3月11号（工程日志第五天）

所学时间：4小时

代码行数：413行

博客园数：1篇

所学知识：今天将学习了安卓开发对于数据库sqlite的增删改查操作，并学会了部分的试图修改操作。

MainActivity

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.annotation.SuppressLint;
import android.content.Intent;
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();

        @SuppressLint({"MissingInflatedId", "LocalSuppress"}) Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent();
                intent.setClass(MainActivity.this,MainActivity2.class);
                startActivity(intent);
            }
        });


        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();
    }
}

DBAdapter

package com.example.myapplication;
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);
        }
    }
}

People

package com.example.myapplication;

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;
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/teal_200"
    >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        >
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="30dp"
            android:textColor="@color/material_dynamic_neutral0"
            android:text="姓名:"/>

        <EditText
            android:id="@+id/e_xm"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:singleLine="true"
            />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        >
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="30dp"
            android:textColor="@color/material_dynamic_neutral0"
            android:text="班级:"/>

        <EditText
            android:id="@+id/e_nl"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:singleLine="true"
            />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        >
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="30dp"
            android:textColor="@color/material_dynamic_neutral0"
            android:text="学号:"/>

        <EditText
            android:id="@+id/e_sg"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:singleLine="true"
            />
    </LinearLayout>


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:gravity="center"
        >
        <Button
            android:id="@+id/b_add"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAlignment="center"
            android:layout_weight="1"
            android:textSize="16dp"
            android:text="添加数据"/>

        <Button
            android:id="@+id/b_allsee"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAlignment="center"
            android:layout_weight="1"
            android:textSize="16dp"
            android:text="全部显示"/>
        <Button
            android:id="@+id/b_clearall"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAlignment="center"
            android:layout_weight="1"
            android:textSize="16dp"
            android:text="清除显示"/>
        <Button
            android:id="@+id/b_delall"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAlignment="center"
            android:layout_weight="1"
            android:textSize="16dp"
            android:text="全部删除"/>
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        >

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="20dp"
            android:textColor="@color/material_dynamic_neutral0"
            android:text="ID:" />

        <EditText
            android:id="@+id/e_id"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="2"
            android:singleLine="true" />

        <Button
            android:id="@+id/b_delid"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:textAlignment="center"
            android:text="ID删除"/>
        <Button
            android:id="@+id/b_seeid"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:textAlignment="center"
            android:text="ID查询"/>
        <Button
            android:id="@+id/b_updid"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:textAlignment="center"
            android:text="ID更新"/>
    </LinearLayout>

    <TextView
        android:id="@+id/t_1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text=""
        />
    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="跳转">

    </Button>

</LinearLayout>