import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class PublicUserActivity extends Activity {

    private TextView mFileView;
    private static final String TARGET_PACKAGE = "org.jssec.android.file.publicfile.readonly";
    private static final String TARGET_CLASS = "org.jssec.android.file.publicfile.readonly.PublicFileActivity";
    private static final String FILE_NAME = "public_file.dat";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.user);
        mFileView = (TextView) findViewById(R.id.file_view);
    }

    private void callFileActivity() {
        Intent intent = new Intent();
        intent.setClassName(TARGET_PACKAGE, TARGET_CLASS);
        try {
            startActivity(intent);
        } catch (ActivityNotFoundException e) {
            mFileView.setText("(File Activity does not exist)");
        }
    }

    /**
     * Call file Activity process
     *
     * @param view
     */
    public void onCallFileActivityClick(View view) {
        callFileActivity();
    }

    /**
     * Read file process
     *
     * @param view
     */
    public void onReadFileClick(View view) {
        FileInputStream fis = null;
        try {
            File file = new File(getFilesPath(FILE_NAME));
            fis = new FileInputStream(file);
            byte[] data = new byte[(int) fis.getChannel().size()];
            fis.read(data);
            // *** POINT 4 *** Regarding the information to be stored in files, handle file data carefully and securely.
            // Опущено, поскольку это пример. Пожалуйста, обратитесь к разделу «3.2 Обработка входных данных с осторожностью и безопасностью».
            String str = new String(data);
            mFileView.setText(str);
        } catch (FileNotFoundException e) {
            android.util.Log.e("PublicUserActivity", "no file");
        } catch (IOException e) {
            android.util.Log.e("PublicUserActivity", "failed to read file");
        } finally {
            if (fis != null) {
                try {
                    fis.close();
                } catch (IOException e) {
                    android.util.Log.e("PublicUserActivity", "failed to close file");
                }
            }
        }
    }

    /**
     * Rewrite file process
     *
     * @param view
     */
    public void onWriteFileClick(View view) {
        FileOutputStream fos = null;
        boolean exception = false;
        try {
            File file = new File(getFilesPath(FILE_NAME));
            // Не удаётся записать. Возникает исключение FileNotFoundException.
            fos = new FileOutputStream(file, true);
            fos.write(new String("Not sensitive information (Public User Activity)¥n").getBytes());
        } catch (IOException e) {
            mFileView.setText(e.getMessage());
            exception = true;
        } finally {
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    exception = true;
                }
            }
        }
        if (!exception)
            callFileActivity();
    }

    private String getFilesPath(String filename) {
        String path = "";
        try {
            Context ctx = createPackageContext(TARGET_PACKAGE,
            Context.CONTEXT_RESTRICTED);
            File file = new File(ctx.getFilesDir(), filename);
            path = file.getPath();
        } catch (NameNotFoundException e) {
            android.util.Log.e("PublicUserActivity", "no file");
        }
        return path;
    }
}