Android 从真实设备和emulator上的资产文件夹复制数据库时出错
我的应用程序崩溃,并在logcat中获取此异常。但当我在DDMS中检查我的数据库文件夹时,我看到文件中的数据被复制到了那个里,但并没有显示在我的listview中。问题在于Android 从真实设备和emulator上的资产文件夹复制数据库时出错,android,database,sqlite,Android,Database,Sqlite,我的应用程序崩溃,并在logcat中获取此异常。但当我在DDMS中检查我的数据库文件夹时,我看到文件中的数据被复制到了那个里,但并没有显示在我的listview中。问题在于createDatabase()函数并从中获取异常。请参阅下面的logcat堆栈跟踪和我的代码。请帮帮我,我口吃得很厉害,不知道该怎么办 04-30 16:04:32.382: E/AndroidRuntime(20086): FATAL EXCEPTION: main 04-30 16:04:32.382: E/Andro
createDatabase()
函数并从中获取异常。请参阅下面的logcat堆栈跟踪和我的代码。请帮帮我,我口吃得很厉害,不知道该怎么办
04-30 16:04:32.382: E/AndroidRuntime(20086): FATAL EXCEPTION: main
04-30 16:04:32.382: E/AndroidRuntime(20086): java.lang.Error: Error copying database
04-30 16:04:32.382: E/AndroidRuntime(20086): at com.WaqasAsgharBhalli.za_traders.DatabaseHandler.createDatabase(DatabaseHandler.java:142)
04-30 16:04:32.382: E/AndroidRuntime(20086): at com.WaqasAsgharBhalli.za_traders.DatabaseHandler.<init>(DatabaseHandler.java:121)
04-30 16:04:32.382: E/AndroidRuntime(20086): at com.WaqasAsgharBhalli.za_traders.MainActivity.onCreate(MainActivity.java:27)
04-30 16:04:32.382: E/AndroidRuntime(20086): at android.app.Activity.performCreate(Activity.java:4465)
04-30 16:04:32.382: E/AndroidRuntime(20086): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
04-30 16:04:32.382: E/AndroidRuntime(20086): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
04-30 16:04:32.382: E/AndroidRuntime(20086): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
04-30 16:04:32.382: E/AndroidRuntime(20086): at android.app.ActivityThread.access$600(ActivityThread.java:122)
04-30 16:04:32.382: E/AndroidRuntime(20086): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
04-30 16:04:32.382: E/AndroidRuntime(20086): at android.os.Handler.dispatchMessage(Handler.java:99)
04-30 16:04:32.382: E/AndroidRuntime(20086): at android.os.Looper.loop(Looper.java:137)
04-30 16:04:32.382: E/AndroidRuntime(20086): at android.app.ActivityThread.main(ActivityThread.java:4340)
04-30 16:04:32.382: E/AndroidRuntime(20086): at java.lang.reflect.Method.invokeNative(Native Method)
04-30 16:04:32.382: E/AndroidRuntime(20086): at java.lang.reflect.Method.invoke(Method.java:511)
04-30 16:04:32.382: E/AndroidRuntime(20086): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
04-30 16:04:32.382: E/AndroidRuntime(20086): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
04-30 16:04:32.382: E/AndroidRuntime(20086): at dalvik.system.NativeStart.main(Native Method)
MainActivity.class
public class DatabaseHandler extends SQLiteOpenHelper {
// All Static variables
private static String TAG = DatabaseHandler.class.getName();
// Database Path
private static String DB_PATH = "/data/data/com.WaqasAsgharBhalli.za_traders/databases/";
private static String DB_NAME = "myDatabase.sqlite";
private SQLiteDatabase myDataBase = null;
private final Context myContext;
// Database Version
private static final int DATABASE_VERSION = 1;
public DatabaseHandler (Context context) throws IOException {
super(context,DB_NAME,null,1);
this.myContext=context;
boolean dbexist = checkDatabase();
if(dbexist)
{
//System.out.println("Database exists");
openDatabase();
}
else
{
System.out.println("Database doesn't exist");
createDatabase();
}
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
public void createDatabase() throws IOException{
boolean dbexist = checkDatabase();
if(dbexist)
{
//System.out.println(" Database exists.");
}
else{
this.getReadableDatabase();
try{
copyDatabase();
}
catch(IOException e){
throw new Error("Error copying database");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each time you open the application.
* @return true if it exists, false if it doesn't
*/
public boolean checkDatabase() {
//SQLiteDatabase checkdb = null;
boolean checkdb = false;
try{
String myPath = DB_PATH + DB_NAME;
File dbfile = new File(myPath);
//checkdb = SQLiteDatabase.openDatabase(myPath,null,SQLiteDatabase.OPEN_READWRITE);
checkdb = dbfile.exists();
}
catch(SQLiteException e){
System.out.println("Database doesn't exist");
}
return checkdb;
}
/**
* 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("/data/data/com.WaqasAsgharBhalli.za_traders/databases/myDatabase.sqlite");
// transfer byte to inputfile to 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;
myDataBase = SQLiteDatabase.openDatabase(mypath, null, SQLiteDatabase.OPEN_READWRITE);
}
@Override
public synchronized void close(){
if(myDataBase != null){
myDataBase.close();
}
super.close();
}
DatabaseHandler myDbHelper = null;
try {
myDbHelper = new DatabaseHandler(this);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
throw new Error("Unable to create database");
}
我建议您使用库在Android中复制数据库。对于不同的Android版本,有很多类似于不同默认路径位置的陷阱。我在我的项目中用于复制数据库,它工作得非常好。显示您的
MainActivity
onCreate
方法的代码。@GrIsHu我已经添加了MainActivity的代码,请检查它。我也尝试过使用sqliteAssetPer扩展类,但onCreate()方法出错。