Android的捆綁和ClassCastException異常

Question

我有一個自定義視圖，其是由它們的碎片稱爲內部的兩個輔助方法：

public Bundle returnInstanceState() { 
     Bundle state = new Bundle(); 
     state.putSerializable("colorData", colorData); 
     return state; 
} 

public void loadInstanceState(Bundle savedInstanceState) { 
    if(savedInstanceState.getSerializable("colorData") != null) 
      colorData = (int[][]) savedInstanceState.getSerializable("colorData"); 
} 

colordata的生命週期：

private int[][] colorData; 

protected void onSizeChanged (int w, int h, int oldw, int oldh) 
{ 
    width = w; 
    height = h; 
    screen = new int[width*height]; 
    cellSize = 0; 
    if(firstLoad && h!= 0 && w!=0) 
    { 

    if(nWidth>nHeight) 
     colorData = new int[nWidth/(nHeight/170 - 1) + 1][170]; 
    else 
      colorData = new int[nHeight/(nWidth/170 - 1) + 1][170]; 
     firstLoad = false; 
    } 
} 

nWidth和nHeight是代表靜態INT原始分辨率。

但是，一旦在藍色的月亮，我給了一個ClassCastException。爲什麼？

從我的測試看來，你可以投null到int[][]雖然這實際上不是我的目標。 colorData是int[][]類型，我從來沒有在任何地方得到NullPointerException，因爲據我所知，除了鑄造Serializable到int[][]之外的所有工作，並且只是偶爾。

這裏是一個堆棧跟蹤，但它是不是在這種情況下多大的用處：

java.lang.RuntimeException: Unable to start activity ComponentInfo{<MYPACKAGENAMEHERE>/<MYPACKAGENAMEHERE>.MusicVisualizerActivity}: java.lang.ClassCastException: [Ljava.lang.Object; 
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1659) 
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1675) 
    at android.app.ActivityThread.access$1500(ActivityThread.java:121) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:943) 
    at android.os.Handler.dispatchMessage(Handler.java:99) 
    at android.os.Looper.loop(Looper.java:130) 
    at android.app.ActivityThread.main(ActivityThread.java:3701) 
    at java.lang.reflect.Method.invokeNative(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:507) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:624) 
    at dalvik.system.NativeStart.main(Native Method) 
Caused by: java.lang.ClassCastException: [Ljava.lang.Object; 
    at <MYPACKAGENAMEHERE>.Visualization_Spectral$RenderView.loadInstanceState(Visualization_Spectral.java:95) 
    at <MYPACKAGENAMEHERE>.Visualization_Spectral.onCreateView(Visualization_Spectral.java:46) 
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:870) 
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1080) 
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062) 
    at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1810) 
    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:501) 
    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129) 
    at android.app.Activity.performStart(Activity.java:3791) 
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1632) 
    ... 11 more 
java.lang.ClassCastException: [Ljava.lang.Object; 
    at <MYPACKAGENAMEHERE>.Visualization_Spectral$RenderView.loadInstanceState(Visualization_Spectral.java:95) 
    at <MYPACKAGENAMEHERE>.visualization.Visualization_Spectral.onCreateView(Visualization_Spectral.java:46) 
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:870) 
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1080) 
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062) 
    at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1810) 
    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:501) 
    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129) 
    at android.app.Activity.performStart(Activity.java:3791) 
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1632) 
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1675) 
    at android.app.ActivityThread.access$1500(ActivityThread.java:121) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:943) 
    at android.os.Handler.dispatchMessage(Handler.java:99) 
    at android.os.Looper.loop(Looper.java:130) 
    at android.app.ActivityThread.main(ActivityThread.java:3701) 
    at java.lang.reflect.Method.invokeNative(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:507) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:624) 
    at dalvik.system.NativeStart.main(Native Method) 

Answer 1

的Serializable接口，如果破綻百出，應該儘量避免，尤其是在Android系統。從代碼的外觀來看，您只是暫時將此對象傳遞到Bundle，因此可以重新創建一個Activity或其他組件，如果沒有其他內容，則序列化該對象將提供較差的性能來滿足這種臨時需求。

如果您處於Activity的環境中，API onRetainNonConfigurationInstance()及其對應的getLastNonConfigurationInstance()將是一種更有效的方法來傳遞該對象。如果您使用的是Fragment API，請參閱setRetainInstance()方法。

HTH

Answer 2

對於我來說，因爲Java（多維）數組是由默認可序列化看起來怪怪的（還是我錯了？）。但看起來，至少在Android中，這有些不同。

你反正應該通過使用Parcelable。實現起來有些繁瑣，但比Serializable更快...下面是一個howto：Passing multidimensional array using Serializable