Android Design: 九种常见Activity及代码解析之"Login Activity"

Login Activity

如果我们是直接new一个“Login Activity”,自动生成的代码如下：
LoginActivity.java

import static android.Manifest.permission.READ_CONTACTS;/** * A login screen that offers login via email/password. */public class LoginActivity extends AppCompatActivity implements LoaderCallbacks {    /**     * Id to identity READ_CONTACTS permission request.     */    private static final int REQUEST_READ_CONTACTS = 0;    /**     * 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"    };    /**     * Keep track of the login task to ensure we can cancel it if requested.     */    private UserLoginTask mAuthTask = null;    // UI references.    private AutoCompleteTextView mEmailView;    private EditText mPasswordView;    private View mProgressView;    private View mLoginFormView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_login);        // Set up the login form.        mEmailView = (AutoCompleteTextView) findViewById(R.id.email);        populateAutoComplete();        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;            }        });        Button mEmailSignInButton = (Button) findViewById(R.id.email_sign_in_button);        mEmailSignInButton.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View view) {                attemptLogin();            }        });        mLoginFormView = findViewById(R.id.login_form);        mProgressView = findViewById(R.id.login_progress);    }    private void populateAutoComplete() {        if (!mayRequestContacts()) {            return;        }        getLoaderManager().initLoader(0, null, this);    }    private boolean mayRequestContacts() {        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {            return true;        }        if (checkSelfPermission(READ_CONTACTS) == PackageManager.PERMISSION_GRANTED) {            return true;        }        if (shouldShowRequestPermissionRationale(READ_CONTACTS)) {            Snackbar.make(mEmailView, R.string.permission_rationale, Snackbar.LENGTH_INDEFINITE)                    .setAction(android.R.string.ok, new View.OnClickListener() {                        @Override                        @TargetApi(Build.VERSION_CODES.M)                        public void onClick(View v) {                            requestPermissions(new String[]{READ_CONTACTS}, REQUEST_READ_CONTACTS);                        }                    });        } else {            requestPermissions(new String[]{READ_CONTACTS}, REQUEST_READ_CONTACTS);        }        return false;    }    /**     * Callback received when a permissions request has been completed.     */    @Override    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,                                           @NonNull int[] grantResults) {        if (requestCode == REQUEST_READ_CONTACTS) {            if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {                populateAutoComplete();            }        }    }    /**     * 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.     */    private void attemptLogin() {        if (mAuthTask != null) {            return;        }        // Reset errors.        mEmailView.setError(null);        mPasswordView.setError(null);        // Store values at the time of the login attempt.        String email = mEmailView.getText().toString();        String password = mPasswordView.getText().toString();        boolean cancel = false;        View focusView = null;        // Check for a valid password, if the user entered one.        if (!TextUtils.isEmpty(password) && !isPasswordValid(password)) {            mPasswordView.setError(getString(R.string.error_invalid_password));            focusView = mPasswordView;            cancel = true;        }        // Check for a valid email address.        if (TextUtils.isEmpty(email)) {            mEmailView.setError(getString(R.string.error_field_required));            focusView = mEmailView;            cancel = true;        } else if (!isEmailValid(email)) {            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.            showProgress(true);            mAuthTask = new UserLoginTask(email, password);            mAuthTask.execute((Void) null);        }    }    private boolean isEmailValid(String email) {        //TODO: Replace this with your own logic        return email.contains("@");    }    private boolean isPasswordValid(String password) {        //TODO: Replace this with your own logic        return password.length() > 4;    }    /**     * 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);            mLoginFormView.setVisibility(show ? View.GONE : 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);                }            });            mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);            mProgressView.animate().setDuration(shortAnimTime).alpha(                    show ? 1 : 0).setListener(new AnimatorListenerAdapter() {                @Override                public void onAnimationEnd(Animator animation) {                    mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);                }            });        } else {            // The ViewPropertyAnimator APIs are not available, so simply show            // and hide the relevant UI components.            mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);            mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);        }    }    @Override    public Loader onCreateLoader(int i, Bundle bundle) {        return new CursorLoader(this,                // Retrieve data rows for the device user's 'profile' contact.                Uri.withAppendedPath(ContactsContract.Profile.CONTENT_URI,                        ContactsContract.Contacts.Data.CONTENT_DIRECTORY), ProfileQuery.PROJECTION,                // Select only email addresses.                ContactsContract.Contacts.Data.MIMETYPE +                        " = ?", new String[]{ContactsContract.CommonDataKinds.Email                .CONTENT_ITEM_TYPE},                // Show primary email addresses first. Note that there won't be                // a primary email address if the user hasn't specified one.                ContactsContract.Contacts.Data.IS_PRIMARY + " DESC");    }    @Override    public void onLoadFinished(Loader cursorLoader, Cursor cursor) {        List emails = new ArrayList<>();        cursor.moveToFirst();        while (!cursor.isAfterLast()) {            emails.add(cursor.getString(ProfileQuery.ADDRESS));            cursor.moveToNext();        }        addEmailsToAutoComplete(emails);    }    @Override    public void onLoaderReset(Loader cursorLoader) {    }    private interface ProfileQuery {        String[] PROJECTION = {                ContactsContract.CommonDataKinds.Email.ADDRESS,                ContactsContract.CommonDataKinds.Email.IS_PRIMARY,        };        int ADDRESS = 0;        int IS_PRIMARY = 1;    }    private void addEmailsToAutoComplete(List emailAddressCollection) {        //Create adapter to tell the AutoCompleteTextView what to show in its dropdown list.        ArrayAdapter adapter =                new ArrayAdapter<>(LoginActivity.this,                        android.R.layout.simple_dropdown_item_1line, emailAddressCollection);        mEmailView.setAdapter(adapter);    }    /**     * Represents an asynchronous login/registration task used to authenticate     * the user.     */    public class UserLoginTask extends AsyncTask {        private final String mEmail;        private final String mPassword;        UserLoginTask(String email, String password) {            mEmail = email;            mPassword = password;        }        @Override        protected Boolean doInBackground(Void... params) {            // TODO: attempt authentication against a network service.            try {                // Simulate network access.                Thread.sleep(2000);            } catch (InterruptedException e) {                return false;            }            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);            if (success) {                finish();            } else {                mPasswordView.setError(getString(R.string.error_incorrect_password));                mPasswordView.requestFocus();            }        }        @Override        protected void onCancelled() {            mAuthTask = null;            showProgress(false);        }    }}
Login Activity

LoginActivity.java

activity_login.xml

更多相关文章

随机推荐
