问题描述
我想我的应用程序的数据库导出到SD卡。它的工作原理优秀的仿真器,车针不是我的电话。
I'm trying to export my application's database to SDcard. It works excellent for emulator, bur not for my phone.
OnClickListener mExportListener = new OnClickListener(){
public void onClick(View v){
try {
File sd = Environment.getExternalStorageDirectory();
File data = Environment.getDataDirectory();
if (sd.canWrite()) {
String currentDBPath = "\\data\\com.mypck.myapp\\databases\\database";
String backupDBPath = "database.db";
File currentDB = new File(data, currentDBPath);
File backupDB = new File(sd, 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{
String msg = activity.getResources().getString(R.string.something_wrong);
Toast toast = Toast.makeText(getApplicationContext(), msg, Toast.LENGTH_LONG);
toast.show();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
};
本 currentDB.exists()
在手机上返回假的,但我检查了文件 - 它的存在。
什么是错我的电话?
This currentDB.exists()
returns false on the phone, but I checked the file - it exists.What is wrong with my phone?
推荐答案
您提供文件
错误的参数。从Android的文档:
You are supplying File
wrong parameters. From Android doc:
File(String parent, String child)
parent - The parent pathname string
child - The child pathname string
在您的code:
parent => \\data
child => \\data\\com.mypck.myapp\\databases\\database
resulting path => \\data\\data\\com.mypck.myapp\\databases\\database => wrong
这可能是这样的:
It could be like this:
String sd = Environment.getExternalStorageDirectory();
if (sd.canWrite()) {
String currentDBPath = "data/data/com.mypck.myapp/databases/your_database_name.db";
String backupDBPath = sd + "/your_output_file_name.db";
File currentDB = new File(currentDBPath);
File backupDB = new File(backupDBPath);
/* ... */
我很惊讶这个工作在模拟器,我对此表示怀疑。它可能会创建一个空文件,原因至少这行做某种感觉,虽然你的变量是不是你叫他们:
It surprises me this works on emulator, I doubt that. It probably creates an empty file becuase at least this line makes some sort of sense, although your variables are not what you named them:
File backupDB = new File(sd, backupDBPath);
另外,你或许应该创建一个最后
块,并做有一些 FileChannel
清理。
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