启动到物理设备时出现黑屏

如何解决启动到物理设备时出现黑屏

我的应用程序在我的模拟器（Google Pixel 2）上运行得非常好，但是当我尝试将应用程序启动到物理设备（Galaxy Note 20）时，我只是出现白屏，可能是物理设备出了问题比模拟器新很多。 我试过了：

flutter upgrade 
flutter clean 

并将 minSDK 更改为 23 而不是 16。我也尝试将依赖项升级到较新版本，但由于不兼容问题，我不得不将它们重置回旧版本。

当启动到模拟器时，我得到这个：

Launching lib\main.dart on Android SDK built for x86 in debug mode...
Running Gradle task 'assembleDebug'...
√ Built build\app\outputs\flutter-apk\app-debug.apk.
Installing build\app\outputs\flutter-apk\app.apk...
Debug service listening on ws://127.0.0.1:54695/lfhRZFuIGMw=/ws
Syncing files to device Android SDK built for x86...
D/EGL_emulation(21851): eglMakeCurrent: 0xebea1000: ver 3 0 (tinfo 0xcc025380)
D/eglCodecCommon(21851): setVertexArrayObject: set vao to 0 (0) 1 0

当启动到物理设备时，这就是我得到的：

Launching lib\main.dart on SM N985F in debug mode...
Running Gradle task 'assembleDebug'...
√ Built build\app\outputs\flutter-apk\app-debug.apk.
Installing build\app\outputs\flutter-apk\app.apk...
Debug service listening on ws://127.0.0.1:54580/fefT1rs2LOk=/ws
Syncing files to device SM N985F...
E/flutter (22977): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: NoSuchMethodError: The getter 'length' was called on null.
E/flutter (22977): Receiver: null
E/flutter (22977): Tried calling: length
E/flutter (22977): #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:54:5)
E/flutter (22977): #1      _parseJson (dart:convert-patch/convert_patch.dart:39:28)
E/flutter (22977): #2      JsonDecoder.convert (dart:convert/json.dart:506:36)
E/flutter (22977): #3      JsonCodec.decode (dart:convert/json.dart:157:41)
E/flutter (22977): #4      jsonDecode (dart:convert/json.dart:96:10)
E/flutter (22977): #5      getList (package:realtime_test/main.dart:27:30)
E/flutter (22977): <asynchronous suspension>
E/flutter (22977): #6      main (package:realtime_test/main.dart:16:3)
E/flutter (22977): <asynchronous suspension>
E/flutter (22977): 
I/ViewRootImpl@46a8966[MainActivity](22977): ViewPostIme pointer 0
I/ViewRootImpl@46a8966[MainActivity](22977): MSG_WINDOW_FOCUS_CHANGED 0 1
I/SurfaceControl(22977): release : mNativeObject = 476773762736 - Surface(name=Surface(name=a38c4 InputMethod)/@0x7a23a73 - animation-leash)/@0xa41f0a1 / android.view.-$$Lambda$Rl1VZmNJ0VZDLK0BAbaVGis0rrA.accept:2 android.view.InsetsSourceControl.release:170 android.view.InsetsSourceConsumer.setControl:202 android.view.ImeInsetsSourceConsumer.setControl:154 
I/SurfaceControl(22977): nativeRelease nativeObject s[476773762736]
I/SurfaceControl(22977): nativeRelease nativeObject e[476773762736]
I/SurfaceControl(22977): release : mNativeObject = 476773765760 - Surface(name=Surface(name=2a9e95b NavigationBar0)/@0x87e7f82 - animation-leash)/@0x2190368 / android.view.-$$Lambda$Rl1VZmNJ0VZDLK0BAbaVGis0rrA.accept:2 android.view.InsetsSourceControl.release:170 android.view.InsetsSourceConsumer.setControl:202 android.view.InsetsController.onControlsChanged:833 
I/SurfaceControl(22977): nativeRelease nativeObject s[476773765760]
I/SurfaceControl(22977): nativeRelease nativeObject e[476773765760]
I/SurfaceControl(22977): release : mNativeObject = 476773740672 - Surface(name=Surface(name=6106940 StatusBar)/@0xd1b68b8 - animation-leash)/@0xe205381 / android.view.-$$Lambda$Rl1VZmNJ0VZDLK0BAbaVGis0rrA.accept:2 android.view.InsetsSourceControl.release:170 android.view.InsetsSourceConsumer.setControl:202 android.view.InsetsController.onControlsChanged:833 
I/SurfaceControl(22977): nativeRelease nativeObject s[476773740672]
I/SurfaceControl(22977): nativeRelease nativeObject e[476773740672]
D/InputTransport(22977): Input channel destroyed: 'ClientS',fd=122
I/SurfaceControl(22977): release : mNativeObject = 476773811120 - Surface(name=Surface(name=a38c4 InputMethod)/@0x7a23a73 - animation-leash)/@0x2fda6bd / android.view.-$$Lambda$Rl1VZmNJ0VZDLK0BAbaVGis0rrA.accept:2 android.view.InsetsSourceControl.release:170 android.view.InsetsSourceConsumer.setControl:202 android.view.ImeInsetsSourceConsumer.setControl:154 
I/SurfaceControl(22977): nativeRelease nativeObject s[476773811120]
I/SurfaceControl(22977): nativeRelease nativeObject e[476773811120]
I/SurfaceView(22977): onWindowVisibilityChanged(8) false io.flutter.embedding.android.FlutterSurfaceView{a0c34fd V.E...... ........ 0,0-1440,3035} of ViewRootImpl@46a8966[MainActivity]
I/SurfaceView(22977): surfaceDestroyed callback.size 1 #2 io.flutter.embedding.android.FlutterSurfaceView{a0c34fd V.E...... ........ 0,3035}
I/mali_egl(22977): eglDestroySurface() in
I/mali_winsys(22977): delete_surface() [1440x3035] return
I/mali_egl(22977): eglDestroySurface() out
W/libEGL  (22977): EGLNativeWindowType 0x7021f7c4a0 disconnect failed
D/SurfaceControl(22977): hide : mNativeObject = 477310781072 - sc.mNativeObject = 476773737760 - Surface(name=SurfaceView - com.example.realtime_test/com.example.realtime_test.MainActivity@a0c34fd@0)/@0x4db9fa2
D/SurfaceControl(22977): nativeSetFlags Done : Surface(name=SurfaceView - com.example.realtime_test/com.example.realtime_test.MainActivity@a0c34fd@0)/@0x4db9fa2
I/SurfaceView(22977): remove() from RT android.view.SurfaceView$2@1fbc4b2 Surface(name=SurfaceView - com.example.realtime_test/com.example.realtime_test.MainActivity@a0c34fd@0)/@0x4db9fa2
I/SurfaceControl(22977): release : mNativeObject = 476773737760 - Surface(name=SurfaceView - com.example.realtime_test/com.example.realtime_test.MainActivity@a0c34fd@0)/@0x4db9fa2 / android.view.SurfaceControl$Transaction.remove:3449 android.view.SurfaceView$2.positionLost:1561 android.graphics.RenderNode$CompositePositionUpdateListener.positionLost:313 <bottom of call stack> 
I/SurfaceControl(22977): nativeRelease nativeObject s[476773737760]
I/SurfaceControl(22977): nativeRelease nativeObject e[476773737760]
I/SurfaceControl(22977): release : mNativeObject = 476773742576 - Surface(name=Background for -SurfaceView - com.example.realtime_test/com.example.realtime_test.MainActivity@a0c34fd@0)/@0x1cd2c03 / android.view.SurfaceControl$Transaction.remove:3449 android.view.SurfaceView$2.positionLost:1562 android.graphics.RenderNode$CompositePositionUpdateListener.positionLost:313 <bottom of call stack> 
I/SurfaceControl(22977): nativeRelease nativeObject s[476773742576]
I/SurfaceControl(22977): nativeRelease nativeObject e[476773742576]
I/mali_egl(22977): eglDestroySurface() in
I/mali_winsys(22977): delete_surface() [1440x3088] return
I/mali_egl(22977): eglDestroySurface() out
W/libEGL  (22977): EGLNativeWindowType 0x7021f7a290 disconnect failed
I/SurfaceControl(22977): release : mNativeObject = 476773781888 - Surface(name=null)/@0x516d780 / android.view.SurfaceControl.assignNativeObject:567 android.view.SurfaceControl.readFromParcel:1115 android.view.IWindowSession$Stub$Proxy.relayout:1777 android.view.ViewRootImpl.relayoutWindow:8953 
I/SurfaceControl(22977): nativeRelease nativeObject s[476773781888]
I/SurfaceControl(22977): nativeRelease nativeObject e[476773781888]
I/SurfaceControl(22977): assignNativeObject: nativeObject = 0 Surface(name=null)/@0x516d780 / android.view.SurfaceControl.readFromParcel:1115 android.view.IWindowSession$Stub$Proxy.relayout:1777 android.view.ViewRootImpl.relayoutWindow:8953 android.view.ViewRootImpl.performTraversals:3312 android.view.ViewRootImpl.doTraversal:2575 android.view.ViewRootImpl$TraversalRunnable.run:9910 android.view.Choreographer$CallbackRecord.run:1010 android.view.Choreographer.doCallbacks:809 android.view.Choreographer.doFrame:744 android.view.Choreographer$FrameDisplayEventReceiver.run:995 
I/SurfaceControl(22977): assignNativeObject: nativeObject = 0 Surface(name=null)/@0x8186ac0 / android.view.SurfaceControl.readFromParcel:1115 android.view.IWindowSession$Stub$Proxy.relayout:1787 android.view.ViewRootImpl.relayoutWindow:8953 android.view.ViewRootImpl.performTraversals:3312 android.view.ViewRootImpl.doTraversal:2575 android.view.ViewRootImpl$TraversalRunnable.run:9910 android.view.Choreographer$CallbackRecord.run:1010 android.view.Choreographer.doCallbacks:809 android.view.Choreographer.doFrame:744 android.view.Choreographer$FrameDisplayEventReceiver.run:995 
I/SurfaceControl(22977): release : mNativeObject = 476773737200 - Surface(name=Bounds for - com.example.realtime_test/com.example.realtime_test.MainActivity@0)/@0xd62f1b9 / android.view.ViewRootImpl.destroySurface:2437 android.view.ViewRootImpl.relayoutWindow:8990 android.view.ViewRootImpl.performTraversals:3312 android.view.ViewRootImpl.doTraversal:2575 
I/SurfaceControl(22977): nativeRelease nativeObject s[476773737200]
I/SurfaceControl(22977): nativeRelease nativeObject e[476773737200]
I/ViewRootImpl@46a8966[MainActivity](22977): Relayout returned: old=(0,1440,3088) new=(0,3088) req=(1440,3088)8 dur=6 res=0x5 s={false 0} ch=true fn=2
I/SurfaceView(22977): windowStopped(true) false io.flutter.embedding.android.FlutterSurfaceView{a0c34fd V.E...... ........ 0,3035} of ViewRootImpl@46a8966[MainActivity]
I/ViewRootImpl@46a8966[MainActivity](22977): stopped(true) old=false

所以显然出了点问题，但我不知道是什么问题。

解决方法

• 出现白屏是因为您的应用无法通过您在启动时执行的初始功能。

• 错误信息说getter length called on null，然后它 在 main.dart 行中断 #27。进一步阅读 错误，您正在调用 jsonDecode，但它没有收到任何信息， 导致您的应用崩溃并且无法加载主页。

• 这不是 技术上崩溃了，但它正在等待第 27 行的逻辑 完成，但还没有完成。由于它说 getter length was called on null 很可能也意味着您正在 for 循环中执行逻辑，或者检查是否存在 isEmpty 或 isNotEmpty，因此在检查这些属性时，{{ 1}} 它在调用此函数时试图检查是否为空。

• 首先仔细检查一下，这很可能是由于您在模拟器上工作时遇到的错误，然后修复了它并使模拟器工作，但没有为您的新用户解决问题，谁正在使用全新安装，例如您的物理设备。

• 如果您从数据库中获取数据，并在模拟器上开发时使用了初始虚拟数据，而忘记为新设备添加该数据，这应该可以解决您的问题，我会开始寻找。>

• 要记住的另一件事是，当您的应用程序成功编译和构建时，您的问题不在于依赖项或 SDK 版本或与构建 gradle 相关的其他内容。并且您的错误表示此 iterable ，因此问题不是由构建时故障引起的，而是运行时错误。