安卓小记——SQlite(增删改查)

安卓

效果图

布局

首先呢，我们要完成的是页面的布局

<RelativeLayout 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:background="@drawable/bg"
    android:paddingLeft="16dp"
    android:paddingTop="16dp"
    android:paddingRight="16dp"
    android:paddingBottom="16dp"
    tools:context=".MainActivity">

    <LinearLayout
        android:id="@+id/ll_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_above="@+id/ll_phone"
        android:layout_alignStart="@+id/ll_btn"
        android:layout_alignLeft="@+id/ll_btn">

        <EditText
            android:id="@+id/et_name"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="请输入姓名"
            android:textSize="16sp" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="姓 名 ："
            android:textSize="18sp" />
    </LinearLayout>

    <LinearLayout
        android:id="@+id/ll_phone"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_above="@+id/ll_btn"
        android:layout_alignStart="@+id/ll_name"
        android:layout_alignLeft="@+id/ll_name"
        android:layout_marginBottom="10dp">

        <EditText
            android:id="@+id/et_phone"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="请输入手机号码"
            android:textSize="16sp" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="电 话 ："
            android:textSize="18sp" />
    </LinearLayout>

    <LinearLayout
        android:id="@+id/ll_btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true">

        <Button
            android:id="@+id/btn_add"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginRight="2dp"
            android:layout_weight="1"
            android:background="#B9B9FF"
            android:text="添加"
            android:textSize="18sp" />

        <Button
            android:id="@+id/btn_query"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginRight="2dp"
            android:layout_weight="1"
            android:background="#DCB5FF"
            android:text="查询"
            android:textSize="18sp" />

        <Button
            android:id="@+id/btn_update"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginRight="2dp"
            android:layout_weight="1"
            android:background="#E6CAFF"
            android:text="修改"
            android:textSize="18sp" />

        <Button
            android:id="@+id/btn_delete"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#ACD6FF"
            android:text="删除"
            android:textSize="18sp" />
    </LinearLayout>

    <TextView
        android:id="@+id/tv_show"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/ll_btn"
        android:layout_marginTop="25dp"
        android:textSize="20sp" />
</RelativeLayout>

SQLite类

页面部分完成后，就是创建SQLite类，以及功能的实现

package com.cbz.blogsqlite;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import androidx.annotation.Nullable;

public class MyHelper extends SQLiteOpenHelper {

    public MyHelper(@Nullable Context context) {
        super(context,"itcast.db",null,1);
    }

    //第一次创建数据库时运行
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE information(_id INTEGER PRIMARY KEY AUTOINCREMENT, name VARCHAR(20), phone VARCHAR(20))");

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

Main

SQLite类写完后就是对它的调用了

package com.cbz.blogsqlite;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentValues;
import android.database.Cursor;
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;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity  implements View.OnClickListener {

    private MyHelper myHelper;
    private EditText mEtName;
    private EditText mEtPhone;
    private TextView mTvShow;
    private Button mBtnAdd;
    private Button mBtnDelete;
    private Button mBtnUpdate;
    private Button mBtnQuery;
    private String name;
    private String phone;
    private SQLiteDatabase db;
    private ContentValues values;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        myHelper = new MyHelper(this);
        init();//初始化
        
    }

    private void init() {
        mEtName = findViewById(R.id.et_name);
        mEtPhone = findViewById(R.id.et_phone);
        mTvShow = findViewById(R.id.tv_show);
        mBtnAdd = findViewById(R.id.btn_add);
        mBtnDelete = findViewById(R.id.btn_delete);
        mBtnUpdate = findViewById(R.id.btn_update);
        mBtnQuery = findViewById(R.id.btn_query);
        mBtnAdd.setOnClickListener(this);
        mBtnDelete.setOnClickListener(this);
        mBtnUpdate.setOnClickListener(this);
        mBtnQuery.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){

            case R.id.btn_add://添加
                name = mEtName.getText().toString();
                phone = mEtPhone.getText().toString();
                //获取可读数据库对象
                db = myHelper.getReadableDatabase();

                values = new ContentValues();
                values.put("name",name);
                values.put("phone",phone);

                db.insert("information",null, values);
                db.close();

                break;
            case R.id.btn_delete://删除
                db = myHelper.getWritableDatabase();
                db.delete("information",null,null);
                Toast.makeText(this,"信息已删除",Toast.LENGTH_LONG).show();
                mTvShow.setText("");
                db.close();
                break;
            case R.id.btn_update://修改
                db = myHelper.getWritableDatabase();
                values = new ContentValues();
                values.put("phone",phone=mEtPhone.getText().toString());
                db.update("information",values,"name=?",new String[]{mEtName.getText().toString()});
                db.close();

                break;
            case R.id.btn_query://查询

                 db = myHelper.getReadableDatabase();
                Cursor cursor = db.query("information", null, null, null, null, null, null);
                if(cursor.getCount() == 0){
                    mTvShow.setText("");
                    Toast.makeText(this,"没有数据",Toast.LENGTH_LONG).show();
                }else {
                    cursor.moveToFirst();
                    mTvShow.setText("Name:"+cursor.getString(1)+"Tel:"+cursor.getString(2));

                }
                while (cursor.moveToNext()){
                    mTvShow.append("\n"+"Name:"+cursor.getString(1)+"Tel:"+cursor.getString(2));

                }
                cursor.close();
                db.close();
                break;
        }
    }
}

完成后的展示

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最后编辑时间为: Jun 16, 2020 at 03:30 pm