如何从一个SQLite数据库表中读取数据？ [英] How to read data from a SQLite database table?

问题描述

我有一个数据库表，我的目标是在每一个从数据表中的值来读取，然后将它们写入一个文本文件通过电子邮件发送。我应该如何去实现呢？

 公共无效FILEWRITE（）
{
    光标remindersCursor = mDbHelper.fetchAllReminders（）;
    startManagingCursor（remindersCursor）;    尝试
    {//捕获IOException异常下方
        的String [] =由新的String [] {} RemindersDbAdapter.KEY_TITLE;
        最后弦乐的TestString =新的String（RemindersDbAdapter.KEY_TITLE +）;
        文件SD卡= Environment.getExternalStorageDirectory（）;
        myfile文件=新的文件（SD卡，测试）;
        FileWriter的作家=新的FileWriter（MYFILE）;
        writer.append（的TestString）;
        writer.flush（）;
        writer.close（）;
        Toast.makeText（TaskReminderActivity.this，计划顺利通过了FILEWRITE！Toast.LENGTH_LONG）.show（）;
    }赶上（例外五）
    {
          Toast.makeText（TaskReminderActivity.this，如果有问题的文件！，Toast.LENGTH_LONG）.show（）;
          Log.e（FILEWRITE，如果有问题的文件！，E）;
    }
}
 

解决方案

首读从你sqllite数据库：

 光标光标= db.rawQuery（SELECT * FROM+ tbl_name表+，NULL）;
startManagingCursor（光标）;
 而（cursor.moveToNext（））{                    。的StringBuffer.append（cursor.getString（1））附加（;​​）;          }
......
 

下一步写作卡上：

  {尝试
        myfile文件=新的文件（/ SD卡/ file.txt的）;
        myFile.createNewFile（）;
        FileOutputStream中FOUT =新的FileOutputStream（MYFILE）;
        OutputStreamWriter myOutWriter =
        新OutputStreamWriter（FOUT）;
        myOutWriter.append（stringBuffer.toString（））;
        myOutWriter.close（）;
        fOut.close（）;
        Toast.makeText（getBaseContext（），
                写完SD'mysdfile.txt'
                Toast.LENGTH_SHORT）.show（）;
    }赶上（例外五）{
        Toast.makeText（getBaseContext（），e.​​getMessage（），
                Toast.LENGTH_SHORT）.show（）;
    }
 

...

请确保您有权限在你的清单文件设置

 ＆LT;使用许可权的android：NAME =android.permission.WRITE_EXTERNAL_STORAG​​E/＆GT;
 

I have a database table, my goal is to read in each of the values from the data table, then write them to a text file to be emailed. How should I go about accomplishing this?

public void FileWrite()
{
    Cursor remindersCursor = mDbHelper.fetchAllReminders();
    startManagingCursor(remindersCursor);

    try
    { // catches IOException below
        String[] from = new String[]{RemindersDbAdapter.KEY_TITLE};
        final String TESTSTRING = new String(RemindersDbAdapter.KEY_TITLE + "   ");
        File sdCard = Environment.getExternalStorageDirectory();
        File myFile = new File(sdCard, "test");
        FileWriter writer = new FileWriter(myFile);
        writer.append(TESTSTRING);
        writer.flush();
        writer.close();


        Toast.makeText(TaskReminderActivity.this, "Program Successfully went through  FileWrite!", Toast.LENGTH_LONG).show();
    } catch(Exception e)
    {
          Toast.makeText(TaskReminderActivity.this, "Had Problems with file!", Toast.LENGTH_LONG).show();
          Log.e("FileWrite", "Had Problems with file!", e);
    }
}

解决方案

First Reading from you sqllite Database :

Cursor  cursor = db.rawQuery("SELECT * FROM " +TBL_NAME+" " ,null);
startManagingCursor(cursor);
 while(cursor.moveToNext()){

                    stringBuffer.append(cursor.getString(1)).append(";");

          }
......

Next Writing on the card :

  try {
        File myFile = new File("/sdcard/file.txt");
        myFile.createNewFile();
        FileOutputStream fOut = new FileOutputStream(myFile);
        OutputStreamWriter myOutWriter = 
        new OutputStreamWriter(fOut);
        myOutWriter.append(stringBuffer.toString());
        myOutWriter.close();
        fOut.close();
        Toast.makeText(getBaseContext(),
                "Done writing SD 'mysdfile.txt'",
                Toast.LENGTH_SHORT).show();
    } catch (Exception e) {
        Toast.makeText(getBaseContext(), e.getMessage(),
                Toast.LENGTH_SHORT).show();
    }

....

Make sure you have permission set in your manifest file

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

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