安卓的ActivityGroup - NullPointerException异常 [英] Android ActivityGroup - NullPointerException
问题描述
我试图用活动组 - 因为我用的标签，并希望有标签的列表项被点击加载和活动后的时候，。但我得到的NullPointerException以下行：
I'm trying to use activity groups - since I use tabs, and want to have the tabs when loading and activity after the list item was clicked,. but I'm getting nullpointerexception in the following line:
View view1 = S1_Group.group.getLocalActivityManager()
.startActivity("S1", intent)
.getDecorView();
code是...。
Code is .. .
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Intent intent = new Intent(getApplicationContext(), S1.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
Log.d("test","Before view");
try{
View view1 = S1_Group.group.getLocalActivityManager()
.startActivity("S1", intent)
.getDecorView();
Settings_Group.group.setContentView(view1);
}
catch (Exception e){
Log.e("test","view failded:"+e);
}
....
感谢您的帮助！
Thanks for you help!!!
更新：这怎么我的团队活动是：我找不到什么问题， 公共类S1_Group扩展的ActivityGroup {
update: this how my group activity is: I couldn't find what was the issue., public class S1_Group extends ActivityGroup {
public static S1_Group group;
private ArrayList<View> history;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
this.history = new ArrayList<View>();
group = this;
View view = getLocalActivityManager().startActivity("F1",
new Intent(this, F1.class).addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)).getDecorView();
setContentView(view);
}
}
推荐答案
遇到了同样的问题，似乎有（或曾经）与当你试图发生的LocalActivityManager错误（重新）启动具有相同ID为$ P $活动pviously破坏活动。它会简单地返回，因为一个错误的destroyActivity方法内。我使用的解决方法，使用反射妥善销毁活动（该变通办法之后详细的说明）：
Came across the same issue and it seems that there is(or was) a bug with the LocalActivityManager that occurs when you're trying to (re)start an Activity with the same ID as a previously destroyed Activity. It will simply return null as Window, because of a bug inside the destroyActivity method. The workaround I'm using, uses reflection to properly destroy a activity (detailed explanation after the workaround) :
public boolean destroyActivityWorkAround(String id) {
final LocalActivityManager activityManager = getLocalActivityManager();
if(activityManager != null){
activityManager.destroyActivity(id, false);
try {
// Use reflection to get to the HashMaps with the records(which activities are started ect.)
// to remove the records properly
// http://code.google.com/p/android/issues/detail?id=10083
final Field mActivitiesField = LocalActivityManager.class.getDeclaredField("mActivities");
if(mActivitiesField != null){
mActivitiesField.setAccessible(true);
@SuppressWarnings("unchecked")
final Map<String, Object> mActivities = (Map<String, Object>)mActivitiesField.get(activityManager);
if(mActivities != null){
mActivities.remove(id);
}
final Field mActivityArrayField = LocalActivityManager.class.getDeclaredField("mActivityArray");
if(mActivityArrayField != null){
mActivityArrayField.setAccessible(true);
@SuppressWarnings("unchecked")
final ArrayList<Object> mActivityArray = (ArrayList<Object>)mActivityArrayField.get(activityManager);
if(mActivityArray != null){
for(Object record : mActivityArray){
final Field idField = record.getClass().getDeclaredField("id");
if(idField != null){
idField.setAccessible(true);
final String _id = (String)idField.get(record);
if(id.equals(_id)){
mActivityArray.remove(record);
break;
}
}
}
}
}
}
} catch (Exception e) {
Log.e(LOGTAG, this.getClass().getSimpleName() + ".destroyActivityWorkAround() removing activity using reflection failed with error:", e);
//e.printStackTrace();
}
return true;
}
return false;
}
这是一种解决方法，因为LocalActivityManager.destroyActivity（...）包含几个API-版本的bug。该方法不正确地从它的HashMap的（<一个删除活动href="http://www.netmite.com/android/mydroid/frameworks/base/core/java/android/app/LocalActivityManager.java"相对=nofollow> LocalActivityManager的源）：
This is a workaround because the LocalActivityManager.destroyActivity(...) contains a bug in several API-versions. The method doesn't remove the Activity properly from its HashMap's (LocalActivityManager's source):
public Window destroyActivity(String id, boolean finish) {
LocalActivityRecord r = mActivities.get(id); //<-- id's are the key's for the HashMap
Window win = null;
if (r != null) {
win = performDestroy(r, finish);
if (finish) {
mActivities.remove(r); //--> This works on id's not the 'r object', this doesn't remove anything
}
}
return win;
}
的，如果（完成）语句应尽可能遵循删除活动的LocalActivityRecord被破坏：
the if(finish) statement should be as followed to remove the LocalActivityRecord of the activity being destroyed:
if (finish) {
mActivities.remove(id); //--> mActivities should remove the id
mActivityArray.remove(r); //--> mActivitiesArray should remove the 'r object' (LocalActivityRecord)
}
虽然他们说这是被固定为Froyo的，但我还是遇到了它在三星Galaxy S2运行2.3.3
Although they say it's being fixed for Froyo but I still encountered it on a Samsung galaxy S2 running 2.3.3
这篇关于安卓的ActivityGroup - NullPointerException异常的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
