我正在研究android中的撤消操作。问题是，目前没有设置位图，我无法绘制它。
这是我的代码，它是从扩展的imageview中提取的：
private ArrayList<Path> paths = new ArrayList<Path>();
private Path mPath;
public ScaleImageView(Context context) {
super(context);
sharedConstructing(context);
}
public void sharedConstructing(Context context) {
super.setClickable(true);
this.context = context;
paint_bmp = new Paint();
paint_line = new Paint();
paint_line.setAntiAlias(true);
paint_line.setStrokeWidth(width);
paint_line.setColor(color);
paint_line.setStyle(Paint.Style.STROKE);
paint_line.setStrokeJoin(Paint.Join.ROUND);
paint_line.setStrokeCap(Paint.Cap.ROUND);
paint_line.setAlpha(alpha);
drawListener = new OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
if (getDrawable() != null) {
int action = event.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
downx = getPointerCoords(event)[0];// event.getX();
downy = getPointerCoords(event)[1];// event.getY();
break;
case MotionEvent.ACTION_MOVE:
upx = getPointerCoords(event)[0];// event.getX();
upy = getPointerCoords(event)[1];// event.getY();
canvas.drawLine(downx, downy, upx, upy, paint_line);
mPath = new Path();
paths.add(mPath);
invalidate();
downx = upx;
downy = upy;
break;
case MotionEvent.ACTION_UP:
upx = getPointerCoords(event)[0];// event.getX();
upy = getPointerCoords(event)[1];// event.getY();
canvas.drawLine(downx, downy, upx, upy, paint_line);
mPath = new Path();
paths.add(mPath);
invalidate();
break;
case MotionEvent.ACTION_CANCEL:
break;
default:
break;
}
}
return true;
}
};
setOnTouchListener(drawListener);
}
//draw view start
public void setNewImage(Bitmap alteredBitmap, Bitmap bmp) {
canvas = new Canvas(alteredBitmap);
matrix_draw = new Matrix();
canvas.drawBitmap(bmp, matrix_draw, paint_bmp);
setImageBitmap(alteredBitmap);
mPath = new Path();
paths.add(mPath);
}
@Override
protected void onDraw(Canvas canvas) {
for (Path p : paths){
canvas.drawPath(p, paint_line);
}
}
public void onClickUndo () {
if (paths.size()>0){
paths.remove(paths.size()-1);
invalidate();
}
}
感谢您的帮助。
答案 0 :(得分：0)
而是删除路径，使用Path.reset（）。我给你一个我用来签名的课程......
public class SignatureView extends View{
signListner sListen;
public SignatureView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
if (context instanceof signListner) {
sListen = (signListner) context;
}
init(context);
}
public SignatureView(Context context, AttributeSet attrs) {
super(context, attrs);
if (context instanceof signListner) {
sListen = (signListner) context;
}
init(context);
}
public SignatureView(Context context) {
super(context);
if (context instanceof signListner) {
sListen = (signListner) context;
}
init(context);
}
Context mContext;
private static final float STROKE_WIDTH = 5f;
private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;
private Paint paint = new Paint();
private Path path = new Path();
private float lastTouchX;
private float lastTouchY;
private final RectF dirtyRect = new RectF();
LinearLayout mContent;
public static String tempDir;
public int count = 1;
public String current = null;
private Bitmap mBitmap;
View mView;
private void init(Context context) {
mContext = context;
// LayoutInflater factory = LayoutInflater.from(context);
/*
* View myView = factory.inflate(R.layout.signature_view, null);
* mContent = (LinearLayout) myView.findViewById(R.id.linearLayout);
*/
paint.setAntiAlias(true);
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(STROKE_WIDTH);
}
public void save() {
Log.v("log_tag", "Width: " + this.getWidth());
Log.v("log_tag", "Height: " + this.getHeight());
if (mBitmap == null) {
mBitmap = Bitmap.createBitmap(this.getWidth(), this.getHeight(),
Bitmap.Config.ARGB_8888);
}
Canvas canvas = new Canvas(mBitmap);
try {
String root = Environment.getExternalStorageDirectory().toString();
File myDir = new File(root + "/GetImages");
myDir.mkdirs();
String fname = "Image-1001.jpg";
File file = new File(myDir, fname);
if (file.exists())
file.delete();
FileOutputStream mFileOutStream = new FileOutputStream(file);
this.draw(canvas);
mBitmap.compress(Bitmap.CompressFormat.PNG, 90, mFileOutStream);
// mFileOutStream.flush();
// mFileOutStream.close();
String url = Images.Media.insertImage(
mContext.getContentResolver(), mBitmap, "title", null);
Log.v("log_tag", "url: " + url);
} catch (Exception e) {
Log.v("log_tag", e.toString());
}
}
public void clear() {
path.reset();
invalidate();
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawPath(path, paint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = event.getX();
float eventY = event.getY();
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
sListen.onSign(true);
path.moveTo(eventX, eventY);
lastTouchX = eventX;
lastTouchY = eventY;
return true;
case MotionEvent.ACTION_MOVE:
resetDirtyRect(eventX, eventY);
int historySize = event.getHistorySize();
for (int i = 0; i < historySize; i++) {
float historicalX = event.getHistoricalX(i);
float historicalY = event.getHistoricalY(i);
expandDirtyRect(historicalX, historicalY);
path.lineTo(historicalX, historicalY);
}
path.lineTo(eventX, eventY);
break;
case MotionEvent.ACTION_UP:
sListen.onSign(false);
resetDirtyRect(eventX, eventY);
int historySize1 = event.getHistorySize();
for (int i = 0; i < historySize1; i++) {
float historicalX = event.getHistoricalX(i);
float historicalY = event.getHistoricalY(i);
expandDirtyRect(historicalX, historicalY);
path.lineTo(historicalX, historicalY);
}
path.lineTo(eventX, eventY);
break;
/*case MotionEvent.ACTION_POINTER_UP:
sListen.onSign(false);
break;*/
default:
debug("Ignored touch event: " + event.toString());
return false;
}
invalidate((int) (dirtyRect.left - HALF_STROKE_WIDTH),
(int) (dirtyRect.top - HALF_STROKE_WIDTH),
(int) (dirtyRect.right + HALF_STROKE_WIDTH),
(int) (dirtyRect.bottom + HALF_STROKE_WIDTH));
lastTouchX = eventX;
lastTouchY = eventY;
return true;
}
private void debug(String string) {
}
private void expandDirtyRect(float historicalX, float historicalY) {
if (historicalX < dirtyRect.left) {
dirtyRect.left = historicalX;
} else if (historicalX > dirtyRect.right) {
dirtyRect.right = historicalX;
}
if (historicalY < dirtyRect.top) {
dirtyRect.top = historicalY;
} else if (historicalY > dirtyRect.bottom) {
dirtyRect.bottom = historicalY;
}
}
private void resetDirtyRect(float eventX, float eventY) {
dirtyRect.left = Math.min(lastTouchX, eventX);
dirtyRect.right = Math.max(lastTouchX, eventX);
dirtyRect.top = Math.min(lastTouchY, eventY);
dirtyRect.bottom = Math.max(lastTouchY, eventY);
}
public boolean isEmpty(){
return path.isEmpty();
}
}
这里clear（）正在清除画布。