第九次作业

<?xml version="1.0" encoding="utf-8"?><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"    tools:context="com.example.myapplication.MainActivity">    <LinearLayout        android:id="@+id/linearlayout1"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_marginTop="140dp"        android:orientation="horizontal">        <TextView            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="姓名："            android:textSize="55px"/>        <EditText            android:id="@+id/et_name"            android:layout_height="wrap_content"            android:layout_width="0dp"            android:layout_weight="2"            android:hint="请输入姓名"/>    </LinearLayout>    <LinearLayout        android:id="@+id/linearlayout2"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_below="@+id/linearlayout1"        android:orientation="horizontal">        <TextView            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="电话："            android:textSize="55px"/>        <EditText            android:id="@+id/et_phone"            android:layout_height="wrap_content"            android:layout_width="0dp"            android:layout_weight="2"            android:hint="请输入电话"/>    </LinearLayout>    <LinearLayout        android:id="@+id/linearlayout3"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_below="@+id/linearlayout2"        android:orientation="horizontal">        <Button            android:id="@+id/btn_add"            android:layout_height="wrap_content"            android:layout_width="0dp"            android:layout_weight="1"            android:text="添加"/>        <Button            android:id="@+id/btn_query"            android:layout_height="wrap_content"            android:layout_width="0dp"            android:layout_weight="1"            android:text="查询"/>        <Button            android:id="@+id/btn_update"            android:layout_height="wrap_content"            android:layout_width="0dp"            android:layout_weight="1"            android:text="修改"/>        <Button            android:id="@+id/btn_delect"            android:layout_height="wrap_content"            android:layout_width="0dp"            android:layout_weight="1"            android:text="删除"/>    </LinearLayout>    <TextView        android:id="@+id/tv_show"        android:layout_height="wrap_content"        android:layout_width="match_parent"        android:layout_below="@+id/linearlayout3"        android:textSize="15dp"/></RelativeLayout>

package com.example.myapplication;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;import androidx.appcompat.app.AppCompatActivity;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 mBtnDelect;    @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);        mBtnDelect = (Button) findViewById(R.id.btn_delect);        mBtnAdd.setOnClickListener(this);        mBtnQuery.setOnClickListener(this);        mBtnUpdate.setOnClickListener(this);        mBtnDelect.setOnClickListener(this);    }    @Override    public void onClick(View v){        String name,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.getReadableDatabase();                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_delect :                db = myHelper.getReadableDatabase();                db.delete("information","name = ?",new String[]{                        mEtName.getText().toString()});                Toast.makeText(this,"信息已删除",Toast.LENGTH_SHORT).show();                db.close();                break;        }    }    class MyHelper extends SQLiteOpenHelper{        public MyHelper(Context context){            super(context,"itcast.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){        }    }}

 

来源：https://www.cnblogs.com/xiaohusha/p/11809620.html