Question

我遇到了一个问题：我在/ data / data / files上有一个存储的数据，并且有一个菜单按钮“export”，当我点击它时，文件很好地导出到SDCARD但是大小为0 （文件中没有数据）。 export.class代码：

public Export(Context context,String nom) {
        this.context = context;
        this.nom=nom;
       }

    public void transfer(){
        try {
    File sdCard = Environment.getExternalStorageDirectory();
    boolean mExternalStorageAvailable = false;
    boolean mExternalStorageWriteable = false;
    String state = Environment.getExternalStorageState();

    if (Environment.MEDIA_MOUNTED.equals(state)) {
        // We can read and write the media
        Log.d("Carburant", "Sdcard can read/write !!" ); 
        mExternalStorageAvailable = mExternalStorageWriteable = true;
        File dir = new File (sdCard.getAbsolutePath() + "/Carburant/");
        dir.mkdirs();
        File file = new File(dir, "settings.dat");
        //FileOutputStream f = new FileOutputStream(file);
        copyfile(nom,file.getAbsolutePath());
    } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
        // We can only read the media
        Log.d("Carburant", "Sdcard only read !!" ); 
        mExternalStorageAvailable = true;
        mExternalStorageWriteable = false;
    } 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;
    }
        }
    catch (Exception e) {
        Log.d("CARBURANT", e.getMessage());
    }

}

    private void copyfile(String srFile, String dtFile){
        try{
            File f1 = new File(srFile);
            File f2 = new File(dtFile);
          InputStream in = new FileInputStream(f1);
          OutputStream out = new FileOutputStream(f2);

          byte[] buf = new byte[1024];
          int len;
          while ((len = in.read(buf)) > 0){
            out.write(buf, 0, len);
          }
          in.close();
          out.close();
          Toast.makeText(context, "Export effectué", Toast.LENGTH_SHORT).show();
        }
        catch(FileNotFoundException ex){
            Toast.makeText(context, "File Not found", Toast.LENGTH_SHORT).show();
            String x=ex.getMessage();
            Log.d("Carburant", x);
        }
        catch(IOException e){
            Toast.makeText(context, "Echec", Toast.LENGTH_SHORT).show();      
        }
      }

    }

代码写入文件的位置：

if (data != "" ) {
              SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
           String fileName = getResources().getString(R.string.fileName);
           String fileDir = ""+ preferences.getString("login", "") + "."+ preferences.getString("marque", "") + ".";
           myIO.WriteSettings(context,fileDir+fileName, data);
           data = "";

WriteSettings方法：

public static void WriteSettings(Context context, String nom, String data) {
        FileOutputStream fOut = null;
        OutputStreamWriter osw = null;

        try {
            fOut = context.openFileOutput(nom, Context.MODE_APPEND);
            osw = new OutputStreamWriter(fOut);
            osw.write(data);
            osw.flush();
            osw.close();
                    fOut.close();

菜单导出按钮：

case R.id.export:
    String mainDirPath = this.getFilesDir() + File.separator + "settings.dat";
    FileOutputStream fos;
    try {
        fos = this.openFileOutput("settings.dat", Context.MODE_PRIVATE);
        Export myExport = new Export(this,mainDirPath);
        myExport.transfer();
    } catch (FileNotFoundException e) {
        Log.d("Carburant","File Not found");
    }catch(IOException e){
        Log.d("Carburant","ERROR");
    }
            return true;

编辑菜单导出按钮：

case R.id.exporter:
            final SharedPreferences preferences = PreferenceManager
            .getDefaultSharedPreferences(context);
    String fileName = getResources().getString(R.string.fileName);
    fileDir = "" + preferences.getString("login", "") + "."+ preferences.getString("marque", "") + ".";

    String mainDirPath = this.getFilesDir() + File.separator + fileDir+fileName;
    Log.d("Carburant",mainDirPath);
    FileOutputStream fos;
    try {
        fos = this.openFileOutput(fileDir+fileName, Context.MODE_PRIVATE);
        Export myExport = new Export(this,mainDirPath);
        myExport.transfer();
    } catch (FileNotFoundException e) {
        Log.d("Carburant","File Not found");
    }catch(IOException e){
        Log.d("Carburant","ERROR");
    }
            return true;

感谢您的帮助。

Answer 1

也许看看这一行“while（（len = in.read（buf））＆gt; 0）”

byte[] buffer = new byte[1024];
int len = in.read(buffer);
while (len != -1) {
    out.write(buffer, 0, len);
    len = in.read(buffer);
}

Answer 2

我建议在调试器中单步执行此操作，并查看copyfile方法中发生的情况。 src文件'nom'是否存在，大小非零？

祝福，

Phil Lello

Answer 3

在上面的菜单导出按钮代码中，您正在执行此操作...

case R.id.export:
    String mainDirPath = this.getFilesDir() + File.separator + "settings.dat";

这意味着mainDirPath将类似......

/data/data/<package name>/files/settings.dat

问题是当您写入文件...

String fileDir = ""+ preferences.getString("login", "") + "."+ preferences.getString("marque", "") + ".";
myIO.WriteSettings(context,fileDir+fileName, data);

这意味着当你创建mainDirPath时，它应该是......

SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
String mainDirPath = this.getFilesDir() + File.separator + preferences.getString("login", "") + "." + preferences.getString("marque", "") + "." + "settings.dat";

混乱就是这条线......

fos = this.openFileOutput("settings.dat", Context.MODE_PRIVATE);

...创建一个名为...

的空文件

/data/data/<package name>/files/settings.dat

该文件是您正在复制的文件，而不是名为login.marque.settings.dat的文件。

这有意义吗？

将文件导出到SDCARD时出现一个小问题

3 个答案: