layout使用继承TextView,Activity未使用,报java.lang.NullPointerException一例

Android 2.3.3         
Eclipse Version: 3.7.0         
LogCat   


AutoScrollTextView继承TextView,用于文字特殊效果显示,代码如下:

public class AutoScrollTextView extends TextView implements OnClickListener {
	……
	public void onDraw(Canvas canvas) {
		……
		canvas.drawText(text, temp_view_plus_text_length - step, y, paint);
		……
	}
	……
}


Activity中使用:

	taobaoTextView = (AutoScrollTextView) findViewById(R.id.text);


Activity对应的layout :

		<com.taobao.util.AutoScrollTextView
			android:id="@+id/text" android:text="text" android:layout_height="fill_parent"
			android:layout_width="40px" android:textColor="#999"
			android:layout_gravity="right" android:background="#333">
		</com.taobao.util.AutoScrollTextView>


当Activity中取消使用AutoScrollTextView,而layout 未删除有关AutoScrollTextView的配置时,
LogCat 报错信息:

02-07 12:06:58.728: DEBUG/AndroidRuntime(1034): Shutting down VM
02-07 12:06:58.728: WARN/dalvikvm(1034): threadid=1: thread exiting with uncaught exception (group=0x40015560)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): FATAL EXCEPTION: main
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): java.lang.NullPointerException
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.graphics.Canvas.drawText(Native Method)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at com.taobao.util.AutoScrollTextView.onDraw(AutoScrollTextView.java:181)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.View.draw(View.java:6880)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewGroup.drawChild(ViewGroup.java:1646)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewGroup.drawChild(ViewGroup.java:1644)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewGroup.drawChild(ViewGroup.java:1644)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewGroup.drawChild(ViewGroup.java:1644)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.View.draw(View.java:6883)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.widget.FrameLayout.draw(FrameLayout.java:357)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1862)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewRoot.draw(ViewRoot.java:1522)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewRoot.performTraversals(ViewRoot.java:1258)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.os.Handler.dispatchMessage(Handler.java:99)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.os.Looper.loop(Looper.java:123)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at android.app.ActivityThread.main(ActivityThread.java:3683)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at java.lang.reflect.Method.invokeNative(Native Method)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at java.lang.reflect.Method.invoke(Method.java:507)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-07 12:06:58.747: ERROR/AndroidRuntime(1034): at dalvik.system.NativeStart.main(Native Method)
02-07 12:06:58.797: WARN/ActivityManager(61): Force finishing activity com.taobao.tmall/.PlayAd
02-07 12:06:58.807: WARN/ActivityManager(61): Force finishing activity com.taobao.tmall/.WakeUp



发生错误原因分析:

	canvas.drawText(text, temp_view_plus_text_length - step, y, paint);

此处的paint为null,报错。

解决办法:在AutoScrollTextView.java中初始化paint,为其赋值。

	paint = getPaint();

 

分析以下代码的错信息:------------------------- 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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