Question

我开发了一个具有C2DM功能的项目。只要服务器上有数据，服务器将数据推送到该应用程序的所有设备（在我的情况下是一个小的消息）。

现在我的问题是每次创建消息来源的数据库和表时都会这样做这是我的代码，

 public class MessageHelper extends Activity
    {
        public String str; 
        public int sts;
        public Date timeStamp;

        protected void onCreate(Bundle savedInstanceState) 
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);

            Bundle extras = getIntent().getExtras();
            if (extras != null) {
                this.str = extras.getString("msgg");
                Log.d("C2DM", this.str);
            }

            // Create a ref of SQLite
            SQLiteDatabase db;

            //use tat ref to open or create a table 
            db = openOrCreateDatabase( "/data/data/de.vogella.android.c2dm.simpleclient/app_database/file__0/0000000000000001.db", SQLiteDatabase.CREATE_IF_NECESSARY, null);

            try 
            {
                //initialsiging a query with all the table fields 
                final String CREATE_TABLE_CONTAIN = "CREATE TABLE IF NOT EXISTS tbl_Message4("
                        + "id INTEGER PRIMARY KEY AUTOINCREMENT,"
                        + "msg TEXT not null," 
                        + "msg_time INTEGER not null,"
                        + "msg_status INTEGER not null);";

                //execute the above query
                db.execSQL(CREATE_TABLE_CONTAIN);

                timeStamp = new Date();

                String sql =
                        "INSERT or replace INTO tbl_Message4 (msg,msg_time,msg_status) VALUES('"+this.str+"' ,'"+this.timeStamp+"' , 0)" ;       
                db.execSQL(sql);
        }
    }

我还有一个名为MessageReceiver的类，它扩展了Broadcastreceiver; eveytime一个消息来执行该类，它将加载MessageHelper.class 这是MessageReceiver的代码，

public class C2DMMessageReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        Log.w("C2DM", "Message Receiver called");
        if ("com.google.android.c2dm.intent.RECEIVE".equals(action)) {
            Log.w("C2DM", "Received message");
            final String payload = intent.getStringExtra("payload");
            Log.d("C2DM", "dmControl: payload = " + payload);
            // TODO Send this to my application server to get the real data
            // Lets make something visible to show that we received the message
            createNotification(context, payload);

        }
    }

    public void createNotification(Context context, String payload) {
        NotificationManager notificationManager = (NotificationManager) context
                .getSystemService(Context.NOTIFICATION_SERVICE);
        Notification notification = new Notification(R.drawable.ic_launcher,
                "Message received", System.currentTimeMillis());
        // Hide the notification after its selected
        notification.flags |= Notification.FLAG_AUTO_CANCEL;

        //Intent intent = new Intent(context, MessageReceivedActivity.class);
        //intent.putExtra("payload", payload);

        Intent intent = new Intent(context, MessageHelper.class);
        intent.putExtra("msgg", payload);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(intent);
        //PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);
        //notification.setLatestEventInfo(context, "Message", "New message received", pendingIntent);
        //notificationManager.notify(0, notification);

    }

}

我在寻找的是，第一次安装应用程序时应该创建一个数据库。

提前致谢，

TheIlleterate

Answer 1

由于未更改名称，因此只会创建一次数据库。是的，它只会在您的应用首次启动活动 MessageHelper 时创建。

Answer 2

只使用一个名称创建一次数据库。

在这里，您可以选择此代码以简化

http://www.vogella.com/articles/AndroidSQLite/article.html

Answer 3

“CREATE TABLE IF NOT EXISTS”只有在表格不存在时才会创建表格。所以它只会创建一次。你在其他地方删除了这个表吗？

Sqlite数据库只应创建一次

3 个答案: