Android example source code file (NumberKeyListener.java)

This example Android source code file (NumberKeyListener.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, basekeylistener, charsequence, editable, inputfilter, keyevent, numberkeylistener, override, spannable, spannablestringbuilder, spanned, text, ui, view

The NumberKeyListener.java Android example source code

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.text.method;

import android.view.KeyEvent;
import android.view.View;
import android.text.Editable;
import android.text.InputFilter;
import android.text.Selection;
import android.text.Spannable;
import android.text.SpannableStringBuilder;
import android.text.Spanned;

/**
 * For numeric text entry
 */
public abstract class NumberKeyListener extends BaseKeyListener
    implements InputFilter
{
    /**
     * You can say which characters you can accept.
     */
    protected abstract char[] getAcceptedChars();

    protected int lookup(KeyEvent event, Spannable content) {
        return event.getMatch(getAcceptedChars(), getMetaState(content));
    }

    public CharSequence filter(CharSequence source, int start, int end,
                               Spanned dest, int dstart, int dend) {
        char[] accept = getAcceptedChars();
        boolean filter = false;

        int i;
        for (i = start; i < end; i++) {
            if (!ok(accept, source.charAt(i))) {
                break;
            }
        }

        if (i == end) {
            // It was all OK.
            return null;
        }

        if (end - start == 1) {
            // It was not OK, and there is only one char, so nothing remains.
            return "";
        }

        SpannableStringBuilder filtered =
            new SpannableStringBuilder(source, start, end);
        i -= start;
        end -= start;

        int len = end - start;
        // Only count down to i because the chars before that were all OK.
        for (int j = end - 1; j >= i; j--) {
            if (!ok(accept, source.charAt(j))) {
                filtered.delete(j, j + 1);
            }
        }

        return filtered;
    }

    protected static boolean ok(char[] accept, char c) {
        for (int i = accept.length - 1; i >= 0; i--) {
            if (accept[i] == c) {
                return true;
            }
        }

        return false;
    }
    
    @Override
    public boolean onKeyDown(View view, Editable content,
                             int keyCode, KeyEvent event) {
        int selStart, selEnd;

        {
            int a = Selection.getSelectionStart(content);
            int b = Selection.getSelectionEnd(content);

            selStart = Math.min(a, b);
            selEnd = Math.max(a, b);
        }

        if (selStart < 0 || selEnd < 0) {
            selStart = selEnd = 0;
            Selection.setSelection(content, 0);
        }

        int i = event != null ? lookup(event, content) : 0;
        int repeatCount = event != null ? event.getRepeatCount() : 0;
        if (repeatCount == 0) {
            if (i != 0) {
                if (selStart != selEnd) {
                    Selection.setSelection(content, selEnd);
                }

                content.replace(selStart, selEnd, String.valueOf((char) i));

                adjustMetaAfterKeypress(content);
                return true;
            }
        } else if (i == '0' && repeatCount == 1) {
            // Pretty hackish, it replaces the 0 with the +

            if (selStart == selEnd && selEnd > 0 &&
                    content.charAt(selStart - 1) == '0') {
                content.replace(selStart - 1, selEnd, String.valueOf('+'));
                adjustMetaAfterKeypress(content);
                return true;
            }
        }

        adjustMetaAfterKeypress(content);
        return super.onKeyDown(view, content, keyCode, event);
    }
}