我正在使用绘图应用，但面临一些撤消问题。当我在图像中绘制然后按下撤消按钮时，它不会撤消我的上一个动作。我坚持下去了。我使用了Floodfill算法。 Here is the image below 看看下面代码中的撤销功能，我想我做得对，但请检查一下，告诉我实际问题在哪里。
public class MainActivity extends AppCompatActivity implements
View.OnTouchListener {
Button red, blue, yellow, undo;
Paint paint;
private RelativeLayout drawingLayout;
private MyView myView;
private ArrayList<Path> paths = new ArrayList<>();
private ArrayList<Path> undonePaths = new ArrayList<Path>();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myView = new MyView(this);
drawingLayout = (RelativeLayout) findViewById(R.id.relative_layout);
drawingLayout.addView(myView);
red = (Button) findViewById(R.id.btn_red);
blue = (Button) findViewById(R.id.btn_blue);
yellow = (Button) findViewById(R.id.btn_yellow);
undo = (Button) findViewById(R.id.undo);
red.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
paint.setColor(Color.RED);
}
});
yellow.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
paint.setColor(Color.YELLOW);
}
});
blue.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
paint.setColor(Color.BLUE);
}
});
undo.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
myView.onClickUndo();
}
});
}
@Override
public boolean onTouch(View v, MotionEvent event) {
return false;
}
public class MyView extends View {
final Point p1 = new Point();
Bitmap mBitmap;
ProgressDialog pd;
Canvas canvas;
private Path path;
public MyView(Context context) {
super(context);
paint = new Paint();
paint.setAntiAlias(true);
pd = new ProgressDialog(context);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(5f);
mBitmap = BitmapFactory.decodeResource(getResources(),
R.drawable.gp1_1).copy(Bitmap.Config.ARGB_8888, true);
this.path = new Path();
}
public void onClickUndo() {
if (paths.size()>0) {
undonePaths.add(paths.remove(paths.size()-1));
invalidate();
} else {
Toast.makeText(getContext(), getString(R.string.nomore), Toast.LENGTH_SHORT).show();
}
}
@Override
protected void onDraw(Canvas canvas) {
this.canvas = canvas;
paint.setColor(Color.GREEN);
canvas.drawBitmap(mBitmap, 0, 0, paint);
for (Path p : paths) {
canvas.drawPath(p, paint);
}
canvas.drawPath(path,paint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
p1.x = (int) x;
p1.y = (int) y;
final int sourceColor = mBitmap.getPixel((int) x, (int) y);
final int targetColor = paint.getColor();
new TheTask(mBitmap, p1, sourceColor, targetColor).execute();
paths.add(path);
invalidate();
}
return true;
}
public void clear() {
path.reset();
invalidate();
}
public int getCurrentPaintColor() {
return paint.getColor();
}
class TheTask extends AsyncTask<Void, Integer, Void> {
Bitmap bmp;
Point pt;
int replacementColor, targetColor;
public TheTask(Bitmap bm, Point p, int sc, int tc) {
this.bmp = bm;
this.pt = p;
this.replacementColor = tc;
this.targetColor = sc;
pd.setMessage(getString(R.string.wait));
pd.show();
}
@Override
protected void onPreExecute() {
pd.show();
}
@Override
protected void onProgressUpdate(Integer... values) {
}
@Override
protected Void doInBackground(Void... params) {
FloodFill f = new FloodFill();
f.floodFill(bmp, pt, targetColor, replacementColor);
return null;
}
@Override
protected void onPostExecute(Void result) {
pd.dismiss();
invalidate();
}
}
}
public class FloodFill {
public void floodFill(Bitmap image, Point node, int targetColor,
int replacementColor) {
int width = image.getWidth();
int height = image.getHeight();
int target = targetColor;
int replacement = replacementColor;
if (target != replacement) {
Queue<Point> queue = new LinkedList<Point>();
do {
int x = node.x;
int y = node.y;
while (x > 0 && image.getPixel(x - 1, y) == target) {
x--;
}
boolean spanUp = false;
boolean spanDown = false;
while (x < width && image.getPixel(x, y) == target) {
image.setPixel(x, y, replacement);
if (!spanUp && y > 0
&& image.getPixel(x, y - 1) == target) {
queue.add(new Point(x, y - 1));
spanUp = true;
} else if (spanUp && y > 0
&& image.getPixel(x, y - 1) != target) {
spanUp = false;
}
if (!spanDown && y < height - 1
&& image.getPixel(x, y + 1) == target) {
queue.add(new Point(x, y + 1));
spanDown = true;
} else if (spanDown && y < height - 1
&& image.getPixel(x, y + 1) != target) {
spanDown = false;
}
x++;
}
} while ((node = queue.poll()) != null);
}
}
}
}