我正在使用Room为我的应用创建一个小的数据库。我知道当我使用DAO类中的某些函数时应该创建一个数据库，但是无法正常工作。
我正在预填充数据库，因此自从安装该应用程序以来，应该在数据库中保存数据，并且我一直在尝试在这里找到的所有内容，并且确定自己犯了一些新手愚蠢的错误。
Video.class
@Entity(tableName = "videos_table")
public class Video {
@PrimaryKey(autoGenerate = true)
private int id;
private String video;
public Video(String video) {
this.video = video;
}
public void setId(int id) { this.id = id; }
public int getId() { return id; }
public String getVideo() { return video; }
}
VideoDatabase.class
@Database(entities = Video.class, version = 1)
public abstract class VideoDatabase extends RoomDatabase {
private static VideoDatabase instance;
public abstract VideoDAO videoDAO();
public static synchronized VideoDatabase getInstance(Context context) {
if (instance == null) {
instance = Room.databaseBuilder(context.getApplicationContext(),
VideoDatabase.class, "note_database")
.fallbackToDestructiveMigration()
.addCallback(roomCallback)
.build();
}
return instance;
}
private static RoomDatabase.Callback roomCallback = new RoomDatabase.Callback() {
@Override
public void onCreate(@NonNull SupportSQLiteDatabase db) {
super.onCreate(db);
new PopulatedDbAsyncTask(instance).execute();
}
};
private static class PopulatedDbAsyncTask extends AsyncTask<Void, Void, Void> {
private VideoDAO videoDAO;
private PopulatedDbAsyncTask(VideoDatabase db) {
videoDAO = db.videoDAO();
}
@Override
protected Void doInBackground(Void... voids) {
videoDAO.insert(new Video("Title 1"));
videoDAO.insert(new Video("Title 2"));
videoDAO.insert(new Video("Title 3"));
return null;
}
}
}
VideoDAO
@Dao
public interface VideoDAO {
@Insert
void insert(Video video);
@Update
void update(Video video);
@Delete
void delete(Video video);
@Query("DELETE FROM videos_table")
void deteleAllVideos();
}
VideoRepository
public class VideoRepository {
private VideoDAO videoDAO;
private LiveData<List<Video>> allNotes;
public VideoRepository(Application application) {
VideoDatabase database = VideoDatabase.getInstance(application);
videoDAO = database.videoDAO();
allNotes = videoDAO.getAllVideos();
}
public void insert(Video note) {
new InsertNoteAsyncTask(videoDAO).execute(note);
}
public void update(Video note) {
new UpdateNoteAsyncTask(videoDAO).execute(note);
}
public void delete(Video note) {
new DeleteNoteAsyncTask(videoDAO).execute(note);
}
public void deleteAllNotes() {
new DeleteAllNotesAsyncTask(videoDAO).execute();
}
public LiveData<List<Video>> getAllNotes() {
return allNotes;
}
private static class InsertNoteAsyncTask extends AsyncTask<Video, Void, Void> {
private VideoDAO videoDAO;
private InsertNoteAsyncTask(VideoDAO videoDAO) {
this.videoDAO = videoDAO;
}
@Override
protected Void doInBackground(Video... notes) {
videoDAO.insert(notes[0]);
return null;
}
}
private static class UpdateNoteAsyncTask extends AsyncTask<Video, Void, Void> {
private VideoDAO videoDAO;
private UpdateNoteAsyncTask(VideoDAO videoDAO) {
this.videoDAO = videoDAO;
}
@Override
protected Void doInBackground(Video... notes) {
videoDAO.update(notes[0]);
return null;
}
}
private static class DeleteNoteAsyncTask extends AsyncTask<Video, Void, Void> {
private VideoDAO videoDAO;
private DeleteNoteAsyncTask(VideoDAO videoDAO) {
this.videoDAO = videoDAO;
}
@Override
protected Void doInBackground(Video... notes) {
videoDAO.delete(notes[0]);
return null;
}
}
private static class DeleteAllNotesAsyncTask extends AsyncTask<Void, Void, Void> {
private VideoDAO videoDAO;
private DeleteAllNotesAsyncTask(VideoDAO videoDAO) {
this.videoDAO = videoDAO;
}
@Override
protected Void doInBackground(Void... voids) {
videoDAO.deteleAllVideos();
return null;
}
}
}
这是logcat
2019-11-12 13:26:49.207 11006-11006/? I/zygote: Not late-enabling -Xcheck:jni (already on)
2019-11-12 13:26:49.258 11006-11006/? W/zygote: Unexpected CPU variant for X86 using defaults: x86
2019-11-12 13:26:49.305 11006-11021/? E/zygote: Failed sending reply to debugger: Broken pipe
2019-11-12 13:26:49.305 11006-11021/? I/zygote: Debugger is no longer active
2019-11-12 13:26:49.636 11006-11006/? I/zygote: Rejecting re-init on previously-failed class java.lang.Class<androidx.core.view.ViewCompat$2>: java.lang.NoClassDefFoundError: Failed resolution of: Landroid/view/View$OnUnhandledKeyEventListener;
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at void androidx.core.view.ViewCompat.setBackground(android.view.View, android.graphics.drawable.Drawable) (ViewCompat.java:2559)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at void androidx.appcompat.widget.ActionBarContainer.<init>(android.content.Context, android.util.AttributeSet) (ActionBarContainer.java:63)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at java.lang.Object java.lang.reflect.Constructor.newInstance0(java.lang.Object[]) (Constructor.java:-2)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at java.lang.Object java.lang.reflect.Constructor.newInstance(java.lang.Object[]) (Constructor.java:334)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at android.view.View android.view.LayoutInflater.createView(java.lang.String, java.lang.String, android.util.AttributeSet) (LayoutInflater.java:647)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at android.view.View android.view.LayoutInflater.createViewFromTag(android.view.View, java.lang.String, android.content.Context, android.util.AttributeSet, boolean) (LayoutInflater.java:790)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at android.view.View android.view.LayoutInflater.createViewFromTag(android.view.View, java.lang.String, android.content.Context, android.util.AttributeSet) (LayoutInflater.java:730)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at void android.view.LayoutInflater.rInflate(org.xmlpull.v1.XmlPullParser, android.view.View, android.content.Context, android.util.AttributeSet, boolean) (LayoutInflater.java:863)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at void android.view.LayoutInflater.rInflateChildren(org.xmlpull.v1.XmlPullParser, android.view.View, android.util.AttributeSet, boolean) (LayoutInflater.java:824)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at android.view.View android.view.LayoutInflater.inflate(org.xmlpull.v1.XmlPullParser, android.view.ViewGroup, boolean) (LayoutInflater.java:515)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at android.view.View android.view.LayoutInflater.inflate(int, android.view.ViewGroup, boolean) (LayoutInflater.java:423)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at android.view.View android.view.LayoutInflater.inflate(int, android.view.ViewGroup) (LayoutInflater.java:374)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at android.view.ViewGroup androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor() (AppCompatDelegateImpl.java:749)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at void androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor() (AppCompatDelegateImpl.java:659)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at void androidx.appcompat.app.AppCompatDelegateImpl.setContentView(int) (AppCompatDelegateImpl.java:552)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at void androidx.appcompat.app.AppCompatActivity.setContentView(int) (AppCompatActivity.java:161)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at void com.example.recordshakerservice.MainActivity.onCreate(android.os.Bundle) (MainActivity.java:34)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at void android.app.Activity.performCreate(android.os.Bundle) (Activity.java:6975)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at void android.app.Instrumentation.callActivityOnCreate(android.app.Activity, android.os.Bundle) (Instrumentation.java:1213)
2019-11-12 13:26:49.637 11006-11006/? I/zygote: at android.app.Activity android.app.ActivityThread.performLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent) (ActivityThread.java:2770)
2019-11-12 13:26:49.638 11006-11006/? I/zygote: at void android.app.ActivityThread.handleLaunchActivity(android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:2892)
2019-11-12 13:26:49.638 11006-11006/? I/zygote: at void android.app.ActivityThread.-wrap11(android.app.ActivityThread, android.app.ActivityThread$ActivityClientRecord, android.content.Intent, java.lang.String) (ActivityThread.java:-1)
2019-11-12 13:26:49.638 11006-11006/? I/zygote: at void android.app.ActivityThread$H.handleMessage(android.os.Message) (ActivityThread.java:1593)
2019-11-12 13:26:49.638 11006-11006/? I/zygote: at void android.os.Handler.dispatchMessage(android.os.Message) (Handler.java:105)
2019-11-12 13:26:49.638 11006-11006/? I/zygote: at void android.os.Looper.loop() (Looper.java:164)
2019-11-12 13:26:49.638 11006-11006/? I/zygote: at void android.app.ActivityThread.main(java.lang.String[]) (ActivityThread.java:6541)
2019-11-12 13:26:49.638 11006-11006/? I/zygote: at java.lang.Object java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object[]) (Method.java:-2)
2019-11-12 13:26:49.638 11006-11006/? I/zygote: at void com.android.internal.os.Zygote$MethodAndArgsCaller.run() (Zygote.java:240)
2019-11-12 13:26:49.638 11006-11006/? I/zygote: at void com.android.internal.os.ZygoteInit.main(java.lang.String[]) (ZygoteInit.java:767)
任何帮助都会很棒，谢谢！
答案 0 :(得分：0)
我认为您的build.gradle中没有房间注释处理器：
implementation androidx.room:room-runtime:2.2.1
//or annotationprocessor
kapt androidx.room:room-compiler:2.2.1 //make sure to apply 'kotlin-kapt' as plugin
最后一个（启用增量ap）：
defaultConfig {
...
javaCompileOptions {
annotationProcessorOptions {
arguments = roomIncrementalAnnotationProcessor
}
}
}