Question

我有一个ViewPager，它包含三个片段（在选项卡式布局中）。第三个也是最后一个片段包含两个ImageButtons（向上和向下箭头）和一个ImageView，它根据击中的方向箭头循环显示不同的图像。到目前为止，我一直无法使ImageButtons上的onClick方法工作。据我所知，代码首先在父Activity的源代码中查找onClick方法，如果我在Fragment的XML中使用onClick。所以我尝试基于StackOverflow上类似问题的现有解决方案来定义onClick监听器，但这种方法似乎不起作用。有人可以帮助我理解我做错了什么或者是否还有其他错误？

这是Fragment的XML：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#2E2E2E" >

   <ImageButton
       android:id="@+id/pageUpButton"
       android:layout_width="fill_parent"
       android:layout_height="0dp"
       android:layout_weight="1"
       android:layout_gravity="center"
       android:src="@drawable/uparrow"
       android:layout_marginTop="5dp"
       android:contentDescription="@string/contentDesc"
       android:background="@drawable/arrow_imagebutton_selector" />

   <ImageView
        android:id="@+id/recipeDirectionsImage"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
       android:layout_weight="10"
        android:contentDescription="@string/contentDesc" />

   <ImageButton
       android:id="@+id/pageDownButton"
       android:layout_width="fill_parent"
       android:layout_height="0dp"
       android:layout_weight="1"
       android:layout_gravity="center"
       android:src="@drawable/downarrow"
       android:contentDescription="@string/contentDesc"
       android:background="@drawable/arrow_imagebutton_selector" />

   <!-- make list recipePagesList --> 
</LinearLayout>

Fragment的java代码： 注意：我只展示了使用此代码中的一个按钮注意：pageUp和pageDown分别是上一页和下一页。

public class RecipeDirectionsFragment extends Fragment //implements OnClickListener
{
    int REQUEST_CODE = 0, RESULT_OK = 1, page_num = 1;
    public ImageView recipePage;

//    private ImageButton pageButton = null;
      private ImageButton upPageButton = null;
      private ImageButton downPageButton = null;


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
    {
        View rootView = inflater.inflate(R.layout.fragment_recipe_directions, container, false);

        recipePage = (ImageView) rootView.findViewById(R.id.recipeDirectionsImage);
        changePage();

        upPageButton = (ImageButton)rootView.findViewById(R.id.upButton);
        downPageButton = (ImageButton)rootView.findViewById(R.id.downButton);

//      pageButton = (ImageButton)rootView.findViewById(R.id.upButton);
//      pageButton.setOnClickListener(this);

        upPageButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                pageUp(v);
            }
        });

        downPageButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                pageDown(v);
            }
        });

        return rootView;
    }

    public void changePage()
    {
        //recipePage = (ImageView) getView().findViewById(R.id.recipeDirectionsImage);
        switch(page_num)
        {
            case 1: recipePage.setImageResource(R.drawable.recipe_1_3); break;
            case 2: recipePage.setImageResource(R.drawable.recipe_1_4); break;
            case 3: recipePage.setImageResource(R.drawable.recipe_1_5); break;
            case 4: recipePage.setImageResource(R.drawable.recipe_1_6); break;
            case 5: recipePage.setImageResource(R.drawable.recipe_1_7); break;
            case 6: recipePage.setImageResource(R.drawable.recipe_1_8); break;
        }
    }

    public void pageUp(View view)
    {
        //Toast.makeText(getActivity(), "up", Toast.LENGTH_SHORT).show();
        page_num = (page_num > 1) ? page_num-1 : 1;
        changePage();
    }

    public void pageDown(View view)
    {
        //Toast.makeText(getActivity(), "down", Toast.LENGTH_SHORT).show();
        page_num = (page_num < 6) ? page_num+1 : 6;
        changePage();
    }

}

使用上面的代码，每次切换到此片段时，应用程序都会崩溃。它甚至没有显示我加载片段。

我甚至尝试过使用这个备用重写的onClick函数，并让类实现onClickListener：

    @Override
        public void onClick(View v) 
        {
            switch (v.getId()) 
            {
                case R.id.upButton: Toast.makeText(getActivity(), "up", Toast.LENGTH_SHORT).show();
                                    break;

                case R.id.downButton: Toast.makeText(getActivity(), "down", Toast.LENGTH_SHORT).show();
                                      break;
            }
        }

这也不起作用并使应用程序崩溃。

我遇到的另一个解决方案建议在活动中使用paeUp和pageDown函数，但我需要使用变量page_num，并且不知道如何使用某种FragmentManager在Activity中访问它。此外，我宁愿将功能保留在片段中，并遵循问题前面所示的方法。

任何帮助都将非常感谢！注意：我正在使用API 21，并且不知道这是否有所不同。

编辑：片段无法加载时的Logcat输出片段（给出对话“不幸已停止”并回滚到上一个活动）

03-12 21:29:19.965: D/AndroidRuntime(25773): Calling main entry com.android.commands.am.Am
03-12 21:29:19.970: I/ActivityManager(546): START u0 {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.example.culami/.WelcomePageActivity} from uid 2000 on display 0
03-12 21:29:19.974: D/AndroidRuntime(25773): Shutting down VM
03-12 21:29:19.977: I/art(25773): Debugger is no longer active
03-12 21:29:19.985: E/art(25773): Thread attaching while runtime is shutting down: Binder_2
03-12 21:29:19.985: I/AndroidRuntime(25773): NOTE: attach of thread 'Binder_2' failed
03-12 21:29:20.017: I/ActivityManager(546): Start proc com.example.culami for activity com.example.culami/.WelcomePageActivity: pid=25791 uid=10088 gids={50088, 9997, 3003} abi=armeabi-v7a
03-12 21:29:20.054: I/art(25791): Late-enabling -Xcheck:jni
03-12 21:29:20.282: D/OpenGLRenderer(25791): Render dirty regions requested: true
03-12 21:29:20.290: D/Atlas(25791): Validating map...
03-12 21:29:20.343: I/Adreno-EGL(25791): <qeglDrvAPI_eglInitialize:410>: QUALCOMM Build: 10/28/14, c33033c, Ia6306ec328
03-12 21:29:20.344: I/OpenGLRenderer(25791): Initialized EGL, version 1.4
03-12 21:29:20.363: D/OpenGLRenderer(25791): Enabling debug mode 0
03-12 21:29:20.507: I/ActivityManager(546): Displayed com.example.culami/.WelcomePageActivity: +527ms
03-12 21:29:20.874: I/MicrophoneInputStream(1077): mic_close com.google.android.speech.audio.w@3d6762c
03-12 21:29:20.916: D/audio_hw_primary(182): disable_audio_route: reset and update mixer path: audio-record
03-12 21:29:20.916: D/audio_hw_primary(182): disable_snd_device: snd_device(36: voice-rec-mic)
03-12 21:29:20.923: I/HotwordRecognitionRnr(1077): Hotword detection finished
03-12 21:29:20.926: I/HotwordRecognitionRnr(1077): Stopping hotword detection.
03-12 21:29:21.733: I/ActivityManager(546): START u0 {cmp=com.example.culami/.UserDashboardActivity} from uid 10088 on display 0
03-12 21:29:21.741: D/audio_hw_primary(182): select_devices: out_snd_device(2: speaker) in_snd_device(0: none)
03-12 21:29:21.741: D/ACDB-LOADER(182): ACDB -> send_afe_cal
03-12 21:29:21.741: D/audio_hw_primary(182): enable_snd_device: snd_device(2: speaker)
03-12 21:29:21.744: D/audio_hw_primary(182): enable_audio_route: apply and update mixer path: low-latency-playback
03-12 21:29:21.926: I/ActivityManager(546): Displayed com.example.culami/.UserDashboardActivity: +188ms
03-12 21:29:22.592: I/ActivityManager(546): START u0 {cmp=com.example.culami/.RecipeDashboardActivity} from uid 10088 on display 0
03-12 21:29:22.914: I/ActivityManager(546): Displayed com.example.culami/.RecipeDashboardActivity: +313ms
03-12 21:29:23.732: I/ActivityManager(546): START u0 {cmp=com.example.culami/.ActiveRecipeActivity} from uid 10088 on display 0
03-12 21:29:24.128: I/ActivityManager(546): Displayed com.example.culami/.ActiveRecipeActivity: +376ms
03-12 21:29:25.487: D/AndroidRuntime(25791): Shutting down VM
03-12 21:29:25.488: E/AndroidRuntime(25791): FATAL EXCEPTION: main
03-12 21:29:25.488: E/AndroidRuntime(25791): Process: com.example.culami, PID: 25791
03-12 21:29:25.488: E/AndroidRuntime(25791): java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
03-12 21:29:25.488: E/AndroidRuntime(25791):    at com.example.culami.RecipeDirectionsFragment.onCreateView(RecipeDirectionsFragment.java:39)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:486)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.support.v4.view.ViewPager.populate(ViewPager.java:1073)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.support.v4.view.ViewPager.populate(ViewPager.java:919)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.support.v4.view.ViewPager$3.run(ViewPager.java:249)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.view.Choreographer.doCallbacks(Choreographer.java:580)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.view.Choreographer.doFrame(Choreographer.java:549)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.os.Handler.handleCallback(Handler.java:739)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.os.Handler.dispatchMessage(Handler.java:95)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.os.Looper.loop(Looper.java:135)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at android.app.ActivityThread.main(ActivityThread.java:5221)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at java.lang.reflect.Method.invoke(Native Method)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at java.lang.reflect.Method.invoke(Method.java:372)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
03-12 21:29:25.488: E/AndroidRuntime(25791):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
03-12 21:29:25.489: W/ActivityManager(546):   Force finishing activity com.example.culami/.ActiveRecipeActivity
03-12 21:29:25.538: I/OpenGLRenderer(546): Initialized EGL, version 1.4
03-12 21:29:25.992: W/ActivityManager(546): Activity pause timeout for ActivityRecord{128c44a3 u0 com.example.culami/.ActiveRecipeActivity t502 f}
03-12 21:29:26.887: D/audio_hw_primary(182): disable_audio_route: reset and update mixer path: low-latency-playback
03-12 21:29:26.887: D/audio_hw_primary(182): disable_snd_device: snd_device(2: speaker)
03-12 21:29:27.052: E/(180): invalid crash request of size 4 (from pid=25647 uid=0)
03-12 21:29:27.153: W/qcom_sensors_hal(546): hal_sensor1_data_cb: SENSOR1_MSG_TYPE_BROKEN_PIPE
03-12 21:29:27.160: E/Diag_Lib(25866):  Diag_LSM_Init: Failed to open handle to diag driver, error = 2
03-12 21:29:27.160: E/Sensors(25866): sns_fsa_la.c(386):fsa: fflush failed, 9
03-12 21:29:27.161: E/Sensors(25866): sns_fsa_la.c(386):fsa: fflush failed, 9
03-12 21:29:27.186: W/Sensors(25866): sns_smr_la.c(446):smr_la: smr_apps_la_thread_main is starting, fd=11, sns_smr.en_rx_msg_ptr=b6f7e9d0
03-12 21:29:27.196: W/Sensors(25866): sns_sam_app.c(6827):sns_sam_reg_algo: Registering algo service 16, err 0
03-12 21:29:27.204: E/Sensors(25866): sns_debug_main.c(565):Debug Config File missing in EFS!
03-12 21:29:27.250: I/Process(25791): Sending signal. PID: 25791 SIG: 9
03-12 21:29:27.265: D/audio_hw_primary(182): select_devices: out_snd_device(2: speaker) in_snd_device(0: none)
03-12 21:29:27.265: D/ACDB-LOADER(182): ACDB -> send_afe_cal
03-12 21:29:27.265: D/audio_hw_primary(182): enable_snd_device: snd_device(2: speaker)
03-12 21:29:27.268: D/audio_hw_primary(182): enable_audio_route: apply and update mixer path: low-latency-playback
03-12 21:29:27.292: I/WindowState(546): WIN DEATH: Window{b7fc8b3 u0 com.example.culami/com.example.culami.UserDashboardActivity}
03-12 21:29:27.300: I/WindowState(546): WIN DEATH: Window{4829921 u0 com.example.culami/com.example.culami.RecipeDashboardActivity}
03-12 21:29:27.304: W/InputDispatcher(546): channel '2e2367ca com.example.culami/com.example.culami.WelcomePageActivity (server)' ~ Consumer closed input channel or an error occurred.  events=0x9
03-12 21:29:27.304: E/InputDispatcher(546): channel '2e2367ca com.example.culami/com.example.culami.WelcomePageActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
03-12 21:29:27.304: W/InputDispatcher(546): channel 'd9487ff com.example.culami/com.example.culami.ActiveRecipeActivity (server)' ~ Consumer closed input channel or an error occurred.  events=0x9
03-12 21:29:27.304: E/InputDispatcher(546): channel 'd9487ff com.example.culami/com.example.culami.ActiveRecipeActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
03-12 21:29:27.308: I/WindowState(546): WIN DEATH: Window{d9487ff u0 com.example.culami/com.example.culami.ActiveRecipeActivity}
03-12 21:29:27.308: W/InputDispatcher(546): Attempted to unregister already unregistered input channel 'd9487ff com.example.culami/com.example.culami.ActiveRecipeActivity (server)'
03-12 21:29:27.313: I/WindowState(546): WIN DEATH: Window{2e2367ca u0 com.example.culami/com.example.culami.WelcomePageActivity}
03-12 21:29:27.313: W/InputDispatcher(546): Attempted to unregister already unregistered input channel '2e2367ca com.example.culami/com.example.culami.WelcomePageActivity (server)'
03-12 21:29:27.423: I/ActivityManager(546): Process com.example.culami (pid 25791) has died
03-12 21:29:27.460: I/ActivityManager(546): Start proc com.example.culami for activity com.example.culami/.RecipeDashboardActivity: pid=25875 uid=10088 gids={50088, 9997, 3003} abi=armeabi-v7a
03-12 21:29:27.545: I/art(25875): Late-enabling -Xcheck:jni
03-12 21:29:27.816: D/OpenGLRenderer(25875): Render dirty regions requested: true
03-12 21:29:27.822: D/Atlas(25875): Validating map...
03-12 21:29:27.848: I/Adreno-EGL(25875): <qeglDrvAPI_eglInitialize:410>: QUALCOMM Build: 10/28/14, c33033c, Ia6306ec328
03-12 21:29:27.849: I/OpenGLRenderer(25875): Initialized EGL, version 1.4
03-12 21:29:27.866: D/OpenGLRenderer(25875): Enabling debug mode 0
03-12 21:29:28.002: W/InputMethodManagerService(546): Got RemoteException sending setActive(false) notification to pid 25791 uid 10088
03-12 21:29:28.013: I/ActivityManager(546): Displayed com.example.culami/.RecipeDashboardActivity: +587ms
: E/(): Device disconnected: 1
: E/(): Device disconnected

Answer 1

你不是findViewById的正确名称。我可以看到你正在使用diff名称膨胀图像按钮，但发现有差异/错误名称。

 pageDownButton is realId and u are using downButton

它可以解决你的问题。

Answer 2

我认为问题只是在你的情况下：

public void pageUp(View view)
{
    page_num = (page_num > 1) ? page_num-1 : 1;
    changePage();
}

起始值为1，因此该语句再次将1分配给page_num。你应该使用：

public void pageUp(View view)
{
    page_num = (page_num < 6) ? page_num++ : 6;
    changePage();
}

Answer 3

日志告诉我 virtual method 'void android.widget.ImageButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference 所以我认为这个问题是 upPageButton = (ImageButton)rootView.findViewById(R.id.upButton); ImageButton upPageButton = (ImageButton) rootView.findViewById(R.id.upButton); upPageButton成为临时变量。您应该知道临时变量和成员变量之间的区别。所以试着删除 ImageButton upPageButton = (ImageButton) rootView.findViewById(R.id.upButton); ImageButton downPageButton = (ImageButton) rootView.findViewById(R.id.downButton); 我希望它能奏效。

无法使用Fragment中的onClick方法使用现有解决方案

3 个答案: