我想在我的 android 应用程序中使用我的 companies.db sqlite 数据库。我将它复制到 android 项目的“ Assets ”文件夹中。并使用 DatabaseHelper 类，如下所示:
public class DatabaseHelper extends SQLiteOpenHelper {
String DB_PATH = null;
public static String DB_NAME = "companies";
private SQLiteDatabase myDataBase;
private final Context myContext;
Context ctx;
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, 2);
this.myContext = context;
DB_PATH = "/data/data/" + context.getPackageName() + "/" + "databases/";
}
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
// do nothing - database already exist
} else {
// By calling this method and empty database will be created into
// the default system path
// of your application so we are gonna be able to overwrite that
// database with our database.
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException(e);
//throw new Error("Error copying database");
}
}
}
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
try {
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) {
e.printStackTrace();
// database does\'t exist yet.
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* Copies your database from your local assets-folder to the just created
* empty database in the system folder, from where it can be accessed and
* handled. This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException {
// Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase() throws SQLException {
// Open the database
String myPath = DB_PATH + DB_NAME;
// SQLiteDatabase.NO_LOCALIZED_COLLATORS
myDataBase = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY
| SQLiteDatabase.NO_LOCALIZED_COLLATORS
| SQLiteDatabase.CREATE_IF_NECESSARY);
}
@Override
public synchronized void close() {
if (myDataBase != null)
myDataBase.close();
super.close();
}
// return cursor
public Cursor query(String table, String[] columns, String selection,
String[] selectionArgs, String groupBy, String having,
String orderBy) {
return myDataBase.query("pwp_singers", null, null, null, null, null,
null);
}
@Override
public void onCreate(SQLiteDatabase arg0) {
// TODO Auto-generated method stub
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if (newVersion > oldVersion)
try {
copyDataBase();
} catch (IOException e) {
e.printStackTrace();
}
}
}
我在需要数据库信息的 Activity 中使用以下代码:
DatabaseHelper myDbHelper=new DatabaseHelper(ListViewActivity.this);
try {
myDbHelper.createDataBase();
}catch(Exception e)
{}
myDbHelper.openDataBase();
db = myDbHelper.getReadableDatabase();
Cursor c;
c= db.rawQuery("select * from companies_fa where id=103", null);
但是当我运行应用程序时，出现了一些异常:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ahmad.exhibition/com.example.ahmad.exhibition.ListViewActivity}: android.database.sqlite.SQLiteException: no such table: companies_fa: , while compiling: select * from companies_fa where id=103
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1815)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1831)
at android.app.ActivityThread.access$500(ActivityThread.java:122)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1024)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:132)
at android.app.ActivityThread.main(ActivityThread.java:4123)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:491)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.database.sqlite.SQLiteException: no such table: companies_fa: , while compiling: select * from companies_fa where id=103
at android.database.sqlite.SQLiteCompiledSql.native_compile(Native Method)
at android.database.sqlite.SQLiteCompiledSql.<init>(SQLiteCompiledSql.java:64)
at android.database.sqlite.SQLiteProgram.compileSql(SQLiteProgram.java:146)
at android.database.sqlite.SQLiteProgram.compileAndbindAllArgs(SQLiteProgram.java:367)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:130)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:94)
at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:46)
at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:47)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1539)
at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1508)
at com.example.ahmad.exhibition.ListViewActivity.onCreate(ListViewActivity.java:70)
at android.app.Activity.performCreate(Activity.java:4397)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1779)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1831)
at android.app.ActivityThread.access$500(ActivityThread.java:122)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1024)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:132)
at android.app.ActivityThread.main(ActivityThread.java:4123)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:491)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
at dalvik.system.NativeStart.main(Native Method)
companies_fa 是我存储我的信息的表，我的代码哪里有问题？我究竟做错了什么？提前致谢。
最佳答案
使用 SQLiteAssetHelper ( https://github.com/jgilfelt/android-sqlite-asset-helper ) 解决了我的问题!
关于android - 如何在 android 应用程序中使用外部 sqlite 数据库，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28589900/