我创建了画布手指绘图应用程序，例如 https://play.google.com/store/apps/details?id=jp.naver.linebrush.android 上的线条画笔，我完成了捏合缩放功能，但问题是在放大和缩小后，没有在画布区域正确绘制位置。为了更好地理解，我分享了我的画布绘制视图课程：
public class DrawingView extends View {
// Zooming Code 16-6-2015 4.12pm
private static final int INVALID_POINTER_ID = -1;
public Bitmap mMyChracter;
private float mPosX;
private float mPosY;
private float mLastTouchX;
private float mLastTouchY;
private int mActivePointerId = INVALID_POINTER_ID;
View currentView;
private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
private float focusX;
private float focusY;
private float lastFocusX = -1;
private float lastFocusY = -1;
static final int IMG_WIDTH = 640;
static final int IMG_HEIGHT = 480;
static final int IMAGE_X_POS = 560;
static final int IMAGE_Y_POS = 20;
float sy;
float sx;
public static Context context;
// -------------------------------------
// ...................................
/*private final Bitmap bitmap;
private final int width;
private final int height;*/
private Matrix transform = new Matrix();
private Vector2D position = new Vector2D();
private float scale = 1;
private float angle = 0;
private TouchManager touchManager = new TouchManager(2);
private boolean isInitialized = false;
// Debug helpers to draw lines between the two touch points
private Vector2D vca = null;
private Vector2D vcb = null;
private Vector2D vpa = null;
private Vector2D vpb = null;
int mWidth;
int mHeight;
// ...............................
private final Paint mDefaultPaint;
private Paint mFillPaint;
float x, y;
private Canvas mLayerCanvas = new Canvas();
private Bitmap mLayerBitmap;
private Stack<DrawOp> mDrawOps = new Stack<>();
private Stack<DrawOp> mUndoOps = new Stack<>();
private SparseArray<DrawOp> mCurrentOps = new SparseArray<>(0);
// For Drag and Pan zoom Code initialization
private static float MIN_ZOOM = 1f;
private static float MAX_ZOOM = 2f;
private float scaleFactor = 1.f;
private static ScaleGestureDetector detector;
boolean mFlagDrawing;
private final Matrix mMatrix = new Matrix();
int y_old=0,y_new=0;int zoomMode=0;
float pinch_dist_old=0,pinch_dist_new=0;
int zoomControllerScale=1;//new and old pinch distance to determine Zoom scale
// These matrices will be used to move and zoom image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();
// Remember some things for zooming
PointF start = new PointF();
PointF mid = new PointF();
float oldDist = 1f;
// We can be in one of these 3 states
static final int NONE = 0;
static final int PAN = 1;
static final int ZOOM = 2;
int mode = NONE;
private static final String TAG = "DebugTag";
// New Code
private Bitmap imgBitmap = null;
private int containerWidth;
private int containerHeight;
Paint background;
//Matrices will be used to move and zoom image
// Matrix matrix = new Matrix();
// Matrix savedMatrix = new Matrix();
// PointF start = new PointF();
float currentScale;
float curX;
float curY;
//We can be in one of these 3 states
// static final int NONE = 0;
// static final int DRAG = 1;
// static final int ZOOM = 2;
// int mode = NONE;
//For animating stuff
float targetX;
float targetY;
float targetScale;
float targetScaleX;
float targetScaleY;
float scaleChange;
float targetRatio;
float transitionalRatio;
float easing = 0.2f;
boolean isAnimating = false;
float scaleDampingFactor = 0.5f;
//For pinch and zoom
// float oldDist = 1f;
// PointF mid = new PointF();
private Handler mHandler = new Handler();
float minScale;
float maxScale = 8.0f;
float wpRadius = 25.0f;
float wpInnerRadius = 20.0f;
float screenDensity;
private GestureDetector gestureDetector;
public static final int DEFAULT_SCALE_FIT_INSIDE = 0;
public static final int DEFAULT_SCALE_ORIGINAL = 1;
private int defaultScale;
private static final String EXTRA_EVENT_LIST = "event_list";
private static final String EXTRA_STATE = "instance_state";
private ArrayList<MotionEvent> eventList = new ArrayList<MotionEvent>(100);
public DrawingView(Context context) {
this(context, null, 0);
}
public DrawingView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
// detector = new ScaleGestureDetector(getContext(), new ScaleListener());
}
public DrawingView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mDefaultPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mDefaultPaint.setStyle(Paint.Style.STROKE);
mDefaultPaint.setStrokeJoin(Paint.Join.ROUND);
mDefaultPaint.setStrokeCap(Paint.Cap.ROUND);
mDefaultPaint.setStrokeWidth(40);
mDefaultPaint.setColor(Color.GREEN);
/*mFillPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mFillPaint.setStyle(Paint.Style.STROKE);
mFillPaint.setStrokeJoin(Paint.Join.ROUND);
mFillPaint.setStrokeCap(Paint.Cap.ROUND);
mDefaultPaint.setStrokeWidth(40);
mFillPaint.setColor(Color.GREEN);*/
setFocusable(true);
setFocusableInTouchMode(true);
setBackgroundColor(Color.WHITE);
setLayerType(LAYER_TYPE_SOFTWARE, null);
setSaveEnabled(true);
// Code for Zoom start
// detector = new ScaleGestureDetector(getContext(), new ScaleListener());
// Code for Zoom finish
mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
}
private static float getDegreesFromRadians(float angle) {
return (float)(angle * 180.0 / Math.PI);
}
// Single Touch Code
@Override
public boolean onTouchEvent(@NonNull MotionEvent event) {
vca = null;
vcb = null;
vpa = null;
vpb = null;
final int pointerCount = MotionEventCompat.getPointerCount(event);
switch (MotionEventCompat.getActionMasked(event)) {
// switch(event.getAction()){
// switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
// case MotionEventCompat.ACTION_POINTER_DOWN:
{
if (mFlagDrawing == true) {
/* final float xx = event.getX() / mScaleFactor;
final float yy = event.getY() / mScaleFactor;
mLastTouchX = xx;
mLastTouchY = yy;
mActivePointerId = event.getPointerId(0);*/
try {
touchManager.update(event);
if (touchManager.getPressCount() == 1) {
vca = touchManager.getPoint(0);
vpa = touchManager.getPreviousPoint(0);
position.add(touchManager.moveDelta(0));
}
else {
if (touchManager.getPressCount() == 2) {
vca = touchManager.getPoint(0);
vpa = touchManager.getPreviousPoint(0);
vcb = touchManager.getPoint(1);
vpb = touchManager.getPreviousPoint(1);
Vector2D current = touchManager.getVector(0, 1);
Vector2D previous = touchManager.getPreviousVector(0, 1);
float currentDistance = current.getLength();
float previousDistance = previous.getLength();
if (previousDistance != 0) {
scale *= currentDistance / previousDistance;
}
angle -= Vector2D.getSignedAngleBetween(current, previous);
}
}
invalidate();
}
catch(Throwable t) {
// So lazy...
}
System.out.println("mFlagDrawing: " + mFlagDrawing);
// Code for Zoom start
// detector.onTouchEvent(event);
// mScaleDetector.onTouchEvent(event);
// Code for Zoom finish
} else if (mFlagDrawing == false) {
System.out.println("mFlagDrawing: " + mFlagDrawing);
for (int p = 0; p < pointerCount; p++) {
final int id = MotionEventCompat.getPointerId(event, p);
DrawOp current = new DrawOp(mDefaultPaint);
current.getPath().moveTo(event.getX(), event.getY());
mCurrentOps.put(id, current);
}
}
// mFlagZoom = true;
// }
}
break;
case MotionEvent.ACTION_MOVE: {
// for(int p = 0; p < pointerCount; p++){
if (mFlagDrawing == true) {
/* final int pointerIndex = event.findPointerIndex(mActivePointerId);
final float xx = event.getX(pointerIndex) / mScaleFactor;
final float yy = event.getY(pointerIndex) / mScaleFactor;
// Only move if the ScaleGestureDetector isn't processing a gesture.
if (!mScaleDetector.isInProgress()) {
final float dx = xx - mLastTouchX;
final float dy = yy - mLastTouchY;
mPosX += dx;
mPosY += dy;
invalidate();
}
mLastTouchX = xx;
mLastTouchY = yy;*/
try {
touchManager.update(event);
if (touchManager.getPressCount() == 1) {
vca = touchManager.getPoint(0);
vpa = touchManager.getPreviousPoint(0);
position.add(touchManager.moveDelta(0));
// current.add(touchManager.moveDelta(0));
}
else {
if (touchManager.getPressCount() == 2) {
vca = touchManager.getPoint(0);
vpa = touchManager.getPreviousPoint(0);
vcb = touchManager.getPoint(1);
vpb = touchManager.getPreviousPoint(1);
Vector2D current = touchManager.getVector(0, 1);
Vector2D previous = touchManager.getPreviousVector(0, 1);
float currentDistance = current.getLength();
float previousDistance = previous.getLength();
if (previousDistance != 0) {
scale *= currentDistance / previousDistance;
}
angle -= Vector2D.getSignedAngleBetween(current, previous);
}
}
invalidate();
}
catch(Throwable t) {
// So lazy...
}
System.out.println("mFlagDrawing: " + mFlagDrawing);
// Code for Zoom start
// detector.onTouchEvent(event);
// mScaleDetector.onTouchEvent(event);
// Code for Zoom finish
} else if (mFlagDrawing == false) {
System.out.println("mFlagDrawing: " + mFlagDrawing);
final int id = MotionEventCompat.getPointerId(event, 0);
DrawOp current = mCurrentOps.get(id);
final int historySize = event.getHistorySize();
for (int h = 0; h < historySize; h++) {
x = event.getHistoricalX(h);
y = event.getHistoricalY(h);
current.getPath().lineTo(x, y);
}
x = MotionEventCompat.getX(event, 0);
y = MotionEventCompat.getY(event, 0);
current.getPath().lineTo(x, y);
// position.add(current.getPath());
// }
}
}
break;
case MotionEvent.ACTION_UP:
// case MotionEventCompat.ACTION_POINTER_UP:
// {
if (mFlagDrawing == true) {
// mActivePointerId = INVALID_POINTER_ID;
try {
touchManager.update(event);
if (touchManager.getPressCount() == 1) {
vca = touchManager.getPoint(0);
vpa = touchManager.getPreviousPoint(0);
position.add(touchManager.moveDelta(0));
}
else {
if (touchManager.getPressCount() == 2) {
vca = touchManager.getPoint(0);
vpa = touchManager.getPreviousPoint(0);
vcb = touchManager.getPoint(1);
vpb = touchManager.getPreviousPoint(1);
Vector2D current = touchManager.getVector(0, 1);
Vector2D previous = touchManager.getPreviousVector(0, 1);
float currentDistance = current.getLength();
float previousDistance = previous.getLength();
if (previousDistance != 0) {
scale *= currentDistance / previousDistance;
}
angle -= Vector2D.getSignedAngleBetween(current, previous);
}
}
invalidate();
}
catch(Throwable t) {
// So lazy...
}
System.out.println("mFlagDrawing: " + mFlagDrawing);
// Code for Zoom start
// detector.onTouchEvent(event);
// mScaleDetector.onTouchEvent(event);
// Code for Zoom finish
} else if (mFlagDrawing == false) {
System.out.println("mFlagDrawing: " + mFlagDrawing);
for (int p = 0; p < pointerCount; p++) {
final int id = MotionEventCompat.getPointerId(event, p);
mDrawOps.push(mCurrentOps.get(id));
mCurrentOps.remove(id);
// }
updateLayer();
}
}
// }
break;
case MotionEvent.ACTION_CANCEL: {
if (mFlagDrawing == true) {
// mActivePointerId = INVALID_POINTER_ID;
try {
touchManager.update(event);
if (touchManager.getPressCount() == 1) {
vca = touchManager.getPoint(0);
vpa = touchManager.getPreviousPoint(0);
position.add(touchManager.moveDelta(0));
}
else {
if (touchManager.getPressCount() == 2) {
vca = touchManager.getPoint(0);
vpa = touchManager.getPreviousPoint(0);
vcb = touchManager.getPoint(1);
vpb = touchManager.getPreviousPoint(1);
Vector2D current = touchManager.getVector(0, 1);
Vector2D previous = touchManager.getPreviousVector(0, 1);
float currentDistance = current.getLength();
float previousDistance = previous.getLength();
if (previousDistance != 0) {
scale *= currentDistance / previousDistance;
}
angle -= Vector2D.getSignedAngleBetween(current, previous);
}
}
invalidate();
}
catch(Throwable t) {
// So lazy...
}
System.out.println("mFlagDrawing: " + mFlagDrawing);
// Code for Zoom start
// detector.onTouchEvent(event);
// mScaleDetector.onTouchEvent(event);
// Code for Zoom finish
} else if (mFlagDrawing == false) {
System.out.println("mFlagDrawing: " + mFlagDrawing);
for (int p = 0; p < pointerCount; p++) {
mCurrentOps
.remove(MotionEventCompat.getPointerId(event, p));
}
}
// mFlagZoom = true;
// }
}
break;
/*case MotionEvent.ACTION_POINTER_UP: {
final int pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
final int pointerId = event.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
// This was our active pointer going up. Choose a new
// active pointer and adjust accordingly.
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mLastTouchX = event.getX(newPointerIndex) / mScaleFactor;
mLastTouchY = event.getY(newPointerIndex) / mScaleFactor;
mActivePointerId = event.getPointerId(newPointerIndex);
}
break;
}*/
default:
return false;
}
invalidate();
return true;
}
@Override
protected void onSizeChanged(int w, int h, int oldW, int oldH) {
super.onSizeChanged(w, h, oldW, oldH);
/*mLayerBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
mLayerCanvas.setBitmap(mLayerBitmap);*/
if(mLayerBitmap == null){
mLayerBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
}else{
Bitmap temporary = Bitmap.createScaledBitmap(mLayerBitmap, w, h, true);
mLayerBitmap = temporary;
}
mLayerCanvas = new Canvas(mLayerBitmap);
// mLayerCanvas.rotate(90);
/* matrix.setTranslate(1.5f,1.5f);
matrix.postRotate(90, 2.5f, 2.5f);*/
// updateLayer();
/* //Reset the width and height. Will draw bitmap and change
containerWidth = w;
containerHeight = h;
if(mLayerBitmap != null) {
int imgHeight = mLayerBitmap.getHeight();
int imgWidth = mLayerBitmap.getWidth();
float scale;
int initX = 0;
int initY = 0;
if(defaultScale == DrawingView.DEFAULT_SCALE_FIT_INSIDE) {
if(imgWidth > containerWidth) {
scale = (float)containerWidth / imgWidth;
float newHeight = imgHeight * scale;
initY = (containerHeight - (int)newHeight)/2;
matrix.setScale(scale, scale);
matrix.postTranslate(0, initY);
}
else {
scale = (float)containerHeight / imgHeight;
float newWidth = imgWidth * scale;
initX = (containerWidth - (int)newWidth)/2;
matrix.setScale(scale, scale);
matrix.postTranslate(initX, 0);
}
curX = initX;
curY = initY;
currentScale = scale;
minScale = scale;
}
else {
if(imgWidth > containerWidth) {
initY = (containerHeight - (int)imgHeight)/2;
matrix.postTranslate(0, initY);
}
else {
initX = (containerWidth - (int)imgWidth)/2;
matrix.postTranslate(initX, 0);
}
curX = initX;
curY = initY;
currentScale = 1.0f;
minScale = 1.0f;
}
invalidate();
}*/
}
private void updateLayer() {
mLayerCanvas.drawColor(0, PorterDuff.Mode.CLEAR);
for (DrawOp drawOp : mDrawOps) {
if (drawOp != null) {
drawOp.draw(mLayerCanvas);
}
}
invalidate();
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (isInEditMode()) {
return;
}
// if(mFlagDrawing == true){
if (!isInitialized) {
int w = getWidth();
int h = getHeight();
position.set(w / 2, h / 2);
isInitialized = true;
}
mWidth = mLayerBitmap.getWidth();
mHeight = mLayerBitmap.getHeight();
// Code for Zoom start
/* canvas.save();
canvas.scale(mScaleFactor, mScaleFactor, focusX, focusY);
canvas.translate(mPosX, mPosY);*/
// canvas.scale(scaleFactor, scaleFactor);
/*canvas.scale(mScaleFactor, mScaleFactor, super.getWidth() * 0.5f,
super.getHeight() * 0.5f);*/
// Code for Zoom finish
// canvas.save();
transform.reset();
transform.postTranslate(-mWidth / 2.0f, -mHeight / 2.0f);
// transform.postRotate(getDegreesFromRadians(angle));
transform.postScale(scale, scale);
transform.postTranslate(position.getX(), position.getY());
canvas.drawBitmap(mLayerBitmap, transform, null);
// }
// else if(mFlagDrawing == false){
// canvas.drawBitmap(mLayerBitmap, 0, 0, null);
for (int i = 0; i < mCurrentOps.size(); i++) {
DrawOp current = mCurrentOps.valueAt(i);
if (current != null) {
current.draw(canvas);
}
}
// }
// Code for Zoom
// canvas.restore();
}
public void operationClear() {
mDrawOps.clear();
mUndoOps.clear();
mCurrentOps.clear();
updateLayer();
}
public void operationUndo() {
if (mDrawOps.size() > 0) {
mUndoOps.push(mDrawOps.pop());
updateLayer();
}
}
public void operationRedo() {
if (mUndoOps.size() > 0) {
mDrawOps.push(mUndoOps.pop());
updateLayer();
}
}
public void setPaintStrokeWidth(float widthPx) {
mDefaultPaint.setStrokeWidth(widthPx);
}
public void setPaintOpacity(int percent) {
int alphaValue = (int) Math.round(percent * (255.0 / 100.0));
mDefaultPaint.setColor(combineAlpha(mDefaultPaint.getColor(),
alphaValue));
}
public void setPaintColor(String color) {
mDefaultPaint.setColor(combineAlpha(Color.parseColor(color), mDefaultPaint.getAlpha()));
}
public void setPaintColor(int color) {
mDefaultPaint.setColor(combineAlpha(color, mDefaultPaint.getAlpha()));
}
public void setPaintMaskFilter(MaskFilter filter) {
mDefaultPaint.setMaskFilter(filter);
}
public void setPaintShader(BitmapShader shader) {
mDefaultPaint.setShader(shader);
}
public void setPaintColorFilter(ColorFilter colorFilter) {
mDefaultPaint.setColorFilter(colorFilter);
}
private static int combineAlpha(int color, int alpha) {
return (color & 0x00FFFFFF) | ((alpha & 0xFF) << 24);
}
private static class DrawOp {
private float x,y;
private final Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final Path mPath = new Path();
public DrawOp(Paint paint) {
reset(paint);
}
/*public void add(Vector2D moveDelta) {
// TODO Auto-generated method stub
this.x += moveDelta.getX();
this.y += moveDelta.getY();
}*/
void reset(Paint paint) {
mPath.reset();
update(paint);
}
void update(Paint paint) {
mPaint.set(paint);
}
void draw(Canvas canvas) {
canvas.drawPath(mPath, mPaint);
}
public Path getPath() {
return mPath;
}
/* public DrawOp add(DrawOp value) {
this.x += value.getX();
this.y += value.getY();
return this;
}*/
/*public float getX() {
return x;
}
public float getY() {
return y;
}*/
}
public void fillShapeColor(){
}
// Code for Zoom
/* private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public boolean onScale(ScaleGestureDetector detector) {
scaleFactor *= detector.getScaleFactor();
scaleFactor = Math.max(MIN_ZOOM, Math.min(scaleFactor, MAX_ZOOM));
invalidate();
return true;
}
}*/
private class ScaleListener extends
ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public boolean onScaleBegin(ScaleGestureDetector detector) {
// float x = detector.getFocusX();
// float y = detector.getFocusY();
lastFocusX = -1;
lastFocusY = -1;
return true;
}
@Override
public boolean onScale(ScaleGestureDetector detector) {
mScaleFactor *= detector.getScaleFactor();
focusX = detector.getFocusX();
focusY = detector.getFocusY();
if (lastFocusX == -1)
lastFocusX = focusX;
if (lastFocusY == -1)
lastFocusY = focusY;
mPosX += (focusX - lastFocusX);
mPosY += (focusY - lastFocusY);
Log.v("Hi Zoom", "Factor:" + mScaleFactor);
// Don't let the object get too small or too large.
mScaleFactor = Math.max(0.5f, Math.min(mScaleFactor, 2.0f));
lastFocusX = focusX;
lastFocusY = focusY;
invalidate();
return true;
}
}
/* @Override
public Parcelable onSaveInstanceState()
{
System.out.println("save instance");
Bundle bundle = new Bundle();
bundle.putParcelable(EXTRA_STATE, super.onSaveInstanceState());
bundle.putParcelableArrayList(EXTRA_EVENT_LIST, eventList);
return bundle;
}
@Override
public void onRestoreInstanceState(Parcelable state)
{
if (state instanceof Bundle)
{
Bundle bundle = (Bundle) state;
super.onRestoreInstanceState(bundle.getParcelable(EXTRA_STATE));
eventList = bundle.getParcelableArrayList(EXTRA_EVENT_LIST);
if (eventList == null) {
eventList = new ArrayList<MotionEvent>(100);
}
for (MotionEvent event : eventList) {
// performTouchEvent(event);
}
return;
}
super.onRestoreInstanceState(state);
}*/
public void setDrawingFlag(boolean flag) {
// System.out.println("Before Set mFlag " + mFlagDrawing);
this.mFlagDrawing = flag;
// System.out.println("After Set mFlag " + mFlagDrawing);
}
public void moveCanvas(float x, float y) {
float dx = x - mLastTouchX;
float dy = y - mLastTouchY;
// Adjust for zoom factor. Otherwise, the user's finger moving 10 pixels
// at 200% zoom causes the image to slide 20 pixels instead of perfectly
// following the user's touch
dx /= (mScaleFactor * 2);
dy /= (mScaleFactor * 2);
mPosX += dx;
mPosY += dy;
// Log.v(TAG, "moving by " + dx + "," + dy + " mScaleFactor: " +
// mScaleFactor);
}
}
我发现了错误并自行纠正。下面是我的代码。
public void resetZoom() {
mPanX = mPanY = 0;
final Matrix m = new Matrix();
m.postScale(1f / DENSITY, 1f / DENSITY);
setZoom(m);
invalidate();
}
public void setZoomPosNoInval(float x, float y) {
mPanX = x;
mPanY = y;
}
public void setZoomPos(float x, float y) {
setZoomPosNoInval(x, y);
invalidate();
}
public void setZoomPosNoInval(float[] pos) {
setZoomPosNoInval(pos[0], pos[1]);
}
public void setZoomPos(float[] pos) {
setZoomPosNoInval(pos);
invalidate();
}
public float[] getZoomPos(float[] pos) {
if (pos == null)
pos = new float[2];
pos[0] = mPanX;
pos[1] = mPanY;
return pos;
}
public float getZoomPosX() {
return mPanX;
}
public float getZoomPosY() {
return mPanY;
}
public Matrix getZoom() {
return mZoomMatrix;
}
public Matrix getZoomInv() {
return mZoomMatrixInv;
}
public void setZoom(Matrix m) {
mZoomMatrix.set(m);
mZoomMatrix.invert(mZoomMatrixInv);
}