Question

我有一个片段作为底部导航的一部分。在片段中，我有一个按钮来选择图像并在recyclerview中显示。

我通过调用fragment类中的方法来处理来自recyclelerview的onBindViewHolder()的此按钮的click事件：

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    if (holder instanceof TrendingHeaderViewHolder){
        ((TrendingHeaderViewHolder) holder).cameraShareIV.setOnClickListener( view -> {
            TrendingFragment.newInstance().selectImage(); // this method is created in fragment class but called here in adapter
        });
    } else if (holder instanceof TrendingItemsViewHolder){
        TestTrends tre = trendsList.get(position - 1);
        Picasso.with(context)
                .load(tre.getTestImage())
                .placeholder(R.drawable.default_profile_photo)
                .into(((TrendingItemsViewHolder) holder).testImgView);
    }
}

在片段中，方法如下：

public void selectImage() {
    Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
    intent.setType("image/*");
    startActivityForResult(intent, GAL_REQ_CODE);
    //context.startActivityForResult(intent, GAL_REQ_CODE); // tried with Activity and Context but still crashes
}

只要点击按钮，应用就会崩溃。这是logcat中的错误：

java.lang.IllegalStateException: Fragment TrendingFragment{171d0a0} not attached to Activity
   at android.support.v4.app.Fragment.startActivityForResult(Fragment.java:1026)
   at android.support.v4.app.Fragment.startActivityForResult(Fragment.java:1017)
   at base.android.com.thumbsapp.UI.Fragments.TrendingFragment.selectImage(TrendingFragment.java:120)
   at base.android.com.thumbsapp.Adapters.TrendingAdapter.lambda$onBindViewHolder$0$TrendingAdapter(TrendingAdapter.java:59)
   at base.android.com.thumbsapp.Adapters.TrendingAdapter$$Lambda$0.onClick(Unknown Source)
   at android.view.View.performClick(View.java:5690)
   at android.view.View$PerformClick.run(View.java:22693)
   at android.os.Handler.handleCallback(Handler.java:836)
   at android.os.Handler.dispatchMessage(Handler.java:103)
   at android.os.Looper.loop(Looper.java:203)
   at android.app.ActivityThread.main(ActivityThread.java:6269)
   at java.lang.reflect.Method.invoke(Native Method)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1063)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:924)

这是我的活动，其中底部导航片段被隐藏起来：

private final BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
        = item -> {
    FragmentTransaction ft = null;
    switch (item.getItemId()) {
        case R.id.navigation_home:
            viewpager.setCurrentItem(0);
            ft = getSupportFragmentManager().beginTransaction()
                    .replace(R.id.fragContainer, new HomeFragment());
            ft.commit();
            return true;
        case R.id.navigation_trending:
            ft = getSupportFragmentManager().beginTransaction()
                    .replace(R.id.fragContainer, new TrendingFragment());
            ft.commit();
            viewpager.setCurrentItem(2);
            return true;
        case R.id.navigation_chats:
            ft = getSupportFragmentManager().beginTransaction()
                    .replace(R.id.fragContainer, new ChatsFragment());
            ft.commit();
            viewpager.setCurrentItem(3);
            return true;
        case R.id.navigation_profile:
            ft = getSupportFragmentManager().beginTransaction()
                    .replace(R.id.fragContainer, new ProfileFragment());
            ft.commit();
            viewpager.setCurrentItem(4);
            return true;
        case R.id.navigation_search:
            ft = getSupportFragmentManager().beginTransaction()
                    .replace(R.id.fragContainer, new SearchFragment());
            ft.commit();
            viewpager.setCurrentItem(1);
            return true;
    }
    return false;
};

和布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="base.android.com.thumbsapp.UI.Activities.MainActivity">

<android.support.v4.view.ViewPager
    android:id="@+id/fragments"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:layout_above="@+id/navigation"/>

<FrameLayout
    android:id="@+id/fragContainer"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="1"
    android:layout_above="@+id/navigation"/>

<android.support.design.widget.BottomNavigationView
    android:id="@+id/navigation"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?android:attr/windowBackground"
    app:itemBackground="@android:color/white"
    app:itemIconTint="@color/nav_bar_behave"
    app:itemTextColor="@color/nav_bar_behave"
    app:menu="@menu/navigation"
    android:layout_alignParentBottom="true"/>

有人可以解释为什么应用程序会崩溃吗？

Answer 1

为什么应用程序崩溃了？因为您的片段未附加到任何活动。

您应该在片段中实现一个侦听器，以便在click事件中从viewHolder调用。

在适配器类中，定义一个接口

{{1}}

最后，在封闭活动中实现此接口，然后让您的片段调用所需的方法。

此外，您应该将onItemClick侦听器事件代码从onBindViewHolder移动到视图持有者

StartActivityForResult不使用片段

1 个答案: