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我正在开发我的第一个 Android 应用程序（有在其他系统中开发的经验，例如 Visual Basic）。

发生了一个奇怪的错误：当我在 java 活动类中的 onCreate 之后使用 onStart 方法时，活动在其启动时立即崩溃。而没有 onStart 一切正常（仅使用 onCreate）。同样的事情是当我把 onRestart 而不是 onStart。

它发生在我的两个不同的活动中，主要和帮助，它们并不相似。为什么我需要使用 onStart (onRestart) 很重要：

  • 在 MainActivity 我希望每次出现时淡入布局，在第一次加载和从其他活动返回后，

  • HelpActivity 在同一框架 (ScrollView) 中使用帮助页面膨胀其他子视图，但在设备旋转时它会返回到帮助目录，最初设置为 onCreate 中的框架。你看，这不是用户想要的。

应用代码和 Logcat。

我使用带有 Android 2.0.1（通过 USB 插入）和第三方模拟器 YouVawe 的旧电子阅读器 Pocketbook iq 701，两者都出现错误。

如果有人遇到过同样的问题，请告诉这是一个 Android 错误还是我做错了什么。也许我可以过度使用它，但根据 docs blablabla 的传统方式，会更可取和更方便。

提前谢谢！

主要活动：

public class MainActivity extends Activity {

    public Animation fadeIn;
    public View mainView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        mainView=(View)findViewById(R.id.linearLayoutMain);
        mainView.setVisibility(View.INVISIBLE);   //to fadein later

        //fade-in animation to use on activity (re)start
        fadeIn = AnimationUtils.loadAnimation(this, R.anim.fadein);
    }

    @Override
    protected void onStart() {
        super.onStart();

        mainView.setVisibility(View.INVISIBLE);
        mainView.startAnimation(fadeIn);
        mainView.setVisibility(View.VISIBLE);
    }

帮助活动：

public class HelpActivity extends Activity {

    public LinearLayout layoutHelpFrame;
    public View viewHelpPage;
    public LayoutInflater inflater;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_help);

        //frame to display help content
        layoutHelpFrame = (LinearLayout)findViewById(R.id.frameHelp);

        //load initially the Help TOC
        inflater = getLayoutInflater();
        viewHelpPage=inflater.inflate(R.layout.help_0, null);
//if no onStart or if onRestart used, add view here:
//      layoutHelpFrame.addView(viewHelpPage);
    }

    @Override
    protected void onStart() {
        super.onStart();
        //when restarted on orientation change, help page is restored
        layoutHelpFrame.addView(viewHelpPage);
    }

    //on click topic links
    public void showHelpTopic(View topiclnk) {

        //clear view
        layoutHelpFrame.removeView(viewHelpPage);   

        //get corresponding topic Id by link textview Id
        String lnkname=getResources().getResourceEntryName(topiclnk.getId()); 
        String topicN=lnkname.substring(lnkname.length()-1); //1 last char (digit)
        int layoutID = MainActivity.getResId("help_"+topicN, R.layout.class);

        //load the Help topic into frame
        viewHelpPage=inflater.inflate(layoutID, null);
        layoutHelpFrame.addView(viewHelpPage);
        layoutHelpFrame.scrollTo(0, 0);
    }

LogCat（从崩溃的那一刻起）：

03-20 06:19:18.136: D/AndroidRuntime(10243): Shutting down VM
03-20 06:19:18.136: W/dalvikvm(10243): threadid=3: thread exiting with uncaught exception (group=0x4001b180)
03-20 06:19:18.136: E/AndroidRuntime(10243): Uncaught handler: thread main exiting due to uncaught exception
03-20 06:19:18.146: E/AndroidRuntime(10243): java.lang.RuntimeException: Unable to start activity ComponentInfo{ru.a_z_b_u_k_a.ourabc/ru.a_z_b_u_k_a.ourabc.HelpActivity}: java.lang.ClassCastException: android.widget.ScrollView
03-20 06:19:18.146: E/AndroidRuntime(10243):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2468)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2484)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at android.app.ActivityThread.access$2200(ActivityThread.java:119)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1835)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at android.os.Handler.dispatchMessage(Handler.java:99)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at android.os.Looper.loop(Looper.java:123)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at android.app.ActivityThread.main(ActivityThread.java:4325)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at java.lang.reflect.Method.invokeNative(Native Method)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at java.lang.reflect.Method.invoke(Method.java:521)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at dalvik.system.NativeStart.main(Native Method)
03-20 06:19:18.146: E/AndroidRuntime(10243): Caused by: java.lang.ClassCastException: android.widget.ScrollView
03-20 06:19:18.146: E/AndroidRuntime(10243):    at ru.a_z_b_u_k_a.ourabc.HelpActivity.onCreate(HelpActivity.java:25)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-20 06:19:18.146: E/AndroidRuntime(10243):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2431)
03-20 06:19:18.146: E/AndroidRuntime(10243):    ... 11 more
03-20 06:19:18.156: I/dalvikvm(10243): threadid=7: reacting to signal 3
03-20 06:19:18.156: E/dalvikvm(10243): Unable to open stack trace file '/data/anr/traces.txt': Permission denied
03-20 06:19:57.116: D/AndroidRuntime(10322): Shutting down VM
03-20 06:19:57.116: W/dalvikvm(10322): threadid=3: thread exiting with uncaught exception (group=0x4001b180)
03-20 06:19:57.116: E/AndroidRuntime(10322): Uncaught handler: thread main exiting due to uncaught exception
03-20 06:19:57.126: E/AndroidRuntime(10322): java.lang.RuntimeException: Unable to start activity ComponentInfo{ru.a_z_b_u_k_a.ourabc/ru.a_z_b_u_k_a.ourabc.MainActivity}: java.lang.NullPointerException
03-20 06:19:57.126: E/AndroidRuntime(10322):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2468)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2484)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at android.app.ActivityThread.access$2200(ActivityThread.java:119)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1835)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at android.os.Handler.dispatchMessage(Handler.java:99)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at android.os.Looper.loop(Looper.java:123)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at android.app.ActivityThread.main(ActivityThread.java:4325)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at java.lang.reflect.Method.invokeNative(Native Method)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at java.lang.reflect.Method.invoke(Method.java:521)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at dalvik.system.NativeStart.main(Native Method)
03-20 06:19:57.126: E/AndroidRuntime(10322): Caused by: java.lang.NullPointerException
03-20 06:19:57.126: E/AndroidRuntime(10322):    at ru.a_z_b_u_k_a.ourabc.MainActivity.onCreate(MainActivity.java:44)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-20 06:19:57.126: E/AndroidRuntime(10322):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2431)
03-20 06:19:57.126: E/AndroidRuntime(10322):    ... 11 more
03-20 06:19:57.136: I/dalvikvm(10322): threadid=7: reacting to signal 3
03-20 06:19:57.136: E/dalvikvm(10322): Unable to open stack trace file '/data/anr/traces.txt': Permission denied
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1 回答 1

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您的 layoutHelpFrame 不能同时是滚动视图和线性布局。您一定混淆了 id 或类似的东西。

为滚动视图和线性布局提供不同的 id 并正确调用它们，它应该可以工作。

于 2014-03-20T06:38:54.803 回答