, Android Dragging and Scaling ( ).
, . , , . BoardView , . X O .
BoardView.java
public class BoardView extends View {
private static final int JUST_SCALED_DURATION = 100;
private static final int MAX_TOUCH_DURATION = 1000;
private static final int MAX_TOUCH_DISTANCE = 10;
private boolean stayedWithinTouchDistance;
private float firstTouchX, firstTouchY;
private long firstTouchTime, lastScaleTime;
private float posX, posY, lastTouchX, lastTouchY;
private ScaleGestureDetector scaleDetector;
private float minScaleFactor = 0.1f;
private float maxScaleFactor = 5.0f;
private float scaleFactor = 1.0f;
private float cellSize = 50.0f;
private int numCells = 50;
private ArrayList<Point> points;
private Paint linePaint, pointPaint;
public BoardView(Context context) {
this(context, null, 0);
}
public BoardView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public BoardView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
points = new ArrayList<>();
linePaint = new Paint();
linePaint.setAntiAlias(true);
linePaint.setColor(-65536);
linePaint.setStrokeWidth(1.0f);
pointPaint = new Paint();
pointPaint.setAntiAlias(true);
pointPaint.setColor(-65536);
pointPaint.setStrokeWidth(1.0f);
posX = linePaint.getStrokeWidth();
posY = linePaint.getStrokeWidth();
scaleDetector = new ScaleGestureDetector(context, new ScaleListener());
}
private static float distancePx(float x1, float y1, float x2, float y2) {
float dx = x1 - x2;
float dy = y1 - y2;
return (float) Math.sqrt(dx * dx + dy * dy);
}
private float distanceDp(float distancePx) {
return distancePx / getResources().getDisplayMetrics().density;
}
private Point coerceToGrid(Point point) {
point.x = (int) ((((int) (point.x / cellSize)) * cellSize) + (cellSize / 2));
point.y = (int) ((((int) (point.y / cellSize)) * cellSize) + (cellSize / 2));
return point;
}
@Override
public boolean onTouchEvent(@NonNull MotionEvent event) {
scaleDetector.onTouchEvent(event);
final int action = MotionEventCompat.getActionMasked(event);
if (action == MotionEvent.ACTION_DOWN) {
stayedWithinTouchDistance = true;
firstTouchX = lastTouchX = event.getRawX();
firstTouchY = lastTouchY = event.getRawY();
firstTouchTime = System.currentTimeMillis();
} else if (action == MotionEvent.ACTION_MOVE) {
float thisTouchX = event.getRawX();
float thisTouchY = event.getRawY();
boolean justScaled = System.currentTimeMillis() - lastScaleTime < JUST_SCALED_DURATION;
float distancePx = distancePx(firstTouchX, firstTouchY, thisTouchX, thisTouchY);
stayedWithinTouchDistance = stayedWithinTouchDistance &&
distanceDp(distancePx) < MAX_TOUCH_DISTANCE;
if (!stayedWithinTouchDistance && !scaleDetector.isInProgress() && !justScaled) {
posX += thisTouchX - lastTouchX;
posY += thisTouchY - lastTouchY;
invalidate();
}
lastTouchX = thisTouchX;
lastTouchY = thisTouchY;
} else if (action == MotionEvent.ACTION_UP) {
long touchDuration = System.currentTimeMillis() - firstTouchTime;
if (touchDuration < MAX_TOUCH_DURATION && stayedWithinTouchDistance) {
int[] location = {0, 0};
getLocationOnScreen(location);
float x = ((lastTouchX - posX - location[0]) / scaleFactor);
float y = ((lastTouchY - posY - location[1]) / scaleFactor);
points.add(coerceToGrid(new Point((int) x, (int) y)));
invalidate();
}
}
return true;
}
private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public boolean onScale(ScaleGestureDetector detector) {
lastScaleTime = System.currentTimeMillis();
float scale = detector.getScaleFactor();
scaleFactor = Math.max(minScaleFactor, Math.min(scaleFactor * scale, maxScaleFactor));
if (scaleFactor > minScaleFactor && scaleFactor < maxScaleFactor) {
float centerX = detector.getFocusX();
float centerY = detector.getFocusY();
float diffX = centerX - posX;
float diffY = centerY - posY;
diffX = diffX * scale - diffX;
diffY = diffY * scale - diffY;
posX -= diffX;
posY -= diffY;
invalidate();
return true;
}
return false;
}
}
private float getScaledCellSize() {
return scaleFactor * cellSize;
}
private float getScaledBoardSize() {
return numCells * getScaledCellSize();
}
private void drawBoard(Canvas canvas) {
for (int i = 0; i <= numCells; i++) {
float total = getScaledBoardSize();
float offset = getScaledCellSize() * i;
canvas.drawLine(offset, 0, offset, total, linePaint);
canvas.drawLine(0, offset, total, offset, linePaint);
}
}
private void drawPoints(Canvas canvas) {
for (Point point : points) {
float x = point.x * scaleFactor;
float y = point.y * scaleFactor;
float r = getScaledCellSize() / 4;
canvas.drawCircle(x, y, r, pointPaint);
}
}
@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
float total = getScaledBoardSize();
float edge = linePaint.getStrokeWidth();
posX = Math.max(Math.min(edge, getWidth() - total - edge), Math.min(edge, posX));
posY = Math.max(Math.min(edge, getHeight() - total - edge), Math.min(edge, posY));
canvas.save();
canvas.translate(posX, posY);
drawBoard(canvas);
drawPoints(canvas);
canvas.restore();
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.example.client.BoardView
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</FrameLayout>