登錄 android studio 后如何加載新活動？

Question

基本上，我想在使用數據庫登錄后開始一個新活動。 我怎樣才能做到這一點？

這是我的登錄 class

public class login extends AppCompatActivity {

    EditText username;
    EditText password;
    Button btn_login;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        username = (EditText) findViewById(R.id.username);
        password = (EditText) findViewById(R.id.password);
        btn_login = (Button) findViewById(R.id.btn_login);

        btn_login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String user = username.getText().toString();
                String pass = password.getText().toString();
                String type = "login";
                System.out.println("IN Onclick login");
                BackgroundTask backgroundTask = new BackgroundTask(getApplicationContext());
                backgroundTask.execute(type,user,pass);

                  if(backgroundTask.statusOK.equals("true"))     {
                      Intent loginIntent = new Intent(login.this,loggedIn.class);
                      startActivity(loginIntent);
                  }

            }




        });


    }


}

您可以在上面的代碼中看到，我正在使用此代碼在成功登錄后開始我的新活動，但這並不是開始新活動。 我不知道為什么？

if(backgroundTask.statusOK.equals("true"))     {
                      Intent loginIntent = new Intent(login.this,loggedIn.class);
                      startActivity(loginIntent);
                  }

這是后台任務 class

public class BackgroundTask extends AsyncTask<String, String, String> {


    Context context;
    public String statusOK="false";




    BackgroundTask(Context ctx){
        this.context = ctx;

    }


    @Override
    protected String doInBackground(String... strings) {
          System.out.println("In doin");
        String type = strings[0];
        String loginURL = "http://192.168.10.119/log/login.php";
        String regURL = "http://192.168.10.119/log/log.php";

        if(type.equals("reg")){
            String name = strings[1];
            String pass = strings[2];
            try{
                URL url = new URL(regURL);
                try {
                    HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
                    httpURLConnection.setRequestMethod("POST");
                    httpURLConnection.setDoOutput(true);
                    httpURLConnection.setDoInput(true);
                    OutputStream outputStream = httpURLConnection.getOutputStream();
                    OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream,"UTF-8");
                    BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter);

                    String insert_data = URLEncoder.encode("Username","UTF-8")+"="+URLEncoder.encode(name,"UTF-8")+
                            "&"+URLEncoder.encode("Password","UTF-8")+ "=" +URLEncoder.encode(pass,"UTF-8");

                    bufferedWriter.write(insert_data);
                    bufferedWriter.flush();
                    bufferedWriter.close();

                    InputStream inputStream = httpURLConnection.getInputStream();
                    InputStreamReader inputStreamReader = new InputStreamReader(inputStream,"ISO-8859-1");
                    BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
                    String result="";
                    String line="";
                    StringBuilder stringBuilder = new StringBuilder();

                    while((bufferedReader.readLine())!= null){
                        stringBuilder.append(line).append("\n");
                    }
                    result = stringBuilder.toString();
                    bufferedReader.close();
                    inputStream.close();
                    httpURLConnection.disconnect();
                    return result;




                } catch (IOException e) {
                    e.printStackTrace();
                }
            } catch (MalformedURLException e) {
                e.printStackTrace();
            }
        }
        else if(type.equals("login")){
            System.out.println("In type = login");
            String name1 = strings[1];
            String pass1 = strings[2];
            try{
                URL url = new URL(loginURL);
                try {
                    System.out.println("In type = login try");
                    HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
                    httpURLConnection.setRequestMethod("POST");
                    httpURLConnection.setDoOutput(true);
                    httpURLConnection.setDoInput(true);
                    OutputStream outputStream = httpURLConnection.getOutputStream();
                    OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream,"UTF-8");
                    BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter);

                    String login_data = URLEncoder.encode("Username","UTF-8")+"="+URLEncoder.encode(name1,"UTF-8")+
                            "&"+URLEncoder.encode("Password","UTF-8")+ "=" +URLEncoder.encode(pass1,"UTF-8");

                    bufferedWriter.write(login_data);
                    bufferedWriter.flush();
                    bufferedWriter.close();

                    InputStream inputStream = httpURLConnection.getInputStream();
                    InputStreamReader inputStreamReader = new InputStreamReader(inputStream,"ISO-8859-1");
                    BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
                    String result="";
                    String line="";
                    StringBuilder stringBuilder = new StringBuilder();

                    while((bufferedReader.readLine())!= null){
                        stringBuilder.append(line).append("\n");
                    }
                    result = stringBuilder.toString();
                    bufferedReader.close();
                    inputStream.close();
                    httpURLConnection.disconnect();

                    return result;



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



        return null;

    }


    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected void onPostExecute(String s) {
        statusOk="true";

        Toast.makeText(context, "Successful", Toast.LENGTH_LONG).show();


        //super.onPostExecute(s);
    }



}

我已經檢查了數據庫和我的應用程序之間的連接是否已建立，並且應用程序正在運行且沒有任何錯誤。

您可以在上面的代碼中看到我創建了一個公共變量statusOk並使用"false"對其進行了初始化。 此變量告訴登錄 class用戶已輸入正確的登錄憑據。

您可以看到我已經將statusOk的值更改為"true" onPostExexute方法。

現在的問題是我的新活動在成功登錄后沒有從登錄 class 打開。 請給我一個解決方案，如何在使用正確的登錄憑據登錄后打開新活動。

Answer 1

Asynctask 用於在后台線程中執行任務（不是您調用execute()的主線程）。

因此，在您的代碼中， if語句在您調用execute()之后立即執行，它仍然將變量statusOK存儲為 false。 因此條件為假。

asynctask 的postExecute()方法用於在主線程中執行代碼，

我的建議：從Login class 中刪除if條件，並檢查postExecute()中的if條件，