在活动中有活动A和B

Question

我有活动A和B.在活动A中，我加载数据，然后在单击列表时将它移动到活动B.当返回到活动A时，数据再次加载。如何防止这一点？

Answer 1

当你从一个活动移动到另一个时，从活动A说到活动B，那么你加载的数据就会丢失。要防止数据重新加载，您需要重写onSaveInstanceState（Bundle savedInstance）。

@Override 
public void onSaveInstanceState(Bundle savedInstanceState) { 
    super.onSaveInstanceState(savedInstanceState); 
    // Save UI state changes to the savedInstanceState. 
    // This bundle will be passed to onCreate if the process is 
    // killed and restarted. 
    savedInstanceState.putBoolean("MyBoolean", true); 
    savedInstanceState.putDouble("myDouble", 1.9); 
    savedInstanceState.putInt("MyInt", 1); 
    savedInstanceState.putString("MyString", "Welcome back to Android"); 
    // etc. 
} 

而且你可以通过覆盖onRestoreInstanceState（Bundle savedInstance）来提取这些值。

@Override 
public void onRestoreInstanceState(Bundle savedInstanceState) { 
    super.onRestoreInstanceState(savedInstanceState); 
    // Restore UI state from the savedInstanceState. 
    // This bundle has also been passed to onCreate. 
    boolean myBoolean = savedInstanceState.getBoolean("MyBoolean"); 
    double myDouble = savedInstanceState.getDouble("myDouble"); 
    int myInt = savedInstanceState.getInt("MyInt"); 
    String myString = savedInstanceState.getString("MyString"); 
} 

此外，您可以存储和检索arraylist。