FragmentRetainInstanceSupport.java 中的 UI 更改

Question

我正在使用 v4 兼容性应用程序的示例。我注意到在这一部分中：

mPosition++;
max = mProgressBar.getMax();
mProgressBar.setProgress(mPosition);

如果我添加 TextView.setText()：

mPosition++;
max = mProgressBar.getMax();
mProgressBar.setProgress(mPosition);
mStatus.setText(String.valueOf(max)); // here, just to test stuff!

它会放弃并出现以下异常：

01-29 18:55:08.889: W/dalvikvm(14565): threadid=11: thread exiting with uncaught exception (group=0x40a791f8)
01-29 18:55:08.889: E/AndroidRuntime(14565): FATAL EXCEPTION: Thread-1035
01-29 18:55:08.889: E/AndroidRuntime(14565): android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:3939)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:701)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.view.View.requestLayout(View.java:12555)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.view.View.requestLayout(View.java:12555)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.view.View.requestLayout(View.java:12555)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.view.View.requestLayout(View.java:12555)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.view.View.requestLayout(View.java:12555)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:268)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.view.View.requestLayout(View.java:12555)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.widget.TextView.checkForRelayout(TextView.java:6716)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.widget.TextView.setText(TextView.java:3256)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.widget.TextView.setText(TextView.java:3110)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at android.widget.TextView.setText(TextView.java:3085)
01-29 18:55:08.889: E/AndroidRuntime(14565):    at com.mytest.ui.PreActivity$RetainedFragment$1.run(PreActivity.java:111)

为什么会发生这种情况？或者更好的是，如何调整文档示例以使用 TextView 而不是 ProgressView？

Answer 1

可能是不同的 UI 线程再次调用保留中的 Fragment 的情况。可以使用 getActivity().runOnUIThread(some code) 来解决。只是我的建议。