【Android】移除FragmentManager裡的BackStack entry

ref:
Is this the right way to clean-up Fragment back stack when leaving a deeply nested stack?
http://shareandopen.tumblr.com/post/35328568659/android-clear-all-back-stack

為了好的使用者體驗，希望在程式運作到某一個情境時，清除所有的back stack entry，讓使用者不要在按下back按鍵時，發生一些悲劇體驗的話，可以利用程式碼來清除back stack entry。

// In your FragmentActivity use getSupprotFragmentManager() to get the FragmentManager.

// Clear all back stack.
int backStackCount = getSupportFragmentManager().getBackStackEntryCount();
for (int i = 0; i < backStackCount; i++) {

    // Get the back stack fragment id.
    int backStackId = getSupportFragmentManager().getBackStackEntryAt(i).getId();

    fm.popBackStack(backStackId, FragmentManager.POP_BACK_STACK_INCLUSIVE);

} /* end of for */

【Android】ActionBar最左邊返回鍵

private ActionBar mActionBar;

mActionBar = getSupportActionBar();

mActionBar.setDisplayShowHomeEnabled(true);   //顯示返回符號，在android 2.3測試，若setDis                                                  //playHomeAsUpEnabled沒寫，則無任何動作發生

mActionBar.setDisplayHomeAsUpEnabled(true);   //不顯示返回符號，在onOptionsItemSelected須設定                                              //按下後動作
mActionBar.setTitle("Title ");

@Override
public boolean onOptionsItemSelected(MenuItem item) {
 switch (item.getItemId()) {
 case android.R.id.home:
 // app icon in action bar clicked; goto parent activity.
  onBackPressed();
  return true;
   ...

}

}

-----------------------------------------

//可改寫返回鍵的內容設定

@Override
public void onBackPressed() {
 Intent intent = new Intent(this, MainActivity.class);
 intent.putExtra("test", "i am come from Mainactivity2activity");
 setResult(RESULT_OK, intent);
 
 closeDB();
 finish();
}