Java 在移动设备上找不到sqlite db，但可以在emulator上工作
我创建了一个sqlite数据库，它由一个表组成，数据库中填充了大约2000行 我能够查询这个表，当我通过模拟器进行查询时，一切都正常工作 但当我在移动设备上测试它时，它会抛出以下错误： android.database.sqlite.SQLiteException:没有这样的表：person（代码 1） ：，编译时：从rowid=292的人员中选择姓名 当我在一台设备上尝试它时，我希望填充的sqlite数据库在我的设备上自动可用，但基于上述错误，看起来情况并非如此 我确实查看了过去的问题，但它们与我的问题不匹配Java 在移动设备上找不到sqlite db，但可以在emulator上工作,java,android,sqlite,Java,Android,Sqlite,我创建了一个sqlite数据库，它由一个表组成，数据库中填充了大约2000行 我能够查询这个表，当我通过模拟器进行查询时，一切都正常工作 但当我在移动设备上测试它时，它会抛出以下错误： android.database.sqlite.SQLiteException:没有这样的表：person（代码 1） ：，编译时：从rowid=292的人员中选择姓名 当我在一台设备上尝试它时，我希望填充的sqlite数据库在我的设备上自动可用，但基于上述错误，看起来情况并非如此 我确实查看了过去的问题，但它们
try {
SQLiteDatabase database = this.openOrCreateDatabase("person", MODE_PRIVATE, null);
database.execSQL("DROP TABLE IF EXISTS person");
database.execSQL("CREATE TABLE IF NOT EXISTS person (name VARCHAR, name_size INT(8))");
BufferedReader br = new BufferedReader(new InputStreamReader(getAssets().open("person.txt")));
String line;
while ((line = br.readLine()) != null) {
String sql = "INSERT INTO person (name, name_size) VALUES ('" + line + "', " + line.length() + ")";
database.execSQL(sql);
}database.close();
}
catch (Exception e){
e.printStackTrace();
}
database = this.openOrCreateDatabase("person", MODE_PRIVATE, null);
private String retrieveNextPerson(int randomIndex){
//error on this raw query
Cursor cursor = database.rawQuery("SELECT name from person WHERE rowid = " + randomIndex, null);
int wordIndex = cursor.getColumnIndex("name");
cursor.moveToFirst();
return cursor.getString(wordIndex);
}
假设您没有错误地认为在模拟器（或任何设备）上运行应用程序会改变软件包，从而使发行版包含已填充的数据库
- 分发预填充的数据库涉及
- a） 填充数据库（通常使用SQLite管理工具）
- b） 将此文件（作为数据库的文件）复制到assets文件夹中，然后：-
- c） 从资产文件夹中检索此
- 使用使这变得容易，注意到使用
DB文件需要存在于databases文件夹中（您很可能需要创建此文件夹））SQLiteAssethelper
- 使用使这变得容易，注意到使用
database = this.openOrCreateDatabase("person", MODE_PRIVATE, null);
database=this.openOrCreateDatabase（“person”，MODE_PRIVATE，null）之后立即添加以下代码
- 注意可以看出，person.txt被“错误地”命名为notperson.txt，以强制执行错误
注意：在此阶段，数据库将存在（由于openOrCreateDatabase
），它将包含两个表（sqlite\u master和android\u元数据），但不包含person表，例如：-
但是，创建正确的资产文件person.txt（将notperson.txt重命名为person.text）将导致创建表并加载数据：-
e、 g.如果person.txt为：-
然后运行应用程序将生成包含以下内容的日志：-
06-10 04:39:04.277 3325-3325/? D/PERSON ROW COUNT: The number of rows in the person table is 11
谢谢你的回复。不确定您是否错过了我提到的数据库创建已经完成的部分，并且该部分已经被注释掉。我调用了一次db创建并加载了数据，db现在就在应用程序中（至少对于emulator是这样）。你提到的初始化应该打开一个现有的数据库和一个现有的表，因此我不认为这是过早的。不，我没有遗漏任何部分。然而，答案将被编辑，包括一个相当坚实的返工，应该克服你的问题。
public class MainActivity extends AppCompatActivity {
public static final String DBNAME = "person";
public static final String TBNAME = "person";
public static final String COL_NAME = "name";
public static final String COL_NAME_SIZE = "name_size";
public static final String ASSET_FILENAME = "person.txt";
public static final String SQLITE_MASTER_TABLE = "sqlite_master";
public static final String COL_SQLITE_MATSER_NAME = "name";
static final int MIMINUM_ROWS_IN_PERSONTABLE = 1;
SQLiteDatabase db;
BufferedReader br;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
checkPersonTable(); // Notes sets db either way
// FOR TESTING
long rows_in_person_table = DatabaseUtils.queryNumEntries(db,TBNAME);
Log.d(
"PERSON ROW COUNT",
"The number of rows in the " +
TBNAME +
" table is " +
String.valueOf(rows_in_person_table)
);
}
private void checkPersonTable() {
db = this.openOrCreateDatabase(DBNAME, Context.MODE_PRIVATE,null);
// Database will now exist but it may or may not contain the person table so check sqlite_master
Cursor csr = db.query(
SQLITE_MASTER_TABLE,
new String[]{COL_SQLITE_MATSER_NAME},
COL_SQLITE_MATSER_NAME + "=?",
new String[]{TBNAME},
null,null,null
);
// Cursor will contain 1 row if the person table exists so check count
int person_table_count = csr.getCount();
csr.close();
// Before attemtping to create the Person table ensure that the assets file exists
// If not then throw a RunTime exception
if (person_table_count < 1) {
try {
if (!Arrays.asList(getResources().getAssets().list("")).contains(ASSET_FILENAME)) {
StringBuilder sb = new StringBuilder();
throw new RuntimeException("Asset file " +
ASSET_FILENAME +
" not found in the assets folder." +
" The following assets were found" +
sb
);
}
} catch (IOException e) {
e.printStackTrace();
}
}
if (person_table_count < 1) {
db.execSQL("CREATE TABLE IF NOT EXISTS " + TBNAME +
"(" +
COL_NAME + " TEXT," +
COL_NAME_SIZE + " INTEGER" +
")"
);
loadPersonsFromAssets();
} else {
// <<<<<<<<<< NOTE Optional will load data from assets if miminum nuber of rows
// aren't in the person table
if (DatabaseUtils.queryNumEntries(db,TBNAME) < MIMINUM_ROWS_IN_PERSONTABLE) {
loadPersonsFromAssets();
}
}
}
// Load the person table from the Assets File
private void loadPersonsFromAssets() {
try {
BufferedReader br = new BufferedReader(new InputStreamReader(getAssets().open(ASSET_FILENAME)));
String line, sql;
int lines_read = 0;
db.beginTransaction();
while ((line = br.readLine()) != null) {
sql = "INSERT INTO " + TBNAME + " VALUES('" + line + "'," + String.valueOf(line.length()) + ")";
db.execSQL(sql);
lines_read++;
}
db.setTransactionSuccessful();
db.endTransaction();
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException("Asset File " + ASSET_FILENAME + " not found in the assets folder.");
}
}
}
06-10 03:58:43.503 3097-3097/personthing.so50777840 E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{personthing.so50777840/personthing.so50777840.MainActivity}: java.lang.RuntimeException: Asset file person.txt not found in the assets folder. The following assets were found
found asset file :- images
found asset file :- notperson.txt
found asset file :- sounds
found asset file :- webkit
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
at android.app.ActivityThread.access$600(ActivityThread.java:130)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.RuntimeException: Asset file person.txt not found in the assets folder. The following assets were found
found asset file :- images
found asset file :- notperson.txt
found asset file :- sounds
found asset file :- webkit
at personthing.so50777840.MainActivity.checkPersonTable(MainActivity.java:83)
at personthing.so50777840.MainActivity.onCreate(MainActivity.java:39)
at android.app.Activity.performCreate(Activity.java:5008)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
... 11 more
06-10 04:39:04.277 3325-3325/? D/PERSON ROW COUNT: The number of rows in the person table is 11