我无法在数据库中找到错误的位置。我正在制作的应用程序在模拟器模拟器上工作，但现在我尝试在4.1.2平台上的移动设备上运行它，它立即获得强制关闭消息。在我开始使用数据库之前，它在一个模拟器和移动设备上运行良好。我保留了最低要求SDK：API 11：Android 3.0（Honeycomb）和Target SDK：API 18：Android 4.3。我也在Manifest文件中添加了活动。
11-25 01:53:50.047: E/Trace(26246): error opening trace file: No such file or directory (2)
11-25 01:53:50.057: D/ActivityThread(26246): setTargetHeapUtilization:0.25
11-25 01:53:50.057: D/ActivityThread(26246): setTargetHeapIdealFree:8388608
11-25 01:53:50.057: D/ActivityThread(26246): setTargetHeapConcurrentStart:2097152
11-25 01:53:50.117: D/AndroidRuntime(26246): Shutting down VM
11-25 01:53:50.117: W/dalvikvm(26246): threadid=1: thread exiting with uncaught exception (group=0x40ecf378)
11-25 01:53:50.127: E/AndroidRuntime(26246): FATAL EXCEPTION: main
11-25 01:53:50.127: E/AndroidRuntime(26246): java.lang.RuntimeException: Unable to create application my.app.cal.CalApplication: android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4196)
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.app.ActivityThread.access$1300(ActivityThread.java:138)
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1267)
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.os.Handler.dispatchMessage(Handler.java:99)
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.os.Looper.loop(Looper.java:213)
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.app.ActivityThread.main(ActivityThread.java:4787)
11-25 01:53:50.127: E/AndroidRuntime(26246): at java.lang.reflect.Method.invokeNative(Native Method)
11-25 01:53:50.127: E/AndroidRuntime(26246): at java.lang.reflect.Method.invoke(Method.java:511)
11-25 01:53:50.127: E/AndroidRuntime(26246): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
11-25 01:53:50.127: E/AndroidRuntime(26246): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
11-25 01:53:50.127: E/AndroidRuntime(26246): at dalvik.system.NativeStart.main(Native Method)
11-25 01:53:50.127: E/AndroidRuntime(26246): Caused by: android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.database.AbstractCursor.checkPosition(AbstractCursor.java:418)
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.database.AbstractWindowedCursor.getLong(AbstractWindowedCursor.java:74)
11-25 01:53:50.127: E/AndroidRuntime(26246): at my.app.cal.CalApplication.readWeighingDetailFromDB(CalApplication.java:45)
11-25 01:53:50.127: E/AndroidRuntime(26246): at my.app.cal.CalApplication.onCreate(CalApplication.java:26)
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.app.Instrumentation.callApplicationOnCreate(Instrumentation.java:999)
11-25 01:53:50.127: E/AndroidRuntime(26246): at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4193)
11-25 01:53:50.127: E/AndroidRuntime(26246): ... 10 more
以下是我的数据库文件： WeighingDetailDatabaseHelper.java：
package my.app.cal;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class WeighingDetailDatabaseHelper extends SQLiteOpenHelper {
public static final String DB_NAME = "MyWeighingDetail.SQLite";
public static final int DB_VERSION = 1;
public static String WEIGHING_DETAIL_TABLE ="WeighingDetailTable";
public static String RECORD_ID = "ID";
public static String DATE ="Date";
public static String WEIGHT = "Weight";
public WeighingDetailDatabaseHelper(Context context){
super (context, DB_NAME, null, DB_VERSION);
}
@Override
public void onCreate(SQLiteDatabase weighingDetailDB) {
String sqlStatement = "create table " + WEIGHING_DETAIL_TABLE
+ " ("
+ RECORD_ID + " integer primary key autoincrement not null,"
+ DATE + " integer,"
+ WEIGHT + " float"
+ ");";
Log.d("Weighing Database", sqlStatement);
weighingDetailDB.execSQL(sqlStatement);
}
@Override
public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
}
}
WeighingDetail.java：
package my.app.cal;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
public class WeighingDetail implements Comparable<WeighingDetail> {
private long id;
private float weight;
private Date date;
private float runningAverage;
public WeighingDetail(float weight, Date date) {
this.weight = weight;
this.date = date;
}
public WeighingDetail(long id, long dateEpoch, float weight) {
this.id = id;
setDateEpoch(dateEpoch);
this.weight = weight;
this.date = date;
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public float getWeight() {
return weight;
}
public void setWeight(float weight) {
this.weight = weight;
}
public Date getDate() {
return date;
}
public long getDateEpoch(){
return date.getTime()/1000;
}
public void setDateEpoch(long seconds){
date = new Date(seconds * 1000);
}
public void setDate(Date date) {
this.date = date;
}
public float getRunningAverage() {
return runningAverage;
}
public void setRunningAverage(float runningAverage) {
this.runningAverage = runningAverage;
}
public float sumofWeight() {
return weight; //Its just the weight itself, its used to calculate the running average weight later
}
public float calculateWeightAverage() {
return weight;// Its the weight itself, used in averageEditText as well as for calculating total of the weights till now added
}
public boolean equals(Object that){
WeighingDetail wd = (WeighingDetail) that;
return this.date.equals(wd.date);
}
@Override
public int compareTo(WeighingDetail that) {
int difference;
difference = this.date.compareTo(date);
return difference;
}
public static void updateRunningAverage (ArrayList<WeighingDetail> allWeighingDetail) {
int weeks = 1;
float total = 0;
Collections.sort(allWeighingDetail);
if(allWeighingDetail.size() >0){
for(WeighingDetail wd : allWeighingDetail){
total +=wd.calculateWeightAverage();
wd.setRunningAverage((float) total / (weeks));// first it was weeks = 3
weeks++;
}
}
}
public String toString() {
String result;
//"ID:" + id + " " +
DateFormat df = DateFormat.getDateInstance(DateFormat.MEDIUM);
result = df.format(date) + " " + weight
+ String.format("%.1f", runningAverage);
return result;
}
}
show history按钮显示数据库以及运行平均值，因此我的java文件是ShowHistory.java。
package my.app.cal;
import java.util.ArrayList;
import android.app.ListActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
public class HistoryActivity extends ListActivity {
private ArrayList<WeighingDetail> allWeighingDetail; //added an instance method to activity
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.history_layout);
//get the data from the App
CalApplication app = (CalApplication) getApplication();
allWeighingDetail = app.getAllWeighingDetail();
WeighingDetail.updateRunningAverage (allWeighingDetail);
// View ------ Adapter ----- Data
setListAdapter(
new ArrayAdapter<WeighingDetail>(this,
android.R.layout.simple_list_item_1,
allWeighingDetail)
);
}
}
CalApplication.java
package my.app.cal;
import java.util.ArrayList;
import android.app.Application;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import static my.app.cal.WeighingDetailDatabaseHelper.*;
public class CalApplication extends Application {
private ArrayList<WeighingDetail> allWeighingDetail;
private SQLiteDatabase weighingDetailDB;
@Override
public void onCreate() {
super.onCreate();
WeighingDetailDatabaseHelper databaseHelper = new WeighingDetailDatabaseHelper(this);
weighingDetailDB = databaseHelper.getWritableDatabase();
// TODO get the data out of the database
readWeighingDetailFromDB ();
}
private void readWeighingDetailFromDB() {
allWeighingDetail = new ArrayList<WeighingDetail>();
Cursor weighingDetailCursor;
weighingDetailCursor = weighingDetailDB.query(WEIGHING_DETAIL_TABLE,
new String[]{RECORD_ID, DATE, WEIGHT},
null, null, null, null,DATE);
weighingDetailCursor.moveToFirst();
WeighingDetail tempWD;
if(weighingDetailCursor.isAfterLast()){
do{
long id = weighingDetailCursor.getLong(0);
long dateEpoch = weighingDetailCursor.getLong(1);
float weight = weighingDetailCursor.getFloat(2);
tempWD = new WeighingDetail(id, dateEpoch, weight);
allWeighingDetail.add(tempWD);
Log.d("Weighing Database", tempWD.toString());
}while(weighingDetailCursor.moveToNext());
}
weighingDetailCursor.close();
}
public void addWeighingDetail(WeighingDetail weighingDetail){
assert weighingDetail != null;
ContentValues cv = new ContentValues();//object that will put the data to the db
cv.put(WeighingDetailDatabaseHelper.DATE, weighingDetail.getDateEpoch());//USE EPOCH
cv.put(WeighingDetailDatabaseHelper.WEIGHT, weighingDetail.getWeight());
Log.d("Weighing Database", "Before Inserting a record" + weighingDetail);
long idPassedBack = weighingDetailDB.insert(WeighingDetailDatabaseHelper.WEIGHING_DETAIL_TABLE, null, cv);
weighingDetail.setId(idPassedBack);
Log.d("Weighing Database", "After Inserting a record" + weighingDetail);
allWeighingDetail.add(weighingDetail);
}
public ArrayList<WeighingDetail> getAllWeighingDetail() {
return allWeighingDetail;
}
private void setAllWeighingDetail(ArrayList<WeighingDetail> allWeighingDetail) {
this.allWeighingDetail = allWeighingDetail;
}
}
答案 0 :(得分：0)
在尝试从光标读取任何内容之前，请检查moveToFirst（）的返回值。看起来好像没有返回任何结果。
if (cursor.moveToFirst()) {
//do your effort
}
答案 1 :(得分：0)
处理游标时始终使用此条件：
if( cursor != null && cursor.moveToFirst() ) {
//do operations with records
}
检查光标是否为空。如果它不为null，则将光标移动到第一个记录。这里的光标可能为null（没有记录）。