Question

我正在尝试从活动A向活动B发送一个ArrayListobject，但是当我尝试启动活动B时，抛出了一个类异常

这是我的发送和接收语法。问题是 - 如何从object []转换为string []？

或者如果它不可能 - 任何其他解决方案？

ACTIVITY A

Intent intent = new Intent(MainActivity.this, CalculationsActivity.class);
intent.putExtra("strObj2D", stringObjects2D);
startActivity(intent);

活动B

private ArrayList <String[][]> stringObjects2D = new ArrayList <String[][]> () ; 
stringObjects2D = (ArrayList<String[][]>) getIntent().getParcelableExtra("strObj2D");

// the size of the arraylist is printed before the crash - so the data seems to be   there, that is 3 2D-arrays. 
System.out.println("size = " + stringObjects2D.size());

// its here the crash comes, trying to get the second listitem in the arraylist
String[] string =  (String[]) stringObjects2D.get(0)[1];

logccat

 08-04 22:00:16.290: E/AndroidRuntime(9458): FATAL EXCEPTION: main
 08-04 22:00:16.290: E/AndroidRuntime(9458): java.lang.RuntimeException: Unable to start activity  ComponentInfo{com.example.celestialnavigationii/com.example.celestialnavigationii.Calculati     onsActivity}: java.lang.ClassCastException: java.lang.Object[] cannot be cast to java.lang.String[][]
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2100)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at android.app.ActivityThread.access$600(ActivityThread.java:140)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at android.os.Handler.dispatchMessage(Handler.java:99)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at android.os.Looper.loop(Looper.java:137)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at android.app.ActivityThread.main(ActivityThread.java:4898)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at java.lang.reflect.Method.invokeNative(Native Method)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at java.lang.reflect.Method.invoke(Method.java:511)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at dalvik.system.NativeStart.main(Native Method)
 08-04 22:00:16.290: E/AndroidRuntime(9458): Caused by: java.lang.ClassCastException: java.lang.Object[] cannot be cast to java.lang.String[][]
 08-04 22:00:16.290: E/AndroidRuntime(9458):    at com.example.celestialnavigationii.CalculationsActivity.onCreate(CalculationsActivity.java:34)
08-04 22:00:16.290: E/AndroidRuntime(9458):     at android.app.Activity.performCreate(Activity.java:5184)
  08-04 22:00:16.290: E/AndroidRuntime(9458):   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1083)
  08-04 22:00:16.290: E/AndroidRuntime(9458):   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2064)
  08-04 22:00:16.290: E/AndroidRuntime(9458):   ... 11 more

编辑：如果我更改为getParcelableExtra，我会得到一个NullPointerException

Answer 1

使用putStringArrayListExtra方法在Acitvity A上添加额外信息，并使用活动B上的getStringArrayListExtra方法进行检索。

Answer 2

尝试使用getIntent().getParcelableArrayListExtra("strObj2D")代替getIntent().getParcelableExtra("strObj2D")

Answer 3

您需要将ArrayList <String[][]>作为Serializable传递。 ArrayList实施Serializable，因此您只需使用putExtra(...)方法。你应该像这样收到它

ArrayList<String[][]> list = (ArrayList<String[][]>) getSerializableExtra("strObj2D");

在两个活动之间传递ArrayList对象时的类转换异常

3 个答案: