putExtra treeMap returns HashMap cannot be cast to TreeMap android
I need your help, I cannot understand what's happening?
I'm trying to send a TreeMap between 2 activities, the code is something like this:
class One extends Activity{
public void send(){
Intent intent = new Intent(One.this, Two.class);
TreeMap<String, String> map = new TreeMap<String, String>();
map.put("1","something");
intent.putExtra("map", map);
startActivity(intent);
finish();
}
}
class Two extends Activity{
public void get(){
(TreeMap<String, String>) getIntent().getExtras().get("map");//Here is the problem
}
}
This returns to me HashMap cannot be cast to TreeMap. What
As alternative to @Jave's suggestions, if you really need the data structure to be a TreeMap , just use the appropriate constructor that takes another map as data source. So on the receiving end ( Two ) do something like:
public class Two extends Activity {
@Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
TreeMap<String, String> map = new TreeMap<String, String>((Map<String, String>) getIntent().getExtras().get("map"));
}
}
However, depending on your project, you probably don't have to worry about the exact Map implementation. So in stead, you could just cast to the Map interface:
public class Two extends Activity {
@Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Map<String, String> map = (Map<String, String>) getIntent().getExtras().get("map");
}
}
Sounds like it serializes to a HashMap and that's what you're getting. Guess you're gonna have to settle for a HashMap. Alternatively you can create your own helper class and implement Parcelable, then serialize the key/strings in order.
不用直接将结果转换为TreeMap ，您可以创建一个新的TreeMap<String, String>并使用putAll()方法：
TreeMap<String, String> myMap = new TreeMap<String, String>;
HashMap<String, String> receivedMap = getIntent().getExtras().get("map");
myMap.putAll(receivedMap);
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