java - 滚动 GridView 时滚动会使程序崩溃

Question

当我尝试滚动单词搜索时，我的程序崩溃并抛出空指针异常。 但我不知道为什么，

我的 GridView 是使用数组创建的

    String [] WordSearch =  new String[FormattedWords.length];

    for(int i = 1; i<FormattedWords.length ;i++)
    {
        WordSearch[i-1] = FormattedWords[i];
    }

，logcat 也给了我这个

04-17 14:19:37.623: E/AndroidRuntime(5969): FATAL EXCEPTION: main
04-17 14:19:37.623: E/AndroidRuntime(5969): java.lang.NullPointerException
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.AbsListView.obtainView(AbsListView.java:2267)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.GridView.makeAndAddView(GridView.java:1331)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.GridView.makeRow(GridView.java:331)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.GridView.fillDown(GridView.java:283)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.GridView.fillGap(GridView.java:243)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.AbsListView.trackMotionScroll(AbsListView.java:5036)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.AbsListView.scrollIfNeeded(AbsListView.java:3193)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.AbsListView.startScrollIfNeeded(AbsListView.java:3138)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.widget.AbsListView.onTouchEvent(AbsListView.java:3463)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.View.dispatchTouchEvent(View.java:7127)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2170)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1905)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1925)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1379)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.app.Activity.dispatchTouchEvent(Activity.java:2396)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1873)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.View.dispatchPointerEvent(View.java:7307)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3172)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3117)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4153)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4132)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4224)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:171)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.InputEventReceiver.nativeConsumeBatchedInputEvents(Native Method)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.InputEventReceiver.consumeBatchedInputEvents(InputEventReceiver.java:163)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewRootImpl.doConsumeBatchedInput(ViewRootImpl.java:4203)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.ViewRootImpl$ConsumeBatchedInputRunnable.run(ViewRootImpl.java:4243)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.Choreographer.doCallbacks(Choreographer.java:555)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.Choreographer.doFrame(Choreographer.java:523)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.os.Handler.handleCallback(Handler.java:615)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.os.Handler.dispatchMessage(Handler.java:92)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.os.Looper.loop(Looper.java:137)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at android.app.ActivityThread.main(ActivityThread.java:4745)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at java.lang.reflect.Method.invokeNative(Native Method)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at java.lang.reflect.Method.invoke(Method.java:511)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-17 14:19:37.623: E/AndroidRuntime(5969):     at dalvik.system.NativeStart.main(Native Method)

有什么想法吗？

Answer 1

为什么for循环从1开始并按原样插入数据？ NullPointerException 很可能是由 for 循环将字符串插入到 WordSearch 数组中引起的。

例如。

假设 FormattedWords 是一个数组(您正在使用 .length 属性)，如果 FormattedWords.length 为 3 并且包含:

FormattedWords[0] = "a";
FormattedWords[1] = "b";
FormattedWords[2] = "c";

在 for 循环之后 WordSearch 将包含:

WordSearch[0] = "b";
WordSearch[1] = "c";
WordSearch[2] = null;

您的问题似乎出在这里。

编辑

如果要省略 FormattedWords 中的第一个值，则应启动 WordSearch 将 FormattedWords.lenght - 1 的大小设置为避免 NPE。

例如。

String [] WordSearch =  new String[FormattedWords.length - 1];