Java 在Android中将EditText输入从一个类传递到另一个类

我看到了更多类似的问题，但没有设法理解它们，或者它们不适用于我的问题，所以这里开始

我有一个活动，允许您登录，另一个活动允许您使用登录凭据发送帖子和获取请求，等等

主要活动：

public class MainActivity extends Activity
{

    private String username;
    private String password;

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

        final EditText usernameField = (EditText) findViewById(R.id.enterUsername);

        final EditText passwordField = (EditText) findViewById(R.id.enterPassword);

        Button startButton = (Button) findViewById(R.id.startButton);
        startButton.setOnClickListener(new View.OnClickListener()
        {
            public void onClick(View view)
            {
                username = usernameField.getText().toString();
                password = passwordField.getText().toString();
                Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
                startActivityForResult(myIntent, 0);
            }
        });
    }

    public String getUser() { return this.username; }
    public String getPassword() { return this.password; }
}

Intent myIntent = new Intent(this, HttpGetPost.class);
myIntent.putExtra("username", username);
myIntent.putExtra("password", password);
startActivity(myIntent);

HttpGetPost：

public class HttpGetPost extends Activity
{

    private MainActivity mainProxy = new MainActivity();
    private Button postButton;
    private Button getButton;
    private Button getMeasureButton;
    private Button getDevicesButton;
    private String access_token;
    private String refresh_token;
    private String device_list;
    private String expires_in;
    private String getRequest;
    private static final String TAG = "MyActivity";
    private static final String USER_AGENT = "Mozilla/5.0";
    private String clientID = some_id;
    private String clientSecret = some_secret;
    private String user = mainProxy.getUser();
    private String pass = mainProxy.getPassword();

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

        Log.v(TAG, "mainProxy.username: "+user);
        Log.v(TAG, "mainProxy.password: "+pass);

        postButton = (Button) findViewById(R.id.postButton);
        postButton.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View view)
            {
                new sendPost().execute("");
            }
        });
    }

    private class sendPost extends AsyncTask<String, Void, String>
    {
        @Override
        protected String doInBackground(String... params)
        {
            try
            {
                String url = some_url;
                URL obj = new URL(url);
                HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();

                //add request header
                con.setRequestMethod("POST");
                con.setRequestProperty("User-Agent", USER_AGENT);
                con.setRequestProperty("Accept-Language", "en-US,en;q=0.5");

                String urlParameters = "grant_type=password&client_id=" +clientID +"&client_secret="
                    +clientSecret +"&username=" +user +"&password=" +pass;

                // Send post request
                con.setDoOutput(true);
                DataOutputStream wr = new DataOutputStream(con.getOutputStream());
                wr.writeBytes(urlParameters);
                wr.flush();
                wr.close();

                int responseCode = con.getResponseCode();
                Log.v(TAG, "\nSending 'POST' request to URL : " + url);
                Log.v(TAG, "Post parameters : " + urlParameters);
                Log.v(TAG, "Response Code : " + responseCode);

                BufferedReader in = new BufferedReader(
                        new InputStreamReader(con.getInputStream()));
                String inputLine;
                StringBuffer response = new StringBuffer();

                while ((inputLine = in.readLine()) != null) {
                    response.append(inputLine);
                }
                in.close();

                //print result
                Log.v(TAG, response.toString());

                if (responseCode == 200)
                {
                    access_token = response.substring(17, 74);
                    refresh_token = response.substring(93,150);
                    expires_in = response.substring(165, 170);
                    getRequest = "http://api.netatmo.net/api/getuser?access_token=" +access_token + " HTTP/1.1";

                    Log.v(TAG, "access token: " +access_token);
                    Log.v(TAG, "refresh token: " +refresh_token);
                    Log.v(TAG, "expires in: " +expires_in);
                }

            }
            catch(Exception e){
                e.printStackTrace();
            }

            return "";
        }
        protected void onPostExecute(String result) {
            Toast.makeText(getApplicationContext(), "ENDED", Toast.LENGTH_LONG).show();
        }
    }

}

---

当我在第二个类中打印用户名和密码时，它们都返回null，POST请求失败。

您应该使用以下putExtra方法将用户名和密码传递给您的活动：

Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
myIntent.putExtra("username", username);
myIntent.putExtra("password", pasword);
startActivityForResult(myIntent, 0);

在第二个活动中，例如在onCreate after setContentView中，可以使用getXXExtras检索它们：

Intent intent = getIntent();

String username = intent.getStringExtra("username");
String password = intent.getStringExtra("password");

---

您应该使用以下方法将用户名和密码传递给您的活动：

Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
myIntent.putExtra("username", username);
myIntent.putExtra("password", pasword);
startActivityForResult(myIntent, 0);

在第二个活动中，例如在onCreate after setContentView中，可以使用getXXExtras检索它们：

Intent intent = getIntent();

String username = intent.getStringExtra("username");
String password = intent.getStringExtra("password");

尝试使用附加功能：

Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
myIntent.putExtra("username", username);
myIntent.putExtra("password", password);
startActivityForResult(myIntent, 0);

在另一个ActvityYourHttpGetPost中

String user = getIntent().getStringExtra("username");
String password = getIntent().getStringExtra("password");

尝试使用附加功能：

Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
myIntent.putExtra("username", username);
myIntent.putExtra("password", password);
startActivityForResult(myIntent, 0);

在另一个ActvityYourHttpGetPost中

String user = getIntent().getStringExtra("username");
String password = getIntent().getStringExtra("password");

下面是一个关于正确使用意图的好例子

尝试调用HttpGetPost活动：

Intent myIntent = new Intent(this, HttpGetPost.class);
myIntent.putExtra("username", username);
myIntent.putExtra("password", password);
startActivity(myIntent);

这样，您就可以在Intent构造函数中传递正确的上下文。将数据放入要发送到活动的目的中。下一点是不要调用startActivityForResult，它用于调用活动、进行一些计算并将结果发送回请求活动

现在，在onCreate中像这样从HttpGetPost活动的意图中获取数据，并将其保存到字段：

getIntent().getExtras().getString("username");
getIntent().getExtras().getString("password");

下面是一个关于正确使用意图的好例子

尝试调用HttpGetPost活动：

Intent myIntent = new Intent(this, HttpGetPost.class);
myIntent.putExtra("username", username);
myIntent.putExtra("password", password);
startActivity(myIntent);

这样，您就可以在Intent构造函数中传递正确的上下文。将数据放入要发送到活动的目的中。下一点是不要调用startActivityForResult，它用于调用活动、进行一些计算并将结果发送回请求活动

现在，在onCreate中像这样从HttpGetPost活动的意图中获取数据，并将其保存到字段：

getIntent().getExtras().getString("username");
getIntent().getExtras().getString("password");

你不需要

private MainActivity mainProxy = new MainActivity();

在HttpGetPost中。它将创建一个新的MainActivity，它不是启动HttpGetPost的原始MainActivity

您可以使用extras跨意图发送数据。以下是我的解决方案：

把这个放在主活动中

Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
myIntent.putExtra(HttpGetPost.KEY_USERNAME, username);
myIntent.putExtra(HttpGetPost.KEY_PASSWORD, password);
startActivityForResult(myIntent, 0);

这是针对HttpGetPost的，可以使用KEY_用户名和KEY_密码来存储额外的密钥，这样可以避免输入错误

public static final String KEY_USERNAME = "username"; // or whatever you like for key
public static final String KEY_PASSWORD = "password"; // or whatever you like for key

private String user; // instead of private String user = mainProxy.getUser();
private String pass; // instead of private String pass = mainProxy.getPassword();

将其放在HttpGetPost的onCreate中，以从intent获取数据

Intent intent = getIntent();

user = intent.getStringExtra(KEY_USERNAME);
pass = intent.getStringExtra(KEY_PASSWORD);

是正式的意向文件。

您不需要

private MainActivity mainProxy = new MainActivity();

在HttpGetPost中。它将创建一个新的MainActivity，它不是启动HttpGetPost的原始MainActivity

您可以使用extras跨意图发送数据。以下是我的解决方案：

把这个放在主活动中

Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
myIntent.putExtra(HttpGetPost.KEY_USERNAME, username);
myIntent.putExtra(HttpGetPost.KEY_PASSWORD, password);
startActivityForResult(myIntent, 0);

这是针对HttpGetPost的，可以使用KEY_用户名和KEY_密码来存储额外的密钥，这样可以避免输入错误

public static final String KEY_USERNAME = "username"; // or whatever you like for key
public static final String KEY_PASSWORD = "password"; // or whatever you like for key

private String user; // instead of private String user = mainProxy.getUser();
private String pass; // instead of private String pass = mainProxy.getPassword();

将其放在HttpGetPost的onCreate中，以从intent获取数据

Intent intent = getIntent();

user = intent.getStringExtra(KEY_USERNAME);
pass = intent.getStringExtra(KEY_PASSWORD);

---

是意图的官方文件。

为了澄清我在jbihan回答的评论中的意思：

我正在更新您的代码：

第一次修订：

Button startButton = (Button) findViewById(R.id.startButton);
startButton.setOnClickListener(new View.OnClickListener()
{
    public void onClick(View view)
    {
        username = usernameField.getText().toString();
        password = passwordField.getText().toString();
        Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
        // ADDITION
        myIntent.putExtra("username", username);
        myIntent.putExtra("password", password);
        // END ADDITION
        startActivityForResult(myIntent, 0);
    }
});

 postButton = (Button) findViewById(R.id.postButton);
 // ADDITION
 final String user = getIntent().getStringExtra("username");
 final String password = getIntent().getStringExtra("password");
 // END ADDITION
 postButton.setOnClickListener(new View.OnClickListener()
 {
     @Override
     public void onClick(View view)
     {
         // EDITED
         new sendPost().execute(user, password);
     }
 });

private class sendPost extends AsyncTask<String, Void, String>
{
    @Override
    protected String doInBackground(String... params)
    {
         // ADDITION
         String user = params[0];
         String password = params[1];
         // END ADDITION             

         // use them in the request
         // rest of code...

    }
}

第二次修订：

Button startButton = (Button) findViewById(R.id.startButton);
startButton.setOnClickListener(new View.OnClickListener()
{
    public void onClick(View view)
    {
        username = usernameField.getText().toString();
        password = passwordField.getText().toString();
        Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
        // ADDITION
        myIntent.putExtra("username", username);
        myIntent.putExtra("password", password);
        // END ADDITION
        startActivityForResult(myIntent, 0);
    }
});

 postButton = (Button) findViewById(R.id.postButton);
 // ADDITION
 final String user = getIntent().getStringExtra("username");
 final String password = getIntent().getStringExtra("password");
 // END ADDITION
 postButton.setOnClickListener(new View.OnClickListener()
 {
     @Override
     public void onClick(View view)
     {
         // EDITED
         new sendPost().execute(user, password);
     }
 });

private class sendPost extends AsyncTask<String, Void, String>
{
    @Override
    protected String doInBackground(String... params)
    {
         // ADDITION
         String user = params[0];
         String password = params[1];
         // END ADDITION             

         // use them in the request
         // rest of code...

    }
}

第三次修订：

Button startButton = (Button) findViewById(R.id.startButton);
startButton.setOnClickListener(new View.OnClickListener()
{
    public void onClick(View view)
    {
        username = usernameField.getText().toString();
        password = passwordField.getText().toString();
        Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
        // ADDITION
        myIntent.putExtra("username", username);
        myIntent.putExtra("password", password);
        // END ADDITION
        startActivityForResult(myIntent, 0);
    }
});

 postButton = (Button) findViewById(R.id.postButton);
 // ADDITION
 final String user = getIntent().getStringExtra("username");
 final String password = getIntent().getStringExtra("password");
 // END ADDITION
 postButton.setOnClickListener(new View.OnClickListener()
 {
     @Override
     public void onClick(View view)
     {
         // EDITED
         new sendPost().execute(user, password);
     }
 });

private class sendPost extends AsyncTask<String, Void, String>
{
    @Override
    protected String doInBackground(String... params)
    {
         // ADDITION
         String user = params[0];
         String password = params[1];
         // END ADDITION             

         // use them in the request
         // rest of code...

    }
}

---

请考虑使用用户名和密码键的常量。

< P>以澄清JBIHAN的回答中的意思：

我正在更新您的代码：

第一次修订：

Button startButton = (Button) findViewById(R.id.startButton);
startButton.setOnClickListener(new View.OnClickListener()
{
    public void onClick(View view)
    {
        username = usernameField.getText().toString();
        password = passwordField.getText().toString();
        Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
        // ADDITION
        myIntent.putExtra("username", username);
        myIntent.putExtra("password", password);
        // END ADDITION
        startActivityForResult(myIntent, 0);
    }
});

 postButton = (Button) findViewById(R.id.postButton);
 // ADDITION
 final String user = getIntent().getStringExtra("username");
 final String password = getIntent().getStringExtra("password");
 // END ADDITION
 postButton.setOnClickListener(new View.OnClickListener()
 {
     @Override
     public void onClick(View view)
     {
         // EDITED
         new sendPost().execute(user, password);
     }
 });

private class sendPost extends AsyncTask<String, Void, String>
{
    @Override
    protected String doInBackground(String... params)
    {
         // ADDITION
         String user = params[0];
         String password = params[1];
         // END ADDITION             

         // use them in the request
         // rest of code...

    }
}

第二次修订：

Button startButton = (Button) findViewById(R.id.startButton);
startButton.setOnClickListener(new View.OnClickListener()
{
    public void onClick(View view)
    {
        username = usernameField.getText().toString();
        password = passwordField.getText().toString();
        Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
        // ADDITION
        myIntent.putExtra("username", username);
        myIntent.putExtra("password", password);
        // END ADDITION
        startActivityForResult(myIntent, 0);
    }
});

 postButton = (Button) findViewById(R.id.postButton);
 // ADDITION
 final String user = getIntent().getStringExtra("username");
 final String password = getIntent().getStringExtra("password");
 // END ADDITION
 postButton.setOnClickListener(new View.OnClickListener()
 {
     @Override
     public void onClick(View view)
     {
         // EDITED
         new sendPost().execute(user, password);
     }
 });

private class sendPost extends AsyncTask<String, Void, String>
{
    @Override
    protected String doInBackground(String... params)
    {
         // ADDITION
         String user = params[0];
         String password = params[1];
         // END ADDITION             

         // use them in the request
         // rest of code...

    }
}

第三次修订：

Button startButton = (Button) findViewById(R.id.startButton);
startButton.setOnClickListener(new View.OnClickListener()
{
    public void onClick(View view)
    {
        username = usernameField.getText().toString();
        password = passwordField.getText().toString();
        Intent myIntent = new Intent(view.getContext(), HttpGetPost.class);
        // ADDITION
        myIntent.putExtra("username", username);
        myIntent.putExtra("password", password);
        // END ADDITION
        startActivityForResult(myIntent, 0);
    }
});

 postButton = (Button) findViewById(R.id.postButton);
 // ADDITION
 final String user = getIntent().getStringExtra("username");
 final String password = getIntent().getStringExtra("password");
 // END ADDITION
 postButton.setOnClickListener(new View.OnClickListener()
 {
     @Override
     public void onClick(View view)
     {
         // EDITED
         new sendPost().execute(user, password);
     }
 });

private class sendPost extends AsyncTask<String, Void, String>
{
    @Override
    protected String doInBackground(String... params)
    {
         // ADDITION
         String user = params[0];
         String password = params[1];
         // END ADDITION             

         // use them in the request
         // rest of code...

    }
}

---

请考虑使用用户名和密码键的常量。

可以尝试将用户名和密码放入数组中。然后，当您开始HttpGetPost活动时，您可以将该数组作为额外的数组放置在intent中。这就是一个例子。您也可以查看文档。您可以尝试将用户名和密码放入数组中。然后，当您开始HttpGetPost活动时，您可以将该数组作为额外的数组放置在intent中。这就是一个例子。您还可以查看文档。HttpGetPost类中的doInBackground无法看到用户名和密码这两个字符串，因为它们在onCreate方法中。回答得好，不过最好使用在两个类中都可见的静态常量作为getXXXExtra方法的键，而不是字符串文本。此外，在分配变量之前，您还可以使用hasExtra方法检查这些值是否确实存在于intent中，以防止出现潜在的空指针异常。@OddCore只需在onCreate方法中获取这些值，并将它们作为参数发送到AsyncTask：new sendPost.executeuser，pass@ItaiHanski我从sendPost类的doInBackground中访问用户并传递变量，因此它不允许我执行新的sendPost.executeuser，pass@OddCore我创建了一个答案来详细说明我的意思，看一看。HttpGetPost类中的doInBackground看不到用户名和密码这两个字符串，因为它们在onCreate方法中。答案很好，但更好

---

actice使用在两个类中都可见的静态常量作为getXXXExtra方法的键，而不是字符串文本。此外，在分配变量之前，您还可以使用hasExtra方法检查这些值是否确实存在于intent中，以防止出现潜在的空指针异常。@OddCore只需在onCreate方法中获取这些值，并将它们作为参数发送到AsyncTask：new sendPost.executeuser，pass@ItaiHanski我从sendPost类的doInBackground中访问用户并传递变量，因此它不允许我执行新的sendPost.executeuser，pass@OddCore我创建了一个答案来阐述我的意思，看一看。谢谢你的回答，你帮助我理解了问题：谢谢你的回答，你帮助我理解了问题：谢谢你的回答，你帮助我理解了问题：谢谢你的回答，你帮助我理解了问题：