有关于Fragment是否应该有empty constructor的问题

http://stackoverflow.com/questions/10450348/do-fragments-really-need-an-empty-constructor?lq=1

147 down vote accepted

Yes they do. You shouldn't really be overriding the constructor anyway. You should have a newInstance() static method defined and pass any parameters via arguments (bundle) For example: public static final AlertFragment newInstance(int title, String message) { AlertFragment f = new AlertFragment(); Bundle bdl = new Bundle(2); bdl.putInt(EXTRA_TITLE, title); bdl.putString(EXTRA_MESSAGE, message); f.setArguments(bdl); return f; } And of course grabbing the args this way: @Override public void onCreate(Bundle savedInstanceState) { title = getArguments().getInt(EXTRA_TITLE); message = getArguments().getString(EXTRA_MESSAGE); //... //etc //... } Then you would instantiate from your fragment manager like so: public onCreate(Bundle savedInstanceState) { if(savedInstanceState == null){ getSupportFragmentManager() .beginTransaction() .replace(R.id.content,AlertFragment.newInstance( R.string.alert_title, "Oh noes an error occured!") ) .commit(); } } This way if detached and re-attached the object state can be stored through the arguments. Much like bundles attached to Intents.

//--------------------------------自己--------------------------------

这个问题有时候在应用中崩溃，有时候又不崩溃，大部分的时候不会出现问题。

@SuppressLint("ValidFragment")

CheckinGuideFragment(id int) {

this.id = id;

}

如上述写法是不会报错的。运行的时候大部分时候正常，有时候就奔溃了。

（1）建议不要用这样子的构造函数；

（2）如果需要传递参数，建议使用newInstance()上面的方法。

147 down vote accepted

Yes they do. You shouldn't really be overriding the constructor anyway. You should have a newInstance() static method defined and pass any parameters via arguments (bundle) For example: public static final AlertFragment newInstance(int title, String message) { AlertFragment f = new AlertFragment(); Bundle bdl = new Bundle(2); bdl.putInt(EXTRA_TITLE, title); bdl.putString(EXTRA_MESSAGE, message); f.setArguments(bdl); return f; } And of course grabbing the args this way: @Override public void onCreate(Bundle savedInstanceState) { title = getArguments().getInt(EXTRA_TITLE); message = getArguments().getString(EXTRA_MESSAGE); //... //etc //... } Then you would instantiate from your fragment manager like so: public onCreate(Bundle savedInstanceState) { if(savedInstanceState == null){ getSupportFragmentManager() .beginTransaction() .replace(R.id.content,AlertFragment.newInstance( R.string.alert_title, "Oh noes an error occured!") ) .commit(); } } This way if detached and re-attached the object state can be stored through the arguments. Much like bundles attached to Intents.