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,这是我唯一更改的地方):
public BuddyListAdapter(Context context, HashMap<String, Buddy> hashMap) {
buddyList = new ArrayList<Buddy>(hashMap.values());
mInflater = LayoutInflater.from(context);
ctx = context;
}
单步执行时,没有任何反应,但在运行时,当我创建一个空的 ArrayList
时,我在 ChoreoGrapher.doCallbacks
中得到一个 NullPointerException
,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 ChoreoGrapher
以及为什么它会导致我的应用崩溃?
我完全不知道可能是什么问题,或者如何找出问题所在。 Eclipse 调试器或崩溃信息并没有真正帮助。
整个堆栈轨迹如下:
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]
我在主要 Activity 中也有一个 Handler
。当它什么都不做时, ListView 不会崩溃。但是,我在打开 ListView 之前删除了它的所有回调。
最佳答案
我的应用程序仅在 Android 4.4 上存在此错误。
在调试器中,它显示与提问者相同的消息。然而,当不调试 DDMS 中的完整堆栈跟踪时:
完整的堆栈跟踪:
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TextView的4.4源码第6124行,原来这是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,您没有在 getView
中提供布局参数。
我曾经为标准微调项目膨胀 android.R.layout.simple_spinner_item
。看起来这个项目使用了 ellipsing
。所以在我的 getView
中,我现在调用:
view.setEllipsize(null);
这解决了我在 Android 4.4 上的问题。
编辑
事实证明问题不是省略,而是 getView
中的 View 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 false
以不立即将 View 附加到父级,因为这是在需要时附加子级的适配器中。否则你会得到错误。
当你正确膨胀时,你不需要将 ellipseSize
设置为 null
。这是因为当您使用父级膨胀的好方法时,它会正确处理 LayoutParams
,导致椭圆代码不会引发 NullPointerException
。
所以,适当充气,就再也不用担心了。
关于java - Android 应用程序在 ChoreoGrapher 中因 NullPointerException 而崩溃,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/12533006/