Android：保存对象onPause（）并读取对象onResume（）

Question

I was not able to save an object(custom) to a file.

The process of my app is to saving the object onPause() and getting the object onResume().

1) I have two activities (Activity A and Activity B)
2) I am saving and reading the object in Activity A 
3) Activity A call Activity B on Button click.

Here are the steps to replicate my problem: (Activity A launches by reading an object from file.)

1) Click on button on Activity A.
2) Save custom object to file in onPause method of Activity A.
3) Activity B launches
4) Click on Action bar back button.
5) Read the object from file saved in onResume() method of Activity A.
6) Again click on the button on Activity A.
7) Saves custom object to file in onPause() method of Activity A.
8) Activity B launches.
9) Click on back button of device.
10) Tries to read the object from file in onResume() method of Activity A.

Please note: the file that I am saving and reading is at same location.

Here at step 10, the object read is incorrect. I suspect that it is at step 7, object was not saved properly.

Can someone help with saving object to file and reading a file to object?

Correct me if I am wrong. As per the Android document, onSaveInstanceState() and onRestoreInstanceState() are not suitable method to save.

here is the manifest:

    <activity
        android:name=".ActivityA"
        android:configChanges="orientation|keyboardHidden|screenSize"
        android:label="@string/app_name"
        >
    </activity>
    <activity
        android:name=".ActivityB"
        android:configChanges="orientation|keyboardHidden|screenSize"
        android:label="@string/app_name" >
    </activity>

Saving and reading object here (ActivityA):

Customer customer;
@Override
protected void onPause() {
    super.onPause();
    save(customer);
}

@Override
protected void onResume() {
    super.onResume();
    customer = read();
}

  private void save(Customer customer) {
    try {
        FileOutputStream fileOutputStream = openFileOutput("Customer.properties", Context.MODE_PRIVATE);
        Properties properties = new Properties();
        properties.put("CUSTOMER_NAME", customer.getName());
        properties.put("CUSTOMER_ID", customer.getId());
        properties.put("CUSTOMER_PLACE", customer.getPlace());

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
}

     private Customer read() {
     try {
          FileInputStream fileInputStream = openFileInput("customer.properties");
          Properties properties = new Properties();
          properties.load(fileInputStream);
          Customer customer = new Customer();
          customer.setName(properties.get("CUSTOMER_NAME"));
          customer.setId(properties.get("CUSTOMER_ID"));
          customer.setPlace(properties.get("CUSTOMER_PLACE"));
          return customer;
     } catch(Exception e) {
     }
   return null;
  }

Answer 1

在@override上，super.onPause（）和super.onResume（）总是首先出现，然后只有您才能放置您的代码。

Answer 2

you should close your input and output streams after you're done with them, otherwise you'll run into a concurrency problem

  private void save(Customer customer) {
     ...
     fileOutputStream.close()
  }

  private Customer read() {
     ...
     fileInputStream.close()
  }