Android登录验证和活动重定向错误

Question

我想重定向我当前的活动到另一个活动后成功登录，我使用Php-MySQL数据库。我不能使用静态关键字登录，比如username=“admin”&&password=“admin”。

package helloworld.krish.com.login2;

import android.app.AlertDialog;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.view.View;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;

import static android.support.v4.content.ContextCompat.startActivity;

public class BackgroundWorker extends AsyncTask <String, Void, String > {
        Context context;
        AlertDialog alertDialog;
        BackgroundWorker (Context ctx) {
                context = ctx;
        }
        boolean statusOk = false;

    @Override
    protected String doInBackground(String... params) {
        String type = params[0];
        String login_url = "http://192.168.0.106/login.php";
        String reg_url = "http://192.168.0.106/register.php";

        System.out.println(1);

        //Login Function

        if(type.equals("login")) {
            try {
                String user_name = params[1];
                String password = params[2];

                URL url = new URL(login_url);
                HttpURLConnection htpurl = (HttpURLConnection)url.openConnection();
                System.out.println(2);
                htpurl.setRequestMethod("POST");
                htpurl.setDoInput(true);
                htpurl.setDoOutput(true);
                System.out.println(3);
                OutputStream outputStream = htpurl.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
                String Post_data = URLEncoder.encode("user_name","UTF-8")+"="+URLEncoder.encode(user_name,"UTF-8")+"&"
                        +URLEncoder.encode("enter code herepassword","UTF-8")+"="+URLEncoder.encode(password,"UTF-8");
                System.out.println(4);
                bufferedWriter.write(Post_data);
                System.out.println(5);
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();

                //response for post request//
                System.out.println(6);

                InputStream inputStream = htpurl.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"));
                String result = "";
                String line = "";

                System.out.println(6.5);
                while((line = bufferedReader.readLine())!= null){
                        System.out.println(7);
                        result += line;
                    }
                bufferedReader.close();
                inputStream.close();
                htpurl.disconnect();
                System.out.println(7.5);
                return result;

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        //Register Activity

        else if (type.equals("register")){
                try {
                    String name = params[1];
                    String designation = params[2];
                    String salary = params[3];
                    String cont = params[4];

                    URL url = new URL(reg_url);
                    HttpURLConnection htpurl = (HttpURLConnection)url.openConnection();
                    System.out.println(2);
                    htpurl.setRequestMethod("POST");
                    htpurl.setDoInput(true);
                    htpurl.setDoOutput(true);
                    System.out.println(3);
                    OutputStream outputStream = htpurl.getOutputStream();
      //Main Code for Register//
                    BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
                    String Post_data = URLEncoder.encode("name","UTF-8")+"="+URLEncoder.encode(name,"UTF-8")+"&"
                            +URLEncoder.encode("designation","UTF-8")+"="+URLEncoder.encode(designation,"UTF-8")
                            +"&"+URLEncoder.encode("salary","UTF-8")+"="+URLEncoder.encode(salary,"UTF-8")
                            +"&"+URLEncoder.encode("cont","UTF-8")+"="+URLEncoder.encode(cont,"UTF-8");
                    System.out.println(4);
                    bufferedWriter.write(Post_data);
                    System.out.println(5);
                    bufferedWriter.flush();
                    bufferedWriter.close();
                    outputStream.close();

                    //response for post request//
                    System.out.println(6);

                    InputStream inputStream = htpurl.getInputStream();
                    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"));
                    String result = "";
                    String line = "";
                    System.out.println(6.5);
                    while((line = bufferedReader.readLine())!= null){
                        System.out.println(7);
                        result += line;
                    }
                    bufferedReader.close();
                    inputStream.close();
                    htpurl.disconnect();
                    System.out.println(7.5);
                    return result;

                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return null;
    }

    @Override
    protected void onPreExecute() {
        System.out.println(8);
        alertDialog = new AlertDialog.Builder(context).create();
        alertDialog.setTitle("Login Status");
    }

    @Override
    protected void onPostExecute(String result) {
        if(result.equals("login done, Welcome USer....")) {

           //Getting error here

            startActivity(new Intent(MainActivity.this, Insertion.class));

        }else {

        }
            //alertDialog.setMessage(result);
            //alertDialog.show();
            //OkDialog.setMessage(result);

    }

    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
    }
}

Answer 1

您不在MainActivity类中，而是在不是活动的BackgroundWorker类中。要创建一个新的意图，您需要当前活动和您想要打开的活动（在本例中）。

如果不实例化一个类，就不能在另一个类内部使用它。为了做到这一点，您可以将MainActivity静态化（我不建议这样做），您可以将BackgroundWorker类放在MainActivity内部，这样MainActivity将是一个内部类，或者您可以创建MainActivity的实例（我不建议这样做）。

请看这个答案