Question

我为我所有的对话片段制作了一个DialogFragment助手类我的应用。我也有一个未知类型的arraylist（泛型）得到它值取决于静态arraylist来自哪个活动。在为了区分静态arraylist来自的活动，我使用布尔类变量。令我惊讶的是这个布尔变量在newInstance（Context c，int dialogNumber）方法中获取其值 onCreateDialog方法，它获取默认的布尔值，即false。

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这是DialogFragmentHelper类的代码：

public class DialogFragmentHelper extends DialogFragment {

private static final ArrayList<FoodRecord> allRecords = FoodActivity.allRecords;
private static final ArrayList<BgRecord> mBgRecords = MainActivity.mBgRecords;
private static ArrayList<?> mRecords;
private int dNumber;
private Context mContext;
private boolean fromFoodActivity;


public DialogFragmentHelper newInstance(Context context, int dialogNumber) {
    mContext = context;
    if(mContext instanceof FoodActivity || mContext instanceof FoodExpandableListActivity) {
        fromFoodActivity = true;
        mRecords = allRecords;
    }
    else {
        fromFoodActivity = false;
        mRecords = mBgRecords;
    }
    DialogFragmentHelper mDialogFragment = new DialogFragmentHelper();

    // Supply dialogNumber input as an argument
    Bundle args = new Bundle();
    args.putInt(DIALOG_NUMBER_KEY, dialogNumber);
    mDialogFragment.setArguments(args);

    return mDialogFragment;
}


// Build AlertDialog using AlertDialog.Builder
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    dNumber = getArguments().getInt(DIALOG_NUMBER_KEY);

    AlertDialog.Builder adb = new AlertDialog.Builder(getActivity());
    LayoutInflater inflater = getActivity().getLayoutInflater();
    Button okButton;
    Button cancelButton;


    switch(dNumber) {
    case CHOOSE_DATES_DIALOG_FULL_HISTORY:
        if(mRecords != null && mRecords.size() != 0) {
            adb.setView(inflater.inflate(R.layout.choose_dates_dialog, null))
            .setCancelable(true)
            .create();

            AlertDialog customChooseDialog = adb.show();
            if(fromFoodActivity) { //here fromFoodActivity is false
                TextView mTitle = (TextView) customChooseDialog.findViewById(R.id.title);
                mTitle.setText(R.string.food_activity_log);
            }
        }
     ....    
     }

从各自的活动中我以这种方式调用DialogFragmentHelper类：

DialogFragmentHelper af = new DialogFragmentHelper();
mDialog = af.newInstance(this, CHOOSE_DATES_DIALOG);
mDialog.show(getFragmentManager(), "Choose");

Answer 1

这是因为在newInstance()方法内部，您创建了一个全新的DialogFragmentHelper实例，其默认值fromFoodActivity为false。

整个建筑有点邪恶。通常需要“帮助者”来访问主要对象，但是帮助者可以帮助创建帮助者。

无论如何，作为快速修复，您可以为此新实例设置fromFoodActivity：

mDialogFragment.fromFoodActivity = fromFoodActivity;

类变量在onCreateDialog中不保持其值

1 个答案: