DialogFragment参数和nullpointer异常

Question

我的类应该将参数传递给DialogFragment,但是我的应用程序在onCreate方法(对话框类)中崩溃,导致NullPointerException.Dialog片段类代码部分:

public class ConfirmDialog extends DialogFragment {

public ConfirmDialog() {}

 ConfirmDialog newInstance(String f) {
    ConfirmDialog d = new ConfirmDialog();

    Bundle args = new Bundle();
    args.putString("FILE_NAME", f);
    d.setArguments(args);

    return d;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    file = getArguments().getString("FILE_NAME");
}

我在这一行有nullpointer:

file = getArguments().getString("FILE_NAME");

我不知道为什么.我也粘贴代码调用对话框

private void showConfirmDialog(String file) {
    FragmentManager fm = getSupportFragmentManager();
    ConfirmDialog dialog = new ConfirmDialog();
    Log.i("SHOWFILEACTIVITY", file);
    dialog.newInstance(file);
    dialog.show(fm, "fragment_confirm_dialog");
}

这里的"文件"字符串不为空,我已经检查过了

Log.i("SHOWFILEACTIVITY", file);

Answer 1

你正在ConfirmDialog通过构造函数创建一个,然后调用newInstance(),创建另一个(正确的)ConfirmDialog.但是,然后您丢弃该正确的实例.

解决这个问题:

你的newInstance()方法应该是静态的:

public static ConfirmDialog newInstance(String f) {
    ConfirmDialog d = new ConfirmDialog();

    Bundle args = new Bundle();
    args.putString("FILE_NAME", f);
    d.setArguments(args);

    return d;
}

而showConfirmDialog()应该改变所以它使用的newInstance()方法正确.

private void showConfirmDialog(String file) {
    FragmentManager fm = getSupportFragmentManager();
    Log.i("SHOWFILEACTIVITY", file);

    ConfirmDialog dialog = ConfirmDialog.newInstance(file);
    dialog.show(fm, "fragment_confirm_dialog");
}