我在Android Studio上非常新，所以我要求初学者级别的解释：）
我正在创建一个名为SyncZ的应用程序，并且我创建了一个登录屏幕，我需要这样做，以便当我按下“登录”或“注册”时它转到我的activity_main.xml
我首先创建了一个空白活动，然后添加了一个登录活动，然后我将activity_login.xml设为main，以便在启动应用程序时首先登录菜单。
所以我真正的问题是，如何使用按钮activity_login
activity_main切换到email_sign_in_button
以下是我的代码（XML和Java）如果文字太多，我很抱歉，我希望你能解决它：）
的AndroidManifest.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity">
<TextView
android:text="@string/hello_world"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
activity_login.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_horizontal"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.administrator.helloworld.LoginActivity"
>
<!-- Login progress -->
<ProgressBar
android:id="@+id/login_progress"
style="?android:attr/progressBarStyleLarge"
android:layout_width="470dp"
android:layout_height="470dp"
android:layout_marginBottom="8dp"
android:visibility="gone"/>
<LinearLayout
android:id="@+id/email_login_form"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:weightSum="1">
<ImageView
android:layout_width="300dp"
android:layout_height="160dp"
android:id="@+id/imageView"
android:layout_gravity="center_horizontal"
android:background="@drawable/syncz"
android:layout_marginTop="50dp"
android:layout_marginBottom="75dp" />
<TextView
android:layout_width="79dp"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Login:"
android:id="@+id/textView"
android:textStyle="bold" />
<AutoCompleteTextView
android:id="@+id/email"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/prompt_email"
android:inputType="textEmailAddress"
android:maxLines="1"
android:singleLine="true"
android:layout_marginTop="16dp"
android:textStyle="italic"
android:layout_marginBottom="10dp" />
<EditText
android:id="@+id/password"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Password"
android:imeActionId="@+id/login"
android:imeActionLabel="@string/action_sign_in_short"
android:imeOptions="actionUnspecified"
android:inputType="textPassword"
android:maxLines="1"
android:singleLine="true"
android:textStyle="italic" />
<Button
android:id="@+id/email_sign_in_button"
style="?android:textAppearanceSmall"
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_marginTop="15dp"
android:text="@string/action_sign_in"
android:layout_weight="0.11"
android:textSize="25dp"
android:onClick="sendMessage" />/>
</LinearLayout>
</LinearLayout>
activity_main.xml中
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity">
<TextView
android:text="@string/hello_world"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
LoginActivity.java
package com.example.administrator.helloworld;
import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.annotation.TargetApi;
import android.app.Activity;
import android.app.LoaderManager.LoaderCallbacks;
import android.content.ContentResolver;
import android.content.CursorLoader;
import android.content.Intent;
import android.content.Loader;
import android.database.Cursor;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Build.VERSION;
import android.os.Build;
import android.os.Bundle;
import android.provider.ContactsContract;
import android.text.TextUtils;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.inputmethod.EditorInfo;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
/**
* A login screen that offers login via email/password.
*/
public class LoginActivity extends Activity implements LoaderCallbacks<Cursor>{
/**
* 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();
Intent intent= new Intent(LoginActivity.this,MainActivity.class);
startActivity(intent);
}
});
mLoginFormView = findViewById(R.id.login);
mProgressView = findViewById(R.id.login_progress);
}
private void populateAutoComplete() {
if (VERSION.SDK_INT >= 14) {
// Use ContactsContract.Profile (API 14+)
getLoaderManager().initLoader(0, null, this);
} else if (VERSION.SDK_INT >= 9) {
// Use AccountManager (API 8+)
new SetupEmailAutoCompleteTask().execute(null, null);
}
}
/**
* 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.
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)
public 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<Cursor> 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<Cursor> cursorLoader, Cursor cursor) {
List<String> emails = new ArrayList<String>();
cursor.moveToFirst();
while (!cursor.isAfterLast()) {
emails.add(cursor.getString(ProfileQuery.ADDRESS));
cursor.moveToNext();
}
addEmailsToAutoComplete(emails);
}
@Override
public void onLoaderReset(Loader<Cursor> cursorLoader) {
}
private interface ProfileQuery {
String[] PROJECTION = {
ContactsContract.CommonDataKinds.Email.ADDRESS,
ContactsContract.CommonDataKinds.Email.IS_PRIMARY,
};
int ADDRESS = 0;
int IS_PRIMARY = 1;
}
/**
* Use an AsyncTask to fetch the user's email addresses on a background thread, and update
* the email text field with results on the main UI thread.
*/
class SetupEmailAutoCompleteTask extends AsyncTask<Void, Void, List<String>> {
@Override
protected List<String> doInBackground(Void... voids) {
ArrayList<String> emailAddressCollection = new ArrayList<String>();
// Get all emails from the user's contacts and copy them to a list.
ContentResolver cr = getContentResolver();
Cursor emailCur = cr.query(ContactsContract.CommonDataKinds.Email.CONTENT_URI, null,
null, null, null);
while (emailCur.moveToNext()) {
String email = emailCur.getString(emailCur.getColumnIndex(ContactsContract
.CommonDataKinds.Email.DATA));
emailAddressCollection.add(email);
}
emailCur.close();
return emailAddressCollection;
}
@Override
protected void onPostExecute(List<String> emailAddressCollection) {
addEmailsToAutoComplete(emailAddressCollection);
}
}
private void addEmailsToAutoComplete(List<String> emailAddressCollection) {
//Create adapter to tell the AutoCompleteTextView what to show in its dropdown list.
ArrayAdapter<String> adapter =
new ArrayAdapter<String>(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<Void, Void, Boolean> {
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);
}
}
}
MainActivity.java
package com.example.administrator.helloworld;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@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
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
错误第82行：
78 Button mEmailSignInButton = (Button) findViewById(R.id.email_sign_in_button);
79 mEmailSignInButton.setOnClickListener(new OnClickListener() {
80 @Override
81 public void onClick(View view) {
82 attemptLogin();
83 Intent intent= new Intent(LoginActivity.this,MainActivity.class);
84 startActivity(intent);
85 }
86 });
错误第151行：
144 if (cancel) {
145 // There was an error; don't attempt login and focus the first
146 // form field with an error.
147 focusView.requestFocus();
148 } else {
149 // Show a progress spinner, and kick off a background task to
150 // perform the user login attempt.
151 showProgress(true);
152 mAuthTask = new UserLoginTask(email, password);
153 mAuthTask.execute((Void) null);
154 }
错误第177行：
177 mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
178 mLoginFormView.animate().setDuration(shortAnimTime).alpha(
179 show ? 0 : 1).setListener(new AnimatorListenerAdapter() {
180 @Override
181 public void onAnimationEnd(Animator animation) {
182 mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
183 }
184 });
答案 0 :(得分：5)
在您的登录活动中编写此代码：这将从LoginActivity切换到MainActivity
startActivity(new Intent(LoginActivity.this, MainActivity.class));
finish();
答案 1 :(得分：4)
在Android中，您可以使用Intent在“活动”之间切换。您定义一个Intent，在激活时，将您的应用程序的用户带到另一个活动（称为显式Intent）。您可以使用Intents在应用程序的活动之间传递信息（例如对象）。
简而言之，如何使用Intent：
我开始时发现误导的一件事是android的活动生命周期和导航设施之间的联系。例如，当用户按下按钮或是否要保留和重用实例等时，您必须考虑是否要启动活动的新实例。
除了显式Intent的基本导航功能外，您还可以使用所谓的隐式Intent来提供对App独立Android功能的访问，例如写一封电子邮件，......
这里有一个更深入的教程： http://developer.android.com/training/basics/firstapp/starting-activity.html
如果您想了解所有内容，请查看指向Google API Doc for Intents的链接： http://developer.android.com/reference/android/content/Intent.html
希望有所帮助。 马库斯
答案 2 :(得分：2)
在活动之间移动的最佳方式通常是使用Intents（不确定是否已经看过这些）。关于它们的资源很多，例如：http://www.vogella.com/tutorials/AndroidIntent/article.html。这个人有一些非常酷的初学者教程。基本上会发生什么是在你的onClickListener方法中将传递一个意图并启动具有该意图的活动。意图有助于跨活动获取信息，尽管它们可用于各种很酷的内置任务，例如照片选择。我希望这会有所帮助。
答案 3 :(得分：1)
Button mEmailSignInButton = (Button) findViewById(R.id.email_sign_in_button);
mEmailSignInButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
Intent intent= new Intent(LoginActivity.this,MainActivity.class);
startActivity(intent);
}
});
答案 4 :(得分：1)
以下代码启动活动：
Intent intent = new Intent(LoginActivity.this, MainActivity.class);
startaActivity(intent);
但是，如果要将数据传递给MainActivity，可以使用putExtra();
Intent intent = new Intent(LoginActivity.this, MainActivity.class);
intent.putExtra("myData", the data here);
startActivity(intent);