從活動的背部按Android的入門片段

Question

你好，我想開始在簡單的活動的回壓

我有這樣

public boolean onKeyDown(int keyCode, KeyEvent event) { 

      Fragment fragment = null; 
       fragment = new MainActivity(); 
      android.support.v4.app.FragmentManager fragmentManager = getSupportFragmentManager(); 
       android.support.v4.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction(); 

       fragmentTransaction.replace(R.id.content_frame, fragment); 



       fragmentTransaction.commit(); 
      return true; 
     } 
     return super.onKeyDown(keyCode, event); 
    } 

但沒有工作做一個片段..

Answer 1

嘗試使用下面的代碼。

@Override 
    public void onBackPressed() { 


Fragment fragment = null; 
       fragment = new MainActivity(); 
      android.support.v4.app.FragmentManager fragmentManager = getSupportFragmentManager(); 
       android.support.v4.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction(); 

       fragmentTransaction.replace(R.id.content_frame, fragment); 



       fragmentTransaction.commit(); 
    } 

希望它能起作用。

Answer 2

嘗試這種情況：

@Override 
public void onBackPressed() { 

    android.support.v4.app.FragmentManager mFragmentManager = getSupportFragmentManager(); 
    android.support.v4.app.FragmentTransaction mFragmentTransaction = mFragmentManager.beginTransaction(); 
    mFragmentTransaction.replace(R.id.fragmentView, new Fragment()).commit(); 
}