android - canWrite() 到 SD 返回 false

Question

当我使用调试器时，sd.canWrite() 语句返回 false 并且不运行其余代码。我用模拟器和真正的三星平板电脑试过了。我有

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

在我的 list 中。

public void exportDatabse(String databaseName) {
        try {
            File sd = Environment.getExternalStorageDirectory();

            File data = Environment.getDataDirectory();


            if (sd.canWrite()) {
                String currentDBPath = "//data//"+getPackageName()+"//databases//"+databaseName+"";
                String backupDBPath = "backupname.db";
                File currentDB = new File(data, currentDBPath);
                File backupDB = new File(sd, backupDBPath);
                Log.d("file", "file copied2");

                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();
                }
                Log.d("file", "file copied3");
            }
        } catch (Exception e) {
            Log.d("file", "file not copied");

        }
        Log.d("file", "method runs");
    }

Answer 1

请检查外部存储是否写保护-

String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {

}