Question

我正在使用以下代码将我的数据库副本导出到我的SD卡。

public class AgUtility extends AgActivity{

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
     setContentView(R.layout.utility);
    try {
        backupDatabase(getBaseContext());
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}        
public static void backupDatabase(Context context) throws IOException {


    // Open your local db as the input stream
    String inFileName = "data/data/com.agmanagement.todaysstudent/databases/todaysstudent.db";
    Toast.makeText(context, "FileName Is "+ inFileName, Toast.LENGTH_LONG).show();
    Log.i("The File In Is ", inFileName);

    File dbFile = new File(inFileName);
    FileInputStream fis = new FileInputStream(dbFile);

    File outputDirectory = new File(
            Environment.getExternalStorageDirectory() + "/student/");
    outputDirectory.mkdir();
    Log.d("MAKE DIR", dbFile.mkdir() + "");
    String backupFileName = "/TodaysStudentTest.db3"; 
    String outFileName = outputDirectory + backupFileName;
    Toast.makeText(context, "Database backup names is " + outFileName , Toast.LENGTH_LONG)
    .show();  

    // Open the empty db as the output stream
    OutputStream output = new FileOutputStream(outFileName);

    // transfer bytes from the inputfile to the outputfile
    byte[] buffer = new byte[1024];
    int length;
    while ((length = fis.read(buffer)) > 0) {
        output.write(buffer, 0, length);
    }
    // Close the streams
    output.flush();
    output.close();
    fis.close();

    Toast.makeText(context, "Database backup complete", Toast.LENGTH_LONG)
            .show();
}
}

代码似乎工作正常，因为我没有得到任何错误，第一个Toast显示正确的数据库名称，第二个toast显示输出目录应该是mnt / sdcard / student，第三个显示最终目标应该是mnt / sdcard / student / TodaysStudentTest.db3

在吐司消失之后，没有任何东西，最终的吐司永远不会出现。

在我的清单中我有

我在三星平板电脑上测试这个，而不是在模拟器上，我也在DroidX上运行它，结果相同，没有错误，但没有创建文件夹。

关于我做错的任何想法？ TIA

我正在使用的权限是

     <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> 
 <uses-permission android:name="android.permission.READ_PHONE_STATE" /> 
 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> 
 <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
 <uses-permission android:name="android.permission.INTERNET" /> 
 <uses-permission android:name="android.premission.WRITE_EXTERNAL_STORAGE" />
 <uses-permission android:name="android.permission.SET_DEBUG_APP" />
 <uses-permission android:name="android.permission.CAMERA"/>
 <uses-permission android:name="android.permission.READ_CALENDAR"/>
 <uses-permission android:name="android.permission.WRITE_CALENDAR"/>

在模拟器中运行时得到相同的结果 - 使用DDMS观察 - Logcat显示MAKE DIR失败。

我用这个

测试了状态

        if (Environment.MEDIA_MOUNTED.equals(state)) {
         // We can read and write the media
         mExternalStorageAvailable = mExternalStorageWriteable = true;
            Toast.makeText(getBaseContext(), "We Can Read And Write To The SDCARD", Toast.LENGTH_LONG).show();
            } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
         // We can only read the media
                mExternalStorageAvailable = true;
                mExternalStorageWriteable = false;
                Toast.makeText(getBaseContext(), "We Can Read The SDCARD", Toast.LENGTH_LONG).show();
            } else {
                // Something else is wrong. It may be one of many other states, but all we need
                //  to know is we can neither read nor write
                mExternalStorageAvailable = mExternalStorageWriteable = false;
                Toast.makeText(getBaseContext(), "We Can't read or write", Toast.LENGTH_LONG).show();
            }

它表明我应该能够读写，所以我写作的方式有问题。我将此添加到文本

       boolean success = false;
        if(!outputDirectory.exists()){
            Toast.makeText(getBaseContext(), "Folder Doesn't Exist ", Toast.LENGTH_LONG)
            .show();  
            success = outputDirectory.mkdirs();
        }
        if (!success){ 
            Toast.makeText(getBaseContext(), "Folder Not Created ", Toast.LENGTH_LONG)
            .show();  
        }
        else{
            Toast.makeText(getBaseContext(), "Folder Created ", Toast.LENGTH_LONG)
            .show();  
        }

结果是文件夹不存在，然后mkdirs（）失败。

Answer 1

尝试在尝试写入文件之前手动创建文件。

Answer 2

<强> REWRITE

这是一种处理数据库文件的不同方法，不使用SQL本身或循环缓冲区。

注意：这实际上并没有复制到SD卡，备份存储在原始数据库文件夹中（我喜欢这样，因为你不需要 WRITE_EXTERNAL_STORAGE权限。）

public class FileIO extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        DBHelper db = new DBHelper(this);

        try { 
            copyFile();
        } catch (IOException ioe) {
            ioe.printStackTrace();
        } finally {
            Log.i("Main", "Complete");
            db.close();
            finish();
        }
    }

    public void copyFile() throws IOException {
        File data = Environment.getDataDirectory();
        String state = Environment.getExternalStorageState();

        /* Create file first
            FileOutputStream created = openFileOutput("copyFile.db", MODE_WORLD_READABLE);
            created.close();
        */

        String currentDBPath = "/data/<your_path>/databases/data.db";
        String backupDBPath = "/data/<your_path>/databases/copyByFile.db";
        File currentDB = new File(data, currentDBPath);
        File backupDB = new File(data, backupDBPath);

        if (currentDB.exists()) {
            FileChannel src = new FileInputStream(currentDB).getChannel();
            FileChannel dst = new FileOutputStream(backupDB).getChannel();
            dst.transferFrom(src, 0, src.size());
            src.close();
            dst.close();
        }
        else
            Log.i("Main", "Current db does not exist");
    }
}

Answer 3

请确保在使用mkdir（）时已经创建了名为“student”的文件夹。它将通过抽象路径名创建目录。如果文件夹“student”不存在则不会创建新文件夹..或者尝试使用mkdirs（）。如有必要，它将创建父文件夹。

Answer 4

重要的是要记住检查拼写。 uses-permission被错误地拼写为use-premission，我已经阅读了很多次，因为我按照我的意愿阅读了它。宝贵的一课，走开，休息一下。

代码没有将数据库写入SD卡

4 个答案: