[Android]fix jira problems: NMS-5412

Author: xgfd3

Android/APIExample/app/src/main/java/io/agora/api/example/common/BaseFragment.java

@@ -59,11 +59,15 @@ protected final void runOnUIThread(Runnable runnable){
     }
 
     protected final void runOnUIThread(Runnable runnable, long delay){
-        if(handler != null && runnable != null){
+        if(handler != null && runnable != null && getContext() != null){
             if (delay <= 0 && handler.getLooper().getThread() == Thread.currentThread()) {
                 runnable.run();
             }else{
-                handler.postDelayed(runnable, delay);
+                handler.postDelayed(() -> {
+                    if(getContext() != null){
+                        runnable.run();
+                    }
+                }, delay);
             }
         }
     }

Android/APIExample/app/src/main/java/io/agora/api/example/examples/advanced/CDNStreaming/HostFragment.java

@@ -438,7 +438,7 @@ private void updateTranscodeLayout() {
 
         @Override
         public void onDirectCdnStreamingStateChanged(DirectCdnStreamingState directCdnStreamingState, DirectCdnStreamingError directCdnStreamingError, String s) {
-            handler.post(new Runnable() {
+            runOnUIThread(new Runnable() {
                 @Override
                 public void run() {
                     switch (directCdnStreamingState) {