短信备份的原理——使用内容提供者

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    public class MainActivity extends Activity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);    }    public void backup(View view){        ContentResolver resolver = getContentResolver();        Uri uri = Uri.parse("content://sms");        Cursor cursor = resolver.query(uri, null, null, null, null);        try {            XmlSerializer serializer = Xml.newSerializer();            File file = new File(Environment.getExternalStorageDirectory(),"back.xml");            OutputStream os = new FileOutputStream(file);            serializer.setOutput(os, "UTF-8");            serializer.startDocument("UTF-8", true);            serializer.startTag(null, "smss");            while(cursor.moveToNext()){                serializer.startTag(null, "sms");                    serializer.startTag(null, "address");                    String address = cursor.getString(cursor.getColumnIndex("address"));                    serializer.text(address);                    serializer.endTag(null, "address");                    serializer.startTag(null, "body");                    String body = cursor.getString(cursor.getColumnIndex("body"));                    serializer.text(body);                    serializer.endTag(null, "body");                    serializer.startTag(null, "date");                    long date = cursor.getLong(cursor.getColumnIndex("date"));                    String dateString = new Date(date).toString();                    serializer.text(dateString);                    serializer.endTag(null, "date");                serializer.endTag(null, "sms");            }            serializer.endTag(null, "smss");            serializer.endDocument();            os.close();            Toast.makeText(this, "备份成功",Toast.LENGTH_SHORT).show();        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}
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