从登陆模版学习，Google Android Templates

2016-07-20 本文已影响2005人 Clone丶记忆

Google Android Templates

缘由：从eclipse时代到“死丢丢”时代，一直存在一个我未曾深入观察过的东西——Google Android Templates。一次偶然我在android studio上面结识了她，遂望一窥究竟。

How to Creat？标题栏File→New→Activity→Login Activity，接下来在弹出的对话框中一直点击Next直到点击Filish。当然上面所说的都是在你的model里面完成的。如下图：

①

image
现象：
- 1.运行时权限申请
- 2.两个输入框的提示性文字有动画效果（且输入内容后未消失）。焦点转移后能看到明显的色彩变化。
- 3.点击登录按钮后有针对email地址输入框的错误提示文字。
- 4.键盘下面有个独特的@符号，一般情况下的英文输入法是没有单独放在这么明显地方的@符号。
- 5.符合效验标准后，点击登录按钮会有进度圈旋转。

source code

activity_login.xml
<ProgressBar
android:id="@+id/login_progress"
style="?android:attr/progressBarStyleLarge"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:visibility="gone"/>

      <ScrollView
          android:id="@+id/login_form"
          android:layout_width="match_parent"
          android:layout_height="match_parent">
  
          <LinearLayout
              android:id="@+id/email_login_form"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:orientation="vertical">
  
              <android.support.design.widget.TextInputLayout
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content">
  
                  <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:inputType="textEmailAddress" 说明软件盘中会有@符号 -->
              </android.support.design.widget.TextInputLayout>
  
              <android.support.design.widget.TextInputLayout
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content">
  
                  <EditText
                      android:id="@+id/password"
                      android:layout_width="match_parent"
                      android:layout_height="wrap_content"
                      android:hint="@string/prompt_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.support.design.widget.TextInputLayout>
  
              <Button
                  android:id="@+id/email_sign_in_button"
                  style="?android:textAppearanceSmall"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  android:layout_marginTop="16dp"
                  android:text="@string/action_sign_in"
                  android:textStyle="bold"/>
  
          </LinearLayout>
      </ScrollView>

上面代码中包含控件：ProgressBar、ScrollView、LinearLayout、TextInputLayout、EditText、Button。
分析：
- ProgressBar是我们登录后出现的进度条。
- ScrollView可滑动界面，内部只能包含一个控件
- LinearLayout是ScrollView可滑动界面下面的最上层控件，有且仅有一个
- TextInputLayout文本输入布局
- EditText输入框
- Button按钮，点击后执行登陆操作
  - 在上面的控件中，我们不是特别常用的仅仅有TextInputLayout，而且根据界面效果来看，我们大胆猜测TextInputLayout可能产生了EditText的提示文字（hint）发生了变化，故此我们需要查看相关资料和官方API文档，根据文章总结，TextInputLayout是一个显示在EditText上方的浮动标签。跟ScrollView一样，TextInputLayout只接受一个子元素。子元素需要是一个EditText元素。
  - 展示效果：一个单一的EditText 在输入文字的时候会隐藏hint，而被包含在TextInputLayout中的EditText则会让hint变成一个在EditText上方的浮动标签。同时还包括一个漂亮的material动画。
  - 处理错误：TextInputLayout可以处理错误，我们先检查输入的信息是否正常，如果不符合我们的要求我们可以设置错误XXX.setError();
  - 样式：TextInputLayout，所有色彩展示都是在style.xml中设置，具体的请自行搜索。

LoginActivity.java

 /**
   * A login screen that offers login via email/password.
   */
  public class LoginActivity extends AppCompatActivity implements LoaderCallbacks<Cursor> {
  
      /**
       * 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<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<>();
          cursor.moveToFirst();
          while (!cursor.isAfterLast()) {
              emails.add(cursor.getString(ProfileQuery.ADDRESS));
              cursor.moveToNext();
          }
  
          addEmailsToAutoComplete(emails);
      }
  
      @Override
      public void onLoaderReset(Loader<Cursor> cursorLoader) {
  
      }
  
      private void addEmailsToAutoComplete(List<String> emailAddressCollection) {
          //Create adapter to tell the AutoCompleteTextView what to show in its dropdown list.
          ArrayAdapter<String> adapter =
                  new ArrayAdapter<>(LoginActivity.this,
                          android.R.layout.simple_dropdown_item_1line, emailAddressCollection);
  
          mEmailView.setAdapter(adapter);
      }
  
      private interface ProfileQuery {
          String[] PROJECTION = {
                  ContactsContract.CommonDataKinds.Email.ADDRESS,
                  ContactsContract.CommonDataKinds.Email.IS_PRIMARY,
          };
  
          int ADDRESS = 0;
          int IS_PRIMARY = 1;
      }
  
      /**
       * 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);
          }
      }
  }

分析：
- 方法列表：
  - onCreate() ——来自activity，初始化控件，事件绑定。
  - populateAutoComplete() ——调用mayRequestContacts()，成功后调用接口（LoaderCallbacks）下面的方法
  - mayRequestContacts() ——动态获取PERMISSION_GRANTED(通讯录权限)
  - onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) ——顾名思义是返回权限申请的结果
  - attemptLogin() ——登录事件
  - isEmailValid(String email) ——是否是email地址的标准
  - isPasswordValid(String password) ——是否符合密码标准
  - showProgress(final boolean show) ——加载进度条
  - onCreateLoader(int i, Bundle bundle) ——接口LoaderCallbacks
  - onLoadFinished(Loader<Cursor> cursorLoader, Cursor cursor) ——接口LoaderCallbacks
  - onLoaderReset(Loader<Cursor> cursorLoader) ——接口LoaderCallbacks
  - addEmailsToAutoComplete(List<String> emailAddressCollection) ——
- 内部接口：
  - ProfileQuery
    - 接口内常量 String[] PROJECTION、ADDRESS、IS_PRIMARY
- 内部类：
  - UserLoginTask extends AsyncTask<Void, Void, Boolean>
    - 构造函数：UserLoginTask(String email, String password)
    - 方法：
      - doInBackground(Void... params)
      - onPostExecute(final Boolean success)
      - onCancelled()
- 流程梳理：
  - 1.加载XML布局→找到mEmailView控件（email输入框）→申请通讯录权限
    - 申请权限成功→遍历通讯录→获取主要的email→有，加载到界面、无，无操作
    - 申请权限失败→无操作
  - 2.找到其他控件→事件绑定→等待用户执行操作
  - 3.操作界面→执行登录事件
- 上面我们列出了方法列表，并且将我们涉及到主体流程、较新技能等的方法均有加粗标记。
解析：

申请权限：

    private boolean mayRequestContacts() {
      //当系统版本低于android_M时，跳过权限检查
      if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
              return true;
          }
      //当系统版本大于等于android_M时，执行权限申请代码
      if (checkSelfPermission(READ_CONTACTS) == PackageManager.PERMISSION_GRANTED) {
      //当自身已经被允许的权限中包含了READ_CONTACTS时，返回True
              return true;
          }
      //当自身已经被允许权限中没有READ_CONTACTS时，申请通讯录读取权限READ_CONTACTS
      //shouldShowRequestPermissionRationale ==> 是否需要调用系统的权限申请界面
      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) {
                          //展示请求权限界面，第一个参数是权限数组，第二个是请求码
                          requestPermissions(new String[]{READ_CONTACTS}, REQUEST_READ_CONTACTS);
                      }
                  });
          } else {
              requestPermissions(new String[]{READ_CONTACTS}, REQUEST_READ_CONTACTS);
          }
          return false;
      }

申请权限返回的响应

    @Override
        public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
       //请求码 对应上面请求的请求码
       if (requestCode == REQUEST_READ_CONTACTS) {
          if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {    //权限申请成功
              populateAutoComplete(); //读取联系人列表内的email
          }
      }}

登录事件

    private void attemptLogin() {
    if (mAuthTask != null) {    //登录信息提交的异步任务已经实例化，则无需进行操作，第一次执行attemptLogin()时，mAuthTask并未初始化
      return;
      }

     // Reset errors.重设用户名和密码框的错误提示
      mEmailView.setError(null);  //setError方法是TextView下面的方法，主要是提示一个错误信息，内部有系统集成的错误提示图标，原理是在TextView的右边出现一个Drawable
      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; //是否退出执行登陆进程
      View focusView = null;  //焦点View，当某个输入框输入信息不符合标准时，不执行登陆进程，并锁定焦点到那个输入控件

      // 当用户名不为空，判断密码是否符合标准
      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) {
          //在上面的操作中出现错误了，不执行具体的登录，并且把焦点切换到上面去
          // There was an error; don't attempt login and focus the first
          // form field with an error.
          focusView.requestFocus();
      } else {
          //开启滚动条，执行登录的异步任务
          // 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);
      }
    }

登录的异步任务

      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) {  //后台任务，耗时操作此处执行，该处代码执行在子线程
              // TODO: attempt authentication against a network service.

              try {
                  // Simulate network access.
                  Thread.sleep(2000); //模拟耗时操作
              } 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) {   //执行完毕耗时操作调用这里
              mAuthTask = null;
              showProgress(false);

              if (success) {
                  finish();
              } else {
                  mPasswordView.setError(getString(R.string.error_incorrect_password));
                  mPasswordView.requestFocus();
              }
          }

          @Override
          protected void onCancelled() {  //退出异步任务调用这里
              mAuthTask = null;
              showProgress(false);
          }
      }

关于更多AsyncTask资料点击查看

总结：

TextInputLayout，这个控件包含EditText后，会产生提示文字的动画效果，且提示文字不会消失。
纵向布局中，为了保证界面能完整展示，最好在外层套上ScrollView。
一个简单的登录流程，耗时操作不能在主线程执行，AsyncTask异步任务执行完毕后，会回归主线程。
需要数据交互的地方，数据需要做效验。
（重点）android6.0以及以后加入了权限申请，我们这里是动态权限申请，也是最容易被用户接受的。
整个登陆界面的操作流程。