使用TabWidgets的Android 2.1 NullPointerException
作者：互联网
我有一个我无法弄清楚的问题,它只发生在运行< 2.1的设备上.它在Android 2.2上运行良好.我有一个同步任务,在加载所有选项卡时显示加载对话框.以下是TabActivity的代码：
public class OppTabsView extends TabActivity {
Dialog dialog;
String errorText;
boolean save;
final int OPP_SAVE = 0;
public static boolean edited;
public void onCreate(Bundle icicle) {
try {
super.onCreate(icicle);
new DoInBackground().execute();
} catch (Exception e) {
Toast.makeText(this, "Error occured. Please try again later.",
Toast.LENGTH_SHORT).show();
}
}
@Override
protected void onResume() {
super.onResume();
}
@Override
protected void onStop() {
super.onStop();
}
@Override
protected void onPause() {
super.onPause();
}
public boolean onCreateOptionsMenu(Menu menu) {
menu.add(0, OPP_SAVE, 0, "Test");
return true;
}
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case OPP_SAVE:
save = true;
new DoInBackground().execute();
return true;
}
return false;
}
public void LoadOpp() {
handler.sendEmptyMessage(0);
}
public void SaveOpp() {
DoStuff();
}
public void LoadLayout() {
setContentView(R.layout.view_opptabs);
/* TabHost will have Tabs */
TabHost tabHost = (TabHost) findViewById(android.R.id.tabhost);
/*
* TabSpec used to create a new tab. By using TabSpec only we can able
* to setContent to the tab. By using TabSpec setIndicator() we can set
* name to tab.
*/
/* tid1 is firstTabSpec Id. Its used to access outside. */
TabSpec firstTabSpec = tabHost.newTabSpec("tid1");
TabSpec secondTabSpec = tabHost.newTabSpec("tid1");
TabSpec thirdTabSpec = tabHost.newTabSpec("tid1");
/* TabSpec setIndicator() is used to set name for the tab. */
/* TabSpec setContent() is used to set content for a particular tab. */
firstTabSpec.setIndicator("General",
getResources().getDrawable(R.drawable.tab_moneybag))
.setContent(new Intent(this, OppTabGeneral.class));
secondTabSpec.setIndicator("Details",
getResources().getDrawable(R.drawable.tab_papers)).setContent(
new Intent(this, OppTabDetails.class));
thirdTabSpec.setIndicator("Contact",
getResources().getDrawable(R.drawable.tab_contact)).setContent(
new Intent(this, OppTabContact.class));
/* Add tabSpec to the TabHost to display. */
tabHost.addTab(firstTabSpec);
tabHost.addTab(secondTabSpec);
tabHost.addTab(thirdTabSpec);
}
private void do_update() {
if (save) {
SaveOpp();
} else {
LoadOpp();
}
}
Handler handler = new Handler() {
public void handleMessage(Message msg) {
LoadLayout();
}
};
private class DoInBackground extends AsyncTask<Void, Void, Void> implements
DialogInterface.OnCancelListener {
protected void onPreExecute() {
String verb = "Connecting";
if (save) {
verb = "Saving";
}
dialog = ProgressDialog.show(OppTabsView.this, "", verb
+ ". Please Wait...", true, true, this);
}
protected Void doInBackground(Void... v) {
do_update();
return null;
}
protected void onPostExecute(Void v) {
dialog.dismiss();
}
public void onCancel(DialogInterface dialog) {
cancel(true);
dialog.dismiss();
finish();
}
}
}
这是错误的堆栈跟踪：
java.lang.NullPointerException
at android.widget.TabWidget.dispatchDraw(TabWidget.java:206)
at android.view.ViewGroup.drawChild(ViewGroup.java:1529)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258)
at android.view.ViewGroup.drawChild(ViewGroup.java:1529)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258)
at android.view.ViewGroup.drawChild(ViewGroup.java:1529)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258)
at android.view.View.draw(View.java:6538)
at android.widget.FrameLayout.draw(FrameLayout.java:352)
at android.view.ViewGroup.drawChild(ViewGroup.java:1531)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258)
at android.view.ViewGroup.drawChild(ViewGroup.java:1529)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258)
at android.view.View.draw(View.java:6538)
at android.widget.FrameLayout.draw(FrameLayout.java:352)
at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1830)
at android.view.ViewRoot.draw(ViewRoot.java:1349)
at android.view.ViewRoot.performTraversals(ViewRoot.java:1114)
at android.view.ViewRoot.handleMessage(ViewRoot.java:1633)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4363)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
at dalvik.system.NativeStart.main(Native Method)
我试过踩过它,但错误似乎是从没有,而不是在特定的行.任何帮助是极大的赞赏.
解决方法:
TabSpec firstTabSpec = tabHost.newTabSpec("tid1");
TabSpec secondTabSpec = tabHost.newTabSpec("tid1");
TabSpec thirdTabSpec = tabHost.newTabSpec("tid1");
您是否可以为多个TabSpec使用相同的“标签”？我会尝试正确设置它们,看它是否修复它.
编辑：好的,所以我的建议没有解决它,但无论如何都有独特的标签是有道理的.
试试这个看看它是否有帮助.添加一个选项,在LoadLayout()方法的末尾设置当前选中的选项卡,如下所示(参见最后一行)…
/* Add tabSpec to the TabHost to display. */
tabHost.addTab(firstTabSpec);
tabHost.addTab(secondTabSpec);
tabHost.addTab(thirdTabSpec);
tabHost.setCurrentTab(0); // <== Add this
EDIT2：我发现TabWidget.java源代码和206行(发生NullPointerException)是……
mBottomLeftStrip.setState(selectedChild.getDrawableState());
……我可以看到有三种可能的异常原因.
> mBottonLeftStrip为空(极不可能)
> selectedCHild为null(TabWidget应该默认为子0并且使用tabHost.setCurrentTab()无论如何都会强制执行)
> selectedChild.getDrawableState()的结果为null
最后似乎是可能的原因,但我不确定是什么原因导致它返回null.
尝试谷歌’TabWidget.java源’ – 第二个结果点在grepcode.com上有行号,你可以看到它在异常点尝试做什么.
标签：android,tabs,tabactivity,tabwidget 来源： https://codeday.me/bug/20190630/1340093.html