Android登录验证 - 图片

Question

任何建议或意见我如何让我的应用程序在图像中具有像这样的验证？

Answer 1

首先，我认为你的全球布局已经是一个RelativeLayout，这样你就可以把你的EditExt下方的图像，并河旁到他的右手边。

那么你一定要在你的EditText实施onTextChangedListener，象下面这样：

yourEditText.addTextChangedListener(new TextWatcher() { 
      @Override 
      public void onTextChanged(CharSequence s, int start, int before, int count) { 
       //test here if s.equal(""); and set your image's visibility 
      } 

      @Override 
      public void beforeTextChanged(CharSequence s, int start, int count, int after) { 
      } 

      @Override 
      public void afterTextChanged(Editable s) { 
      } 
     }); 

如果你的文本是空的，只是设置图像的可见性消失了，否则可见。

Answer 2

要使用Android对象模板：

右键单击要添加代码组件的Android应用程序的项目文件夹。 选择新建>其他... 选择Android> Android对象，然后单击下一步。然后选择登录活动。

要显示错误，这样做： -

userName.setError("This field is required"); 

参考下面这个例子： -

package com.example.login; 

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; 

/** 
* Activity which displays a login screen to the user, offering registration as 
* well. 
*/ 
public class LoginActivity extends Activity { 
    /** 
    * 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); 

     // Set up the login form. 
     mEmail = getIntent().getStringExtra(EXTRA_EMAIL); 
     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(); 
        } 
       }); 
    } 

    @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); 
      } 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); 
     } 
    } 
} 


    <merge xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    tools:context=".LoginActivity" > 

    <!-- Login progress --> 

    <LinearLayout 
     android:id="@+id/login_status" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_gravity="center" 
     android:gravity="center_horizontal" 
     android:orientation="vertical" 
     android:visibility="gone" > 

     <ProgressBar 
      style="?android:attr/progressBarStyleLarge" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_marginBottom="8dp" /> 

     <TextView 
      android:id="@+id/login_status_message" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_marginBottom="16dp" 
      android:fontFamily="sans-serif-light" 
      android:text="@string/login_progress_signing_in" 
      android:textAppearance="?android:attr/textAppearanceMedium" /> 
    </LinearLayout> 

    <!-- Login form --> 

    <ScrollView 
     android:id="@+id/login_form" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" > 

     <LinearLayout 
      style="@style/LoginFormContainer" 
      android:orientation="vertical" > 

      <EditText 
       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" /> 

      <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" /> 

      <Button 
       android:id="@+id/sign_in_button" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:layout_gravity="right" 
       android:layout_marginTop="16dp" 
       android:paddingLeft="32dp" 
       android:paddingRight="32dp" 
       android:text="@string/action_sign_in_register" /> 
     </LinearLayout> 
    </ScrollView> 

</merge>