[英]Why i can't start activity in my android app?
如果我在Samsung Galaxy 2上進行一些測試,則此代碼有效:
for(int i = 0; i < all_ids.size(); i++)
{
if(i == position)
{
System.out.println("Rabotaet if");
String topic = null;
String message_id = null;
Intent activity = new Intent(getApplicationContext(), MessageActivity.class);
activity.putExtra(SESSION_ID, sess_id);
activity.putExtra(DATE,date);
activity.putExtra(TYPE,folder_type);
activity.putExtra(TOPIC,all_subjects.get(i));
activity.putExtra(MESSAGE_ID, all_ids.get(i));
activity.putExtra(FROM, all_emails_address.get(i));
startActivity(activity);
}
}
但是,如果我在Samsung Tab 3上進行了此測試,則無法正常工作。 在調試中,我看到以下消息:
04-14 12:27:10.760: W/System.err(24669): java.lang.IndexOutOfBoundsException: Invalid index 4, size is 0
有任何想法嗎?
更新后,我有代碼:
for(int i = 0; i < all_ids.size(); i++)
{
if(i == position)
{
System.out.println("Rabotaet if");
String topic = null;
String message_id = null;
Intent activity = new Intent(getApplicationContext(), MessageActivity.class);
activity.putExtra(SESSION_ID, sess_id);
activity.putExtra(DATE,date);
activity.putExtra(TYPE,folder_type);
if (i < all_ids.size())
activity.putExtra(MESSAGE_ID,all_ids.get(i));
if (i < all_subjects.size())
activity.putExtra(TOPIC,all_subjects.get(i));
if (i < all_emails_address.size())
activity.putExtra(FROM, all_emails_address.get(i));
startActivity(activity);
}
}
但是現在我有這個錯誤:
04-14 12:39:59.480: E/AndroidRuntime(26359): FATAL EXCEPTION: main
04-14 12:39:59.480: E/AndroidRuntime(26359): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.gdes.earchive/com.gdes.earchive.MessageActivity}: java.lang.NullPointerException
04-14 12:39:59.480: E/AndroidRuntime(26359): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2249)
04-14 12:39:59.480: E/AndroidRuntime(26359): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2299)
04-14 12:39:59.480: E/AndroidRuntime(26359): at android.app.ActivityThread.access$700(ActivityThread.java:154)
04-14 12:39:59.480: E/AndroidRuntime(26359): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1284)
04-14 12:39:59.480: E/AndroidRuntime(26359): at android.os.Handler.dispatchMessage(Handler.java:99)
04-14 12:39:59.480: E/AndroidRuntime(26359): at android.os.Looper.loop(Looper.java:137)
04-14 12:39:59.480: E/AndroidRuntime(26359): at android.app.ActivityThread.main(ActivityThread.java:5306)
04-14 12:39:59.480: E/AndroidRuntime(26359): at java.lang.reflect.Method.invokeNative(Native Method)
04-14 12:39:59.480: E/AndroidRuntime(26359): at java.lang.reflect.Method.invoke(Method.java:511)
04-14 12:39:59.480: E/AndroidRuntime(26359): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
04-14 12:39:59.480: E/AndroidRuntime(26359): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
04-14 12:39:59.480: E/AndroidRuntime(26359): at dalvik.system.NativeStart.main(Native Method)
04-14 12:39:59.480: E/AndroidRuntime(26359): Caused by: java.lang.NullPointerException
04-14 12:39:59.480: E/AndroidRuntime(26359): at com.gdes.earchive.MessageActivity.onCreate(MessageActivity.java:37)
04-14 12:39:59.480: E/AndroidRuntime(26359): at android.app.Activity.performCreate(Activity.java:5255)
04-14 12:39:59.480: E/AndroidRuntime(26359): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1097)
04-14 12:39:59.480: E/AndroidRuntime(26359): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2213)
04-14 12:39:59.480: E/AndroidRuntime(26359): ... 11 more
您的循環基於all_ids
的大小。 您還使用了另外2種數組類型的變量: all_subjects
和all_emails_address
。 其中之一的大小為0(無元素)。
使用它們之前,您需要檢查它們的大小:
if (i < all_subjects.size())
activity.putExtra(TOPIC,all_subjects.get(i));
if (i < all_emails_address.size())
activity.putExtra(FROM, all_emails_address.get(i));
似乎您沒有一個(或兩個)列表的索引4的數據:
all_subjects或/和all_emails_address
請進一步檢查all_subjects.size()和all_emails_address.size()
logcat中捕獲的錯誤非常清楚:提供的索引以及基於大小列表的all_ids也無法到達其他列表的列表。
因此,一種好的做法是在使用列表之前先檢查列表的索引
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