ADD file via upload

EatWhatActivity.java

@@ -0,0 +1,132 @@
+package com.example.WhatMeal;
+
+import android.content.ContentValues;
+import android.content.Intent;
+import android.content.Context;
+import android.database.Cursor;
+import android.database.sqlite.SQLiteDatabase;
+import android.database.sqlite.SQLiteOpenHelper;
+import androidx.appcompat.app.AppCompatActivity;
+import android.os.Bundle;
+import android.view.View;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.TextView;
+import android.widget.Toast;
+
+public class MenuActivity extends AppCompatActivity implements View.OnClickListener
+{
+    MyHelper myHelper;
+    private Button back;
+    private EditText mEtName;
+    private EditText mEtStore;
+    private TextView mShow;
+    private Button mBtnAdd;
+    private Button mBtnQuery;
+    private Button mBtnUpdate;
+    private Button mBtnDelete;
+    @Override
+    protected void onCreate(Bundle savedInstanceState)
+    {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_menu);
+        myHelper = new com.example.WhatMeal.MenuActivity.MyHelper(this);
+        back = (Button) findViewById(R.id.back);
+        back.setOnClickListener(new View.OnClickListener()
+        {
+            @Override
+            public void onClick(View v)
+            {
+                Intent intent = new Intent(MenuActivity.this, MainActivity.class);
+                startActivity(intent);
+            }
+        });
+        init();//初始化控件
+    }
+    private void init()
+    {
+        mEtName = (EditText) findViewById(R.id.et_name);
+        mEtStore = (EditText) findViewById(R.id.et_store);
+        mShow = (TextView) findViewById(R.id.show);
+        mBtnAdd = (Button) findViewById(R.id.btn_add);
+        mBtnQuery = (Button) findViewById(R.id.btn_query);
+        mBtnUpdate = (Button) findViewById(R.id.btn_update);
+        mBtnDelete = (Button) findViewById(R.id.btn_delete);
+        mBtnAdd.setOnClickListener(this);
+        mBtnQuery.setOnClickListener(this);
+        mBtnUpdate.setOnClickListener(this);
+        mBtnDelete.setOnClickListener(this);
+    }
+    @Override
+    public void onClick(View v)
+    {
+        String name;
+        String store;
+        SQLiteDatabase db;
+        ContentValues values;
+        switch (v.getId())
+        {
+            case R.id.btn_add: //添加数据
+                name = mEtName.getText().toString();
+                store = mEtStore.getText().toString();
+                db = myHelper.getWritableDatabase();//获取可读写SQLiteDatabase对象
+                values = new ContentValues();       //创建ContentValue对象
+                values.put("foodname", name);       //将数据添加到ContentValues对象
+                values.put("foodstore", store);
+                db.insert("information", "name", values);
+                Toast.makeText(this, "信息已添加", Toast.LENGTH_SHORT).show();
+                db.close();
+                break;
+            case R.id.btn_query: //查询数据
+                db = myHelper.getReadableDatabase();
+                Cursor cursor = db.query("information", null, null, null, null, null, null);
+                if(cursor.getCount() == 0)
+                {
+                    mShow.setText("");
+                    Toast.makeText(this, "没有数据", Toast.LENGTH_SHORT).show();
+                }
+                else
+                {
+                    cursor.moveToFirst();
+                    mShow.setText("菜名：" + cursor.getString(1) + "；店名：" + cursor.getString(2));
+                }
+                while (cursor.moveToNext())
+                {
+                    mShow.append("\n" + "菜名：" + cursor.getString(1) + "；店名：" + cursor.getString(2));
+                }
+                cursor.close();
+                db.close();
+                break;
+            case R.id.btn_update: //修改数据
+                db = myHelper.getWritableDatabase();
+                values = new ContentValues();
+                values.put("foodstore", store = mEtStore.getText().toString());
+                db.update("information", values, "foodname=?", new String[]{mEtName.getText().toString()});
+                Toast.makeText(this, "信息已修改", Toast.LENGTH_SHORT).show();
+                db.close();
+                break;
+            case R.id.btn_delete: //删除数据
+                db = myHelper.getWritableDatabase();
+                db.delete("information", null, null);
+                Toast.makeText(this, "信息已删除", Toast.LENGTH_SHORT).show();
+                mShow.setText("");
+                db.close();
+                break;
+        }
+    }
+
+    static class MyHelper extends SQLiteOpenHelper
+    {
+        public MyHelper(Context context)    //数据库第一次被创建时调用方法
+        {
+            super(context, "EatWhat.db", null, 2);
+        }
+        @Override
+        public void onCreate(SQLiteDatabase db) //初始化数据库的表结构，执行一条建表的SQL语句
+        {
+            db.execSQL("CREATE TABLE information(_id INTEGER PRIMARY KEY AUTOINCREMENT, foodname VARCHAR(40), foodstore VARCHAR(40))");
+        }
+        @Override
+        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {} //当数据库的版本号增加时调用
+    }
+}