Touch.java revision b2beb92073cea6e472748e729ac8e265ca83a925 
1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.text.method;
18
19import android.text.Layout;
20import android.text.Layout.Alignment;
21import android.text.NoCopySpan;
22import android.text.Spannable;
23import android.view.KeyEvent;
24import android.view.MotionEvent;
25import android.view.ViewConfiguration;
26import android.widget.TextView;
27
28public class Touch {
29    private Touch() { }
30
31    /**
32     * Scrolls the specified widget to the specified coordinates, except
33     * constrains the X scrolling position to the horizontal regions of
34     * the text that will be visible after scrolling to the specified
35     * Y position.
36     */
37    public static void scrollTo(TextView widget, Layout layout, int x, int y) {
38        final int verticalPadding = widget.getTotalPaddingTop() + widget.getTotalPaddingBottom();
39        final int top = layout.getLineForVertical(y);
40        final int bottom = layout.getLineForVertical(y + widget.getHeight() - verticalPadding);
41
42        int left = Integer.MAX_VALUE;
43        int right = 0;
44        Alignment a = layout.getParagraphAlignment(top);
45        boolean ltr = layout.getParagraphDirection(top) > 0;
46
47        for (int i = top; i <= bottom; i++) {
48            left = (int) Math.min(left, layout.getLineLeft(i));
49            right = (int) Math.max(right, layout.getLineRight(i));
50        }
51
52        final int hoizontalPadding = widget.getTotalPaddingLeft() + widget.getTotalPaddingRight();
53        final int availableWidth = widget.getWidth() - hoizontalPadding;
54        final int actualWidth = right - left;
55
56        if (actualWidth < availableWidth) {
57            if (a == Alignment.ALIGN_CENTER) {
58                x = left - ((availableWidth - actualWidth) / 2);
59            } else if ((ltr && (a == Alignment.ALIGN_OPPOSITE)) || (a == Alignment.ALIGN_RIGHT)) {
60                // align_opposite does NOT mean align_right, we need the paragraph
61                // direction to resolve it to left or right
62                x = left - (availableWidth - actualWidth);
63            } else {
64                x = left;
65            }
66        } else {
67            x = Math.min(x, right - availableWidth);
68            x = Math.max(x, left);
69        }
70
71        widget.scrollTo(x, y);
72    }
73
74    /**
75     * Handles touch events for dragging.  You may want to do other actions
76     * like moving the cursor on touch as well.
77     */
78    public static boolean onTouchEvent(TextView widget, Spannable buffer,
79                                       MotionEvent event) {
80        DragState[] ds;
81
82        switch (event.getActionMasked()) {
83        case MotionEvent.ACTION_DOWN:
84            ds = buffer.getSpans(0, buffer.length(), DragState.class);
85
86            for (int i = 0; i < ds.length; i++) {
87                buffer.removeSpan(ds[i]);
88            }
89
90            buffer.setSpan(new DragState(event.getX(), event.getY(),
91                            widget.getScrollX(), widget.getScrollY()),
92                    0, 0, Spannable.SPAN_MARK_MARK);
93            return true;
94
95        case MotionEvent.ACTION_UP:
96            ds = buffer.getSpans(0, buffer.length(), DragState.class);
97
98            for (int i = 0; i < ds.length; i++) {
99                buffer.removeSpan(ds[i]);
100            }
101
102            if (ds.length > 0 && ds[0].mUsed) {
103                return true;
104            } else {
105                return false;
106            }
107
108        case MotionEvent.ACTION_MOVE:
109            ds = buffer.getSpans(0, buffer.length(), DragState.class);
110
111            if (ds.length > 0) {
112                if (ds[0].mFarEnough == false) {
113                    int slop = ViewConfiguration.get(widget.getContext()).getScaledTouchSlop();
114
115                    if (Math.abs(event.getX() - ds[0].mX) >= slop ||
116                        Math.abs(event.getY() - ds[0].mY) >= slop) {
117                        ds[0].mFarEnough = true;
118                    }
119                }
120
121                if (ds[0].mFarEnough) {
122                    ds[0].mUsed = true;
123                    boolean cap = (event.getMetaState() & KeyEvent.META_SHIFT_ON) != 0
124                            || MetaKeyKeyListener.getMetaState(buffer,
125                                    MetaKeyKeyListener.META_SHIFT_ON) == 1
126                            || MetaKeyKeyListener.getMetaState(buffer,
127                                    MetaKeyKeyListener.META_SELECTING) != 0;
128                    float dx;
129                    float dy;
130                    if (cap) {
131                        // if we're selecting, we want the scroll to go in
132                        // the direction of the drag
133                        dx = event.getX() - ds[0].mX;
134                        dy = event.getY() - ds[0].mY;
135                    } else {
136                        dx = ds[0].mX - event.getX();
137                        dy = ds[0].mY - event.getY();
138                    }
139                    ds[0].mX = event.getX();
140                    ds[0].mY = event.getY();
141
142                    int nx = widget.getScrollX() + (int) dx;
143                    int ny = widget.getScrollY() + (int) dy;
144
145                    int padding = widget.getTotalPaddingTop() + widget.getTotalPaddingBottom();
146                    Layout layout = widget.getLayout();
147
148                    ny = Math.min(ny, layout.getHeight() - (widget.getHeight() - padding));
149                    ny = Math.max(ny, 0);
150
151                    int oldX = widget.getScrollX();
152                    int oldY = widget.getScrollY();
153
154                    scrollTo(widget, layout, nx, ny);
155
156                    // If we actually scrolled, then cancel the up action.
157                    if (oldX != widget.getScrollX() || oldY != widget.getScrollY()) {
158                        widget.cancelLongPress();
159                    }
160
161                    return true;
162                }
163            }
164        }
165
166        return false;
167    }
168
169    public static int getInitialScrollX(TextView widget, Spannable buffer) {
170        DragState[] ds = buffer.getSpans(0, buffer.length(), DragState.class);
171        return ds.length > 0 ? ds[0].mScrollX : -1;
172    }
173
174    public static int getInitialScrollY(TextView widget, Spannable buffer) {
175        DragState[] ds = buffer.getSpans(0, buffer.length(), DragState.class);
176        return ds.length > 0 ? ds[0].mScrollY : -1;
177    }
178
179    private static class DragState implements NoCopySpan {
180        public float mX;
181        public float mY;
182        public int mScrollX;
183        public int mScrollY;
184        public boolean mFarEnough;
185        public boolean mUsed;
186
187        public DragState(float x, float y, int scrollX, int scrollY) {
188            mX = x;
189            mY = y;
190            mScrollX = scrollX;
191            mScrollY = scrollY;
192        }
193    }
194}
195