andriod studio短信备份代码

以下是一个简单的Android Studio短信备份代码示例：

public class MainActivity extends AppCompatActivity {

    private static final int PERMISSIONS_REQUEST_READ_SMS = 100;

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

        // 检查是否已经授权读取短信权限
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_SMS) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_SMS}, PERMISSIONS_REQUEST_READ_SMS);
        } else {
            backupSms();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == PERMISSIONS_REQUEST_READ_SMS) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                backupSms();
            } else {
                Toast.makeText(this, "未授权读取短信权限，无法备份短信", Toast.LENGTH_SHORT).show();
            }
        }
    }

    private void backupSms() {
        StringBuilder smsBuilder = new StringBuilder();

        Cursor cursor = getContentResolver().query(Uri.parse("content://sms/"), null, null, null, null);
        if (cursor.moveToFirst()) {
            do {
                String address = cursor.getString(cursor.getColumnIndex("address"));
                String body = cursor.getString(cursor.getColumnIndex("body"));
                String date = cursor.getString(cursor.getColumnIndex("date"));

                smsBuilder.append(address).append(" ").append(date).append("\n").append(body).append("\n\n");

            } while (cursor.moveToNext());
        }
        cursor.close();

        if (smsBuilder.length() > 0) {
            writeToFile(smsBuilder.toString());
            Toast.makeText(this, "短信备份成功", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(this, "没有短信可以备份", Toast.LENGTH_SHORT).show();
        }
    }

    private void writeToFile(String data) {
        try {
            File file = new File(Environment.getExternalStorageDirectory(), "sms_backup.txt");
            FileOutputStream outputStream = new FileOutputStream(file, false);
            outputStream.write(data.getBytes());
            outputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

该代码首先检查是否已经授权读取短信权限。如果没有授权，则会提示用户请求该权限。如果已经授权，则会备份所有的短信到一个名为`sms_backup.txt`的文件中。

请注意，这只是一个简单的示例代码，您可能需要根据您的需求进行修改。