【Debug-Fragment】..v4.app.FragmentActivity.getSupportFragmentManager()' on a null object reference

本文探讨了在自定义Fragment中遇到的NullPointerException错误,特别是在调用getSupportFragmentManager()方法时。通过对比getActivity()和getFragmentManager()的方法,作者分享了如何避免此错误,并提供了修改后的代码示例。

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错误:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.support.v4.app.FragmentManager android.support.v4.app.FragmentActivity.getSupportFragmentManager()' on a null object reference
        at xxx.assistant.fragment.xxxxxx.replaceFragment(xxxxxxxx.java:148)
        at xxx.assistant.fragment.xxxxxx.access$200(xxxxxx.java:41)
        at xxx.assistant.fragment.xxxxxx$2.onRequestKnightSuccess(xxxxxx.java:119)
        at vertu.assistant.request.xxxx$1.onResponse(xxxx.java:209)

用在自定义的Fragment中,该Fragment继承自“android.support.v4.app.Fragment;”

代码:

    private void replaceFragment(Fragment fragment) {
        FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.fl_homepage_follow_fragment_content, fragment);
        fragmentTransaction.commit();
    }

参考:https://blog.youkuaiyun.com/suyan_why/article/details/52574197

感觉用“getActivity()”不太妥,想换成在Fragment中适用的方式

参考:https://www.cnblogs.com/earl-yongchang/p/5747860.html

感觉使用【getFragmentManager()】更方便一下,所以把

FragmentManager fragmentManager = getActivity().getSupportFragmentManager();

替换成:

FragmentManager fragmentManager = getFragmentManager();

暂时不报错,再看看吧~

分析以下代码的报错信息:------------------------- PROCESS STARTED (7432) for package com.example.myapplication ---------------------------- 2025-07-09 13:27:09.041 7432-7432 e.myapplicatio com.example.myapplication W ClassLoaderContext classpath size mismatch. expected=0, found=1 (PCL[] | PCL[/data/data/com.example.myapplication/code_cache/.overlay/base.apk/classes3.dex*4250602868]) 2025-07-09 13:27:09.042 7432-7432 e.myapplicatio com.example.myapplication W Found duplicate classes, falling back to extracting from APK : /data/app/~~dh0o8WK_fXecSV_JJz78RQ==/com.example.myapplication-RE5zX8NpQzXhviy1xPMobA==/base.apk 2025-07-09 13:27:09.042 7432-7432 e.myapplicatio com.example.myapplication W NOTE: This wastes RAM and hurts startup performance. 2025-07-09 13:27:09.042 7432-7432 e.myapplicatio com.example.myapplication W Found duplicated class when checking oat files: 'Lcom/example/myapplication/ListActivity$1;' in /data/data/com.example.myapplication/code_cache/.overlay/base.apk/classes3.dex and /data/app/~~dh0o8WK_fXecSV_JJz78RQ==/com.example.myapplication-RE5zX8NpQzXhviy1xPMobA==/base.apk!classes3.dex 2025-07-09 13:27:09.172 7432-7432 NetworkSecurityConfig com.example.myapplication D No Network Security Config specified, using platform default 2025-07-09 13:27:09.173 7432-7432 NetworkSecurityConfig com.example.myapplication D No Network Security Config specified, using platform default 2025-07-09 13:27:09.201 7432-7456 libEGL com.example.myapplication D loaded /vendor/lib/egl/libEGL_emulation.so 2025-07-09 13:27:09.202 7432-7456 libEGL com.example.myapplication D loaded /vendor/lib/egl/libGLESv1_CM_emulation.so 2025-07-09 13:27:09.204 7432-7456 libEGL com.example.myapplication D loaded /vendor/lib/egl/libGLESv2_emulation.so 2025-07-09 13:27:09.246 7432-7432 AppCompatDelegate com.example.myapplication D Checking for metadata for AppLocalesMetadataHolderService : Service not found 2025-07-09 13:27:09.305 7432-7432 e.myapplicatio com.example.myapplication W Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (greylist, reflection, allowed) 2025-07-09 13:27:09.305 7432-7432 e.myapplicatio com.example.myapplication W Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (greylist, reflection, allowed) 2025-07-09 13:27:09.397 7432-7454 HostConnection com.example.myapplication D HostConnection::get() New Host Connection established 0xe9a68250, tid 7454 2025-07-09 13:27:09.403 7432-7454 HostConnection com.example.myapplication D HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_has_shared_slots_host_memory_allocator ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit ANDROID_EMU_sync_buffer_data ANDROID_EMU_vulkan_async_qsri ANDROID_EMU_read_color_buffer_dma GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_gles_max_version_2 2025-07-09 13:27:09.404 7432-7454 OpenGLRenderer com.example.myapplication W Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without... 2025-07-09 13:27:09.411 7432-7454 EGL_emulation com.example.myapplication D eglCreateContext: 0xe9a68170: maj 2 min 0 rcv 2 2025-07-09 13:27:09.414 7432-7454 EGL_emulation com.example.myapplication D eglMakeCurrent: 0xe9a68170: ver 2 0 (tinfo 0xe9db64d0) (first time) 2025-07-09 13:27:09.438 7432-7454 Gralloc4 com.example.myapplication I mapper 4.x is not supported 2025-07-09 13:27:09.439 7432-7454 HostConnection com.example.myapplication D createUnique: call 2025-07-09 13:27:09.439 7432-7454 HostConnection com.example.myapplication D HostConnection::get() New Host Connection established 0xe9a6acc0, tid 7454 2025-07-09 13:27:09.467 7432-7454 HostConnection com.example.myapplication D HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_has_shared_slots_host_memory_allocator ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit ANDROID_EMU_sync_buffer_data ANDROID_EMU_vulkan_async_qsri ANDROID_EMU_read_color_buffer_dma GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_gles_max_version_2 2025-07-09 13:27:10.478 7432-7432 AndroidRuntime com.example.myapplication D Shutting down VM 2025-07-09 13:27:10.479 7432-7432 AndroidRuntime com.example.myapplication E FATAL EXCEPTION: main Process: com.example.myapplication, PID: 7432 android.view.WindowManager$BadTokenException: Unable to add window -- token null is not valid; is your activity running? at android.view.ViewRootImpl.setView(ViewRootImpl.java:1068) at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:409) at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:109) at android.app.Dialog.show(Dialog.java:340) at android.app.AlertDialog$Builder.show(AlertDialog.java:1131) at com.example.myapplication.MyBaseAdapter$1.onClick(MyBaseAdapter.java:55) at android.view.View.performClick(View.java:7448) at android.view.View.performClickInternal(View.java:7425) at android.view.View.access$3600(View.java:810) at android.view.View$PerformClick.run(View.java:28305) at android.os.Handler.handleCallback(Handler.java:938) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:223) at android.app.ActivityThread.main(ActivityThread.java:7656) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 2025-07-09 13:27:10.509 7432-7432 Process com.example.myapplication I Sending signal. PID: 7432 SIG: 9 ---------------------------- PROCESS ENDED (7432) for package com.example.myapplication ----------------------------
最新发布
07-10
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