Question

在我的应用程序中，我一直使用共享首选项来保存各种类型的数据。我之前已经能够使用共享首选项获得所需的结果，但我无法解决它的问题我在onPause方法的共享首选项中保存一个ArrayList，在OnCreate方法中获取保存的数据并清除onBackPressed方法中的首选项。我已经能够完成此活动并且仍然能够在Oncreate中获取ArrayList的数据，但是当我按下手机的后退按钮两次并且再次创建活动时，我会丢失ArrayList中的数据。

以下是我的代码的一部分：

public class RecipientAddressActivity extends FragmentActivity {

    private ArrayList<Person> prev_recArray;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_recipient_address);
        prev_recArray = new ArrayList<Person>();
        loadPreferences();
        addListeners();
    }

    private void loadPreferences() {
        SharedPreferences sharedPreferences = PreferenceManager
            .getDefaultSharedPreferences(this);
        Gson gson = new Gson();
        if (prev_recArray.size() == 0) {
            int prev_recArraysize = sharedPreferences.getInt(
                "Prev_Rec_Size", 0);
            if (prev_recArraysize > 0) {
                for (int i = 0; i < prev_recArraysize; i++) {
                    String json = sharedPreferences.getString(
                        "PrevRecList_" + i, "");
                    Person p = gson.fromJson(json, Person.class);
                    prev_recArray.add(p);
                }
            }
        }
    }
}

在按钮的点击事件中，我在prev_recArray中添加了一个项目：

{
    Intent Recipient_info = new Intent();
    Person recipient = new Person(edt_rec_name.getText().toString(),
        edt_rec_addr1.getText().toString(), edt_rec_addr2.getText()
            .toString(), edt_rec_city.getText().toString(), edt_rec_state
            .getText().toString(), edt_rec_pcode.getText().toString(),
        edt_rec_country.getText().toString());
    prev_recArray.add(recipient);
    // ...
    finish();
}

private void showRecPicker() {
    final RecipientPicker rec_picker = RecipientPicker
        .newInstance("Select a    Recipient");
    Log.e("Before passing it to getAllRecipients Size", "RecPicker = "
        + prev_recArray.size());
    rec_picker.getAllRecipients(prev_recArray);
    if ((prev_recArray.size() == 0)) {
        AlertDialog no_recipients = new AlertDialog.Builder(
            RecipientAddressActivity.this).create();
        no_recipients.setMessage("No previous recipients.");
        no_recipients.setButton(RESULT_OK, "OK",
            new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {}
            });
        no_recipients.show();
    } else {
        rec_picker.setListener(new RecipientPickerListener() {

            @Override
            public void onSelectRecipient(Person p) {
                loadPersonValues(p);
                rec_picker.dismiss();
            }
        });
        rec_picker.show(getSupportFragmentManager(), "RECIPIENT_PICKER");
    }
}

@Override
protected void onPause() {
    Log.e("In RecipientAddress", "On Pause");
    SharedPreferences sharedPreferences = PreferenceManager
        .getDefaultSharedPreferences(this);
    Editor editor = sharedPreferences.edit();
    Gson gson = new Gson();
    for (int i = 0; i < prev_recArray.size(); i++) {
        String json = gson.toJson(prev_recArray.get(i));
        editor.putString("PrevRecList_" + i, json);
    }
    editor.putInt("Prev_Rec_Size", prev_recArray.size());
    editor.commit();
    super.onPause();
}

@Override
public void onBackPressed() {
    Log.e("Phone's back button is presed", "Clearing SP");
    SharedPreferences sharedPreferences = PreferenceManager
        .getDefaultSharedPreferences(this);
    Editor editor = sharedPreferences.edit();
    editor.clear();
    editor.commit();
    super.onBackPressed();
}

有人可以指出我做错了什么或遗失了什么。

保存在共享首选项中的ArrayList行为异常

0 个答案: