title: Android Why switchCompat.setChecked(true) not working after back from BackStack
body: <p>I excute <code>switchCompat.setChecked(true)</code> in the <code>onViewCreated(...)</code> of <strong>Fragment</strong>.It works well first time but not working after back from the BackStack.<br><br>The log show that <code>switchCompat.isChecked()</code> is <strong>true</strong>,but the UI state of <strong>SwitchCompat</strong> is off.It is so strage that the parms named <strong>isChecked</strong> of <strong>onCheckedChanged</strong> in <strong>OnCheckedChangeListener</strong> is also <strong>false</strong>.
  <br><br>
  Could anyone tell me why ?</p>
  
  <p><strong>The Fragment</strong></p>
  
  <pre><code>  @Override
  public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
      super.onViewCreated(view, savedInstanceState);
  
      ......other code......
  
      initialSnooze();
  
  }
  
  
  private void initialSnooze() {
      mSwitchSnooze.setChecked(mAlarm.isSnooze());
      Log.d("TAG", "initialSnooze: "+mAlarm.toString()+" "+mSwitchSnooze.isChecked());
  }
  </code></pre>
  
  <p><strong>Switch to next Fragemnt</strong></p>
  
  <pre><code> private void switchFragment(Fragment fragment,String tag){
          FragmentTransaction fragmentTransaction=getSupportFragmentManager().beginTransaction();
          fragmentTransaction.addToBackStack(tag);        
          fragmentTransaction.replace(android.R.id.content, fragment, tag);
          fragmentTransaction.commit();
      }
  </code></pre>
  
  <p><strong>Back button to back from BackStack</strong></p>
  
  <pre><code>    @Override
  public void onBackPressed() {
      //回退栈中有Fragment
      int count = getSupportFragmentManager().getBackStackEntryCount();
      if (count == 0) {
          super.onBackPressed();
      } else {
          getSupportFragmentManager().popBackStack();
      }
  }
  </code></pre>
  
  <p>**In the Second Frahment **</p>
  
  <pre><code>    @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      if (getArguments() != null) {
          mAlarm = getArguments().getParcelable(PARAM_ALARM);
      }
      mAlarm.setSnooze(true);
  }
  </code></pre>