android - 即使在实现 close() 之后，也从未在数据库上显式调用 Close()

Question

即使我已经实现了上述方法 close()，Eclipse 仍向我显示上述错误。

代码如下:

public void update_project(View view) {

    EditText cinone = (EditText) findViewById(R.id.pname);
    pname = cinone.getText().toString();

    String fDate = pday + ". " + pmonth + ". " + pyear;

    projectdatabase dbupdate = new projectdatabase(UpdateProject.this);

    dbupdate.open();
    dbupdate.updateProject(id, pname, fDate); 
    dbupdate.close();

}

日志:

12-31 22:05:51.114: E/SQLiteDatabase(4180): close() was never explicitly called on  
database '/data/data/com.kk.project/databases/project_db' 
12-31 22:05:51.114: E/SQLiteDatabase(4180):  
android.database.sqlite.DatabaseObjectNotClosedException: Application did not close the     
cursor or database object that was opened here
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at  
android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1943)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at 
android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:1007)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at   
android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:986)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at 
android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:1051)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at 
android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:770)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at  
android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:221)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at 
android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:157)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at     
com.kk.project.projectdatabase.open(projectdatabase.java:66)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at  
com.kk.project.ProjectExplorer.getinfo(ProjectExplorer.java:30)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at    
com.kk.project.ProjectExplorer.onCreate(ProjectExplorer.java:25)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at  
android.app.Activity.performCreate(Activity.java:4465)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at  
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at 
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at 
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at  
android.app.ActivityThread.access$600(ActivityThread.java:123)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at 
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at  
android.os.Handler.dispatchMessage(Handler.java:99)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at 
android.os.Looper.loop(Looper.java:137)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at  
android.app.ActivityThread.main(ActivityThread.java:4424)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at   
java.lang.reflect.Method.invokeNative(Native Method)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at     
java.lang.reflect.Method.invoke(Method.java:511)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at 
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at   
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
12-31 22:05:51.114: E/SQLiteDatabase(4180):     at 
dalvik.system.NativeStart.main(Native Method)
12-31 22:05:51.165: E/System(4180): Uncaught exception thrown by finalizer
12-31 22:05:51.174: D/dalvikvm(4180): GREF has increased to 201
12-31 22:05:51.204: I/dalvikvm(4180): threadid=3: reacting to signal 3
12-31 22:05:51.324: E/System(4180): java.lang.IllegalStateException: Don't have   
database lock!
12-31 22:05:51.324: E/System(4180):     at  
android.database.sqlite.SQLiteDatabase.verifyLockOwner(SQLiteDatabase.java:2090)
12-31 22:05:51.324: E/System(4180):     at  
android.database.sqlite.SQLiteDatabase$1.entryRemoved(SQLiteDatabase.java:2182)
12-31 22:05:51.324: E/System(4180):     at   
android.database.sqlite.SQLiteDatabase$1.entryRemoved(SQLiteDatabase.java:2178)
12-31 22:05:51.324: E/System(4180):     at  
android.util.LruCache.trimToSize(LruCache.java:197)
12-31 22:05:51.324: E/System(4180):     at   
android.util.LruCache.evictAll(LruCache.java:285)
12-31 22:05:51.324: E/System(4180):     at   
android.database.sqlite.SQLiteDatabase.deallocCachedSqlStatements  
(SQLiteDatabase.java:2143)
12-31 22:05:51.324: E/System(4180):     at  
android.database.sqlite.SQLiteDatabase.closeClosable(SQLiteDatabase.java:1126)
12-31 22:05:51.324: E/System(4180):     at  
android.database.sqlite.SQLiteDatabase.finalize(SQLiteDatabase.java:1914)
12-31 22:05:51.324: E/System(4180):     at   
java.lang.Daemons$FinalizerDaemon.doFinalize(Daemons.java:182)
12-31 22:05:51.324: E/System(4180):     at  
java.lang.Daemons$FinalizerDaemon.run(Daemons.java:168)
12-31 22:05:51.324: E/System(4180):     at java.lang.Thread.run(Thread.java:856)

奇怪的是，我使用了类似的代码，但它运行得非常完美。此外，来自同一数据库类的其他方法也能完美运行。

调用 updateProject 的 Activity 代码:

public class UpdateProject extends Activity implements OnItemSelectedListener,  DatePickerDialog.OnDateSetListener {

int mPos;
String mSelection;

String pname;
String pdifficulty;

int pday;
int pmonth;
int pyear;

String id;


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

    id = getIntent().getExtras().getString("idforupdate");

    userdatabase viewname = new userdatabase(this);             //Get username
    viewname.open();
    String name = viewname.getusername();
    viewname.close();

    if(name.equals("")) {

        DialogFragment newFragment = new NouserexitFragment();
        newFragment.show(getFragmentManager(), "exit");

    }

    Spinner spinner = (Spinner) findViewById(R.id.difficultyspinner); ArrayAdapter<CharSequence> 
    adapter = ArrayAdapter.createFromResource(this,R.array.difficultyarray, android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adapter);
    spinner.setOnItemSelectedListener(this);

    pdifficulty = spinner.getSelectedItem().toString();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_update_project, menu);
    return true;
}

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public void datepicker(View v) {                                                        //Date picker   
    DialogFragment newFragment = new DatePickerForUpdate();
    newFragment.show(getFragmentManager(), "datePickerforupdate");

}


    @Override
public void onDateSet(DatePicker view, int year, int month, int day) {
    // TODO Auto-generated method stub

    pday = day;
    pmonth = month +1;
    pyear = year;

    month = month + 1;
    Button activityButton = (Button)findViewById(R.id.datebutton);
    activityButton.setText (day + "." + month + "." + year);

}

@Override
public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
    // TODO Auto-generated method stub

    UpdateProject.this.mPos = pos;
    UpdateProject.this.mSelection = parent.getItemAtPosition(pos).toString();

}

@Override
public void onNothingSelected(AdapterView<?> arg0) {
    // TODO Auto-generated method stub

}

public void update_project(View view) {

EditText cinone = (EditText) findViewById(R.id.pname);
pname = cinone.getText().toString();

String fdate = pday + ". " + pmonth + ". " + pyear;

projectdatabase update = new projectdatabase(UpdateProject.this);
update.open();
update.updateProject(id, pname, fdate);
update.close();


}

数据库类代码:

public class projectdatabase {

public static final String KEY_ROWID = "_id";
public static final String PROJECT_NAME = "project_name";
public static final String PROJECT_ID = "project_id";
public static final String PROJECT_DIFFICULTY = "project_difficulty";
public static final String PROJECT_STATUS = "project_status";
public static final String PROJECT_START_DATE = "project_start_date";
public static final String PROJECT_FINISH_DATE = "project_finsish_date";

private static final String DATABASE_NAME = "project_db";
static final String DATABASE_TABLE = "project_details";
private static final int DATABASE_VERSION = 1;

private DbHelper ourHelper;
private final Context projectdbContext;
private SQLiteDatabase projectDatabase;

private static class DbHelper extends SQLiteOpenHelper {
    public DbHelper(Context context) {

        super(context, DATABASE_NAME, null, DATABASE_VERSION);

    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub

        db.execSQL("CREATE TABLE "+ DATABASE_TABLE + " (" +
                KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                PROJECT_NAME + " TEXT NOT NULL, " +
                PROJECT_ID + " INTEGER, " +
                PROJECT_START_DATE + " TEXT, " +
                PROJECT_FINISH_DATE + " TEXT, " +
                PROJECT_DIFFICULTY + " TEXT, " +
                PROJECT_STATUS + " TEXT);"
               ); 

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

        db.execSQL("DROP TABLE IF EXIST " + DATABASE_NAME);
        onCreate(db);

    }
}

public projectdatabase (Context c) {                            
     projectdbContext = c;
}

public projectdatabase open() {                                                 //Open database
    ourHelper = new DbHelper(projectdbContext);
    projectDatabase = ourHelper.getWritableDatabase();
    return this;
}

public void close() {                                                           //Close database
    ourHelper.close();
}

public long createEntry(String name, String pid, String startdate, String finishdate, String difficulty, String Status) {           //Enter project data into database

    ContentValues cv = new ContentValues();
    cv.put(PROJECT_NAME, name);
    cv.put(PROJECT_ID, pid);
    cv.put(PROJECT_START_DATE, startdate);
    cv.put(PROJECT_FINISH_DATE, finishdate);
    cv.put(PROJECT_DIFFICULTY, difficulty);
    cv.put(PROJECT_STATUS, Status);

    return projectDatabase.insert(DATABASE_TABLE, null, cv);
}

public String getData() {                                                       //Retrieve all project data

    String[] columns = new String[] {KEY_ROWID, PROJECT_NAME, PROJECT_ID, PROJECT_START_DATE, PROJECT_FINISH_DATE, PROJECT_DIFFICULTY, PROJECT_STATUS};
    Cursor c = projectDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);
    String result = "";

    int iRow = c.getColumnIndex(KEY_ROWID);
    int iName = c.getColumnIndex(PROJECT_NAME);
    int iID = c.getColumnIndex(PROJECT_ID);
    int iStartDate = c.getColumnIndex(PROJECT_START_DATE);
    int iFinishDate = c.getColumnIndex(PROJECT_FINISH_DATE);
    int iDifficulty = c.getColumnIndex(PROJECT_DIFFICULTY);
    int iStatus = c.getColumnIndex(PROJECT_STATUS);

    for(c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {

        result = result + c.getString(iRow) + "|" + c.getString(iName) + "|" + c.getString(iID) + "|" + c.getString(iStartDate) + "|" + c.getString(iFinishDate) + "|" + c.getString(iDifficulty) + "|" + c.getString(iStatus) + "\n";

    }

    return result;
}

public Cursor getDataforDisplay () {                                            //Project data for list view

    String[] columns = new String[] {KEY_ROWID, PROJECT_NAME, PROJECT_FINISH_DATE, PROJECT_DIFFICULTY, PROJECT_STATUS};
    Cursor c = projectDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);

    c.moveToFirst();
    return c;

}

public String getProjectName(String id) {                   

    String[] columns = new String[] {PROJECT_NAME,KEY_ROWID};
    Cursor c = projectDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "=" + id, null, null, null, null);

    if(c != null) {

        int iName = c.getColumnIndex(PROJECT_NAME);

        c.moveToFirst();
        String name = c.getString(iName);
        return name;

    }

    return null;
}

public String getProjectStatus(String id) {

    String[] columns = new String[] {PROJECT_STATUS,KEY_ROWID};
    Cursor c = projectDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "=" + id, null, null, null, null);

    if(c != null) {

        int iStatus = c.getColumnIndex(PROJECT_STATUS);

        c.moveToFirst();
        String status = c.getString(iStatus);
        return status;

    }

    return null;
}

public String getProjectDifficulty(String id) {

String[] columns = new String[] {PROJECT_DIFFICULTY,KEY_ROWID};
Cursor c = projectDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "=" + id, null, null, null, null);

if(c != null) {

    int iDiff = c.getColumnIndex(PROJECT_DIFFICULTY);

    c.moveToFirst();
    String diff = c.getString(iDiff);
    return diff;

}

return null;

public String getProjectstartdate(String id) {

String[] columns = new String[] {PROJECT_START_DATE,KEY_ROWID};
Cursor c = projectDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "=" + id, null, null, null, null);

if(c != null) {

    int iSdate = c.getColumnIndex(PROJECT_START_DATE);

    c.moveToFirst();
    String sdate = c.getString(iSdate);
    return sdate;

}

return null;

public String getProjectfinishdate(String id) {

String[] columns = new String[] {PROJECT_FINISH_DATE,KEY_ROWID};
Cursor c = projectDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "=" + id, null, null, null, null);

if(c != null) {

    int iFdate = c.getColumnIndex(PROJECT_FINISH_DATE);

    c.moveToFirst();
    String fdate = c.getString(iFdate);
    return fdate;

}

return null;

public void updateProject(String id, String PName, String FDate) {//更新数据库的方法

ContentValues cvUpdate = new ContentValues();
cvUpdate.put(PROJECT_NAME, PName);
cvUpdate.put(PROJECT_FINISH_DATE, FDate);

projectDatabase.update(DATABASE_TABLE, cvUpdate, KEY_ROWID + "=" + id, null); 

编辑:如果我用数据库类中的任何其他方法替换 updateProject() 方法，错误就会消失并且应用程序可以正常运行。

Answer 1

您需要正确设计您的SQLiteOpenHelper 类。许多大师建议做一个静态引用，这将确保在任何时候都只存在一个 DatabaseHelper 实例。

下面的代码会给你一些想法。 (这不是完整的代码，但会给你一些提示)

public class DatabaseHelper extends SQLiteOpenHelper { 
    private static DatabaseHelper mDBHelper;

    public static DatabaseHelper getInstance(Context ctx) {

        if (mDBHelper == null) { //this will ensure no multiple instances out there.
            mDBHelper = new DatabaseHelper(ctx.getApplicationContext());
        }
        return mDBHelper;
    }

}

现在，做一个把戏。

打开数据库

private SQLiteDatabase db;
    public synchronized SQLiteDatabase open() throws SQLException {

        if(db ==null){
            db = DBHelper.getWritableDatabase();
        }

        return db;
    }

关闭数据库。

public synchronized void close() {

        //do nothing. This is a trick.
    }

原因:对于移动应用，不需要打开和关闭机制。它最适合多个用户尝试访问数据库的 Web 应用程序，但在移动应用程序的情况下，只有单个用户会使用您的应用程序。

这个 hack 还将确保您永远不会遇到 Close() was never explicitly called on database 错误。 当您打开的 SQLiteDatabase 实例多于关闭的实例时会抛出此异常，而现在在我们的例子中只有一个 SQLiteDatabse 实例。这也将处理并发数据库访问/写入问题。

希望这篇 hack 能帮助您理解实际问题。

为了更好的理解，可以引用这个link .