Android 尝试重新打开已关闭的对象_Android

Android 尝试重新打开已关闭的对象

android

Android 尝试重新打开已关闭的对象,android,Android,当我开始运行我的应用程序时，我试图重新打开一个已经关闭的对象。出于某种原因，它正在buildCourseList方法中爆炸，但直到方法调用的最后，我才关闭数据库连接。知道我做错了什么吗？谢谢 public class MainActivity extends ActionBarActivity { //Create objects to match to UI views in the main activity ImageButton addCourseButton; ListView cr

当我开始运行我的应用程序时，我试图重新打开一个已经关闭的对象。出于某种原因，它正在buildCourseList方法中爆炸，但直到方法调用的最后，我才关闭数据库连接。知道我做错了什么吗？谢谢

public class MainActivity extends ActionBarActivity {

//Create objects to match to UI views in the main activity
ImageButton addCourseButton;
ListView createdList;
DBAdapter myDBAdapter = new DBAdapter(this);

/** Will be used to create an ArrayList to hold the data in */
ArrayList<String> listToHoldValues= new ArrayList<String>();
ArrayList<String> assignmentList = new ArrayList<String>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_activity);


    addCourseButton = (ImageButton)findViewById(R.id.btnAddCourse);
    createdList = (ListView)findViewById(R.id.listHolder);

    /*Create default list on create, which is the course list*/
    buildCourseList();
    setListViewItems();
}

/*************** Insertion Methods ************************************************************/
public void insertNewCourse(String newCourse){
    myDBAdapter.open();
    long id;
    id = myDBAdapter.insertCourse(newCourse);
    myDBAdapter.close();
}

public void insertNewCategory(String newCategory, String associatedCourse){
    myDBAdapter.open();
    long id;
    id= myDBAdapter.insertCategory(newCategory, associatedCourse);
    myDBAdapter.close();
}

public void insertNewGrade(
        int newGrade, String newAssignment, String associatedCourse, String associatedCategory){
    myDBAdapter.open();
    long id;
    id = myDBAdapter.insertGrade(newGrade, newAssignment, associatedCourse, associatedCategory);
    myDBAdapter.close();
}


/*************** Display Methods **************************************************************/
/* Will take the items from the Course table and insert them into an array*/
public void buildCourseList(){
    myDBAdapter.open();
    listToHoldValues.clear();       // Clear list to ensure that garbage isn't produced

    /*Provides access to the data in the database*/
    Cursor courseCursor = myDBAdapter.getAllCourses();

    /*Loops through the data in the course table to populate a list of courses to return to UI*/
    if(courseCursor.moveToFirst()){
        do{
            listToHoldValues.add(courseCursor.getString(1));
        }while (courseCursor.moveToNext());
    }
    myDBAdapter.close();
}

/* Will take the items from the Category table and insert them into an array*/
public void buildCategoryList(){
    myDBAdapter.open();
    listToHoldValues.clear();       // Clear list to ensure that garbage isn't produced

    /*Provides access to data in the database*/
    Cursor categoryCursor = myDBAdapter.getAllCategories();

    /*Loops through data in the category table to populate list of categories to return to ui*/
    if(categoryCursor.moveToFirst()){
        do {
            listToHoldValues.add(categoryCursor.getString(1));
        }while (categoryCursor.moveToNext());
    }
    myDBAdapter.close();
}

/* Will take the items from the Grade table and insert them into an array*/
public void buildGradeList(){
    myDBAdapter.open();
    listToHoldValues.clear();

    /*Provides access to the data in the database*/
    Cursor gradeCursor = myDBAdapter.getAllGrades();

    /*Loops through the data to populate list of assignments and grades to return to the UI*/
    if(gradeCursor.moveToFirst()){
        do {
            listToHoldValues.add(gradeCursor.getString(1));
            assignmentList.add(gradeCursor.getString(2));
        }while (gradeCursor.moveToNext());
    }
    myDBAdapter.close();
}

/**********************************Deletion Methods********************************************/

/*Will delete item from Course table depending course name passed in*/
public void deleteACourse(String course) {
    myDBAdapter.open();
    if (myDBAdapter.deleteCourse(course)) {
        Toast.makeText(this, course + " deleted!", Toast.LENGTH_LONG).show();
    } else {
        Toast.makeText(this, "Delete failed", Toast.LENGTH_LONG).show();
    }
    myDBAdapter.close();
}

/*Will delete item from Category table depending on the category name passed in*/
public void deleteACategory(String category){
    myDBAdapter.open();
    if(myDBAdapter.deleteCategory(category)){
        Toast.makeText(this, category + " deleted!", Toast.LENGTH_LONG).show();
    }else{
        Toast.makeText(this, "Delete failed!", Toast.LENGTH_LONG).show();
    }
    myDBAdapter.close();
}

/*Will delete item from grade table depending in assignment name passed in*/
public void deleteAGrade(String assignment){
    myDBAdapter.open();
    if (myDBAdapter.deleteCategory(assignment)){
        Toast.makeText(this, assignment + " deleted!", Toast.LENGTH_LONG).show();
    }else{
        Toast.makeText(this, "Delete failed!", Toast.LENGTH_LONG).show();
    }
    myDBAdapter.close();
}

/********************************** Update Methods ********************************************/
/*Will update requested course to new value*/
public void updateACourse(String courseToUpdate, String name){
    myDBAdapter.open();
    if(myDBAdapter.updateCourse(courseToUpdate, name)){
        Toast.makeText(this, "Update successful!", Toast.LENGTH_LONG).show();
    }else{
        Toast.makeText(this, "Update failed!", Toast.LENGTH_LONG).show();
    }
    myDBAdapter.close();
}

/*Will update requested category to new value*/
public void updateACategory(
        String categoryToUpdate, String courseCategoryIsIn, String updateName){
    myDBAdapter.open();
    if(myDBAdapter.updateCategory(categoryToUpdate, courseCategoryIsIn, updateName)){
        Toast.makeText(this, "Update successful!", Toast.LENGTH_LONG).show();
    }else{
        Toast.makeText(this, "Update failed!", Toast.LENGTH_LONG).show();
    }
    myDBAdapter.close();
}

/*Will updated a grade attached to an assignment to a new value*/
public void updateAGrade(String newGrade, String assignmentGradeAttachedTo,
                         String associatedCategory, String associatedCourse){
    myDBAdapter.open();
    if(myDBAdapter.updateGrade(newGrade, assignmentGradeAttachedTo,
            associatedCategory, associatedCourse)){
        Toast.makeText(this, "Update successful!", Toast.LENGTH_LONG).show();
    }else{
        Toast.makeText(this, "Update failed!", Toast.LENGTH_LONG).show();
    }
    myDBAdapter.close();
}


public double getCategoryAvg(){
    double average = 0.0;
    return average;
}

public double getCourseAverage(){
    double average = 0.0;
    return average;
}

/*Creates a ArrayAdapter to pass values to the list*/
public void setListViewItems(){
    ArrayAdapter<String> listAdapter = new ArrayAdapter<String>
            (this, android.R.layout.simple_list_item_1, listToHoldValues);

    // Set Adapter
    createdList.setAdapter(listAdapter);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

}

这就是logcat在爆炸时给我的信息：

*07-05 16:34:44.770    1027-1027/com.example.gradetracker.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.gradetracker.app, PID: 1027
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gradetracker.app/com.example.gradetracker.app.MainActivity}: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/data/com.example.gradetracker.app/databases/MyGrades
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/data/com.example.gradetracker.app/databases/MyGrades
            at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:55)
            at android.database.sqlite.SQLiteDatabase.endTransaction(SQLiteDatabase.java:520)
            at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:263)
            at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
            at com.example.gradetracker.app.DBAdapter.open(DBAdapter.java:100)
            at com.example.gradetracker.app.MainActivity.buildCourseList(MainActivity.java:68)
            at com.example.gradetracker.app.MainActivity.onCreate(MainActivity.java:37)
            at android.app.Activity.performCreate(Activity.java:5231)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)*

为什么在

DatabaseHelper

中的

onCreate（）

方法之后调用db.close？你不需要那个

始终确保您没有连续两次调用

open（）

或

close（）

方法。通过对

SQLDatabase

对象调用

isOpen（）

，可以检查数据库是否已打开

请检查以了解有关此问题的更多信息。

您可以显示堆栈跟踪吗？你的错误是什么？什么都看不见。用它编辑您的问题。我更改了它并编辑了主要帖子，logcat消息太长，无法用作评论，对此表示抱歉。为什么在DatabaseHelper中的onCreate（）方法之后调用db.close？确保您没有连续两次调用open（）或close（）。通过对SQLDatabase对象调用isOpen（），可以检查数据库是否已打开。有关详细信息，请参阅。

*07-05 16:34:44.770    1027-1027/com.example.gradetracker.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.gradetracker.app, PID: 1027
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gradetracker.app/com.example.gradetracker.app.MainActivity}: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/data/com.example.gradetracker.app/databases/MyGrades
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/data/com.example.gradetracker.app/databases/MyGrades
            at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:55)
            at android.database.sqlite.SQLiteDatabase.endTransaction(SQLiteDatabase.java:520)
            at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:263)
            at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
            at com.example.gradetracker.app.DBAdapter.open(DBAdapter.java:100)
            at com.example.gradetracker.app.MainActivity.buildCourseList(MainActivity.java:68)
            at com.example.gradetracker.app.MainActivity.onCreate(MainActivity.java:37)
            at android.app.Activity.performCreate(Activity.java:5231)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)*