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Android example source code file (ScrollingMovementMethod.java)

This example Android source code file (ScrollingMovementMethod.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, keyevent, layout, motionevent, scrollingmovementmethod, spannable, text, ui, util, utilities, view

The ScrollingMovementMethod.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.util.Log;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.text.*;
import android.widget.TextView;
import android.view.View;

public class
ScrollingMovementMethod
implements MovementMethod
{
    /**
     * Scrolls the text to the left if possible.
     */
    protected boolean left(TextView widget, Spannable buffer) {
        Layout layout = widget.getLayout();
        
        int scrolly = widget.getScrollY();
        int scr = widget.getScrollX();
        int em = Math.round(layout.getPaint().getFontSpacing());

        int padding = widget.getTotalPaddingTop() +
                      widget.getTotalPaddingBottom();
        int top = layout.getLineForVertical(scrolly);
        int bottom = layout.getLineForVertical(scrolly + widget.getHeight() -
                                               padding);
        int left = Integer.MAX_VALUE;

        for (int i = top; i <= bottom; i++) {
            left = (int) Math.min(left, layout.getLineLeft(i));
        }

        if (scr > left) {
            int s = Math.max(scr - em, left);
            widget.scrollTo(s, widget.getScrollY());
            return true;
        }

        return false;
    }

    /**
     * Scrolls the text to the right if possible.
     */
    protected boolean right(TextView widget, Spannable buffer) {
        Layout layout = widget.getLayout();

        int scrolly = widget.getScrollY();
        int scr = widget.getScrollX();
        int em = Math.round(layout.getPaint().getFontSpacing());

        int padding = widget.getTotalPaddingTop() +
                      widget.getTotalPaddingBottom();
        int top = layout.getLineForVertical(scrolly);
        int bottom = layout.getLineForVertical(scrolly + widget.getHeight() -
                                               padding);
        int right = 0;

        for (int i = top; i <= bottom; i++) {
            right = (int) Math.max(right, layout.getLineRight(i));
        }

        padding = widget.getTotalPaddingLeft() + widget.getTotalPaddingRight();
        if (scr < right - (widget.getWidth() - padding)) {
            int s = Math.min(scr + em, right - (widget.getWidth() - padding));
            widget.scrollTo(s, widget.getScrollY());
            return true;
        }

        return false;
    }

    /**
     * Scrolls the text up if possible.
     */
    protected boolean up(TextView widget, Spannable buffer) {
        Layout layout = widget.getLayout();

        int areatop = widget.getScrollY();
        int line = layout.getLineForVertical(areatop);
        int linetop = layout.getLineTop(line);

        // If the top line is partially visible, bring it all the way
        // into view; otherwise, bring the previous line into view.
        if (areatop == linetop)
            line--;

        if (line >= 0) {
            Touch.scrollTo(widget, layout,
                           widget.getScrollX(), layout.getLineTop(line));
            return true;
        }

        return false;
    }

    /**
     * Scrolls the text down if possible.
     */
    protected boolean down(TextView widget, Spannable buffer) {
        Layout layout = widget.getLayout();

        int padding = widget.getTotalPaddingTop() +
                      widget.getTotalPaddingBottom();

        int areabot = widget.getScrollY() + widget.getHeight() - padding;
        int line = layout.getLineForVertical(areabot);

        if (layout.getLineTop(line+1) < areabot + 1) {
            // Less than a pixel of this line is out of view,
            // so we must have tried to make it entirely in view
            // and now want the next line to be in view instead.

            line++;
        }

        if (line <= layout.getLineCount() - 1) {
            widget.scrollTo(widget.getScrollX(), layout.getLineTop(line+1) -
                            (widget.getHeight() - padding));
            Touch.scrollTo(widget, layout,
                                widget.getScrollX(), widget.getScrollY());
            return true;
        }

        return false;
    }

    public boolean onKeyDown(TextView widget, Spannable buffer, int keyCode, KeyEvent event) {
        return executeDown(widget, buffer, keyCode);
    }

    private boolean executeDown(TextView widget, Spannable buffer, int keyCode) {
        boolean handled = false;

        switch (keyCode) {
        case KeyEvent.KEYCODE_DPAD_LEFT:
            handled |= left(widget, buffer);
            break;

        case KeyEvent.KEYCODE_DPAD_RIGHT:
            handled |= right(widget, buffer);
            break;

        case KeyEvent.KEYCODE_DPAD_UP:
            handled |= up(widget, buffer);
            break;

        case KeyEvent.KEYCODE_DPAD_DOWN:
            handled |= down(widget, buffer);
            break;
        }

        return handled;
    }

    public boolean onKeyUp(TextView widget, Spannable buffer, int keyCode, KeyEvent event) {
        return false;
    }

    public boolean onKeyOther(TextView view, Spannable text, KeyEvent event) {
        int code = event.getKeyCode();
        if (code != KeyEvent.KEYCODE_UNKNOWN
                && event.getAction() == KeyEvent.ACTION_MULTIPLE) {
            int repeat = event.getRepeatCount();
            boolean first = true;
            boolean handled = false;
            while ((--repeat) > 0) {
                if (first && executeDown(view, text, code)) {
                    handled = true;
                    MetaKeyKeyListener.adjustMetaAfterKeypress(text);
                    MetaKeyKeyListener.resetLockedMeta(text);
                }
                first = false;
            }
            return handled;
        }
        return false;
    }
    
    public boolean onTrackballEvent(TextView widget, Spannable text,
            MotionEvent event) {
        return false;
    }
    
    public boolean onTouchEvent(TextView widget, Spannable buffer,
                                 MotionEvent event) {
        return Touch.onTouchEvent(widget, buffer, event);
    }

    public void initialize(TextView widget, Spannable text) { }

    public boolean canSelectArbitrarily() {
        return false;
    }

    public void onTakeFocus(TextView widget, Spannable text, int dir) {
        Layout layout = widget.getLayout();

        if (layout != null && (dir & View.FOCUS_FORWARD) != 0) {
            widget.scrollTo(widget.getScrollX(),
                            layout.getLineTop(0));
        }
        if (layout != null && (dir & View.FOCUS_BACKWARD) != 0) {
            int padding = widget.getTotalPaddingTop() +
                          widget.getTotalPaddingBottom();
            int line = layout.getLineCount() - 1;

            widget.scrollTo(widget.getScrollX(),
                            layout.getLineTop(line+1) -
                            (widget.getHeight() - padding));
        }
    }

    public static MovementMethod getInstance() {
        if (sInstance == null)
            sInstance = new ScrollingMovementMethod();

        return sInstance;
    }

    private static ScrollingMovementMethod sInstance;
}

Other Android examples (source code examples)

Here is a short list of links related to this Android ScrollingMovementMethod.java source code file:

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