撤消/重做不适用于Android Canvas
撤消和重做功能不适用于下面的代码。 以下是我的绘图代码实现。
下面的代码有问题吗？
public class DrawingArea extends View {
private Path drawPath;
private Paint drawPaint, canvasPaint;
private int paintColor = 0xFF660000;
private Canvas drawCanvas;
private Bitmap canvasBitmap;
private ArrayList paths = new ArrayList();
private ArrayList undonePaths = new ArrayList();
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
// for Undo, Redo
private int historyPointer = 0;
private boolean erase = false;
public DrawingArea(Context context) {
super(context);
setupDrawing();
}
public DrawingArea(Context context, AttributeSet attrs) {
super(context, attrs);
setupDrawing();
}
public void setupDrawing() {
drawPath = new Path();
drawPaint = new Paint();
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);
//paths.add(drawPath);
}
public void setColor(String newColor) {
invalidate();
paintColor = Color.parseColor(newColor);
drawPaint.setColor(paintColor);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
canvas.drawPath(drawPath, drawPaint);
}
@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 event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
}
private void touch_start(float x, float y) {
drawPath.reset();
drawPath.moveTo(x, y);
mX = x;
mY = y;
}
private void touch_move(float x, float y) {
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
drawPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
mX = x;
mY = y;
}
}
private void touch_up() {
drawPath.lineTo(mX, mY);
// commit the path to our offscreen
drawCanvas.drawPath(drawPath, drawPaint);
// kill this so we don't double draw
drawPath = new Path();
paths.add(drawPath);
}
public void setErase() {
canvasBitmap.eraseColor(Color.TRANSPARENT);
drawPath.reset();
invalidate();
}
public void startNew() {
drawCanvas.drawColor(0, PorterDuff.Mode.CLEAR);
invalidate();
}
public void undo() {
if (paths.size() > 0) {
undonePaths.add(paths.remove(paths.size() - 1));
invalidate();
}
}
public void redo() {
if (undonePaths.size() > 0) {
paths.add(undonePaths.remove(undonePaths.size() - 1));
invalidate();
}
}
}
像这样改变你的OnDraw（）
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawBitmap(mBitmap, 0, 0, canvasPaint);
canvas.drawPath(mPath,drawPaint);
for (Path p : paths) {
canvas.drawPath(p, drawPaint);
}
}
并且不要忘记添加通过路径arraylist保存的数据类型
ArrayList<Path> paths = new ArrayList<Path>();