                list.remove(i);
                adapter.notifyDataSetChanged();
                return true;
            }
        });

        lv_user.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                editor.putString("name",list.get(i).get("name"));
                editor.putString("price",list.get(i).get("price"));
                editor.putString("id", list.get(i).get("id"));
                editor.commit();
                Intent intent = new Intent(find.this,alt.class);
                startActivity(intent);
            }
        });
    }

    public void deleteStudent(String i){
        mySqlite=new MySqlite(this,1);
        db=mySqlite.getWritableDatabase();
        db.delete("cais","id=?",new String[]{i});
        db.close();
    }

    @Override
    protected void onResume() {
        super.onResume();
        getData();
        adapter = new MyAdapter(
                find.this,
                list,
                R.layout.item,
                new String[]{"name","price"},
                new int[]{R.id.tv_name,R.id.tv_price}
        );

        lv_user.setAdapter(adapter);
    }

    private class MyAdapter extends SimpleAdapter {
        public MyAdapter(Context context, List<? extends Map<String, ?>> data, int resource,
                         String[] from, int[] to) {
            super(context, data, resource, from, to);
        }

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            View v = super.getView(position, convertView, parent);
            tv_name = v.findViewById(R.id.tv_name);
            tv_price = v.findViewById(R.id.tv_price);

            tv_name.setText(list.get(position).get("name"));
            tv_price.setText(list.get(position).get("price"));
            return v;
        }
    }

    public List<Map<String,String>> getData(){
        list.clear();
        MySqlite mySQLite = new MySqlite(this, 1);
        SQLiteDatabase database = mySQLite.getReadableDatabase();
        Cursor cursor = database.rawQuery("select * from cais", null);
        System.out.println(cursor.getCount());
        while (cursor.moveToNext()) {
            String name = cursor.getString(cursor.getColumnIndex("name"));
            String price = cursor.getString(cursor.getColumnIndex("price"));
            String id = cursor.getString(cursor.getColumnIndex("id"));

            Map<String,String> map = new HashMap<>();
            map.put("name",name);
            map.put("price",price);
            map.put("id",id);

            list.add(map);
        }
        return list;
    }



}