I know there have been a couple questions asked/answered on this topic but I need more specific help as this is my first time attempting something like this. I have tried to implement the answers to those questions and am still having errors. I need to write a dynamic amount of serialized objects to a file and then read from that file to retrieve the objects. I'm working in android FYI.
Here's my write() and overridden writeStreamHeader():
//check and see if there is a file already created to hold patterns, if not, make one
//only created once or if file is deleted; append to it if it's already created
if(!new File(getFilesDir()+"/Patterns").exists())
{
try {
fos = new FileOutputStream(getFilesDir()+FILENAME, true);
out = new ObjectOutputStream(fos);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
else
{
try {
out = new AppendingObjectOutputStream(fos);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//create a pattern of points. Max amount of Patterns is 100.
if(patternindex!=100)
{
Patterns[patternindex] = new Pattern(ActivePoints, name, xshift, yshift, scaling, rotation);
try {
//out.reset();
out.writeObject(Patterns[patternindex]); //write the object
//out.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
patternindex++;
dialog.dismiss();
}
public class AppendingObjectOutputStream extends ObjectOutputStream {
public AppendingObjectOutputStream(OutputStream out) throws IOException {
super(out);
}
@Override
protected void writeStreamHeader() throws IOException {
out.reset();
// do not write a header
}
}
I check to see if that file exists (it does because I've run this code) and then my writeObject() crashes the program with a NULLPointerException after creating the "special" ObjectOutputStream.
Here is my deserializing/read:
String PatternNames[] = new String[2];
Pattern Patterns[] = new Pattern[2];
FileInputStream fis;
ObjectInputStream in;
try {
fis = new FileInputStream(getFilesDir()+"/Patterns");
in = new ObjectInputStream(fis);
for(int i=0;i<2;i++)//just trying to read 2 objects to start with
{
{
Patterns[i] = (Pattern) in.readObject();
PatternNames[i] = Patterns[i].getName();
}
}
in.close();
} catch (ClassNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
Any help is greatly appreciated as I have spent a fair amount of time trying to figure this out. I know there have been people who have got this whole thing to work. As a side note, I have gotten serialize/deserialize working with one object saved to a different file but this is mostly useless given my project requirements.