在Android中，可以使用SQLite数据库来存储和查询数据。以下是一个简单的示例，演示如何查询并显示数据库中的数据：
首先，在Android项目的app/build.gradle文件中添加SQLite依赖项：dependencies { implementation 'androidx.sqlite:sqlite:2.1.0' implementation 'androidx.sqlite:sqlite-framework:2.1.0'}DatabaseHelper类来管理数据库的创建和升级：import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DatabaseHelper extends SQLiteOpenHelper { private static final String DATABASE_NAME = "mydatabase.db"; private static final int DATABASE_VERSION = 1; private static final String TABLE_NAME = "mytable"; private static final String COLUMN_ID = "id"; private static final String COLUMN_NAME = "name"; private static final String COLUMN_AGE = "age"; public DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { String createTableQuery = "CREATE TABLE " + TABLE_NAME + "(" + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," + COLUMN_NAME + " TEXT," + COLUMN_AGE + " INTEGER)"; db.execSQL(createTableQuery); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { String dropTableQuery = "DROP TABLE IF EXISTS " + TABLE_NAME; db.execSQL(dropTableQuery); onCreate(db); } public Cursor getAllData() { SQLiteDatabase db = this.getReadableDatabase(); return db.query(TABLE_NAME, null, null, null, null, null, null); }}DatabaseHelper类并查询数据：import androidx.appcompat.app.AppCompatActivity;import android.database.Cursor;import android.os.Bundle;import android.widget.TextView;public class MainActivity extends AppCompatActivity { private TextView textViewData; private DatabaseHelper databaseHelper; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); textViewData = findViewById(R.id.text_view_data); databaseHelper = new DatabaseHelper(this); Cursor cursor = databaseHelper.getAllData(); StringBuilder stringBuilder = new StringBuilder(); if (cursor.moveToFirst()) { do { String name = cursor.getString(cursor.getColumnIndex(DatabaseHelper.COLUMN_NAME)); int age = cursor.getInt(cursor.getColumnIndex(DatabaseHelper.COLUMN_AGE)); stringBuilder.append("Name: ").append(name).append(", Age: ").append(age).append("\n"); } while (cursor.moveToNext()); } textViewData.setText(stringBuilder.toString()); cursor.close(); databaseHelper.close(); }}activity_main.xml中添加一个TextView控件用于显示数据：<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" android:orientation="vertical" android:padding="16dp"> <TextView android:id="@+id/text_view_data" android:layout_width="match_parent" android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" /></LinearLayout>这样，当应用程序启动时，它将查询数据库并在TextView中显示数据。请确保在查询数据库后关闭游标和数据库连接，以避免资源泄漏。
