将整数从 Fragment 传递到 Fragment -sectionPageAdapter、ViewPager

Question

我想做什么：

我有一个托管两个片段的活动 - 托管 Fragment1.java 和 Fragment2.java 的 CreateActivity.java。

当在Fragment1中点击ListFragment中的某一项时，我想切换到查看Fragment2，并根据在Fragment1中列表中点击的位置显示一些信息。

我正在尝试像这样传递列表的“位置”值：

用户点击 Fragment1 中的 ListFragment 项，此代码然后将 "position" 的值发送到 CreateActivity.java：

OnMemeSelectedListener mCallback;

public interface OnListSelectedListener {
    public void onArticleSelected(int position);
}

public void onAttach(Activity activity) {
    super.onAttach(activity);
    try {
        mCallback = (OnListSelectedListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString()
                + " must implement OnHeadlineSelectedListener");
    }
}

@Override
public void onListItemClick(ListView l, View v, int position, long id) {
    super.onListItemClick(l, v, position, id);
    mCallback.onArticleSelected(position);
}

在 CreateActivity.java 中调用以下方法获取整数“位置”：

    @Override
public void onArticleSelected(int position) {
    // Fragment2 newFragment = new Fragment2();
    Bundle args = new Bundle();
    args.putInt(Fragment2.ARG_POSITION, position);
    Fragment2 fragobj = new Fragment2();
    fragobj.setArguments(args);
    Log.w("myApp", "" + position);
    //Switch to Fragment2 Tab
    mViewPager.setCurrentItem(1);
}

到这里为止，它是完整的，因为日志输出了正确的位置列表。现在要获取 Fragment2.class 中的整数，我编写以下行：

int Position = getArguments().getInt(ARG_POSITION, position);

但是，在启动 CreateActivity.java 时，我的日志中出现 NullPointError：

08-31 17:45:04.102: E/AndroidRuntime(14779): FATAL EXCEPTION: main
08-31 17:45:04.102: E/AndroidRuntime(14779): java.lang.NullPointerException
08-31 17:45:04.102: E/AndroidRuntime(14779):    at com.meme.hdmeme.Fragment2.onCreateView(Fragment2.java:59)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.support.v4.app.Fragment.performCreateView(Fragment.java:1478)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1460)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.View.measure(View.java:15518)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.View.measure(View.java:15518)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:847)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.View.measure(View.java:15518)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2313)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.View.measure(View.java:15518)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1874)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1089)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1265)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.Choreographer.doCallbacks(Choreographer.java:562)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.Choreographer.doFrame(Choreographer.java:532)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.os.Handler.handleCallback(Handler.java:725)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.os.Handler.dispatchMessage(Handler.java:92)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.os.Looper.loop(Looper.java:137)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at android.app.ActivityThread.main(ActivityThread.java:5195)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at java.lang.reflect.Method.invokeNative(Native Method)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at java.lang.reflect.Method.invoke(Method.java:511)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
08-31 17:45:04.102: E/AndroidRuntime(14779):    at dalvik.system.NativeStart.main(Native Method)

我已经被困了几个小时，根本找不到解决办法，第 59 行（导致 NPE）是：

int Position = getArguments().getInt(ARG_POSITION, position);

我必须在创建 Fragment2 之前设置它的参数吗？我想在活动中创建后将这些数据传递给 Fragment2，有什么想法吗？

谢谢

Answer 1

看起来你在onCreateView 中调用getArguments()。那时还没有论据。

在您的 Fragment2 中覆盖 setArguments 并将显示您从第一个 Fragment 获得的内容的相关代码放在那里。

这必须进入你的 Fragment2：

 @Override
    public void setArguments(Bundle args) {
        super.setArguments(args);
        int Position = args.getInt(ARG_POSITION, position);

        // now adjust what ever you want to display
    }