我有以下JAVA代码，其中案例在NIO应用程序的Runnable中。
作为应用程序的一部分，我正在尝试解码myBuffer的内容
while ((bytesRead = myChannel.read(myBuffer)) > 0) {
myBuffer.flip();
myBuffer.mark();
//... do stuff ...
switch (myType) {
case '1':
// ... read buffer and do stuff ...
break;
case '2':
// ... read buffer and do stuff ...
break;
}
}
// I should not be here
我注意到中断而不是破坏了switch语句，打破了while循环，将我发送到I should not be here。
有没有办法阻止此行为并将进程发送回myBuffer.flip（）？
完整的代码在这里：
答案 0 :(得分：3)
我对上面发布的答案感到惊讶，我认为我对java如何运行代码有一些误解，而break可能会破坏while循环，但我尝试使用简单的java代码段清除误解：
Random r = new Random();
while (true)
{
System.out.println(" Inside while");
int myType = r.nextInt();
switch (myType) {
case 1:
// ... read buffer and do stuff ...
break;
case 2:
// ... read buffer and do stuff ...
break;
default :
break;
}
}
System.out.println(" Outside while");
令我惊讶的是，Java代码在行System.out.println(" Outside while");上提出异常，说无法访问的代码。
因此，我确信您的问题中的while因条件while ((bytesRead = myChannel.read(myBuffer)) > 0)而导致break或switch以外的erminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'
*** First throw call stack:
声明错误{/ 1}}
答案 1 :(得分：3)
您的actual code上写着：
public class CategoryBaseAdapter extends BaseExpandableListAdapter {
private Context mContext;
private HashMap<String, List<ProfessionChildEntity>> mListDataChild; private ArrayList<ProfessionEntity> mListDataGroup;
private HashMap<Integer, boolean[]> mChildCheckStates;
private ChildViewHolder childViewHolder;
private GroupViewHolder groupViewHolder;
private String groupText;
private String childText;
public CategoryBaseAdapter(Activity context,ArrayList<ProfessionEntity>listDataGroup, HashMap<String, List<ProfessionChildEntity>> listDataChild) {
mContext = context;
mListDataGroup = listDataGroup;
mListDataChild = listDataChild;
mChildCheckStates = new HashMap<Integer, boolean[]>();}
@Override
public boolean areAllItemsEnabled() {
return true;
}
@Override
public int getGroupCount() {
return mListDataGroup.size();
}
/*
* This defaults to "public object getGroup" if you auto import the methods
* I've always make a point to change it from "object" to whatever item
* I passed through the constructor
*/
@Override
public ProfessionEntity getGroup(int groupPosition) {
return mListDataGroup.get(groupPosition);
}
@Override
public long getGroupId(int groupPosition) {
return groupPosition;
}
@Override
public View getGroupView(int groupPosition, boolean isExpanded,
View convertView, ViewGroup parent) {
groupText = getGroup(groupPosition).getDecription();
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) mContext .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.group_item, null);
groupViewHolder = new GroupViewHolder();
groupViewHolder.mGroupText = (CheckBox) convertView.findViewById(R.id.groupTextView);
convertView.setTag(groupViewHolder);
} else {
groupViewHolder = (GroupViewHolder) convertView.getTag();
}
groupViewHolder.mGroupText.setText(groupText);
return convertView;
}
@Override
public int getChildrenCount(int groupPosition) {
return mListDataChild.get(mListDataGroup.get(groupPosition).getUsesr_type()).size();
}
@Override
public ProfessionChildEntity getChild(int groupPosition, int childPosition) { return mListDataChild.get(mListDataGroup.get(groupPosition).getDecription()).get(childPosition);
}
@Override
public long getChildId(int groupPosition, int childPosition) {
return childPosition;
}
@Override
public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
final int mGroupPosition = groupPosition;
final int mChildPosition = childPosition;
childText = getChild(mGroupPosition, mChildPosition).getDescription();
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) this.mContext
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.child_item, null);
childViewHolder = new ChildViewHolder();
childViewHolder.mChildText = (TextView) convertView
.findViewById(R.id.childTextView);
childViewHolder.mCheckBox = (CheckBox) convertView
.findViewById(R.id.checkBox);
convertView.setTag(R.layout.child_item, childViewHolder);
} else {
childViewHolder = (ChildViewHolder) convertView
.getTag(R.layout.child_item);
}
childViewHolder.mChildText.setText(childText);
childViewHolder.mCheckBox.setOnCheckedChangeListener(null);
if (mChildCheckStates.containsKey(mGroupPosition)) {
boolean getChecked[] = mChildCheckStates.get(mGroupPosition); childViewHolder.mCheckBox.setChecked(getChecked[mChildPosition]);
} else {
boolean getChecked[] = new boolean[getChildrenCount(mGroupPosition)];
mChildCheckStates.put(mGroupPosition, getChecked);
childViewHolder.mCheckBox.setChecked(false);
}
childViewHolder.mCheckBox.setOnCheckedChangeListener(new OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
boolean getChecked[] = mChildCheckStates.get(mGroupPosition);
getChecked[mChildPosition] = isChecked;
mChildCheckStates.put(mGroupPosition, getChecked);
} else {
boolean getChecked[] = mChildCheckStates.get(mGroupPosition);
getChecked[mChildPosition] = isChecked;
mChildCheckStates.put(mGroupPosition, getChecked);
}
}
public void onCheckedChanged(RadioGroup group, int checkedId) {
}
}); return convertView;} @Override public boolean isChildSelectable(int groupPosition, int childPosition) {
return true;
}
@Override
public boolean hasStableIds() {
return true;
}
public final class GroupViewHolder {
CheckBox mGroupText;
}
public final class ChildViewHolder
TextView mChildText;
CheckBox mCheckBox;
}
}
此消息的内容不正确 - 内部循环。
您的主要问题可能在于：
public class Signup_catgegory2 extends Activity {
ExpandableListView listView1;
ArrayList<ProfessionEntity> listProfession = new ArrayList<ProfessionEntity>();
List<ProfessionChildEntity> listChildProfession=new ArrayList<ProfessionChildEntity>();
DatabaseHandler databaseHandler;
String typeOfUser;
HashMap<String, List<ProfessionChildEntity>> listDataChild;
Context context = null;
CategoryBaseAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_signup_category);
listView1=(ExpandableListView)findViewById(R.id.listView1);
InitDatabase();
Intent in = getIntent();
typeOfUser = in.getStringExtra("typeOfUser");
loadProfessionData(typeOfUser);
/*listChild.put("parent_key",listChildProfession);
listDataChild.add(listChild);*/
adapter=new CategoryBaseAdapter(Signup_catgegory2.this, listProfession,listDataChild);
listView1.setAdapter(adapter);
}
private void loadProfessionData(String pos) {
listProfession = databaseHandler.getParentCategory(typeOfUser);
ArrayList<String> list = new ArrayList<String>();
for (int i = 0; i < listProfession.size(); i++) {
Log.d("prfoession:", listProfession.get(i).getDecription());
list.add("" + listProfession.get(i).getDecription());
loadChildProfessionData(i);
}
}
private void loadChildProfessionData(int pos) {
listChildProfession = databaseHandler.getPChildCategory(pos);
String parent_key=String.valueOf(pos);
List<ProfessionChildEntity> list = new ArrayList<ProfessionChildEntity>();
for (int i = 0; i < listChildProfession.size(); i++) {
//for(int j=0;j<listChildProfession.size();j++){
Log.d("prfoession:", listChildProfession.get(i).getDescription());
list.add(listChildProfession.get(i).getDescription());
//}
}
listDataChild.put(parent_key,list);
}
private void InitDatabase() {
// TODO Auto-generated method stub
try {
databaseHandler = new DatabaseHandler(Signup_catgegory2.this);
databaseHandler.createdatabase();
} catch (IOException ioe) {
throw new Error("Unable to create database");
}
try {
databaseHandler.opendatabase();
} catch (SQLException sqle) {
throw sqle;
}
}
}
由于NIO是异步的，public ArrayList<ProfessionChildEntity> getPChildCategory(int Parent_key){
ArrayList<ProfessionChildEntity> flashcardentity=new ArrayList<ProfessionChildEntity>();
String selectQuery="SELECT * FROM "+"Child WHERE Parent_key ="+"'"+Parent_key+"'";
Log.d("selectQuery",selectQuery);
Cursor cursor=db.rawQuery(selectQuery, null);
Log.d("Cusorfav","c"+cursor.getCount()+""+selectQuery);
if(cursor.moveToFirst()){
do{
Log.d("cursorfav", "cinside");
ProfessionChildEntity pce=new ProfessionChildEntity();
pce.setUser_type(cursor.getString(0));
pce.setChild_key(cursor.getInt(2));
pce.setDescription(cursor.getString(3));
flashcardentity.add(pce);
}while(cursor.moveToNext());
}
return flashcardentity;
}
很可能会返回logger.info("We are outside the loop and position is " + String.valueOf(socketBuffer.position()));
。 Thjis并未表示cahnnel已完成 - 这只表示此时频道中没有更多数据。你应该真的使用：
while ((bytesRead = myChannel.read(myBuffer)) > 0)
自己处理read案例。
答案 2 :(得分：1)
你可以使用一个标签，它会教你如何标记一个循环，但是在这个例子中没有它，它的工作方式是相同的：
while ((bytesRead = myChannel.read(myBuffer)) > 0) {
myBuffer.flip();
myBuffer.mark();
//... do stuff ...
choose: switch (myType) {
case '1':
// ... read buffer and do stuff ...
break choose;
case '2':
// ... read buffer and do stuff ...
break choose;
}
}
// I should not be here
}
但它工作正常，案件中的突破只打破案件，你的时间可能已经结束，你被这种情况所取代。
答案 3 :(得分：1)
myChannel.read(myBuffer)不能保证读取myBuffer的全长，你需要写出更好的阅读方法，以确保你完全填满myBuffer，这可能就是原因。