我创建了一个包含几个表的数据库。
我已将此数据库保存在资产文件夹中。
我试图从该数据库中简单地访问EXERCISESTABLE，然后在修改后的listView中显示其值。但是，我不断收到错误：
W/System.err: java.io.FileNotFoundException.
这是我的MainActivity扩展的活动类：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lvExercise = (ListView)findViewById(R.id.listView_exercises);
mDBHelper = new DatabaseHelper(this);
//Check exists database
File database = getApplicationContext().getDatabasePath(DatabaseHelper.DBNAME);
if(false == database.exists()){
mDBHelper.getReadableDatabase();
// Copy Database
if(copyDatabase(this)){
Toast.makeText(this, "Copy database success", Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(this, "Copy data error", Toast.LENGTH_SHORT).show();
return;
}
}
//Get exercise List in db when db exists
mExercisesList = mDBHelper.getListExercise();
//Init adapter
adapter = new ListExerciseAdapter(this, mExercisesList);
//Set adapter for list view
lvExercise.setAdapter(adapter);
}
private boolean copyDatabase(Context context){
try{
InputStream inputStream = context.getAssets().open(DatabaseHelper.DBNAME);
String outFileName = DatabaseHelper.DBLOCATION + DatabaseHelper.DBNAME;
OutputStream outputStream = new FileOutputStream(outFileName);
byte[]buff = new byte[1024];
int length =0;
while ((length = inputStream.read(buff)) >0){
outputStream.write(buff, 0, length);
}
outputStream.flush();
outputStream.close();
Log.w("MainActivity", "DB copied");
return true;
}catch(Exception e){
e.printStackTrace();
return false;
}
}
我在assets文件夹中有我的execution_program.db数据库文件，但是即使看起来对我来说我似乎都无法访问它。
这里是我的DBHelper扩展了SQLiteOpenHelper代码：
private Context mContext;
private SQLiteDatabase mDatabase;
public DatabaseHelper(Context context){
super(context, DBNAME, null, 1);
this.mContext = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
public void openDatabase() {
String dbPath = mContext.getDatabasePath(DBNAME).getPath();
if(mDatabase != null && mDatabase.isOpen()){
return;
}
mDatabase = SQLiteDatabase.openDatabase(dbPath,null,SQLiteDatabase.OPEN_READWRITE);
}
public void closeDatabase(){
if(mDatabase!=null){
mDatabase.close();
}
}
public List<Exercise> getListExercise(){
Exercise exercise = null;
List<Exercise> exerciseList = new ArrayList<>();
openDatabase();
Cursor cursor = mDatabase.rawQuery("SELECT * FROM EXERCISESTABLE ", null);
cursor.moveToFirst();
while(!cursor.isAfterLast()){
exercise = new Exercise(cursor.getInt(0),cursor.getString(1), cursor.getInt(2), cursor.getInt(3));
exerciseList.add(exercise);
cursor.moveToNext();
closeDatabase();
}
return exerciseList;
}
这是我的运动课：
public class Exercise {
private int exercise_id;
private String exercise_name;
private int exercise_type_id;
private int exercise_equipment_id;
public Exercise(int exercise_id, String exercise_name, int exercise_type_id, int exercise_equipment_id) {
this.exercise_id = exercise_id;
this.exercise_name = exercise_name;
this.exercise_type_id = exercise_type_id;
this.exercise_equipment_id = exercise_equipment_id;
}
public int getExercise_id() {
return exercise_id;
}
public void setExercise_id(int exercise_id) {
this.exercise_id = exercise_id;
}
public String getExercise_name() {
return exercise_name;
}
public void setExercise_name(String exercise_name) {
this.exercise_name = exercise_name;
}
public int getExercise_type_id() {
return exercise_type_id;
}
public void setExercise_type_id(int exercise_type_id) {
this.exercise_type_id = exercise_type_id;
}
public int getExercise_equipment_id() {
return exercise_equipment_id;
}
public void setExercise_equipment_id(int exercise_equipment_id) {
this.exercise_equipment_id = exercise_equipment_id;
}
}
这是我的ListExerciseAdapter扩展BaseAdapter类：
public ListExerciseAdapter(Context mContext, List<Exercise> exercisesList) {
this.mContext = mContext;
this.mExercisesList = exercisesList;
}
@Override
public int getCount() {
return mExercisesList.size();
}
@Override
public Object getItem(int position) {
return mExercisesList.get(position);
}
@Override
public long getItemId(int position) {
return mExercisesList.get(position).getExercise_id();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = View.inflate(mContext, R.layout.exercises_listview_layout, null);
TextView exercise_name = (TextView)v.findViewById(R.id.exercise_name);
TextView exercise_type_id = (TextView)v.findViewById(R.id.exercise_type_id);
TextView exercise_equipment_id = (TextView)v.findViewById(R.id.exercise_equipment_id);
exercise_name.setText(mExercisesList.get(position).getExercise_name());
exercise_type_id.setText(String.valueOf(mExercisesList.get(position).getExercise_type_id()));
exercise_equipment_id.setText(String.valueOf(mExercisesList.get(position).getExercise_equipment_id()));
return v;
}
任何帮助将不胜感激。
根据official documentation中预先填充的房间数据库。您有2个选项：
1] createFromAssets：在此选项中，您可以在资产文件夹下创建一个名为“数据库”的目录因此您可能会如下所示：
.createFromAssets("/databases/YOUR DATABASE FILENAME")
2）createFromFile：此选项可能与您为其分配路径的文件一起使用。
.createFromFile(File("YOUR FILE PATH"))
如果您对这两种解决方案感到困惑，可以尝试使用手动解决方案，我们可以将其称为手动解决方案！通过访问资产文件夹中的数据库文件。
private fun copyDBFromStorage(databaseName: String) {
if (checkIfDBExists(this, databaseName)) return
val databaseFile = File(this.getDatabasePath(databaseName).toString())
val sourceLocation = assets.open("Your database file path")
try {
val inputStream = sourceLocation
val os = FileOutputStream(databaseFile)
val buffer = ByteArray(1024 * 32)
var length = inputStream.read(buffer)
while (length > 0) {
os.write(buffer, 0, length)
length = inputStream.read(buffer)
}
os.flush()
os.close()
inputStream.close()
} catch (ex: IOException) {
ex.printStackTrace();
throw RuntimeException("Error copying storage database");
}
}
private fun checkIfDBExists(
context: Context,
databaseName: String
): Boolean {
val dbfile = File(context.getDatabasePath(databaseName).toString())
if (dbfile.exists()) return true
if (!dbfile.parentFile.exists()) {
dbfile.parentFile.mkdirs()
}
return false
}
Note：您可以使用Android Studio代码转换功能将此Kotlin代码转换为Java。
如果发现任何问题，请回复。
快乐编码🤓