第四周星期三每日总结

  今日学习了Android Studio的数据库SQLite的查询操作，用以完善每日打卡app的查看打卡记录功能。查询功能的实质是利用

Cursor cursor = db.rawQuery("select * from wm where biao = ? ", new String[]{n_search});语句寻找表中与之匹配的记录。

cursor.moveToNext()语句实现光标的下移操作。

cursor.getString(i)语句得到表中第i-1列的数据
最后将得到的数据显示在Textview中。
查询部分代码：
activity_revise.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    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"
    tools:context=".revise">

    <LinearLayout
        android:id="@+id/linearLayout3"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">
        <!-- 用户名部分 -->
        <TextView
            android:layout_width="fill_parent"
            android:layout_height="35dp"
            android:text="请输入打卡关键字进行查询:" />

        <EditText
            android:id="@+id/search"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="" />
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal">
            <Button
                android:id="@+id/revis"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:layout_margin="5dp"
                android:text="查询"
                />
            <Button
                android:id="@+id/index"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:layout_margin="5dp"
                android:text="首页"
                />
        </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:layout_weight="1"
                android:id="@+id/tv_show"
                android:textSize="20sp"
                android:gravity="center_horizontal"/>
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:id="@+id/tv_showAge"
                android:textSize="20sp"
                android:gravity="center_horizontal"
                />
        </LinearLayout>
    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

revise.java

package com.example.null001;
import android.content.Intent;
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;

import androidx.appcompat.app.AppCompatActivity;

public class revise extends AppCompatActivity {
    final Mysql dbHelper = new Mysql(this,"wm",null,1);
    private Button searchButton, indexButton;
    private EditText search;
    private TextView tv_show, tv_showAge;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_revise);
        searchButton = findViewById(R.id.revis);
        indexButton = findViewById(R.id.index);
        search = findViewById(R.id.search);
        tv_show = findViewById(R.id.tv_show);
        tv_showAge = findViewById(R.id.tv_showAge);
        searchButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                String n_search = search.getText().toString();
                tv_show.setText(null);
                if (n_search.equals("")) {
                    myShow();

                    db.close();
                } else {
                    tv_show.setText("关键字");
                    tv_showAge.setText("内容");
                    Cursor cursor = db.rawQuery("select * from wm where biao = ? ", new String[]{n_search});

                    while (cursor.moveToNext()) {
                        String newbiao = cursor.getString(3);
                        String newnei = cursor.getString(4);
                        tv_show.setText(tv_show.getText() + "\n" + newbiao);
                        tv_showAge.setText(tv_showAge.getText() + "\n" + newnei);
                    }

                    cursor.close();
                    db.close();
                }
            }
        });
        indexButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Intent intent = new Intent();
                intent.setClass(revise.this,Welcome.class);          //跳转到注册页面
                startActivity(intent);
                Toast.makeText(revise.this,"返回首页！",Toast.LENGTH_SHORT).show();
            }
        });
    }
    public void myShow(){
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        tv_show.setText("关键字");
        tv_showAge.setText("内容");
        Cursor cursor = db.rawQuery("select * from wm", null);

        while (cursor.moveToNext()) {
            String newName = cursor.getString(3);
            String newAge = cursor.getString(4);
            tv_show.setText(tv_show.getText() + "\n" + newName);
            tv_showAge.setText(tv_showAge.getText() + "\n" + newAge);
        }
        cursor.close();
    }
}