Question

如何将sqlite数据库导出到外部存储器`我正在尝试此方法，但它显示异常

 public void exportdb() {


    Log.e("data ","export");
    File sd=Environment.getExternalStorageDirectory();
    File data = Environment.getDataDirectory();
    FileChannel source=null;
    FileChannel destination=null;
    String currentDBPath = "/data/"+ "com.example.kishababy.myapplication.DataBase" +"/databases/"+ "contactsManager";
    String backupDBPath = "contactsManager";
    File currentDB = new File(data, currentDBPath);
    File backupDB = new File(sd, backupDBPath);
    try {
        source = new FileInputStream(currentDB).getChannel();
        destination = new FileOutputStream(backupDB).getChannel();
        destination.transferFrom(source, 0, source.size());
        source.close();
        destination.close();
        Log.e("Toast","befor");

        Toast.makeText(getApplicationContext(), "DB Exported!", Toast.LENGTH_LONG).show();
    } catch(IOException e) {
        e.printStackTrace();
        Log.e("Exception",e.toString());
    }






}

品酒时的例外情况 enter image description here

Answer 1

我认为您需要为您的应用获取或授予lists:foldl权限（您的手机运行的是Android 7.0，这是我最好的猜测）

Answer 2

可能你必须给出路径：

String currentDBPath = "//data//"+ "com.example.kishababy.myapplication.DataBase" +"//databases//"+ "contactsManager";

并确保您已添加

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

首先检查你的SD卡状态：

String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
    Log.d("Test", "sdcard mounted and writable");
}
else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
    Log.d("Test", "sdcard mounted readonly");
}
else {
    Log.d("Test", "sdcard state: " + state);
}

Answer 3

使用

String currentDBPath = "/data/data/"+ "com.example.kishababy.myapplication.DataBase" +"/databases/"+ "contactsManager";

而不是

String currentDBPath = "/data/"+ "com.example.kishababy.myapplication.DataBase" +"/databases/"+ "contactsManager";

此外，您必须调用权限并确保在进行备份之前已创建数据库。

您可以使用以下完全集成：

将用户权限添加到清单文件中以进行存储

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

使用此代码段进行备份：

public void exportDb() {
try {
    String inFileName =  "/data/data/<com.abc.app>/databases/app.db";

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

    String outFileName = Environment.getExternalStorageDirectory() + "/app_copy.db";

    OutputStream output = new FileOutputStream(outFileName);

    byte[] buffer = new byte[1024];
    int length;
    while ((length = fis.read(buffer)) > 0) {
        output.write(buffer, 0, length);
    }

    output.flush();
    output.close();
    fis.close();
} catch (Exception e) {
    e.printStackTrace();
}
}

检查存储权限并调用备份方法：

private void backupData() {
if ((ContextCompat.checkSelfPermission(mActivity, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED)) {
    ActivityCompat.requestPermissions(mActivity, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 11);
} else {
    exportDb();
}

}

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
if (requestCode == 11) {
    if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
        exportDb();
    }
}
}

我如何将我的sqllite数据库导出到SD卡

3 个答案: