在bundle savedInstanceState中保存ArrayList

Question

the ArrayList is defined on class level. these are my savedInstance methods:

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putStringArrayList("savedList", list);
}


@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    list=savedInstanceState.getStringArrayList("savedList");
}

but still, when i change orientation the ArrayList is blank

Answer 1

When you use onRestoreInstanceState() to restore state, its called after onStart() so you update your list with the saved state after you define your adapter. Your best option is to restore the list in onCreate() the same way you do it on onRestoreInstanceState() . You can also redefine the adapter or call notifyDataSetChanged() .

Answer 2

TextView textviewname;
String textname;

 @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);   
          setContentView(R.layout.activity_main);

       //declare the ui like this
    textviewname = (TextView) findViewById(R.id.textviewid);
       if(savedInstanceState==null){
       //the first time the activity was created
       //do the normal flow of the code
       //Example:getting the intent data for(savedList)or processing it
       Intent i = getIntent();
       textname = i.getStringExtra("savetext");
      //or textname="name_data";
       }else{
       //this is called when orientation change occur
       //get the savedata
        list=savedInstanceState.getStringArrayList("savedList");
        textname=savedInstanceState.getString("savetext");
       }

       textviewname.setText(textname);

}   
@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    //saving data when orientation change trigger
    //saving  data before ondestroy happens
//onSaveInstanceState is called before going to another activity or orientation change
    outState.putStringArrayList("savedList", list);
    outState.putString("savetext", textname);
    //all imnportant data saved and can be restored
}


@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    //this is  only called after ondestroy-> oncreate occur
    list=savedInstanceState.getStringArrayList("savedList");
    textname=savedInstanceState.getString("savetext");
    //oncreate->onSaveInstanceState->ondestroy->oncreate->onRestoreInstanceState
}

Answer 3

try to use

list.addAll(savedInstanceState.getStringArrayList("savedList"));

instead

list=savedInstanceState.getStringArrayList("savedList");