Re-enable the undo demo activity

The UI now shows these input fields:
* A normal field with buttons for programmatic SetText, append and insert.
* A field with undo disabled.
* A field with a length limit (via InputFilter).
* A field with a credit card input formatter (via TextWatcher)

Bug: 19332904
Change-Id: I41df56c84dd5232918e7ee5e6ed5874b2023cc78

samples/ApiDemos/src/com/example/android/apis/content/TextUndoActivity.java

@@ -16,58 +16,123 @@
 
 package com.example.android.apis.content;
 
-import android.app.Activity;
-//import android.content.UndoManager;
-import android.os.Parcelable;
-import android.view.View;
-import android.widget.Button;
 import com.example.android.apis.R;
 
+import android.app.Activity;
 import android.os.Bundle;
-import android.widget.TextView;
+import android.text.Editable;
+import android.text.InputFilter;
+import android.text.Spanned;
+import android.text.TextWatcher;
+import android.text.method.DigitsKeyListener;
+import android.util.Log;
+import android.view.View;
+import android.widget.Button;
+import android.widget.EditText;
 
 /**
  * Simple example of using an UndoManager for editing text in a TextView.
  */
 public class TextUndoActivity extends Activity {
-    //UndoManager mUndoManager;
+    // Characters allowed as input in the credit card field.
+    private static final String CREDIT_CARD_CHARS = "0123456789 ";
+
+    EditText mDefaultText;
+    EditText mLengthLimitText;
+    EditText mCreditCardText;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
 
-        /*
-        mUndoManager = new UndoManager();
-        if (savedInstanceState != null) {
-            Parcelable p = savedInstanceState.getParcelable("undo");
-            if (p != null) {
-                mUndoManager.restoreInstanceState(p);
-            }
-        }
-        */
-
         setContentView(R.layout.text_undo);
 
-        /*
-        ((TextView)findViewById(R.id.text)).setUndoManager(mUndoManager, "text");
-        ((Button)findViewById(R.id.undo)).setOnClickListener(new View.OnClickListener() {
+        mDefaultText = (EditText) findViewById(R.id.default_text);
+        ((Button) findViewById(R.id.set_text)).setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
-                mUndoManager.undo(null, 1);
+                mDefaultText.setText("some text");
             }
         });
-        ((Button)findViewById(R.id.redo)).setOnClickListener(new View.OnClickListener() {
+        ((Button) findViewById(R.id.append_text)).setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
-                mUndoManager.redo(null, 1);
+                mDefaultText.append(" append");
             }
         });
-        */
+        ((Button) findViewById(R.id.insert_text)).setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                Editable editable = mDefaultText.getText();
+                editable.insert(0, "insert ");
+            }
+        });
+
+        mLengthLimitText = (EditText) findViewById(R.id.length_limit_text);
+        mLengthLimitText.setFilters(new InputFilter[] { new InputFilter.LengthFilter(4) });
+
+        mCreditCardText = (EditText) findViewById(R.id.credit_card_text);
+        mCreditCardText.setKeyListener(DigitsKeyListener.getInstance(CREDIT_CARD_CHARS));
+        mCreditCardText.addTextChangedListener(new CreditCardTextWatcher());
      }
 
-    @Override
-    protected void onSaveInstanceState(Bundle outState) {
-        super.onSaveInstanceState(outState);
-        //outState.putParcelable("undo", mUndoManager.saveInstanceState());
+    /**
+     * A simple credit card input formatter that adds spaces every 4 characters.
+     */
+    private static class CreditCardTextWatcher implements 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) {
+            String original = s.toString();
+            String formatted = addSpaces(getNumbers(original));
+            // This is an ugly way to avoid infinite recursion, but it's common in app code.
+            if (!formatted.equals(original)) {
+                s.replace(0, s.length(), formatted);
+            }
+        }
+
+        /**
+         * @return Returns a string with a space added every 4 characters.
+         */
+        private static String addSpaces(CharSequence str) {
+            StringBuilder builder = new StringBuilder();
+            int len = str.length();
+            for (int i = 0; i < len; i += 4) {
+                if (i + 4 < len) {
+                    builder.append(str.subSequence(i, i + 4));
+                    builder.append(' ');
+                } else {
+                    // Don't put a space after the end.
+                    builder.append(str.subSequence(i, len));
+                }
+            }
+            return builder.toString();
+        }
+
+        /**
+         * @return Returns a string containing only the digits from a character sequence.
+         */
+        private static String getNumbers(CharSequence cc) {
+            StringBuilder sb = new StringBuilder(16);
+            for (int i = 0, count = cc.length(); i < count; ++i) {
+                char c = cc.charAt(i);
+                if (isNumber(c)) {
+                    sb.append(c);
+                }
+            }
+            return sb.toString();
+        }
+
+        private static boolean isNumber(char c) {
+            return c >= '0' && c <= '9';
+        }
+
     }
 }