房间 (android) 中的数据访问对象 Class 未运行

Question

我正在开发一个任务应用程序，我想使用 Room 来保存我的数据。所以我创建了 3 个必需的 classes。但是，在我的 DAO class 中，我的 @Query 语句不起作用，正如它所说：

Cannot resolve certain symbols

我不知道为什么会这样。请帮忙

子任务详细信息（第一个 class）的代码：

package com.example.taskmasterv3;
     
    import androidx.room.ColumnInfo;
    import androidx.room.Entity;
    import androidx.room.PrimaryKey;
    import java.text.SimpleDateFormat;
    import java.util.Date;
     
    public class SubtaskDetails {
     
        String subbuname, subbupri, subbutime;
     
        public SubtaskDetails(String subbuname, String subbupri, String subbutime) {
            this.subbuname = subbuname;
            this.subbupri = subbupri;
            this.subbutime = subbutime;
        }
     
     
        @PrimaryKey(autoGenerate = true)
        public int uid;
     
        @ColumnInfo(name = "subtaskname")
        public String getSubbuname;
     
        @ColumnInfo(name = "priority")
        public String getSubbupri;
     
        @ColumnInfo(name = "time")
        public String getSubbutime;
     
        // for debugging purpose
        public String getDebugString(){
            return "UID: "+ uid + "Subtask Name : "+ getSubbuname + "Priority: "+getSubbupri + "Time required :"+getSubbutime;
        }                                    
    }

DAO 的代码Class:

package com.example.taskmasterv3;
              
    import java.util.List;
     
    import androidx.room.Dao;
    import androidx.room.Delete;
    import androidx.room.Insert;
    import androidx.room.Query;
     
    @Dao
    public interface UserDao {
        @Query("SELECT * FROM subtaskDetails")
        List<SubtaskDetails> getAll();
     
        @Query("SELECT * FROM subtaskDetails WHERE uid = :id")
        List<SubtaskDetails> loadAllById(int id);
     
        @Insert
        void insertAll(SubtaskDetails... users);
     
        @Delete
        void delete(SubtaskDetails user);
     
        @Query("DELETE FROM SubtaskDetails")
        void deleteAll();
    }

数据库的代码Class:

package com.example.taskmasterv3;
     
    import android.content.Context;
     
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
     
    import androidx.room.Database;
    import androidx.room.Room;
    import androidx.room.RoomDatabase;
     
    @Database(entities = {SubtaskDetails.class}, version = 1)
    public abstract class AppDatabase extends RoomDatabase {
     
        public abstract UserDao userDao();
     
     
        private static volatile AppDatabase INSTANCE;
        private static final int NUMBER_OF_THREADS = 1;
        static final ExecutorService databaseWriteExecutor =
                Executors.newFixedThreadPool(NUMBER_OF_THREADS);
     
     
        static AppDatabase getDatabase(final Context context) {
            if (INSTANCE == null) {
                synchronized (AppDatabase.class){
                    if (INSTANCE == null){
                        INSTANCE = Room.databaseBuilder(context.getApplicationContext(),AppDatabase.class, "subtaskDatabase").build();
                    }
                }
            }
            return INSTANCE;
        }

编辑:

Class 我正在尝试使用它的地方：

package com.example.taskmasterv3;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.room.Dao;
import androidx.room.Database;
import androidx.room.Delete;
import androidx.room.Entity;
import androidx.room.Insert;
import androidx.room.PrimaryKey;
import androidx.room.Query;
import androidx.room.Room;
import androidx.room.RoomDatabase;

import android.content.Intent;
import android.database.SQLException;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class SubtaskActivity extends AppCompatActivity {

    EditText etSubtaskName;
    EditText etTaskName;
    Button btnDone, btnCancel;
    RadioGroup radgrpPri, radgrpTime;
    RadioButton radbtnPriHigh, radbtnPriMed, radbtnPriLow, radbtnTimeMore, radbtnTimeMed, radbtnTimeLess;
    boolean priHigh, priMed, priLow, timeMore, timeMed, timeLess;
    String subtaskName;
    String pri;
    String time;


    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_subtask);

        btnDone = findViewById(R.id.btnDone);
        radgrpPri = findViewById(R.id.radgrpPri);
        radgrpTime = findViewById(R.id.radgrpTime);
        radbtnPriHigh = findViewById(R.id.radbtnPriHigh);
        radbtnPriMed = findViewById(R.id.radbtnPriMed);
        radbtnPriLow = findViewById(R.id.radbtnPriLow);
        radbtnTimeMore = findViewById(R.id.radbtnTimeMore);
        radbtnTimeMed = findViewById(R.id.radbtnTimeMed);
        radbtnTimeLess = findViewById(R.id.radbtnTimeLess);
        etSubtaskName = findViewById(R.id.etSubtaskName);
        btnCancel = findViewById(R.id.btnCancel);





        radgrpPri.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) {

                if (radbtnPriHigh.isChecked())
                {
                    priHigh = true;
                    priLow = false;
                    priMed = false;
                    pri = "h";

                }
                else if (radbtnPriMed.isChecked())
                {
                    priHigh = false;
                    priLow = false;
                    priMed = true;
                    pri = "m";


                }
                else if (radbtnPriLow.isChecked())
                {
                    priHigh = false;
                    priLow = true;
                    priMed = false;
                    pri = "l";
                }
                else {
                    priLow = true;
                    pri = "l";

                }

            }
        });

        radgrpTime.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) {

                if (radbtnTimeMore.isChecked())
                {
                    timeMore = true;
                    timeMed = false;
                    timeLess = false;

                    time = "more";
                }
               else if (radbtnTimeMed.isChecked())
                {
                    timeMore = false;
                    timeMed = true;
                    timeLess = false;
                    time = "med";
                }
               else if (radbtnTimeLess.isChecked())
                {
                    timeMore = false;
                    timeMed = false;
                    timeLess = true;
                    time = "less";
                }
               else
                {
                    timeLess = true;
                    time = "less";
                }

            }
        });

    
        btnDone.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

               String name = etSubtaskName.getText().toString().trim();

               Intent intent = new Intent(SubtaskActivity.this, TaskInfo.class);
               intent.putExtra("subtaskName", name);
               intent.putExtra("priHigh", priHigh);
               intent.putExtra("priMed", priMed);
               intent.putExtra("priLow", priLow);
               intent.putExtra("timeMore", timeMore);
               intent.putExtra("timeMed", timeMed);
               intent.putExtra("timeLess", timeLess);
               setResult(RESULT_OK, intent);
               SubtaskActivity.this.finish();

                AsyncTask.execute(new Runnable() {
                    @Override
                    public void run() {
                        SubtaskDetails subtaskDetails = new SubtaskDetails(etSubtaskName.toString().trim(), pri, time);
                        AppDatabase.getDatabase(getApplicationContext()).userDao().insertAll(subtaskDetails);
                    }
                });

                AppDatabase.databaseWriteExecutor.execute(new Runnable() {
                    @Override
                    public void run() {
                        List<SubtaskDetails> users = AppDatabase.getDatabase(getApplicationContext()).userDao().getAll();
                        for(SubtaskDetails subtaskDetails : users) {
                            Log.d("User", subtaskDetails.getDebugString());
                        }
                    }
                });    

            }
        });



        btnCancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                etSubtaskName.setText("");
                radgrpPri.clearCheck();
                radgrpTime.clearCheck();
                finish();



            }
        });






    }

}

Edit : A screenshot of the error I am facing if it helps

Answer 1

您省略了@Entity 注解

即而不是：-

public class SubtaskDetails {
 
    String subbuname, subbupri, subbutime;
    ....

使用

@Entity 
public class SubtaskDetails {
 
    String subbuname, subbupri, subbutime;
    ....

房间 (android) 中的数据访问对象 Class 未运行

Data Access Object Class in Room (android) isn't functioning

java

android

android-room