我试图使用 ZipInputStream （code is here）解压缩文件

public class Async_unzipping extends AsyncTask<String, String, String> {
    Activity mActivity;
    private ProgressDialog mProgressDialog;

    public Async_unzipping(Activity activity) {
        this.mActivity = activity;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        mProgressDialog = new ProgressDialog(mActivity);
        mProgressDialog.setMessage("Extracting file..");
        mProgressDialog.setCancelable(false);
        mProgressDialog.show();
    }

    @Override
    protected String doInBackground(String... params) {

        try {
            FileInputStream fin = new FileInputStream(Constant.SDCARD + Constant.FILENAME);
            ZipInputStream zin = new ZipInputStream(fin);
            ZipEntry ze = null;
            while ((ze = zin.getNextEntry()) != null) {

                FileOutputStream fout = new FileOutputStream(Constant.SDCARD + ze.getName());
                for (int c = zin.read(); c != -1; c = zin.read()) {
                    fout.write(c);
                }

                zin.closeEntry();
                fout.close();
            }

            zin.close();
        } catch (Exception e) {
        }


        return null;
    }

    @Override
    protected void onPostExecute(String unused) {
        mProgressDialog.dismiss();
    }

}

问题是这个类永远不会被调用，它永远不会工作或显示任何对话框 . 我正在使用它

public void unzip(View view) {
    Toast.makeText(getBaseContext(), "method was called", Toast.LENGTH_LONG).show();
    Async_unzipping async_unzipping = new Async_unzipping(Main.this);
    async_unzipping.execute("");
}

当我按下解压缩按钮时没有日志，所以我无法分辨最新情况 . 我在清单中读过写权限

android