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Android example source code file (BaseKeyListener.java)

This example Android source code file (BaseKeyListener.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, characters, charsequence, editable, keyevent, keylistener, layout, meta_alt_on, metakeykeylistener, sentences, text, textview, ui, view, widget, words

The BaseKeyListener.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.*;
import android.text.method.TextKeyListener.Capitalize;
import android.widget.TextView;

public abstract class BaseKeyListener
extends MetaKeyKeyListener
implements KeyListener {
    /* package */ static final Object OLD_SEL_START = new NoCopySpan.Concrete();

    /**
     * Performs the action that happens when you press the DEL key in
     * a TextView.  If there is a selection, deletes the selection;
     * otherwise, DEL alone deletes the character before the cursor,
     * if any;
     * ALT+DEL deletes everything on the line the cursor is on.
     *
     * @return true if anything was deleted; false otherwise.   
     */
    public boolean backspace(View view, Editable content, int keyCode,
                             KeyEvent event) {
        int selStart, selEnd;
        boolean result = true;

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

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

        if (selStart != selEnd) {
            content.delete(selStart, selEnd);
        } else if (altBackspace(view, content, keyCode, event)) {
            result = true;
        } else {
            int to = TextUtils.getOffsetBefore(content, selEnd);

            if (to != selEnd) {
                content.delete(Math.min(to, selEnd), Math.max(to, selEnd));
            }
            else {
                result = false;
            }
        }

        if (result)
            adjustMetaAfterKeypress(content);

        return result;
    }

    private boolean altBackspace(View view, Editable content, int keyCode,
                                 KeyEvent event) {
        if (getMetaState(content, META_ALT_ON) != 1) {
            return false;
        }

        if (!(view instanceof TextView)) {
            return false;
        }

        Layout layout = ((TextView) view).getLayout();

        if (layout == null) {
            return false;
        }

        int l = layout.getLineForOffset(Selection.getSelectionStart(content));
        int start = layout.getLineStart(l);
        int end = layout.getLineEnd(l);

        if (end == start) {
            return false;
        }

        content.delete(start, end);
        return true;
    }

    static int makeTextContentType(Capitalize caps, boolean autoText) {
        int contentType = InputType.TYPE_CLASS_TEXT;
        switch (caps) {
            case CHARACTERS:
                contentType |= InputType.TYPE_TEXT_FLAG_CAP_CHARACTERS;
                break;
            case WORDS:
                contentType |= InputType.TYPE_TEXT_FLAG_CAP_WORDS;
                break;
            case SENTENCES:
                contentType |= InputType.TYPE_TEXT_FLAG_CAP_SENTENCES;
                break;
        }
        if (autoText) {
            contentType |= InputType.TYPE_TEXT_FLAG_AUTO_CORRECT;
        }
        return contentType;
    }
    
    public boolean onKeyDown(View view, Editable content,
                             int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_DEL) {
            backspace(view, content, keyCode, event);
            return true;
        }
        
        return super.onKeyDown(view, content, keyCode, event);
    }
    
    /**
     * Base implementation handles ACTION_MULTIPLE KEYCODE_UNKNOWN by inserting
     * the event's text into the content.
     */
    public boolean onKeyOther(View view, Editable content, KeyEvent event) {
        if (event.getAction() != KeyEvent.ACTION_MULTIPLE
                || event.getKeyCode() != KeyEvent.KEYCODE_UNKNOWN) {
            // Not something we are interested in.
            return false;
        }
        
        int selStart, selEnd;

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

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

        CharSequence text = event.getCharacters();
        if (text == null) {
            return false;
        }
        
        content.replace(selStart, selEnd, text);
        return true;
    }
}

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