Question

我从数据库中提取数据并将其放入哈希映射中。

HashMap<String,Object> players= new HashMap();
        for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
            players.put(childSnapshot.getKey(), childSnapshot.getValue());
        }
        for (Map.Entry<String, Object> entry : players.entrySet()) {
            Log.d("asd","Key = " + entry.getKey() + ", Value = " + entry.getValue());
        }

Log.d输出为：

D/asd: Key = lastpeony, Value = {lat=40.89, long=29.37, avatar=dino}
D/asd: Key = lifesuxtr, Value = {lat=40.8901765, long=29.377306, avatar =petyr}

我要做的是访问每个键的lat long和avatar值。我怎么做？因为稍后我将使用这些值在地图上绘制标记。

感谢

Answer 1

如果要在HashMap<String,Object> players地图的每个值中提取特定内容（latti或longi），则值类型应该比Object类型更具体。因此，请使用HashMap<String,Object>

，而不是使用players来存储HashMap<String,SomeSpecificType>

Answer 2

您使用hashmap .get https://developer.android.com/reference/java/util/HashMap.html#get(java.lang.Object)

String key = "lastpeon";
Object value = players.get(key);

Answer 3

更改

HashMap<String,Object> players= new HashMap();

到

HashMap<String,Map<String,Object>> players= new HashMap<>();

然后使用：

初始化Map

for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
    players.put(childSnapshot.getKey(), (Map<String,Object>)childSnapshot.getValue());
}

然后你可以遍历内部Map s：

for (Map.Entry<String, Map<String,Object>> entry : players.entrySet()) {
    for (Map.Entry<String, Object> ientry : entry.getValue().entrySet()) {
        Log.d("asd","Key = " + ientry.getKey() + ", Value = " + ientry.getValue());
    }
}

访问HashMap Java Android中的对象的属性

3 个答案: