當我將 id 初始化為主鍵并添加唯一屬性時，我收到此錯誤。
資料類代碼：
@Entity(tableName = "tbl_data" , indices = {@Index(value = {"id"},
unique = true)})
public class Data {
@PrimaryKey
private Integer id ;
private Integer year;
private Double dowry;
public Data(Integer id,Integer year, Double dowry) {
this.id = id;
this.year = year;
this.dowry = dowry;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getYear() {
return year;
}
public void setYear(int year) {
this.year = year;
}
public Double getDowry() {
return dowry;
}
public void setDowry(Double dowry) {
this.dowry = dowry;
}
資料庫類代碼：
@Database(version = 1 , exportSchema = false , entities = {Data.class} )
public abstract class AppDatabase extends RoomDatabase {
private static AppDatabase appDatabase;
public static AppDatabase getAppDatabase(Context context) {
if (appDatabase == null)
appDatabase = Room.databaseBuilder(context.getApplicationContext(),
AppDatabase.class,
"db_app")
.allowMainThreadQueries().fallbackToDestructiveMigration()
.build();
return appDatabase;
}
public abstract DataDao getDataDao();
}
和主要活動代碼：
db = AppDatabase.getAppDatabase(this);
dataDao = db.getDataDao();
dataDao.insertC(new Data(1,1315, 0.004 ), new Data(2,1316, 0.005), new Data(3,1317, 0.006), new Data(4,1318, 0.007));
和 logat 中的完整錯誤：
2021-11-07 12:20:45.070 24994-24994/com.mohajer.kitset2 E/AndroidRuntime: FATAL EXCEPTION: main Process: com.mohajer.kitset2, PID: 24994 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mohajer.kitset2/com.mohajer.kitset2.MainActivity}: android.database.sqlite.SQLiteConstraintException: UNIQUE constraint failed: tbl_data.id (Sqlite code 1555 SQLITE_CONSTRAINT_PRIMARYKEY), (OS error - 2:No such file or directory) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3430) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3614) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:86) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2199) at android.os.Handler.dispatchMessage(Handler.java:112) at android.os.Looper.loop(Looper.java:216) at android.app.ActivityThread.main(ActivityThread.java:7625) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987) Caused by: android.database.sqlite.SQLiteConstraintException: UNIQUE constraint failed: tbl_data.id (Sqlite code 1555 SQLITE_CONSTRAINT_PRIMARYKEY), (OS error - 2:No such file or directory) at android.database.sqlite.SQLiteConnection.nativeExecuteForLastInsertedRowId(Native Method) at android.database.sqlite.SQLiteConnection.executeForLastInsertedRowId(SQLiteConnection.java:841) at android.database.sqlite.SQLiteSession.executeForLastInsertedRowId(SQLiteSession.java:803) at android.database.sqlite.SQLiteStatement.executeInsert(SQLiteStatement.java:86) at androidx.sqlite.db.framework.FrameworkSQLiteStatement.executeInsert(FrameworkSQLiteStatement.java:51) at androidx.room.EntityInsertionAdapter.insertAndReturnIdsArrayBox(EntityInsertionAdapter.java:199) at com.mohajer.kitset2.DataDao_Impl.insertC(DataDao_Impl.java:50) at com.mohajer.kitset2.MainActivity.onCreate(MainActivity.java:36) at android.app.Activity.performCreate(Activity.java:7458) at android.app.Activity.performCreate(Activity.java:7448) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1286) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3409) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3614) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:86) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2199) at android.os.Handler.dispatchMessage(Handler.java:112) at android.os.Looper.loop(Looper.java:216) at android.app.ActivityThread.main(ActivityThread.java:7625) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987)
uj5u.com熱心網友回復：
使用 @PrimaryKey 意味著一個 UNIQUE 約束，因此不需要在 id 列上設定唯一索引（索引只是一種浪費）。
插入時使用 id 值對插入進行硬編碼（沒有忽略沖突的 onConflict 約束），在從全新安裝（重新運行）運行一次后，將導致 UNIQUE 沖突，因為 id 的 1、2、3 和 4 已經存在.
將@Dao 編碼為@Insert(onConflict = OnConflictStrategy.IGNORE)將忽略沖突而不會失敗并且不會插入重復項。
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標籤：爪哇 安卓 sql 安卓工作室 android-room
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