在活動中有活動A和B

Question

我有活動A和B.在活動A中，我加載數據，然後在單擊列表時將它移動到活動B.當返回到活動A時，數據再次加載。如何防止這一點？

Answer 1

當你從一個活動移動到另一個時，從活動A說到活動B，那麼你加載的數據就會丟失。要防止數據重新加載，您需要重寫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. 
} 

而且你可以通過覆蓋onRestoreInstanceState（Bundle savedInstance）來提取這些值。

@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，您可以存儲和檢索arraylist。