Android应用程序崩溃，ChoreoGrapher中出现NullPointerException

Question

我有以下代码，试图在ListView中创建一个简单的ListAdapter（我以前使用过这段代码，这是我唯一更改内容的地方）：

public BuddyListAdapter(Context context, HashMap<String, Buddy> hashMap) {
    buddyList = new ArrayList<Buddy>(hashMap.values());
    mInflater = LayoutInflater.from(context);
    ctx = context;
}

当单步执行时，什么都不会发生，但当运行时，我在ChoreoGrapher中得到了一个null点异常。doCallbacks，当我创建一个空的数组列表时，它不会崩溃：

public BuddyListAdapter(Context context, HashMap<String, Buddy> hashMap) {
    buddyList = new ArrayList<Buddy>();
    mInflater = LayoutInflater.from(context);
    ctx = context;
}

什么是编舞，为什么它会使我的应用程序崩溃？

我完全被困在可能的问题上，或者如何找出问题所在。Eclipse调试器或崩溃信息没有真正的帮助。

整个堆栈跟踪如下：

Thread [<1> main] (Suspended (exception NullPointerException))  
    Choreographer.doCallbacks(int, long) line: 558  
    Choreographer.doFrame(long, int) line: 525  
    Choreographer$FrameDisplayEventReceiver.run() line: 711 
    Handler.handleCallback(Message) line: 615   
    Choreographer$FrameHandler(Handler).dispatchMessage(Message) line: 92   
    Looper.loop() line: 137 
    ActivityThread.main(String[]) line: 4745    
    Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]  
    Method.invoke(Object, Object...) line: 511  
    ZygoteInit$MethodAndArgsCaller.run() line: 786  
    ZygoteInit.main(String[]) line: 553 
    NativeStart.main(String[]) line: not available [native method]  

我在主活动中还有一个Handler。当它不做任何事情时，列表视图不会崩溃。但是，我在打开列表视图之前从中删除所有回调。

Answer 1

检查在代码中操作视图时可能存在无效类型转换的地方。我对这一行有完全相同的错误

picture.setLayoutParams(new ViewGroup.LayoutParams(50, 50));

编舞抛出此错误“android.view.ViewGroup$LayoutParams不能强制转换为android.widget.LinearLayout$LayoutParams”

将其更改为

picture.setLayoutParams(new android.widget.LinearLayout.LayoutParams(50, 50));

解决问题。

Answer 2

我在另一个应用程序中再次遇到同样的事情。它似乎是由列表适配器中getView中未处理的异常引起的。

Answer 3

我的应用程序中只有在Android 4.4上有这个错误。

在调试器中，它显示与提问者相同的消息。但是，当不调试DDMS中的完整堆栈跟踪时：

完整堆栈跟踪：

11-13 16:34:53.088: E/AndroidRuntime(1964): FATAL EXCEPTION: main
11-13 16:34:53.088: E/AndroidRuntime(1964): Process: appname, PID: 1964
11-13 16:34:53.088: E/AndroidRuntime(1964): java.lang.NullPointerException
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.TextView.makeNewLayout(TextView.java:6124)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.TextView.onMeasure(TextView.java:6419)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.View.measure(View.java:16458)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.Spinner.setUpChild(Spinner.java:632)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.Spinner.makeView(Spinner.java:585)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.Spinner.getBaseline(Spinner.java:431)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1262)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:590)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.View.measure(View.java:16458)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.View.measure(View.java:16458)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.View.measure(View.java:16458)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.View.measure(View.java:16458)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2289)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.View.measure(View.java:16458)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1914)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1111)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1293)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5582)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.Choreographer.doCallbacks(Choreographer.java:562)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.Choreographer.doFrame(Choreographer.java:532)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.os.Handler.handleCallback(Handler.java:733)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.os.Handler.dispatchMessage(Handler.java:95)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.os.Looper.loop(Looper.java:137)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at android.app.ActivityThread.main(ActivityThread.java:4998)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at java.lang.reflect.Method.invokeNative(Native Method)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at java.lang.reflect.Method.invoke(Method.java:515)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
11-13 16:34:53.088: E/AndroidRuntime(1964):     at dalvik.system.NativeStart.main(Native Method)

查看第6124行的TextView的4.4源代码，结果表明这是由于省略时缺少布局参数造成的。这很奇怪，因为代码在ListAdapter中失败，您在getView中没有提供布局参数。

我曾经给Android充气。R、 布局。标准微调器项的simple\u微调器项。该项似乎使用了省略号。因此，在我的getView中，我现在调用：

view.setEllipsize(null);

这解决了我在Android4.4上的问题。

编辑

事实证明，问题不在于省略号，而在于getView中视图的膨胀不当。

inflater.inflate(android.R.layout.simple_spinner_item, null);//WRONG
inflater.inflate(android.R.layout.simple_spinner_item, parent, false);//GOOD

请注意，您提供了false以不立即将视图附加到父视图，因为这是在需要时附加子视图的适配器中。否则你会出错。

当您正确充气时，您不需要将ellipseSize设置为null。这是因为当您使用父级充气好方法时，它会正确处理LayoutParams，导致椭圆代码不会引发NullPointerException。

所以，适当充气，然后就再也不用担心了。