Android 保存一个 ArrayList<Object>作为共享首选项 [英] Android saving an ArrayList&lt;Object&gt; as SharedPreference

问题描述

我目前正在尝试将包含 POJO 的 ArrayList 保存为 SharedPreference，以便在用户重新进入应用程序时检索它，但它似乎不起作用.

I'm currently trying to save an ArrayList containing POJOs as a SharedPreference to retrieve it when the user re-enters the application, but it doesn't seem to work.

这就是我所做的:

回调方法

ArrayList<myObject> myList;
ArrayList<Boolean> myobject_repeat;
MyListAdapter adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.myview);
    lw = (ListView) findViewById(R.id.lw);
    myList= new ArrayList<myObject>();
    myobject_repeat = new ArrayList<Boolean>();
    adapter = new MyListAdapter(this, myList);
    lw.setAdapter(adapter);
}

@Override
protected void onPause() {
    saveArray();
    super.onPause();
}

@Override
protected void onResume() {
    loadArray(this);
    super.onResume();
}

保存/加载数组的方法

public boolean saveArray() {
    SharedPreferences pref = PreferenceManager
            .getDefaultSharedPreferences(this);
    SharedPreferences.Editor edit = pref.edit();
    edit.putInt("list_size", myList.size());

    for (int i = 0; i < myList.size(); i++) {
        edit.remove("id" + i);
        edit.remove("repeat" + i);
        edit.putLong("id" + i, myList.get(i).getId());
        edit.putBoolean("repeat" + i, myList.get(i).isRepeat());
    }

    return edit.commit();
}

public void loadArray(Context c) {
    SharedPreferences pref = PreferenceManager
            .getDefaultSharedPreferences(c);
    myList.clear();
    myList2.clear();
    int listsize = pref.getInt("list_size", 0);

    for (int i = 0; i < listsize; i++) {
        MyObject tmpObject = new MyObject();
        tmpObject.setId(pref.getLong("id" + i, 0));
        tmpObject.setRepeat(pref.getBoolean("repeat" + i, false));
        myList.add(tmpObject);
    }

}

这是我向数组中添加对象的地方

This is where I add an object to the array

@Override
protected void onActivityResult(int requestCode, int resultCode,
        Intent result) {
    super.onActivityResult(requestCode, resultCode, result);

    if (resultCode == RESULT_OK) {
        int hour = result.getExtras().getInt("hour");
        int minute = result.getExtras().getInt("minute");
        boolean repeat = result.getExtras().getBoolean("repeat");
        setUpObject(hour, minute, repeat);
    }
}

private void setUpObject(int hour, int minute, boolean repeat) {

    //Doing magic tricks

    MyObject tmpObject= new MyObject ();
    tmpObject.setHours(hour);
    tmpObject.setMinutes(minute);
    tmpObject.setRepeat(repeat);
    tmpObject.setId(timeInMs);

    myList.add(tmpObject);
    adapter.remove(tmpObject);
    adapter.add(tmpObject);
    adapter.notifyDataSetChanged();
}

这似乎不起作用.当我调试它时，列表是空的.如果我在没有加载/保存方法的情况下运行应用程序，它会按预期工作，但如您所见，列表不会保留在 SharedPreferences 中，因此在用户导航回我的活动时不可用.

This does not seem to work. When I debug it the lists are empty. If I run the app without the load/save methods it works as intended but as you can see, the lists wont be persisted in SharedPreferences and therefore not available when the user navigates back to my activity.

非常感谢这里的任何帮助.

Any help here is really appreciated.

马库斯

推荐答案

我在这里发现了问题:在 onActivityResult 之后调用了 onPause，它用空数组覆盖了我的数组.

I found out the problem here: onPause was called after onActivityResult which overwrite my array with an empty array.

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