我试图找到我在持久性存储上存储的对象的大小。我以编程方式找到了对象的大小，如代码所示，但是当它存储在持久性存储中时，我无法找到该对象的大小。 数据在存储时会自动压缩。 我正在使用Memory.getFlashStats（）。getFree（）;在commitnig要存储的对象之前和之后获取持久性存储的可用大小，并且两个值之间的差异应该等于我已经计算的对象的大小。 请参阅代码
package Bean;
import java.util.Enumeration;
import java.util.Vector;
import net.rim.device.api.system.Memory;
import net.rim.device.api.system.MemoryStats;
import net.rim.device.api.system.PersistentObject;
import net.rim.device.api.system.PersistentStore;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.MenuItem;
import net.rim.device.api.ui.component.ButtonField;
import net.rim.device.api.ui.component.Dialog;
import net.rim.device.api.ui.component.EditField;
import net.rim.device.api.ui.container.MainScreen;
import bean.UserCredentials;
public class MyStoreScreen extends MainScreen implements FieldChangeListener
{
private int nObjectSize;
static final long PERSISTENT_STORE_DEMO_ID = 0x42c16456ab0b5eabL;
private static PersistentObject oPersistenStore;
private int nFreePersistenceInStarting=Memory.getPersistentStats().getFree();
private int nFreePersistenceAtEnd;
ButtonField oCalculateMemButton ;
private MenuItem saveItem = new MenuItem("Save ", 110, 10)
{
public void run()
{
Dialog.alert("initially free memory ----------------------"+nFreePersistenceInStarting);
oPersistenStore = PersistentStore.getPersistentObject(PERSISTENT_STORE_DEMO_ID);
Vector storeVector = (Vector)oPersistenStore.getContents();
Vector userinfo ;
int size = (storeVector == null) ? 0 : storeVector.size();
if(size == 0)
{
userinfo = new Vector();
}
else
{
userinfo = storeVector;
}
UserCredentials oUserCredentials = new UserCredentials("akanksha","chandra",1,3434.3434,343545646);
for(int i =0;i<=100;i++)
{
userinfo.addElement(oUserCredentials);
}
nObjectSize= fnCalculateSizeOfObject(userinfo);
Dialog.alert("size of object is "+ nObjectSize);
synchronized(oPersistenStore)
{
oPersistenStore.setContents(userinfo);
oPersistenStore.commit();
}
}
};
private MenuItem getItem = new MenuItem( "Get item", 110, 11 )
{
public void run()
{
oPersistenStore = PersistentStore.getPersistentObject(PERSISTENT_STORE_DEMO_ID);
synchronized(oPersistenStore)
{
Vector arrCredential = (Vector)oPersistenStore.getContents();
if(arrCredential != null)
{
String dataContents = "";
int nSize = (arrCredential == null) ? 0 : arrCredential.size();
if(nSize != 0)
{
for (int i = 0; i < nSize; i++)
{
UserCredentials oUserCredentials = (UserCredentials)arrCredential.elementAt(i);
dataContents+="\n size of vector is "+nSize+ " username : "+oUserCredentials.getStrUsername()+"\n password : "+oUserCredentials.getStrPassword();
dataContents += "\n\nUser sal : "+oUserCredentials.getdSalary();
dataContents += "\n amount : "+oUserCredentials.getlAmount();
dataContents += "\n s no "+oUserCredentials.getnSerialNo();
}
Dialog.alert(dataContents);
}
else
{
Dialog.alert("Zero Elements ");
}
}
else
{
Dialog.alert("No contents ");
}
}
}
};
private MenuItem resetStoreItem = new MenuItem( "Delete Store", 110, 11 )
{
public void run()
{
int choice = Dialog.ask(Dialog.D_OK_CANCEL, "Do you want to delete ?");
if(choice == Dialog.D_OK)
{
// oPersistenStore = PersistentStore.getPersistentObject(PERSISTENT_STORE_DEMO_ID);
PersistentStore.destroyPersistentObject(PERSISTENT_STORE_DEMO_ID);
}
else
{
}
}
};
private MenuItem CalculateTotalFlashUsed = new MenuItem("calculate used flash size ", 0, 7)
{
public void run()
{
Dialog.alert("used size of Persistence Store is "+fnUsedPersistenceSize());
};
};
public MyStoreScreen()
{
oCalculateMemButton = new ButtonField("calculate free flash memory in starting", ButtonField.CONSUME_CLICK);
oCalculateMemButton.setChangeListener(this);
this.add(oCalculateMemButton);
this.addMenuItem(saveItem);
this.addMenuItem(getItem);
this.addMenuItem(resetStoreItem);
this.addMenuItem(CalculateTotalFlashUsed);
oPersistenStore = PersistentStore.getPersistentObject(PERSISTENT_STORE_DEMO_ID);
}
public void fieldChanged(Field field, int context)
{
if(field ==oCalculateMemButton)
{
// nFreeFlashInStarting =Memory.getFlashTotal();
// nFreeFlashInStarting =Memory.getFlashStats().getFree();
// nFreeFlashAtEnd =Memory.getFlashStats().getFree();
// String message = "total flash is Memory.getFlashStats().getAllocated(); "+nFreeFlashInStarting+" Memory.getFlashTotal() is : "+Memory.getFlashTotal();
String message = "total free flash memory in starting is :"+ nFreePersistenceInStarting;
Dialog.alert(message);
}
}
private int fnCalculateSizeOfObject(Vector userInfo )
{
int nSize = 0;
Enumeration oEnumeration = userInfo.elements();
while(oEnumeration.hasMoreElements())
{
UserCredentials oUserCredentials = (UserCredentials) oEnumeration.nextElement();
String UserName = oUserCredentials.getStrUsername();
String password = oUserCredentials.getStrPassword();
int nSerialNo = oUserCredentials.getnSerialNo();
double dSalary = oUserCredentials.getdSalary();
long lAmount = oUserCredentials.getlAmount();
nSize+= 4+8+8+fnCalculateSizeOfString(UserName)+fnCalculateSizeOfString(password);
}
return nSize;
}
private int fnCalculateSizeOfString(String strInputString)
{
//convert String to char array
char[] characterArray = strInputString.toCharArray();
int nlength = characterArray.length;
return nlength;
}
public int fnUsedPersistenceSize()
{
nFreePersistenceAtEnd = Memory.getPersistentStats().getFree();
int nUsedPersistenceMemory = nFreePersistenceInStarting -nFreePersistenceAtEnd;
return nUsedPersistenceMemory;
}
}
答案 0 :(得分：0)
Memory.getFlashStats().getFree()不准确，你可以在多次测量同一物体的存储时看到它 - 每次的值可能不同。
测量对象大小的最佳方法是计算其字段大小（您实际执行的操作）。