file.createFile 不起作用。 安卓 10

Question

 val filePath = getString(R.string.file_path)
    val file = File(filePath)
    var lines: List<String?> = ArrayList()
    if(!file.exists()) {
            try {
               if (Environment.getExternalStorageState()==Environment.MEDIA_MOUNTED) {

                   file.createNewFile()
               }
            } catch (e: IOException) {
                AlertDialog.Builder(this)
                    .setTitle(getString(R.string.No_records_file))
                    .setMessage(getString(R.string.cant_create_file))
                    .setNeutralButton(
                        R.string.Exit
                    ) { dialog, id -> finish() }.show()
            }
        }

It works on Android 8.0.0, 9.0 . I am not sure about android, but this problem appeared on Mi9T pro

Answer 1

With Android Q, you can no longer directly access to the file system. Use the SAF (Storage Access Framework) instead.

Answer 2

在 Android API 29 上，不推荐使用 getExternalStorageDirectory，您应该改用 getExternalFilesDir。

Answer 3

First add this rules;

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

Ask permissions from activity;

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

    //ASK HERE...
    if (shouldAskPermissions()) {
        askPermissions();
    }

}

-

  //// ASK METHODS
    protected boolean shouldAskPermissions() {
        return (Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP_MR1);
    }

    protected void askPermissions() {
        String[] permissions = {
                "android.permission.READ_EXTERNAL_STORAGE",
                "android.permission.WRITE_EXTERNAL_STORAGE"
        };
        int requestCode = 200;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            requestPermissions(permissions, requestCode);
        }
    }

then for create file use this code;

        File directory = new File(Environment.getExternalStorageDirectory()+java.io.File.separator +"AppName");

             try{
                     if(!directory.exists()) {
                         System.out.println("Directory created");
                         directory.mkdirs();
                     } else {
                         System.out.println("Directory is not created");
                     }

                     File f = new File(directory.getPath()+"/"+ "ENTER_FILE_NAME" + ".jpg");
                     f.createNewFile();
                     FileOutputStream fo = new FileOutputStream(f);
                     fo.write(bytes.toByteArray());
                     fo.close();

                     System.out.println("FILE PATH:" + f.getPath());

                 }catch(Exception e){
                     e.printStackTrace();
                 }