工具：Android Studio

activity_main.xml

xmlns:app="http://schemas.android.com/apk/res-auto"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:background="@drawable/bg"

android:paddingBottom="16dp"

android:paddingLeft="16dp"

android:paddingRight="16dp"

android:paddingTop="16dp"

tools:context=".MainActivity">

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:id="@+id/ll_name"

android:layout_above="@+id/ll_phone"

android:layout_alignLeft="@+id/ll_btn"

android:layout_alignStart="@+id/ll_btn">

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textSize="18sp"

android:hint="姓 名："/>

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:id="@+id/et_name"

android:textSize="16sp"

android:hint="请输入姓名："/>

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:id="@+id/ll_phone"

android:layout_marginBottom="10dp"

android:layout_above="@+id/ll_btn"

android:layout_alignLeft="@id/ll_name"

android:layout_alignStart="@id/ll_name">

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textSize="18sp"

android:text="电 话："/>

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:id="@+id/et_phone"

android:textSize="16sp"

android:hint="请输入手机号码"/>

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:id="@+id/ll_btn"

android:layout_centerVertical="true">

android:layout_width="0dp"

android:layout_height="wrap_content"

android:id="@+id/btn_add"

android:layout_weight="1"

android:textSize="18sp"

android:background="#DCB5FF"

android:layout_marginRight="2dp"

android:text="添加"/>

android:layout_width="0dp"

android:layout_height="wrap_content"

android:id="@+id/btn_update"

android:layout_weight="1"

android:textSize="18sp"

android:background="#E6CAFF"

android:layout_marginRight="2dp"

android:text="修改"/>

android:layout_width="0dp"

android:layout_height="wrap_content"

android:id="@+id/btn_delete"

android:layout_weight="1"

android:textSize="18sp"

android:background="#ACD6FF"

android:layout_marginRight="2dp"

android:text="删除"/>

android:layout_width="0dp"

android:layout_height="wrap_content"

android:id="@+id/btn_query"

android:layout_weight="1"

android:textSize="18sp"

android:background="#DCB5FF"

android:layout_marginRight="2dp"

android:text="查询"/>

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:id="@+id/tv_show"

android:layout_marginTop="25dp"

android:layout_below="@id/ll_btn"

android:textSize="20sp"/>

MainActivity.java

package cn.itcast.directory;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentValues;

import android.content.Context;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteOpenHelper;

import android.view.View;

import android.widget.EditText;

import android.widget.Button;

import android.widget.TextView;

import android.widget.Toast;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

MyHelper myHelper;

private EditText mEtName;

private EditText mEtPhone;

private TextView mTvShow;

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_main);

myHelper = new MyHelper(this);

init();

private void init(){

mEtName = (EditText) findViewById(R.id.et_name);

mEtPhone = (EditText) findViewById(R.id.et_phone);

mTvShow = (TextView) findViewById(R.id.tv_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 phone;

SQLiteDatabase db;

ContentValues values;

switch (v.getId()){

case R.id.btn_add:

name = mEtName.getText().toString();

phone = mEtPhone.getText().toString();

db = myHelper.getWritableDatabase();

values = new ContentValues();

values.put("name",name);

values.put("phone",phone);

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

Toast.makeText(this,"信息已添加",Toast.LENGTH_SHORT).show();

db.close();

break;

case R.id.btn_query:

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_SHORT).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;

case R.id.btn_update:

db = myHelper.getWritableDatabase();

values = new ContentValues();

values.put("phone",phone = mEtPhone.getText().toString());

db.update("information",values,"name=?",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:

db = myHelper.getWritableDatabase();

db.delete("information",null,null);

Toast.makeText(this,"信息已删除",Toast.LENGTH_SHORT).show();

mTvShow.setText("");

db.close();

break;

}

}

class MyHelper extends SQLiteOpenHelper{

public MyHelper(Context context){

super(context,"example.db",null,1);

}

@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){

}

}

}