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在进程或页面通信时需要使用Intent传递数据; 在对象持久化时需要存储数据. 对于复杂的对象, 进行序列化才可传递或存储, 可以使用Java的Serializable方式或Android的Parcelable方式. 本文介绍Serializable和Parcelable的使用方式, 含有Demo.
序列化User类, 实现Serializable接口即可. 注意serialVersionUID用于辅助序列化与反序列化, 只有相同时, 才会正常进行. 如不指定, 则系统会自动生成Hash值, 修改类代码, 可能会导致无法反序列化, 所以强制指定.
public class UserSerializable implements Serializable {
// 标准序列ID, 用于判断版本
private static final long serialVersionUID = 1L;
public int userId;
public String userName;
public boolean isMale;
public UserSerializable(int userId, String userName, boolean isMale) {
this.userId = userId;
this.userName = userName;
this.isMale = isMale;
}
}序列化对象, 使用ObjectOutputStream存储已经序列化的对象数据, 通过writeObject写入对象.
public void serialIn(View view) {
Context context = view.getContext();
File cache = new File(context.getCacheDir(), "cache.txt");
try {
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(cache));
UserSerializable user = new UserSerializable(0, "Spike", false);
out.writeObject(user);
out.close();
Toast.makeText(context, "序列化成功", Toast.LENGTH_SHORT).show();
} catch (IOException e) {
e.printStackTrace();
}
}缓存文件位置:
new File(context.getCacheDir(), "cache.txt").
反序列对象, 使用ObjectInputStream反序列化对象, 通过readObject读取对象的持久化信息.
public void serialOut(View view) {
Context context = view.getContext();
File cache = new File(context.getCacheDir(), "cache.txt");
UserSerializable newUser = null;
try {
ObjectInputStream in = new ObjectInputStream(new FileInputStream(cache));
newUser = (UserSerializable) in.readObject();
in.close();
} catch (Exception e) {
e.printStackTrace();
Toast.makeText(context, "请先序列化", Toast.LENGTH_SHORT).show();
}
if (newUser != null) {
String content = "序号: " + newUser.userId
+ ", 姓名: " + newUser.userName
+ ", 性别: " + (newUser.isMale ? "男" : "女");
mSerialTvContent.setText(content);
} else {
mSerialTvContent.setText("无数据");
}
}Android推荐的序列化对象方式. 实现Parcelable接口, writeToParcel写入对象的变量, UserParcelable提供解析对象方式. CREATOR是创建序列化对象的匿名类, 必须实现, 包含创建单个对象与数组的方式. describeContents只有在含有文件描述符是返回1, 默认都是返回0, 不需要修改.
public class UserParcelable implements Parcelable {
public int userId;
public String userName;
public boolean isMale;
public BookParcelable book;
public UserParcelable(int userId, String userName, boolean isMale, String bookName) {
this.userId = userId;
this.userName = userName;
this.isMale = isMale;
this.book = new BookParcelable(bookName);
}
@Override public int describeContents() {
return 0;
}
@Override public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(userId);
dest.writeString(userName);
dest.writeInt(isMale ? 1 : 0);
dest.writeParcelable(book, 0);
}
public static final Parcelable.Creator<UserParcelable> CREATOR = new Parcelable.Creator<UserParcelable>() {
@Override public UserParcelable createFromParcel(Parcel source) {
return new UserParcelable(source);
}
@Override public UserParcelable[] newArray(int size) {
return new UserParcelable[size];
}
};
private UserParcelable(Parcel source) {
userId = source.readInt();
userName = source.readString();
isMale = source.readInt() == 1;
book = source.readParcelable(Thread.currentThread().getContextClassLoader());
}
}使用Intent传递对象数据, 编号0, 姓名Spike, 性别女, 喜欢书籍三国演义.
public void parcelSend(View view) {
Intent intent = new Intent(PASS_PARCEL_FILTER);
intent.putExtra(PARCEL_EXTRA, new UserParcelable(0, "Spike", false, "三国演义"));
mLBM.sendBroadcast(intent);
}解析广播Intent的数据, 使用getParcelableExtra方法即可.
private BroadcastReceiver mParcelReceiver = new BroadcastReceiver() {
@Override public void onReceive(Context context, Intent intent) {
UserParcelable newUser = intent.getParcelableExtra(PARCEL_EXTRA);
if (newUser != null) {
String content = "序号: " + newUser.userId
+ ", 姓名: " + newUser.userName
+ ", 性别: " + (newUser.isMale ? "男" : "女")
+ ", 书: " + newUser.book.bookName;
Toast.makeText(context, content, Toast.LENGTH_SHORT).show();
mParcelTvContent.setText(content);
}
}
};Serializable序列化需要大量的IO操作, Parcelable序列化虽然使用复杂, 但是效率很高, 是Android开发的首选. Parcelable主要应用于内存序列化, 如Intent广播等.
OK, that's all! Enjoy it!