这基本上是我的第一个 android 应用程序,我一直在尝试使用预填充的 sqllite 数据库来解决我的要求。
我的问题是 onCreate 函数没有被调用。
我从很多地方获取了一些代码并将它们组合起来形成了这个类。
http://www.androidhive.info/2011/11/android-sqlite-database-tutorial/
还有一些来自 android.com
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Locale;
import java.util.Random;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DatabaseHandler extends SQLiteOpenHelper {
SQLiteDatabase db;
private static final String TAG = "DataBaseHelper";
int id = 0;
Random random = new Random();
private SQLiteDatabase myDataBase;
private final Context myContext;
// Constructor
public DatabaseHandler(Context context) {
super(context, DefinitionContract.DATABASE_NAME, null, DefinitionContract.DATABASE_VERSION);
Log.d(TAG, "DatabaseHandler constructor called\n");
db = getWritableDatabase();
this.myContext = context;
//createDB();
}
@Override
public void onCreate(SQLiteDatabase db){
Log.d(TAG, "onCreate called\n");
createDB();
}
// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.d(TAG, "onUpgrade called\n");
Log.w(TAG, "Upgrading DB from version " + oldVersion + " to " +
newVersion + ", which will destroy all old data");
// Drop older table if existed
String sql = "DROP TABLE IF EXISTS " + DefinitionContract.CATEGORY_TABLE_NAME;
db.execSQL(sql);
sql = "DROP TABLE IF EXISTS " + DefinitionContract.CONTENTS_TABLE_NAME;
db.execSQL(sql);
// Create table again
onCreate(db);
}
public void createDataBase(SQLiteDatabase db) {
Log.d(TAG, "createDataBase called\n");
createDB();
db.execSQL(DefinitionContract.CREATE_CATEGORY_TABLE);
db.execSQL(DefinitionContract.CREATE_CONTENTS_TABLE);
}
private void createDB() {
Log.d(TAG, "createDB called\n");
boolean dbExist = dbExists();
Log.d("SQL Helper", "Condition:\n");
if(!dbExist) {
Log.d("SQL Helper", "Condition 1\n");
copyDataBase();
} else if(dbExist) {
Log.d("SQL Helper", "Condition 2\n");
copyDataBase();
}
}
private boolean dbExists() {
Log.d(TAG, "dbExists called\n");
//File dbFile = new File(DefinitionContract.DATABASE_PATH + DefinitionContract.DATABASE_NAME);
//return dbFile.exists();
SQLiteDatabase db = null;
try {
String dbPath = DefinitionContract.DATABASE_PATH + DefinitionContract.DATABASE_NAME;
db = SQLiteDatabase.openDatabase(dbPath, null, SQLiteDatabase.OPEN_READWRITE);
db.setLocale(Locale.getDefault());
db.setLockingEnabled(true);
db.setVersion(DefinitionContract.DATABASE_VERSION);
}
catch(SQLiteException e){
Log.e("SQL Helper", "database not found");
}
if(db != null) {
db.close();
}
return db != null ? true : false;
}
private void copyDataBase() {
Log.d(TAG, "copyDataBase called \n");
InputStream iStream = null;
OutputStream oStream = null;
String outFilePath = DefinitionContract.DATABASE_PATH + DefinitionContract.DATABASE_NAME;
try{
iStream = myContext.getAssets().open(DefinitionContract.DATABASE_NAME_EXT);
oStream = new FileOutputStream(outFilePath);
byte[] buffer = new byte[1024];
int length;
while((length = iStream.read(buffer))>0) {
oStream.write(buffer,0,length);
}
oStream.flush();
oStream.close();
iStream.close();
}
catch(IOException ioe){
throw new Error("Problem copying database from resource file.");
}
}
public void openDataBase() throws SQLException {
String myPath = DefinitionContract.DATABASE_PATH + DefinitionContract.DATABASE_NAME_EXT;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}
@Override
public synchronized void close() {
Log.d(TAG, "close called\n");
if (myDataBase != null)
myDataBase.close();
super.close();
}
public void readDB() {
Log.d(TAG, "readDB called\n");
String selectQuery = "SELECT * FROM " + DefinitionContract.DATABASE_ONLYNAME+"."+DefinitionContract.CATEGORY_TABLE_NAME;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
int arraySize = cursor.getColumnCount();
String newlog = "arraySize=" + arraySize + "*****";
for(int i = 0; i < arraySize; i++) {
newlog = newlog + cursor.getString(i)+ "\n";
}
Log.d("Details: ", newlog);
} while (cursor.moveToNext());
}
}
}
我已经进行了谷歌搜索并尝试修复它,但它还没有工作。
Android SQLiteOpenHelper:未调用 onCreate() 方法。为什么?
SQLiteOpenHelper 无法调用 onCreate?
LogCat 仅显示“调用 DataBaseHandler 构造函数”,然后显示“关闭 VM”
但是如果我删除db = getWritableDatabase(); 我的构造函数中的行进一步工作并显示正在调用 readDB() 函数。
一些可能有助于理解我的代码的定义:
public static final String DATABASE_NAME = "mydb.db";
public static final String DATABASE_NAME_EXT = "mydb.sqllite";
// Database path
public static final String DATABASE_PATH = "/data/data/com.abhishekgdotcom.collection/databases/";
有帮助吗?