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我想刪除我的畫布上繪製的最後一條路徑。我已嘗試到目前爲止添加我的路徑在ArrayList中，但我沒有找到任何方法從畫布中刪除路徑easilly。如何從Canvas android中撤消路徑？
public class PaintView extends View {
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mPaint;
private static final int TOUCH_TOLERANCE_DP = 20;
private static final int BACKGROUND = Color.TRANSPARENT;
private List<Point> mPoints = new ArrayList<Point>();
private int mLastPointIndex = 0;
private int mTouchTolerance;
private boolean isPathStarted = false;
private boolean canCreatePoints = true;
private Polygon poly;
private Builder build;
private ArrayList<Polygon> polyList;
private ArrayList<Path> undoPath, redoPath;
public PaintView(Context context) {
super(context);
mCanvas = new Canvas();
mPath = new Path();
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(Color.BLACK);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(12);
mTouchTolerance = dp2px(TOUCH_TOLERANCE_DP);
polyList = new ArrayList<Polygon>();
undoPath = new ArrayList<Path>();
redoPath = new ArrayList<Path>();
}
@Override
protected void onSizeChanged(int width, int height, int oldWidth,
int oldHeight) {
super.onSizeChanged(width, height, oldWidth, oldHeight);
clear();
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(BACKGROUND);
canvas.drawBitmap(mBitmap, 0, 0, null);
canvas.drawPath(mPath, mPaint);
for(Path p : undoPath) {
canvas.drawPath(p, mPaint);
}
for (Point point : mPoints) {
canvas.drawPoint(point.x, point.y, mPaint);
}
}
下面是onTouch方法，我創建一個使用路徑線時可變canCreatePoints它true.If canCreatePoints這是假的我在一個ArrayList<Polygon>檢查我的接觸點是多邊形內。
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
if(canCreatePoints == true)
{
create_point(x,y);
if(mPoints.size() > 1)
{
// start point
Point p = mPoints.get(mLastPointIndex);
mPath.moveTo(p.x, p.y);
// end point
p = mPoints.get(mLastPointIndex + 1);
mPath.lineTo(p.x, p.y);
mCanvas.drawPath(mPath, mPaint);
undoPath.add(mPath);
mPath.reset();
// increment point index
++mLastPointIndex;
}
}
if(canCreatePoints == false)
{
Points pp = new Points(Math.round(x), Math.round(y));
boolean contains;
for(Polygon tempPoly:polyList){
contains = tempPoly.contains(pp);
if(contains == true)
{
Log.i("TEST","Poligonul contine punctul");
Toast.makeText(getContext(),"Test poly "+polyList.indexOf(tempPoly),
Toast.LENGTH_SHORT).show();
}
}
}
invalidate();
break;
}
return true;
}
private void create_point(float x, float y){
Point p = new Point(Math.round(x),Math.round(y));
mPoints.add(p);
}
貝婁我通過按鈕的動作芬蘭我的多邊形形式。我創建了一個從最後一點到第一點的路徑並在畫布上繪製。
public void finnishDraw(){
if(mPoints.size() > 1)
{
// start point
Point p = mPoints.get(0);
mPath.moveTo(p.x, p.y);
// end point
p = mPoints.get(mPoints.size() - 1);
mPath.lineTo(p.x, p.y);
mCanvas.drawPath(mPath, mPaint);
mPath.reset();
invalidate();
int x[] = new int[mPoints.size()];
int y[] = new int[mPoints.size()];
build = new Builder();
for(int i=0 ; i<mPoints.size() ; i++)
{
p = mPoints.get(i);
x[i] = p.x;
y[i] = p.y;
build.addVertex(new Points(x[i],y[i]));
Log.i("TEST","Adaug la builder punctele "+x[i]+" si "+y[i]);
}
poly = build.build();
polyList.add(poly);
mPoints.clear();
mLastPointIndex = 0;
}
}
到目前爲止，我只找到一個備用位圖解決畫線之前，但我不明白它是如何真正起作用。