Question

我正在尝试在片段中创建一个快餐栏。我尝试了很多其他类似的问题，但无法找到解决方案。当片段打开时，应用程序崩溃。我不知道问题是什么。有人能帮我吗。提前致谢。这是我的片段：

public class MainFragment extends Fragment {


    public MainFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_main, null);
        ImageView test = new ImageView(getContext());
        ImageView nyimg = (ImageView)view.findViewById(R.id.glidimg);

        Glide.with(getContext()).load("http://inthecheesefactory.com/uploads/source/glidepicasso/cover.jpg").into(nyimg);

        Snackbar.make(view, "Some Message", Snackbar.LENGTH_INDEFINITE).show();

       // Picasso.with(getContext()).load("http://inthecheesefactory.com/uploads/source/glidepicasso/cover.jpg").into(test);
        return view;
        //return inflater.inflate(R.layout.fragment_main, container, false);
    }
}

这是我的xml文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    tools:context="com.example.imran.myapp.MainFragment"
   >

    <TextView
        android:id="@+id/main_title"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textSize="35sp"
        android:textColor="@color/white"
        android:textAlignment="center"
        android:background="@drawable/title_background"
        android:layout_gravity="center"
        android:text="Welcome" />
    <LinearLayout android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:layout_marginTop="40dp"
            android:textSize="25sp"
            android:textStyle="bold"
            android:textAlignment="center"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="You are logged in."
            />

        <ImageView
            android:id="@+id/glidimg"
            android:layout_width="fill_parent"
            android:layout_height="match_parent"
            android:contentDescription="my image"
            android:src="@drawable/ic_menu_gallery"
            />

    </LinearLayout>

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="www.mirzaphotos.com"
        android:layout_gravity="bottom"
        android:textAlignment="center"
        android:textSize="15sp"
        android:textStyle="bold"
        android:textColor="@color/darkorange"

        android:layout_alignParentBottom="true"
        />

</RelativeLayout>

我收到此错误：

04-08 17:57:18.559 4049-4049/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                 Process: com.example.imran.myapp, PID: 4049
                                                 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.imran.myapp/com.example.imran.myapp.Home}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.view.ViewGroup.getContext()' on a null object reference
                                                     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2808)
                                                     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2873)
                                                     at android.app.ActivityThread.access$900(ActivityThread.java:181)
                                                     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1482)
                                                     at android.os.Handler.dispatchMessage(Handler.java:102)
                                                     at android.os.Looper.loop(Looper.java:145)
                                                     at android.app.ActivityThread.main(ActivityThread.java:6145)
                                                     at java.lang.reflect.Method.invoke(Native Method)
                                                     at java.lang.reflect.Method.invoke(Method.java:372)
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
                                                  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.view.ViewGroup.getContext()' on a null object reference
                                                     at android.support.design.widget.Snackbar.<init>(Snackbar.java:180)
                                                     at android.support.design.widget.Snackbar.make(Snackbar.java:206)
                                                     at com.example.imran.myapp.MainFragment.onCreateView(MainFragment.java:42)
                                                     at android.support.v4.app.Fragment.performCreateView(Fragment.java:1962)
                                                     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1026)
                                                     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1207)
                                                     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
                                                     at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1572)
                                                     at android.support.v4.app.FragmentController.execPendingActions(FragmentController.java:330)
                                                     at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:511)
                                                     at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1234)
                                                     at android.app.Activity.performStart(Activity.java:6412)
                                                     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2771)
                                                     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2873) 
                                                     at android.app.ActivityThread.access$900(ActivityThread.java:181) 
                                                     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1482) 
                                                     at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                     at android.os.Looper.loop(Looper.java:145) 
                                                     at android.app.ActivityThread.main(ActivityThread.java:6145) 
                                                     at java.lang.reflect.Method.invoke(Native Method) 
                                                     at java.lang.reflect.Method.invoke(Method.java:372) 
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399) 
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194) 
04-08 17:57:18.559 4068-4097/? D/AcmsCertificateMngr: handleAppRemoved() Enter com.example.imran.myapp
04-08 17:57:18.569 1036-1514/? V/ApplicationPolicy: isApplicationStateBlocked userId 0 pkgname com.example.imran.myapp
04-08 17:57:18.579 1036-1514/? W/ActivityManager:   Force finishing activity com.example.imran.myapp/.Home

Answer 1

当View未附加到父级时，它无法创建Snackbar（它从getContext返回null）。将您的Snackbar.create()移至onActivityCreated或其他方法，如onResume()等生命周期。

public class MainFragment extends Fragment {

    View view;
    public MainFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.fragment_main, null);
        ImageView test = new ImageView(getContext());
        ImageView nyimg = (ImageView)view.findViewById(R.id.glidimg);

        Glide.with(getContext()).load("http://inthecheesefactory.com/uploads/source/glidepicasso/cover.jpg").into(nyimg);



       // Picasso.with(getContext()).load("http://inthecheesefactory.com/uploads/source/glidepicasso/cover.jpg").into(test);
        return view;
        //return inflater.inflate(R.layout.fragment_main, container, false);
    }
    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        Snackbar.make(view, "Some Message", Snackbar.LENGTH_INDEFINITE).show();
    }
}

Answer 2

请尝试使用CoordinatorLayout。

Snackbar将向上查看树，试图找到合适的父级，该父级被定义为CoordinatorLayout或窗口装饰的内容视图，以先到者为准。

http://www.androidhive.info/2015/09/android-material-design-snackbar-example/

Snackbar不在片段中工作，尝试过其他问题的解决方案

2 个答案: