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java - 启动新 Activity 时出现空指针异常

转载 作者:塔克拉玛干 更新时间:2023-11-03 01:09:23 24 4
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好的,当我开始我的第三个 Activity 时,我遇到了一个空指针异常。这是 LogCat 消息:

12-28 04:38:00.350: ERROR/AndroidRuntime(776): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.acithium.main/com.acithium.rss.ShowDescription}: java.lang.NullPointerException12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2401)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at android.app.ActivityThread.access$2100(ActivityThread.java:116)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at android.os.Handler.dispatchMessage(Handler.java:99)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at android.os.Looper.loop(Looper.java:123)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at android.app.ActivityThread.main(ActivityThread.java:4203)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at java.lang.reflect.Method.invokeNative(Native Method)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at java.lang.reflect.Method.invoke(Method.java:521)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at dalvik.system.NativeStart.main(Native Method)12-28 04:38:00.350: ERROR/AndroidRuntime(776): Caused by: java.lang.NullPointerException12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at com.acithium.rss.ShowDescription.onCreate(ShowDescription.java:48)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364)12-28 04:38:00.350: ERROR/AndroidRuntime(776):     ... 11 more

Here is the section of code where I call the activity:

public void onItemClick(AdapterView parent, View v, int position, long id)
{
Log.i(tag,"item clicked! [" + feed.getItem(position).getTitle() + "]");

Intent itemintent = new Intent(this,com.acithium.rss.ShowDescription.class);
//Intent itemintent = new Intent();
//itemintent.setClassName("com.acithium.main", "com.acithium.rss.ShowDescription");
Bundle b = new Bundle();
b.putString("title", feed.getItem(position).getTitle());
b.putString("description", feed.getItem(position).getDescription());
b.putString("link", feed.getItem(position).getLink());
itemintent.putExtra("android.intent.extra.INTENT", b);

startActivityForResult(itemintent,0);
}

这里是新的 Activity 类,叫做:

public class ShowDescription extends Activity 
{

public void onCreate(Bundle icicle)
{
super.onCreate(icicle);
setContentView(R.layout.showdescription);

String theStory = null;


Intent startingIntent = getIntent();


if (startingIntent != null)
{
Bundle b = startingIntent.getBundleExtra("android.intent.extra.INTENT");
if (b == null)
{
theStory = "bad bundle?";
}
else
{
theStory = b.getString("title") + "\n\n" + b.getString("description") + "\n\nMore information:\n" + b.getString("link");
}
}
else
{
theStory = "Information Not Found.";

}
TextView db= (TextView) findViewById(R.id.storybox);
db.setText(theStory);

Button backbutton = (Button) findViewById(R.id.back);

backbutton.setOnClickListener(new Button.OnClickListener()
{
public void onClick(View v)
{
finish();
}
});
}
}

这里是 showdescription.xml 文件:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<ScrollView android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:autoLink="all"
android:text="story goes here ...."
android:id="@+id/storybox" />
<Button
android:layout_height="wrap_content"
android:text="Back"
android:id="@+id/back"
android:layout_width="100px"
android:layout_marginLeft="100px"/>
</LinearLayout>
</ScrollView>
</LinearLayout>

最佳答案

这是你的线索,来自堆栈跟踪:

12-28 03:47:21.670: ERROR/AndroidRuntime(862): Caused by: java.lang.NullPointerException
12-28 03:47:21.670: ERROR/AndroidRuntime(862): at com.acithium.rss.ShowDescription.onCreate(ShowDescription.java:47)

ShowDescription.java 中的第 47 行是什么?

关于java - 启动新 Activity 时出现空指针异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/4543373/

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