java为什么当我通过NavController返回时，我的片段*有时*是空白的。navigateUp（）？
当通过navigateUp（）返回IpFragment时，它有时是空的，这时它应该显示几个简单的文本视图。有时渲染正确，但如果失败，唯一的错误似乎是无关的
返回时显示为空白的片段：
public class IpFragment extends Fragment implements ...{
private static final String TAG = "IpFragment";
private NavController navController;
private Context context;
private TextView tvIp;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
navController = NavHostFragment.findNavController(this);
View v = inflater.inflate(R.layout.fragment_ip, container, false);
context = v.getContext();
return v;
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Log.d(TAG, "onViewCreated");
ConnectivitySingleton.getInstance().registerCallback(this);
tvIp = view.findViewById(R.id.tvIp);
tvIp.setText(getDeviceIp());
}
@Override
public void onDestroyView() {
super.onDestroyView();
ConnectivitySingleton.getInstance().unregisterCallback(this);
}
...
}
我们返回的片段：
public class InterviewFragment extends Fragment implements ConnectionCallback, StreamStatusCallback, TextureView.SurfaceTextureListener, SpeakCallback {
private static final String TAG = "InterviewFragment";
private NavController navController;
private AutoFitDrawableView autoFitDrawableView;
private Context context;
public boolean isStreaming;
private MessageConnection messageConnection;
private TextView tvQuestion;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
Log.d(TAG, "onCreateView");
// return super.onCreateView(inflater, container, savedInstanceState);
navController = NavHostFragment.findNavController(this);
View v = inflater.inflate(R.layout.fragment_interview, container, false);
context = v.getContext();
return v;
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
Log.d(TAG, "onViewCreated");
super.onViewCreated(view, savedInstanceState);
ConnectivitySingleton.getInstance().registerCallback(this);
VisionSingleton.getInstance().registerCallback(this);
SpeakSingleton.getInstance().registerCallback(this);
autoFitDrawableView = view.findViewById(R.id.autofit);
// need to set autoFitDrawableView's display size / rotation
int rotation = ((Activity) context).getWindowManager().getDefaultDisplay().getRotation();
autoFitDrawableView.setPreviewSizeAndRotation(800, 600, rotation); // w 800 h 600
// set listener to stream frames
autoFitDrawableView.setSurfaceTextureListenerForPreview(this);
tvQuestion = view.findViewById(R.id.question);
}
@Override
public void onDestroyView() {
Log.d(TAG, "onDestroyView");
super.onDestroyView();
ConnectivitySingleton.getInstance().unregisterCallback(this);
VisionSingleton.getInstance().unregisterCallback(this);
SpeakSingleton.getInstance().unregisterCallback(this);
}
@Override
public void onConnected() {
}
@Override
public void onDisconnected() {
navController.navigateUp();
}
@Override
/**
* Passes surfaceTexture to VisionSingleton once ST is available. VisionSingleton then sets up
* DTS camera to stream to surfaceTexture.
*/
public void onSurfaceTextureAvailable(SurfaceTexture surfaceTexture, int i, int i1) {
Log.d(TAG, "onSurfaceTextureAvailable");
VisionSingleton.getInstance().initPreview(surfaceTexture);
}
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture surfaceTexture, int i, int i1) { }
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture surfaceTexture) {
Log.d(TAG, "onSurfaceTextureDestroyed");
VisionSingleton.getInstance().stopPreview();
return false;
}
@Override
/**
* If a 'vision start' command has been received, then surfaceTexture's frame should be sent to
* the phone app via messageConnection.
*/
public void onSurfaceTextureUpdated(SurfaceTexture surfaceTexture) {
if(isStreaming) {
try {
int tvWidth = autoFitDrawableView.getPreview().getWidth();
int tvHeight = autoFitDrawableView.getPreview().getHeight();
// Get bitmap from TextureView
Bitmap bm = Bitmap.createBitmap(tvWidth, tvHeight, Bitmap.Config.ARGB_8888);
autoFitDrawableView.getPreview().getBitmap(bm);
// Compress via JPG
ByteArrayOutputStream os = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.JPEG, 50, os);
byte[] byteArray = os.toByteArray();
Log.d(TAG, "Byte size: " + byteArray.length);
if (byteArray.length > 1000000) {
Log.w(TAG, "Byte size is > 1 MB! Exceeds max sending size.");
} else {
messageConnection.sendMessage(new BufferMessage(byteArray));
}
} catch (Exception e) {
e.printStackTrace();
Log.e(TAG, e.getMessage());
}
}
}
@Override
public void onStartStream(final MessageConnection messageConnection) {
Log.d(TAG, "onStartStream");
isStreaming = true;
this.messageConnection = messageConnection;
}
@Override
public void onStopStream() {
Log.d(TAG, "onStopStream");
isStreaming = false;
}
@Override
public void onSpeakCommandReceived(String question) {
tvQuestion.setText(question);
}
}
有时在InterviewFragment中，我会发现这个错误，当时它不会破坏任何东西，但稍后返回到IpFragment时，它会显示为空白
08-07 22:45:54.921 5196-5275/edu.unc.etlab.robojloomo W/MessageListener: Exception occured during command launch
安卓.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
at 安卓.view.ViewRootImpl.checkThread(ViewRootImpl.java:6357)
at 安卓.view.ViewRootImpl.requestLayout(ViewRootImpl.java:874)
at 安卓.view.View.requestLayout(View.java:17476)
at 安卓.view.View.requestLayout(View.java:17476)
at 安卓.view.View.requestLayout(View.java:17476)
at 安卓.view.View.requestLayout(View.java:17476)
at 安卓.view.View.requestLayout(View.java:17476)
at 安卓.view.View.requestLayout(View.java:17476)
at 安卓.support.constraint.ConstraintLayout.requestLayout(ConstraintLayout.java:3172)
at 安卓.view.View.requestLayout(View.java:17476)
at 安卓.view.View.requestLayout(View.java:17476)
at 安卓.widget.RelativeLayout.requestLayout(RelativeLayout.java:360)
at 安卓.view.View.requestLayout(View.java:17476)
at 安卓.widget.TextView.checkForRelayout(TextView.java:6865)
at 安卓.widget.TextView.setText(TextView.java:4057)
at 安卓.widget.TextView.setText(TextView.java:3915)
at 安卓.widget.TextView.setText(TextView.java:3890)
at edu.unc.etlab.robojloomo.InterviewFragment.onSpeakCommandReceived(InterviewFragment.java:168)
at edu.unc.etlab.robojloomo.loomo_services.SpeakSingleton.speak(SpeakSingleton.java:69)
at edu.unc.etlab.robojloomo.listeners.SpeakCommand.execute(SpeakCommand.java:14)
at edu.unc.etlab.robojloomo.listeners.MessageListener.onMessageReceived(MessageListener.java:85)
at com.segway.robot.sdk.connectivity.RobotMessageConnection.handleMessage(RobotMessageConnection.java:219)
at 安卓.os.Handler.dispatchMessage(Handler.java:98)
at 安卓.os.Looper.loop(Looper.java:135)
at 安卓.os.HandlerThread.run(HandlerThread.java:61)
在InterviewFragment中设置textView的文本时会发生此错误：
public void onSpeakCommandReceived(String question) {
tvQuestion.setText(question);
}
# 1 楼答案
好的，在发布这个问题后，我很快就解决了它。我参考了这篇帖子来修复我遇到的错误：Android "Only the original thread that created a view hierarchy can touch its views."。我把onSpeakCommandReceived（）改为：
仍然不确定这个错误是如何导致下一个屏幕空白的，因为它们发生在不同的时间，但现在这个错误已经修复，一切似乎都正常