我有一个在绘制和缩放ImageView时遇到的问题，请求帮助。
当我绘制一些东西并拖动或缩放图像时，绘图保留在原地，正如您在屏幕截图中所看到的那样。 我需要简单地在图片上绘制，并有可能缩放和拖动该图片。
我有一个自定义的ImageView，具有以下功能：
public class DrawingView extends ImageView {
// onTouch
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
private Path mPath;
private boolean zoomEnabled = true;
private Paint drawPaint, canvasPaint;
//initial color
private int paintColor = 0xFF660000;
//canvas
private Canvas drawCanvas;
//canvas bitmap
private Bitmap canvasBitmap;
private static final int INVALID_POINTER_ID = -1;
private float mPosX;
private float mPosY;
private float mLastTouchX;
private float mLastTouchY;
private float mLastGestureX;
private float mLastGestureY;
private int mActivePointerId = INVALID_POINTER_ID;
private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
public DrawingView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
mScaleDetector = new ScaleGestureDetector(getContext(), new ScaleListener());
setupDrawing();
}
public DrawingView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
setupDrawing();
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
drawCanvas = new Canvas(canvasBitmap);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
final int action = ev.getAction();
mScaleDetector.onTouchEvent(ev);
if (zoomEnabled) {
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN: {
if (!mScaleDetector.isInProgress()) {
final float x = ev.getX();
final float y = ev.getY();
mLastTouchX = x;
mLastTouchY = y;
mActivePointerId = ev.getPointerId(0);
}
break;
}
case MotionEvent.ACTION_POINTER_1_DOWN: {
if (mScaleDetector.isInProgress()) {
final float gx = mScaleDetector.getFocusX();
final float gy = mScaleDetector.getFocusY();
mLastGestureX = gx;
mLastGestureY = gy;
}
break;
}
case MotionEvent.ACTION_MOVE: {
// Only move if the ScaleGestureDetector isn't processing a gesture.
if (!mScaleDetector.isInProgress()) {
final int pointerIndex = ev.findPointerIndex(mActivePointerId);
final float x = ev.getX(pointerIndex);
final float y = ev.getY(pointerIndex);
final float dx = x - mLastTouchX;
final float dy = y - mLastTouchY;
mPosX += dx;
mPosY += dy;
invalidate();
mLastTouchX = x;
mLastTouchY = y;
} else {
final float gx = mScaleDetector.getFocusX();
final float gy = mScaleDetector.getFocusY();
final float gdx = gx - mLastGestureX;
final float gdy = gy - mLastGestureY;
mPosX += gdx;
mPosY += gdy;
invalidate();
mLastGestureX = gx;
mLastGestureY = gy;
}
break;
}
case MotionEvent.ACTION_UP: {
mActivePointerId = INVALID_POINTER_ID;
break;
}
case MotionEvent.ACTION_CANCEL: {
mActivePointerId = INVALID_POINTER_ID;
break;
}
case MotionEvent.ACTION_POINTER_UP: {
final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK)
>> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
final int pointerId = ev.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 = ev.getX(newPointerIndex);
mLastTouchY = ev.getY(newPointerIndex);
mActivePointerId = ev.getPointerId(newPointerIndex);
} else {
final int tempPointerIndex = ev.findPointerIndex(mActivePointerId);
mLastTouchX = ev.getX(tempPointerIndex);
mLastTouchY = ev.getY(tempPointerIndex);
}
break;
}
}
return true;
} else {
switch (action) {
case MotionEvent.ACTION_DOWN:
touchStart(ev.getX(), ev.getY());
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touchMove(ev.getX(), ev.getY());
invalidate();
break;
case MotionEvent.ACTION_UP:
touchUp();
invalidate();
break;
}
return true;
}
}
@Override
public void onDraw(Canvas canvas) {
canvas.save();
canvas.translate(mPosX, mPosY);
if (mScaleDetector.isInProgress()) {
canvas.scale(mScaleFactor, mScaleFactor, mScaleDetector.getFocusX(), mScaleDetector.getFocusY());
}
else{
canvas.scale(mScaleFactor, mScaleFactor, mLastGestureX, mLastGestureY);
}
super.onDraw(canvas);
canvas.restore();
canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
canvas.drawPath(mPath, drawPaint);
}
private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public boolean onScale(ScaleGestureDetector detector) {
mScaleFactor *= detector.getScaleFactor();
// Don't let the object get too small or too large.
mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f));
invalidate();
return true;
}
}
private void setupDrawing(){
mPath = new Path();
drawPaint = new Paint();
drawPaint.setColor(paintColor);
drawPaint.setAntiAlias(true);
drawPaint.setStrokeWidth(20);
drawPaint.setStyle(Paint.Style.STROKE);
drawPaint.setStrokeJoin(Paint.Join.ROUND);
drawPaint.setStrokeCap(Paint.Cap.ROUND);
canvasPaint = new Paint(Paint.DITHER_FLAG);
}
public void setZoomEnabled(boolean b){
this.zoomEnabled = b;
}
private void touchStart(float x, float y) {
// mPath.reset();
mPath.moveTo(x, y);
mX = x;
mY = y;
}
private void touchMove(float x, float y) {
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
mX = x;
mY = y;
}
}
private void touchUp() {
mPath.lineTo(mX, mY);
// commit the path to our offscreen
drawCanvas.drawPath(mPath, drawPaint);
// kill this so we don't double draw
mPath.reset();
}
活动：
public class DrawActivity extends Activity{
DrawingView image;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.draw);
final Paint paint = new Paint();
paint.setColor(MyApp.getColorRes(R.color.primary));
paint.setStrokeWidth(10);
image = (DrawingView) findViewById(R.id.image);
Bitmap bmp = BitmapFactory.decodeByteArray(
getIntent().getByteArrayExtra("byteArray"), 0, getIntent().getByteArrayExtra("byteArray").length);
Bitmap alteredBmp = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
final Canvas canvas = new Canvas(alteredBmp);
canvas.drawBitmap(bmp, 0, 0, paint);
image.setImageBitmap(alteredBmp);
ImageButton paintBtn = (ImageButton) findViewById(R.id.paint_btn);
paintBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View button) {
button.setSelected(!button.isSelected());
image.setZoomEnabled(!button.isSelected());
}
});
}