Question

我是Android开发的新手，在使用AppInventor进行短暂的刺激后，我正在使用Android Studio。

我已经阅读了有关开始活动并获得结果以及检查示例的信息。

在我的MainActivity上，我有一个Login按钮，用于启动LoginActivity。为了举例，我将调用活动（MainActivity）中的“额外”传递给被调用活动（LoginActivity），如下所示，并在返回时（它没有真正登录到任何地方）它设置两个应该传递回MainActivity的额外参数：

我的LoginActivity是New Activity Wizard创建的模板的略微修改版本。基本上我定义了OUTPARAM静态字符串（额外参数的名称）并添加了代码来读取传入参数并设置传出参数：

package com.example.testapp.ui;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.annotation.TargetApi;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.View;
import android.view.inputmethod.EditorInfo;
import android.widget.EditText;
import android.widget.TextView;
import android.view.MenuItem;
import android.support.v4.app.NavUtils;

/**
 * Activity which displays a login screen to the user, offering registration as
 * well.
 */
public class LoginActivity extends Activity {
    // DEGT : Activity parameters passed via intent.putExtra
    static public final String INPARAM_METHOD = "com.example.testapp.ui.loginMethod";
    static public final String OUTPARAM_USERID = "com.example.testapp.ui.userId";
    static public final String OUTPARAM_PASSW = "com.example.testapp.ui.password";

    /**
     * A dummy authentication store containing known user names and passwords.
     * TODO: remove after connecting to a real authentication system.
     */
    private static final String[] DUMMY_CREDENTIALS = new String[]{
            "foo@example.com:hello",
            "bar@example.com:world"
    };

    /**
     * The default email to populate the email field with.
     */
    public static final String EXTRA_EMAIL = "com.example.android.authenticatordemo.extra.EMAIL";

    /**
     * Keep track of the login task to ensure we can cancel it if requested.
     */
    private UserLoginTask mAuthTask = null;

    // Values for email and password at the time of the login attempt.
    private String mEmail;
    private String mPassword;

    // UI references.
    private EditText mEmailView;
    private EditText mPasswordView;
    private View mLoginFormView;
    private View mLoginStatusView;
    private TextView mLoginStatusMessageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_login);
        setupActionBar();

        // Set up the login form.
        mEmail = getIntent().getStringExtra(EXTRA_EMAIL);   // TODO modify
        mEmailView = (EditText) findViewById(R.id.email);
        mEmailView.setText(mEmail);

        mPasswordView = (EditText) findViewById(R.id.password);
        mPasswordView.setOnEditorActionListener(new TextView.OnEditorActionListener() {
            @Override
            public boolean onEditorAction(TextView textView, int id, KeyEvent keyEvent) {
                if (id == R.id.login || id == EditorInfo.IME_NULL) {
                    attemptLogin();
                    return true;
                }
                return false;
            }
        });

        mLoginFormView = findViewById(R.id.login_form);
        mLoginStatusView = findViewById(R.id.login_status);
        mLoginStatusMessageView = (TextView) findViewById(R.id.login_status_message);

        findViewById(R.id.sign_in_button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                attemptLogin();
            }
        });
    }

    /**
     * Set up the {@link android.app.ActionBar}, if the API is available.
     */
    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    private void setupActionBar() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            // Show the Up button in the action bar.
            getActionBar().setDisplayHomeAsUpEnabled(true);
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                // This ID represents the Home or Up button. In the case of this
                // activity, the Up button is shown. Use NavUtils to allow users
                // to navigate up one level in the application structure. For
                // more details, see the Navigation pattern on Android Design:
                //
                // http://developer.android.com/design/patterns/navigation.html#up-vs-back
                //
                // TODO: If Settings has multiple levels, Up should navigate up
                // that hierarchy.
                NavUtils.navigateUpFromSameTask(this);
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);
        getMenuInflater().inflate(R.menu.login, menu);
        return true;
    }

    /**
     * Attempts to sign in or register the account specified by the login form.
     * If there are form errors (invalid email, missing fields, etc.), the
     * errors are presented and no actual login attempt is made.
     */
    public void attemptLogin() {
        if (mAuthTask != null) {
            return;
        }

        // Reset errors.
        mEmailView.setError(null);
        mPasswordView.setError(null);

        // Store values at the time of the login attempt.
        mEmail = mEmailView.getText().toString();
        mPassword = mPasswordView.getText().toString();

        boolean cancel = false;
        View focusView = null;

        // Check for a valid password.
        if (TextUtils.isEmpty(mPassword)) {
            mPasswordView.setError(getString(R.string.error_field_required));
            focusView = mPasswordView;
            cancel = true;
        } else if (mPassword.length() < 4) {
            mPasswordView.setError(getString(R.string.error_invalid_password));
            focusView = mPasswordView;
            cancel = true;
        }

        // Check for a valid email address.
        if (TextUtils.isEmpty(mEmail)) {
            mEmailView.setError(getString(R.string.error_field_required));
            focusView = mEmailView;
            cancel = true;
        } else if (!mEmail.contains("@")) {
            mEmailView.setError(getString(R.string.error_invalid_email));
            focusView = mEmailView;
            cancel = true;
        }

        if (cancel) {
            // There was an error; don't attempt login and focus the first
            // form field with an error.
            focusView.requestFocus();
        } else {
            // Show a progress spinner, and kick off a background task to
            // perform the user login attempt.
            mLoginStatusMessageView.setText(R.string.login_progress_signing_in);
            showProgress(true);
            mAuthTask = new UserLoginTask();
            mAuthTask.execute((Void) null);
        }
    }

    /**
     * Shows the progress UI and hides the login form.
     */
    @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
    private void showProgress(final boolean show) {
        // On Honeycomb MR2 we have the ViewPropertyAnimator APIs, which allow
        // for very easy animations. If available, use these APIs to fade-in
        // the progress spinner.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
            int shortAnimTime = getResources().getInteger(android.R.integer.config_shortAnimTime);

            mLoginStatusView.setVisibility(View.VISIBLE);
            mLoginStatusView.animate()
                    .setDuration(shortAnimTime)
                    .alpha(show ? 1 : 0)
                    .setListener(new AnimatorListenerAdapter() {
                        @Override
                        public void onAnimationEnd(Animator animation) {
                            mLoginStatusView.setVisibility(show ? View.VISIBLE : View.GONE);
                        }
                    });

            mLoginFormView.setVisibility(View.VISIBLE);
            mLoginFormView.animate()
                    .setDuration(shortAnimTime)
                    .alpha(show ? 0 : 1)
                    .setListener(new AnimatorListenerAdapter() {
                        @Override
                        public void onAnimationEnd(Animator animation) {
                            mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
                        }
                    });
        } else {
            // The ViewPropertyAnimator APIs are not available, so simply show
            // and hide the relevant UI components.
            mLoginStatusView.setVisibility(show ? View.VISIBLE : View.GONE);
            mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
        }
    }

    /**
     * Represents an asynchronous login/registration task used to authenticate
     * the user.
     */
    public class UserLoginTask extends AsyncTask<Void, Void, Boolean> {
        @Override
        protected Boolean doInBackground(Void... params) {
            // TODO: attempt authentication against a network service.

            try {
                // Simulate network access.
                Thread.sleep(2000);
                // TODO DEGT
                // 1. Use Server setting to select Login Service URL
                // 2. Download list of exhibition rooms to populate spinner on MainActivity


            } catch (InterruptedException e) {
                return false;
            }

            // get the intent extras (parameters passed to activity)
            android.content.Intent intent = getIntent();
            if (intent.getStringExtra(LoginActivity.INPARAM_METHOD).equalsIgnoreCase("manual"))
            {
                for (String credential : DUMMY_CREDENTIALS) {
                    String[] pieces = credential.split(":");
                    if (pieces[0].equals(mEmail)) {
                        // Account exists, return true if the password matches.
                        return pieces[1].equals(mPassword);
                    }
                }
            }


            // TODO: register the new account here.
            return true;
        }

        @Override
        protected void onPostExecute(final Boolean success) {
            mAuthTask = null;
            showProgress(false);

            // get the intent extras passed to the activity by calling activity
            android.content.Intent intent = getIntent();
            if (success) {
                // TO-TEST pass the credentials back to the calling activity
                intent.putExtra(OUTPARAM_USERID, mEmailView.getText());
                intent.putExtra(OUTPARAM_PASSW, mPasswordView.getText());
                setResult(RESULT_OK, intent);   // otherwise it returns RESULT_CANCELED

                    setIntent(intent);
                finish();
            } else {
                // TO-TEST pass the credentials back to the calling activity
                intent.putExtra(OUTPARAM_USERID, "");
                intent.putExtra(OUTPARAM_PASSW, "");
                    setIntent(intent);

                mPasswordView.setError(getString(R.string.error_incorrect_password));
                mPasswordView.requestFocus();
            }
        }

        @Override
        protected void onCancelled() {
            mAuthTask = null;
            showProgress(false);
        }
    }
}

在UserLoginTask类（在LoginActivity类中定义）中，我检查doInBackground（）方法的输入参数（INPARAM_ *）。调试断点表示我获得了MainActivity设置的正确值。

在onPostExecute（）方法中，我设置了两个OUTPARAM附加组件。在调试期间，我确认这些值实际上是插入到Intent的Bundle中的。但是，当控制权传递回（调用）MainActivity时，所有参数（INPARAM，OUTPARAM）都是来自onActivityResult方法的data参数中传递的Intent的ABENT：

（调用）MainActivity如下：

package com.example.testapp.ui;

import android.os.Bundle;
import android.app.Activity;
import android.provider.ContactsContract;
import android.view.Menu;
import android.widget.Button;   // Button
import android.view.View;       // View
import android.content.Intent;  // Intent
import android.widget.TextView;

public class MainActivity extends Activity {
    static public final int AUTHENTICATE_TICKET = 2;   // Login to server

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

        // Create the Login button onClick to start LoginActivity
        Button button= (Button) findViewById(R.id.buttonLogin);
        button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                //startActivity(new Intent(MainActivity.this, LoginActivity.class));
                Intent intent = new Intent(MainActivity.this, LoginActivity.class);
                intent.putExtra(LoginActivity.INPARAM_METHOD, "manual"); // DEGT dummy for now
                startActivityForResult(intent, AUTHENTICATE_TICKET);

            }
        });
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);

        return true;
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        // Check which request we're responding to
        if (requestCode == AUTHENTICATE_TICKET)
        {   // Successful LoginActivity result.
            if (resultCode == RESULT_OK)
            {
                // Get a reference to the TextView we will update
                final TextView txtMainMessage = (TextView)findViewById(R.id.textViewMainMessage);
                // Update the TextView with a personalized message. TODO Localize

                String userId = data.getExtras().getString(LoginActivity.OUTPARAM_USERID);
                String msg = "Hello " + userId + ". Now select the exhibition room please.";
                txtMainMessage.setText(msg);
            }
        }
    }
}

Answer 1

密钥必须匹配。不要使用静态字符串作为键。当finish()您的活动中的电话onPostExecute()被销毁时。因此静态字段可能是垃圾收集的。因此不会匹配。我不确定是猜测。

在onPostExecute()

中

  Intent intent = getIntent();
  if (success) 
  {
      Toast.makeText(LoginActivity.this, mEmailView.getText(),1000).show();
      intent.putExtra("key",mEmailView.getText().toString());
      // intent.putExtra(OUTPARAM_PASSW, mPasswordView.getText());
      setResult(RESULT_OK, intent);   // otherwise it returns RESULT_CANCELED
      finish();
  }

在onActivityResult

中

   final TextView txtMainMessage = (TextView)findViewById(R.id.textView1);
            // Update the TextView with a personalized message. TODO Localize

            String userId = data.getStringExtra("key");
            if(userId==null)
            {
                txtMainMessage.setText("Null");
            }else
            {
                    String msg = "Hello " + userId + ". Now select the exhibition room please.";
                 txtMainMessage.setText(msg);
            }

模拟器的快照

enter image description here

Answer 2

创建一个新的Intent，通过onActivityResult发送数据，而不是使用getIntent()。

Intent intent = new Intent();
if (success) {
    // TO-TEST pass the credentials back to the calling activity
    intent.putExtra(OUTPARAM_USERID, mEmailView.getText());
    intent.putExtra(OUTPARAM_PASSW, mPasswordView.getText());
    setResult(RESULT_OK, intent);   // otherwise it returns RESULT_CANCELED

    finish();
} else {
    ...
}

Answer 3

您必须在活动中使用onNewIntent来读取传递的参数。

Intent值未传递回启动活动

3 个答案: