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Diffstat (limited to 'java/src/com/android/inputmethod/latin/SwipeTracker.java')
| -rw-r--r-- | java/src/com/android/inputmethod/latin/SwipeTracker.java | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/java/src/com/android/inputmethod/latin/SwipeTracker.java b/java/src/com/android/inputmethod/latin/SwipeTracker.java new file mode 100644 index 000000000..007c8e7a4 --- /dev/null +++ b/java/src/com/android/inputmethod/latin/SwipeTracker.java @@ -0,0 +1,133 @@ +/* + * Copyright (C) 2010 Google Inc. + * + * 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 com.android.inputmethod.latin; + +import android.view.MotionEvent; + +class SwipeTracker { + + static final int NUM_PAST = 4; + static final int LONGEST_PAST_TIME = 200; + + final float mPastX[] = new float[NUM_PAST]; + final float mPastY[] = new float[NUM_PAST]; + final long mPastTime[] = new long[NUM_PAST]; + + float mYVelocity; + float mXVelocity; + + public void clear() { + mPastTime[0] = 0; + } + + public void addMovement(MotionEvent ev) { + if (ev.getAction() == MotionEvent.ACTION_DOWN) { + clear(); + return; + } + long time = ev.getEventTime(); + final int N = ev.getHistorySize(); + for (int i=0; i<N; i++) { + addPoint(ev.getHistoricalX(i), ev.getHistoricalY(i), + ev.getHistoricalEventTime(i)); + } + addPoint(ev.getX(), ev.getY(), time); + } + + private void addPoint(float x, float y, long time) { + int drop = -1; + int i; + final long[] pastTime = mPastTime; + for (i=0; i<NUM_PAST; i++) { + if (pastTime[i] == 0) { + break; + } else if (pastTime[i] < time-LONGEST_PAST_TIME) { + drop = i; + } + } + if (i == NUM_PAST && drop < 0) { + drop = 0; + } + if (drop == i) drop--; + final float[] pastX = mPastX; + final float[] pastY = mPastY; + if (drop >= 0) { + final int start = drop+1; + final int count = NUM_PAST-drop-1; + System.arraycopy(pastX, start, pastX, 0, count); + System.arraycopy(pastY, start, pastY, 0, count); + System.arraycopy(pastTime, start, pastTime, 0, count); + i -= (drop+1); + } + pastX[i] = x; + pastY[i] = y; + pastTime[i] = time; + i++; + if (i < NUM_PAST) { + pastTime[i] = 0; + } + } + + public void computeCurrentVelocity(int units) { + computeCurrentVelocity(units, Float.MAX_VALUE); + } + + public void computeCurrentVelocity(int units, float maxVelocity) { + final float[] pastX = mPastX; + final float[] pastY = mPastY; + final long[] pastTime = mPastTime; + + final float oldestX = pastX[0]; + final float oldestY = pastY[0]; + final long oldestTime = pastTime[0]; + float accumX = 0; + float accumY = 0; + int N=0; + while (N < NUM_PAST) { + if (pastTime[N] == 0) { + break; + } + N++; + } + + for (int i=1; i < N; i++) { + final int dur = (int)(pastTime[i] - oldestTime); + if (dur == 0) continue; + float dist = pastX[i] - oldestX; + float vel = (dist/dur) * units; // pixels/frame. + if (accumX == 0) accumX = vel; + else accumX = (accumX + vel) * .5f; + + dist = pastY[i] - oldestY; + vel = (dist/dur) * units; // pixels/frame. + if (accumY == 0) accumY = vel; + else accumY = (accumY + vel) * .5f; + } + mXVelocity = accumX < 0.0f ? Math.max(accumX, -maxVelocity) + : Math.min(accumX, maxVelocity); + mYVelocity = accumY < 0.0f ? Math.max(accumY, -maxVelocity) + : Math.min(accumY, maxVelocity); + } + + public float getXVelocity() { + return mXVelocity; + } + + public float getYVelocity() { + return mYVelocity; + } +}
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