我有一个问题，我现在几天都无法解决。 我已经创建了从数据库写入和检索数据的方法，但这是一个我无法找到的问题。 这是代码：
public void writeEntry(String name, long period, long frequency, long recievingTime, String stats){
ContentValues cv = new ContentValues();
cv.put(KEY_NAME, name);
cv.put(KEY_PERIOD, period);
cv.put(KEY_FREQUENCY, frequency);
cv.put(KEY_RECIEVINGTIME, recievingTime);
cv.put(KEY_STATS, stats);
myDatabase.insert(DATABASE_TABLE, null, cv);
}
public Cursor query(String[] columns, String selection, String[] selectionArgs, String groupBy) {
// TODO Auto-generated method stub
Cursor c = myDatabase.query(DATABASE_TABLE, columns, selection, selectionArgs, groupBy, null, null);
return c;
}
以下是将数据写入db的方法：
public void save(){
sharedPrefs = context.getSharedPreferences(SPNAME, 0);
Log.v(" info", sharedPrefs.getAll().toString());
Database database = new Database(context);
database.open();
database.writeEntry(
sharedPrefs.getString(NAME, "No data was found"),
sharedPrefs.getLong(PERIOD, 0),
sharedPrefs.getLong(FREQUENCY, 0),
sharedPrefs.getLong(RECIEVINGTIME, 0),
sharedPrefs.getString(STATS, "No data was found")
);
database.close();
}
以下是我检索它的方法：
public List<String> getReportInfo(String rowId){
List<String> result = new ArrayList<String>();
database = new Database(context);
database.open();
cursor = database.query(new String[]{
Database.KEY_NAME,
Database.KEY_PERIOD,
Database.KEY_FREQUENCY,
Database.KEY_RECIEVINGTIME,
Database.KEY_STATS},
Database.KEY_ROWID +" = "+rowId, null, null);
for(cursor.moveToFirst(); cursor.isAfterLast(); cursor.moveToNext()){
result.add(cursor.getString(cursor.getPosition()));
}
cursor.close();
database.close();
return result;
}
稍后，我在getView方法的BaseAdapter中使用db中的数据来填充ListView，如下所示：
public class MyArrayAdapter extends BaseAdapter{
private Activity activity;
private LayoutInflater inflater;
TextView tvMyReportsPeriod, tvMyReportsFrequency, tvMyReportsReceivingTime, tvMyReportTitle;
LinearLayout llMyReportsStats;
Database database;
Report report;
Cursor cursor;
public MyArrayAdapter(Activity a) {
super();
// TODO Auto-generated constructor stub
activity = a;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
report = new Report(activity);
}
public int getCount() {
// TODO Auto-generated method stub
int count = 2;
try{
cursor = database.query(new String[]{Database.KEY_NAME}, null, null, null);
count= cursor.getCount();
cursor.close();
}catch(Exception e){}
return count;
}
public Object getItem(int position) {
// TODO Auto-generated method stub
List<String> list = report.getReportInfo(String.valueOf(position));
return list;
}
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
if(convertView==null){
convertView = inflater.inflate(R.layout.my_reports_view_holder, null, false);
tvMyReportsPeriod = (TextView)convertView.findViewById(R.id.tvMyReportsPeriod);
tvMyReportsFrequency = (TextView)convertView.findViewById(R.id.tvMyReportsFrequency);
tvMyReportsReceivingTime = (TextView)convertView.findViewById(R.id.tvMyReportsReceivingTime);
tvMyReportTitle = (TextView)convertView.findViewById(R.id.tvMyReportTitle);
llMyReportsStats = (LinearLayout)convertView.findViewById(R.id.llMyReportsStats);
List<String> data = report.getReportInfo(String.valueOf(position));
if(data!=null){
tvMyReportTitle.setText(data.get(0));
tvMyReportsPeriod.setText(report.convertMillis(Long.parseLong(data.get(1))));
tvMyReportsFrequency.setText(report.convertMillis(Long.parseLong(data.get(2))));
tvMyReportsReceivingTime.setText(report.convertMillis(Long.parseLong(data.get(3))));
String[] stats = data.get(4).toString().split(" ");
for(int x=0; x<stats.length; x++){
TextView textView = new TextView(activity);
for(Constants dc: Constants.values()){
if(dc.getId()==Integer.parseInt(stats[x])){
textView.setText(dc.getText());
}
}
llMyReportsStats.addView(textView);
}
}else{System.out.println("ERROR: data=null");}
}
return convertView;
}
我希望每次为每个ListView项目从db获取一行，但我得到这个logcat：
09-27 11:03:03.173: E/AndroidRuntime(25768): android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.database.AbstractCursor.checkPosition(AbstractCursor.java:580)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:214)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:41)
09-27 11:03:03.173: E/AndroidRuntime(25768): at com.dailyreports.ainius.Report.getReportInfo(Report.java:107)
09-27 11:03:03.173: E/AndroidRuntime(25768): at com.dailyreports.ainius.MyReports$MyArrayAdapter.getView(MyReports.java:88)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.widget.AbsListView.obtainView(AbsListView.java:1430)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.widget.ListView.measureHeightOfChildren(ListView.java:1216)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.widget.ListView.onMeasure(ListView.java:1127)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.view.View.measure(View.java:8313)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.widget.LinearLayout.measureVertical(LinearLayout.java:386)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.view.View.measure(View.java:8313)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.view.View.measure(View.java:8313)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.widget.LinearLayout.measureVertical(LinearLayout.java:531)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.view.View.measure(View.java:8313)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.view.View.measure(View.java:8313)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.view.ViewRoot.performTraversals(ViewRoot.java:841)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.view.ViewRoot.handleMessage(ViewRoot.java:1861)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.os.Handler.dispatchMessage(Handler.java:99)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.os.Looper.loop(Looper.java:123)
09-27 11:03:03.173: E/AndroidRuntime(25768): at android.app.ActivityThread.main(ActivityThread.java:3729)
09-27 11:03:03.173: E/AndroidRuntime(25768): at java.lang.reflect.Method.invokeNative(Native Method)
09-27 11:03:03.173: E/AndroidRuntime(25768): at java.lang.reflect.Method.invoke(Method.java:507)
09-27 11:03:03.173: E/AndroidRuntime(25768): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:874)
09-27 11:03:03.173: E/AndroidRuntime(25768): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:632)
09-27 11:03:03.173: E/AndroidRuntime(25768): at dalvik.system.NativeStart.main(Native Method)
不知道问题出在哪里。请帮忙。
答案 0 :(得分：0)
您应该检查cursor.moveToFirst()是否返回true。
如果您正在进行的查询没有任何结果，您将获得CursorIndexOutOfBoundsException例外...
另外，正如阿普里安所指出的那样。 cursor.getString将列索引作为参数，而不是光标的位置。
将result.add(cursor.getString(cursor.getPosition()));替换为result.add(cursor.getString(Database.KEY_STATS));
答案 1 :(得分：0)
此cursor.getString(cursor.getPosition())不会导致您发布的错误，但稍后会导致其他错误。如果您阅读文档，那么期望的参数是列索引，而不是行索引。
您正在观察的错误可能是由于moveToFirst返回False但您没有测试它。你的数据库是空的。
再次阅读之后，你的for循环（虽然非常好看）完全关闭。您将isAfterLast测试为循环条件，而最多应该是退出条件。您没有检查移动到第一个的结果。你不检查moveToNext的结果。
用
替换你的for循环while(cursor.moveToNext()) {
// Do stuff
}
答案 2 :(得分：0)
问题似乎也在这里：
result.add(cursor.getString(cursor.getPosition()));
因为如果获取的记录数超过查询中请求的列数，则会抛出错误。这不是您应该从游标中读取值的方式，实际上您应该确定应该读取哪些列值。例如：
result.add(cursor.getString(cursor.getColumnIndex(Database.KEY_NAME)));
或者可能具有固定的索引值，例如：
result.add(cursor.getString(0));
答案 3 :(得分：0)
编辑：看起来像你想从数据库中检索一行。
您应该使用MyObject代替List<String>来实现您想要的目标。
以下是MyObject的示例，请参阅POJO
public class MyObject {
String name = "", stats = "";
Long period = 0, frequency = 0, receivingtime = 0;
// empty constructor
public MyObject() {
}
// simple getter method
public String getName() {
return name;
}
// simple setter method
public void setName(String name) {
this.name = name;
}
...
// You may want to override toString() method when implementing searching or using ArrayAdapter
@Override
public String toString() {
return name + " " + stats;
}
}
将您的getReportInfo更改为：
public MyObject getReportInfo(String rowId){
MyObject result = new MyObject();
database = new Database(context);
database.open();
cursor = database.query(new String[]{
Database.KEY_NAME,
Database.KEY_PERIOD,
Database.KEY_FREQUENCY,
Database.KEY_RECIEVINGTIME,
Database.KEY_STATS},
Database.KEY_ROWID +" = "+rowId, null, null);
// this will prevent CursorIndexOutofBoundsException
if (cursor.moveToFirst()) {
result.setName(cursor.getString(0));
result.setPeriod(cursor.getLong(1));
result.setFrequency(cursor.getLong(2));
result.setReceivingTime(cursor.getLong(3));
result.setStats(cursor.getString(4));
}
cursor.close();
database.close();
return result;
}