所花时间：四十分钟

代码量：今天就写了一个查

package com.example.sqlitetest271;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

import com.example.sqlitetest271.bean.Student;
import com.example.sqlitetest271.util.ToastUtil;

import java.util.List;

public class QueryActivity extends AppCompatActivity {
private EditText etName;
private TextView tvResult;
private MySQLiteOpenHelper mMySQLiteOpenHelper;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_query);
etName = findViewById(R.id.et_name);
tvResult = findViewById(R.id.tv_result);
mMySQLiteOpenHelper = new MySQLiteOpenHelper(this);
}

public void query(View view) {
String name = etName.getText().toString().trim();
if (TextUtils.isEmpty(name)) {
// 查询所有数据
List<Student> students = mMySQLiteOpenHelper.queryAllFromDb();
showData(students);
return;
}

// 按姓名从数据库中查询
List<Student> students = mMySQLiteOpenHelper.queryFromDbByName(name);
showData(students);
}

private void showData(List<Student> students) {

// String result = "";
// for (Student stu : students) {
// result = result + "姓名：" + stu.getName() + "，学号：" + stu.getNumber() + ",性别："
// + stu.getGender() + ",分数：" + stu.getScore()+"\n";
// }

StringBuilder stringBuilder = new StringBuilder();
for (Student stu : students) {
stringBuilder.append("姓名：");
stringBuilder.append(stu.getName());
stringBuilder.append("，学号：");
stringBuilder.append(stu.getNumber());
stringBuilder.append(",性别：");
stringBuilder.append(stu.getGender());
stringBuilder.append(",分数：");
stringBuilder.append(stu.getScore() + "\n");
}

tvResult.setText(stringBuilder.toString());
}


}

知识点：