[英]Class Cast Exception when DeSerializing an Object
總覽
我是Android開發的新手,我正在嘗試序列化然后反序列化對象的值,但是我遇到了異常。
例外
致命異常:主要
java.lang.ClassCastException:java.io.File無法轉換為com.testingapplication.SchoolNameDetails com.testingapplication.fragment.HomeFragment $ 1.onClick(HomeFragment.java:62)
我嘗試了什么
SchoolNameDetails類如下:
public class SchoolNameDetails implements Serializable {
private int id;
private String schoolname;
private String level;
private String pkno;
private String nano;
private String ucname;
private String officeno;
private static final long serialVersionUID = 46548923;
public SchoolNameDetails(){}
public SchoolNameDetails(String schoolname, String level, String pkno,String nano, String ucname, String officeno){
this.schoolname=schoolname;
this.level=level;
this.pkno=pkno;
this.nano=nano;
this.ucname=ucname;
this.officeno=officeno;
}
public SchoolNameDetails(int id, String schoolname, String level, String pkno,String nano, String ucname, String officeno){
this.id=id;
this.schoolname=schoolname;
this.level=level;
this.pkno=pkno;
this.nano=nano;
this.ucname=ucname;
this.officeno=officeno;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getSchoolname() {
return schoolname;
}
public void setSchoolname(String schoolname) {
this.schoolname = schoolname;
}
public String getLevel() {
return level;
}
public void setLevel(String level) {
this.level = level;
}
public String getPkno() {
return pkno;
}
public void setPkno(String pkno) {
this.pkno = pkno;
}
public String getNano() {
return nano;
}
public void setNano(String nano) {
this.nano = nano;
}
public String getUcname() {
return ucname;
}
public void setUcname(String ucname) {
this.ucname = ucname;
}
public String getOfficeno() {
return officeno;
}
public void setOfficeno(String officeno) {
this.officeno = officeno;
}
}
在這里我要序列化對象
@Override
protected void onStop() {
super.onStop();
SchoolNameDetails details = new SchoolNameDetails();
details.setSchoolname(t2.getText().toString());
details.setLevel(t2a.getText().toString());
details.setPkno(t5.getText().toString());
details.setNano(t6.getText().toString());
details.setUcname(t7.getText().toString());
details.setOfficeno(t8.getText().toString());
saveObject(details);
}
public void saveObject(SchoolNameDetails d) {
try
{
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File("/sdcard/save_object.ser")));
oos.flush();
oos.close();
}
catch(Exception ex)
{
Log.v("Error",ex.getMessage());
ex.printStackTrace();
}
}
在這里我正在反序列化Fragment類中的對象
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_home,
container, false);
Button b1= (Button) view.findViewById(R.id.button1);
final TextView t1 = (TextView) view.findViewById(R.id.textView1);
b1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
SchoolNameDetails details = (SchoolNameDetails)loadSerializedObject(new File("/sdcard/save_object.ser"));
System.out.println("Name : " + details.getSchoolname());
}
});
return view;
}
public Object loadSerializedObject(File f)
{
try
{
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(f));
Object o = ois.readObject();
}
catch(Exception ex)
{
Log.v("Error : ","" + ex.getMessage());
ex.printStackTrace();
}
return f;
}
現在,最后一個返回值給出了異常。 我嘗試使用return null,但隨后給出了null指針異常。 請幫忙,我在這里呆了幾個小時,還沒有找到任何解決方案
首先,將您的saveObject
方法更改為實際寫入對象:
public void saveObject(SchoolNameDetails d) {
try
{
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File("/sdcard/save_object.ser")));
//write to ObjectOutputStream
oos.writeObject(d);
oos.flush();
oos.close();
}
catch(Exception ex)
{
Log.v("Error",ex.getMessage());
ex.printStackTrace();
}
}
接下來,更改您的loadSerializedObject
方法以從輸入流返回對象:
public SchoolNameDetails loadSerializedObject(File f)
{
try
{
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(f));
SchoolNameDetails o = (SchoolNameDetails ) ois.readObject();
return o;
}
catch(Exception ex)
{
Log.v("Error : ","" + ex.getMessage());
ex.printStackTrace();
}
return null;
}
最后,在onClick
確保該對象不為null:
@Override
public void onClick(View view) {
SchoolNameDetails details = loadSerializedObject(new File("/sdcard/save_object.ser"));
if (details != null) {
System.out.println("Name : " + details.getSchoolname());
}
}
您將在函數末尾返回f。 但是您必須返回o(從方法ois.readObject()中獲得的內容。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.