第九次作业

package com.example.myapplication;
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.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 {
    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);
    }
    public void onClick(View view){
        String name,phone;
        SQLiteDatabase db;
        ContentValues values;
        switch (view.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_LONG).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_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;
            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_LONG).show();
                db.close();
                break;
            case R.id.btn_delete:
                db=myHelper.getWritableDatabase();
                db.delete("information","name=?",new String[]{mEtName.getText().toString()});
                Toast.makeText(this,"信息已删除",Toast.LENGTH_LONG).show();
                mTvShow.setText("");
                db.close();
                break;
        }
    }
    class MyHelper extends SQLiteOpenHelper{
        public MyHelper(Context context){
            super(context,"itcast.db",null,1);
        }
        public void onCreate(SQLiteDatabase db){
            db.execSQL("CREATE TABLE information(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20),phone VARCHAR(20))");
        }
        public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion){

        }
    }
}


<?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"
    tools:context=".MainActivity"
    android:padding="16dp"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="130dp"
        android:orientation="horizontal"
        >
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="姓 名："
            android:textSize="18sp"
            />

        <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" />
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_marginTop="15dp"
        >
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="电 话："
            android:textSize="18sp"
            />

        <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" />
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="15dp"
        >
        <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="#E6CAFF"
            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="#E6CAFF"
            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_marginRight="2dp"
            android:layout_weight="1"
            android:background="#E6CAFF"
            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_marginTop="25dp"
        android:textSize="20sp"
        />

</LinearLayout>