android: Add TextInputLayout child class that displays a helper text below the text field

Also hides the error message if the text is changed.

src/frontends/android/app/src/main/java/org/strongswan/android/ui/widget/TextInputLayoutHelper.java

@@ -0,0 +1,180 @@
+/*
+ * Copyright (C) 2016 Tobias Brunner
+ * HSR Hochschule fuer Technik Rapperswil
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * for more details.
+ */
+
+package org.strongswan.android.ui.widget;
+
+import android.content.Context;
+import android.content.res.TypedArray;
+import android.support.annotation.Nullable;
+import android.support.design.widget.TextInputLayout;
+import android.support.v4.view.ViewCompat;
+import android.support.v4.view.ViewPropertyAnimatorListenerAdapter;
+import android.text.Editable;
+import android.text.TextWatcher;
+import android.util.AttributeSet;
+import android.util.TypedValue;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.EditText;
+import android.widget.LinearLayout;
+import android.widget.TextView;
+
+import org.strongswan.android.R;
+
+/**
+ * Layout that extends {@link android.support.design.widget.TextInputLayout} with a helper text
+ * displayed below the text field when it receives the focus. Also, any error message shown with
+ * {@link #setError(CharSequence)} is hidden when the text field is changed (this mirrors the
+ * behavior of {@link android.widget.EditText}).
+ */
+public class TextInputLayoutHelper extends TextInputLayout
+{
+	private LinearLayout mHelperContainer;
+	private TextView mHelperText;
+
+	public TextInputLayoutHelper(Context context)
+	{
+		this(context, null);
+	}
+
+	public TextInputLayoutHelper(Context context, AttributeSet attrs)
+	{
+		this(context, attrs, 0);
+	}
+
+	public TextInputLayoutHelper(Context context, AttributeSet attrs, int defStyleAttr)
+	{
+		super(context, attrs);
+		TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.TextInputLayoutHelper);
+		String helper = a.getString(R.styleable.TextInputLayoutHelper_helper_text);
+		a.recycle();
+		if (helper != null)
+		{
+			mHelperContainer = new LinearLayout(context);
+			mHelperContainer.setOrientation(LinearLayout.HORIZONTAL);
+			mHelperContainer.setVisibility(View.INVISIBLE);
+			addView(mHelperContainer, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
+
+			mHelperText = new TextView(context);
+			mHelperText.setText(helper);
+			mHelperText.setTextSize(TypedValue.COMPLEX_UNIT_SP, 12);
+			a = context.obtainStyledAttributes(attrs, new int[]{android.R.attr.textColorSecondary});
+			mHelperText.setTextColor(a.getColor(0, mHelperText.getCurrentTextColor()));
+			a.recycle();
+
+			mHelperContainer.addView(mHelperText, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
+		}
+	}
+
+	@Override
+	public void addView(View child, int index, ViewGroup.LayoutParams params)
+	{
+		super.addView(child, index, params);
+		if (child instanceof EditText)
+		{
+			EditText text = (EditText)child;
+			text.addTextChangedListener(new TextWatcher() {
+				@Override
+				public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
+
+				@Override
+				public void onTextChanged(CharSequence s, int start, int before, int count) {}
+
+				@Override
+				public void afterTextChanged(Editable s)
+				{
+					if (getError() != null)
+					{
+						setError(null);
+					}
+				}
+			});
+			if (mHelperContainer != null)
+			{
+				text.setOnFocusChangeListener(new OnFocusChangeListener() {
+					@Override
+					public void onFocusChange(View v, boolean hasFocus)
+					{
+						showHelper(hasFocus);
+					}
+				});
+				ViewCompat.setPaddingRelative(mHelperContainer, ViewCompat.getPaddingStart(text),
+											  0, ViewCompat.getPaddingEnd(text), text.getPaddingBottom());
+			}
+		}
+	}
+
+	@Override
+	public void setError(@Nullable CharSequence error)
+	{
+		super.setError(error);
+		if (mHelperContainer != null)
+		{
+			if (error == null)
+			{	/* this frees up space used by the now invisible error message */
+				setErrorEnabled(false);
+			}
+			else
+			{	/* re-add the helper as the error message should be displayed directly under the textbox */
+				removeView(mHelperContainer);
+				addView(mHelperContainer, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
+			}
+		}
+	}
+
+	/**
+	 * Set the helper text to be displayed below the text field.
+	 *
+	 * @attr ref R.styleable#TextInputLayoutHelper_helper_text
+	 */
+	public void setHelperText(CharSequence text)
+	{
+		mHelperText.setText(text);
+	}
+
+	private void showHelper(boolean show)
+	{
+		if (show == (mHelperContainer.getVisibility() == View.VISIBLE))
+		{
+			return;
+		}
+		if (show)
+		{
+			ViewCompat.animate(mHelperContainer)
+					  .alpha(1f)
+					  .setDuration(200)
+					  .setListener(new ViewPropertyAnimatorListenerAdapter() {
+						  @Override
+						  public void onAnimationStart(View view)
+						  {
+							  view.setVisibility(View.VISIBLE);
+						  }
+					  }).start();
+		}
+		else
+		{
+			ViewCompat.animate(mHelperContainer)
+					  .alpha(0f)
+					  .setDuration(200)
+					  .setListener(new ViewPropertyAnimatorListenerAdapter() {
+						  @Override
+						  public void onAnimationEnd(View view)
+						  {
+							  view.setVisibility(View.INVISIBLE);
+						  }
+					  }).start();
+		}
+	}
+}

src/frontends/android/app/src/main/res/values/attrs.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!--
-    Copyright (C) 2012 Tobias Brunner
+    Copyright (C) 2012-2016 Tobias Brunner
-    Hochschule fuer Technik Rapperswil
+    HSR Hochschule fuer Technik Rapperswil
 
     This program is free software; you can redistribute it and/or modify it
     under the terms of the GNU General Public License as published by the
@@ -17,4 +17,7 @@
     <declare-styleable name="Fragment">
         <attr name="read_only" format="boolean" />
     </declare-styleable>
+    <declare-styleable name="TextInputLayoutHelper">
+        <attr name="helper_text" format="string" />
+    </declare-styleable>
 </resources>