java.lang.NullPointerException at android.widget.TabHost.dispatchWindowFocusChanged(TabHost.java:32-优快云博客

本文探讨了一个在Android应用开发过程中遇到的问题：当Tab布局中的数据为空时，出现NullPointerException异常。通过分析代码逻辑，作者发现了问题所在，并提供了解决方案。文章详细解释了错误发生的场景以及如何避免此类问题，对于Android开发者来说具有实用价值。

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01-01 17:29:35.613: ERROR/AndroidRuntime(23590): java.lang.NullPointerException 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.widget.TabHost.dispatchWindowFocusChanged(TabHost.java:321) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.widget.TabHost.dispatchWindowFocusChanged(TabHost.java:321) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:661) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.view.ViewRoot.handleMessage(ViewRoot.java:1819) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.os.Handler.dispatchMessage(Handler.java:99) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.os.Looper.loop(Looper.java:123) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at android.app.ActivityThread.main(ActivityThread.java:4363) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at java.lang.reflect.Method.invokeNative(Native Method) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at java.lang.reflect.Method.invoke(Method.java:521) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 01-01 17:29:35.613: ERROR/AndroidRuntime(23590): at dalvik.system.NativeStart.main(Native Method)

这个问题困扰了我好几天了。

先贴一段代码

//产品规格 final TabHost tabHost = (TabHost) this.findViewById(android.R.id.tabhost); tabHost.setup(); //必须setup //如果不存在info，则添加一个空的tab, 否则会莫名其妙的报错 //java.lang.NullPointerException at android.widget.TabHost.dispatchWindowFocusChanged(TabHost.java:321) if(saleDetail.getInfoList().size() == 0){ TextView view = new TextView(context); tabHost.addTab(tabHost.newTabSpec("") .setContent(new TabFacroty(""))// 该ID必须位于layout里面 .setIndicator(view)); tabHost.getTabWidget().setVisibility(View.GONE); return; } for(GoodsInfoBean info : saleDetail.getInfoList()){ TextView view = new TextView(context); view.setLayoutParams(new LinearLayout.LayoutParams(-2, -2)); view.setText(info.getTitle()); view.setFocusable(true); view.setFocusableInTouchMode(true); view.setGravity(Gravity.CENTER); view.setTextColor(context.getResources().getColor(R.color.sale_tab_default)); view.setBackgroundResource(R.drawable.sale_detail_spec_selector); tabHost.addTab(tabHost.newTabSpec("") .setContent(new TabFacroty(info.getAlt()))// 该ID必须位于layout里面 .setIndicator(view)); }
如果saleDetail.getInfoList() == 0 起初的时候不会创建tab

然后如果单击spinner 或者是弹出alert的时候会报错，如上。。。。

通过测试，发现如果tab个数大于1的时候则不会报错

于是乎。。。揣测跟tab有关加上该段代码。如果不存在的时候默认加一个不可见的tab

if(saleDetail.getInfoList().size() == 0){、、、、、

至此问题解决