Question

我已经开始使用Android Studio两天了，我也没有太多的java经验。我做了一个简单的登录应用程序连接到Sql server作为数据库进行检查。我写了这个代码来自http://seotoolzz.com/android/android-login-app-with-mssql-server.php。但是在下一行中它显示了一个错误：必须从ui线程调用方法gettext。请帮忙，因为我非常新的Android应用程序开发。非常感谢。

String usernam = username.getText（）。toString（）;

String passwordd = password.getText（）。toString（）;

 public class MainActivity extends AppCompatActivity

{

Button login;
EditText username,password;
ProgressBar progressBar;



Connection con;
String un,pass,db,ip;


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


    login = (Button) findViewById(R.id.button);
    username = (EditText) findViewById(R.id.editText);
    password = (EditText) findViewById(R.id.editText2);
    progressBar = (ProgressBar) findViewById(R.id.progressBar);



    ip = "1IP";
    db = "ADB";
    un = "your username for that database here";
    pass = "your password for that database here";
     login.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            CheckLogin checkLogin = new CheckLogin();
                checkLogin.execute("");
        }
    });

}

public class CheckLogin extends AsyncTask<String,String,String>
{
    String z = "";
    Boolean isSuccess = false;

    @Override
    protected void onPreExecute()
    {
        progressBar.setVisibility(View.VISIBLE);
    }

    @Override
    protected void onPostExecute(String r)
    {
        progressBar.setVisibility(View.GONE);
        Toast.makeText(MainActivity.this, r, Toast.LENGTH_SHORT).show();
        if(isSuccess)
        {
            Toast.makeText(MainActivity.this , "Login Successfull" , Toast.LENGTH_LONG).show();
            //finish();
        }
    }
    @Override
    protected String doInBackground(String... params)
    {
        String usernam = username.getText().toString();
        String passwordd = password.getText().toString();
        if(usernam.trim().equals("")|| passwordd.trim().equals(""))
            z = "Please enter Username and Password";
        else
        {
            try
            {
                con = connectionclass(un, pass, db, ip);       
                if (con == null)
                {
                    z = "Check Your Internet Access!";
                }
                else
                {
                                           String query = "select * from Login where UserName= '" + usernam.toString() + "' and Password = '"+ passwordd.toString() +"'  ";
                    Statement stmt = con.createStatement();
                    ResultSet rs = stmt.executeQuery(query);
                    if(rs.next())
                    {
                        z = "Login successful";
                        isSuccess=true;
                        con.close();
                    }
                    else
                    {
                        z = "Invalid Credentials!";
                        isSuccess = false;
                    }
                }
            }
            catch (Exception ex)
            {
                isSuccess = false;
                z = ex.getMessage();
            }
        }
        return z;
    }
}


@SuppressLint("NewApi")
public Connection connectionclass(String user, String password, String database, String server)
{
    StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
    StrictMode.setThreadPolicy(policy);
    Connection connection = null;
    String ConnectionURL = null;
    try
    {
        Class.forName("net.sourceforge.jtds.jdbc.Driver");
        ConnectionURL = "jdbc:jtds:sqlserver://" + server + database + ";user=" + user+ ";password=" + password + ";";
        connection = DriverManager.getConnection(ConnectionURL);
    }
    catch (SQLException se)
    {
        Log.e("error here 1 : ", se.getMessage());
    }
    catch (ClassNotFoundException e)
    {
        Log.e("error here 2 : ", e.getMessage());
    }
    catch (Exception e)
    {
        Log.e("error here 3 : ", e.getMessage());
    }
    return connection;
}

}

Answer 1

您正在尝试的问题是访问外部类中的当前视图元素（编辑：或者更确切地说是另一个非UI线程）。

解决方法是使用Activity.runOnUIThread（Runnable），如下所示：

String usernam, passwordd;
getActivity().runOnUIThread(new Runnable(){
    usernam = username.getText().toString();
    passwordd = password.getText().toString();
}

你也可以在调用它时将Strings作为输入传递给AsyncTask：

@Override
public void onClick(View v)
{
    CheckLogin checkLogin = new CheckLogin();
    checkLogin.execute(usernam.getText(),passwordd.getText());
}

并在AsyncTask.doInBackground中访问它：

@Override
protected String doInBackground(String... params)
{
    usernam = params[0];
    passwordd = params[1];
    ....
}

希望这有用。

Answer 2

Asyntask是一个单独的线程，无法访问UI线程元素。不能将值存储为全局成员变量并访问它们。

 String usernam,password;

然后在你的onclickListener中存储值。

login.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            usernam=username.getText().toString();
            password=password.getText().toString();
            CheckLogin checkLogin = new CheckLogin();
            checkLogin.execute("");
        }
    });

方法gettext必须从ui线程调用当前推断的线程是worker

2 个答案: