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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