用于笔按钮
int black = color.BLACK; mDrawPaint = new DrawPaint(Capture.this,null,black);
DrawPaint扩展VIEw的位置
现在创建橡皮擦我刚刚将笔颜色改为白色,这是画布的背景颜色.像这样
用于橡皮擦按钮
int white = color.WHITE; mDrawPaint = new DrawPaint(Capture.this,white);
但是,如果我选择笔颜色为黑色并在画布上绘制某些东西的笔按钮,它会再次自动重绘之前我在绘制之前绘制的颜色.橡皮擦也擦除了一个大的矩形区域.请解释我出了什么问题.谢谢.
这是DrawPaint构造函数
public DrawPaint(Context context,AttributeSet attrs,int color) { super(context,attrs); this.destroyDrawingCache(); paint.setAntiAlias(true); paint.setcolor(color); paint.setStyle(Paint.Style.stroke); paint.setstrokeJoin(Paint.Join.ROUND); paint.setstrokeWIDth(stroke_WIDTH);} public boolean ontouchEvent(MotionEvent event) { eventX = event.getX(); eventY = event.getY(); button1.setEnabled(true); switch (event.getAction()) { case MotionEvent.ACTION_DOWN: path.moveto(eventX,eventY); lasttouchX = eventX; lasttouchY = eventY; return true; case MotionEvent.ACTION_MOVE: case MotionEvent.ACTION_UP: 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; 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; }解决方法 对于橡皮擦,您可以使用此代码… mPaint.setMaskFilter(null);mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
关于那个方形颜色问题……
看一下这个..
这是画布绘制的最佳示例,具有擦除,模糊和浮雕效果……
public class FingerText extends Activity implements colorPickerDialog.OncolorChangedListener { @OverrIDeprotected voID onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentVIEw(new MyVIEw(this)); mPaint = new Paint(); mPaint.setAntiAlias(true); mPaint.setDither(true); //this is the line that sets the initial pen color mPaint.setcolor(inkcolor); mPaint.setStyle(Paint.Style.stroke); mPaint.setstrokeJoin(Paint.Join.ROUND); mPaint.setstrokeCap(Paint.Cap.ROUND); mPaint.setstrokeWIDth(2);}private Paint mPaint;private Bitmap mBitmap;private boolean inkChosen;private int bgcolor = 0xFFFFFFFF; //set initial bg color var to whiteprivate int inkcolor = 0xFF000000; //set initial ink color var to blackpublic voID colorChanged(int color) { //This is the implementation of the interface from colorpickerdialog.java if (inkChosen){ mPaint.setcolor(color); inkcolor = color; } else { mBitmap.erasecolor (color); bgcolor = color; //set the color to the user's last ink color choice mPaint.setcolor(inkcolor); }}public class MyVIEw extends VIEw { private Canvas mCanvas; private Path mPath; private Paint mBitmapPaint; public MyVIEw(Context c) { super(c); mBitmap = Bitmap.createBitmap(320,480,Bitmap.Config.ARGB_8888); //this sets the bg color for the bitmap mBitmap.erasecolor (bgcolor); mCanvas = new Canvas(mBitmap); mPath = new Path(); mBitmapPaint = new Paint(Paint.DITHER_FLAG); } @OverrIDe protected voID onSizeChanged(int w,int h,int olDW,int oldh) { super.onSizeChanged(w,h,olDW,oldh); } @OverrIDe protected voID onDraw(Canvas canvas) { //this is the line that changes the bg color in the initial canvas canvas.drawcolor(bgcolor); canvas.drawBitmap(mBitmap,mBitmapPaint); canvas.drawPath(mPath,mPaint); } private float mX,mY; private static final float touch_TolERANCE = 4; private voID touch_start(float x,float y) { mPath.reset(); mPath.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) { mPath.quadTo(mX,mY,(x + mX)/2,(y + mY)/2); mX = x; mY = y; } } private voID touch_up() { mPath.lineto(mX,mY); // commit the path to our offscreen mCanvas.drawPath(mPath,mPaint); // kill this so we don't double draw mPath.reset(); } @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 static final int BG_color_ID = Menu.FirsT;private static final int INK_MENU_ID = Menu.FirsT + 1;private static final int CLEAR_MENU_ID = Menu.FirsT + 2;private static final int ERASER_MENU_ID = Menu.FirsT + 3;private static final int SEND_MENU_ID = Menu.FirsT + 4;@OverrIDepublic boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu); menu.add(0,BG_color_ID,"Background color").setShortcut('3','b'); menu.add(0,INK_MENU_ID,"Ink color").setShortcut('4','c'); menu.add(0,CLEAR_MENU_ID,"Clear All").setShortcut('5','e'); menu.add(0,ERASER_MENU_ID,"Eraser").setShortcut('6','x'); menu.add(0,SEND_MENU_ID,"Send").setShortcut('7','s'); /**** Is this the mechanism to extend with filter effects? Intent intent = new Intent(null,getIntent().getData()); intent.addcategory(Intent.category_ALTERNATIVE); menu.addIntentoptions( Menu.ALTERNATIVE,new Componentname(this,NotesList.class),intent,null); *****/ return true;}@OverrIDepublic boolean onPrepareOptionsMenu(Menu menu) { super.onPrepareOptionsMenu(menu); return true;}@OverrIDepublic boolean onoptionsItemSelected(MenuItem item) { mPaint.setXfermode(null); mPaint.setAlpha(0xFF); switch (item.getItemID()) { case BG_color_ID: new colorPickerDialog(this,this,mPaint.getcolor()).show(); inkChosen = false; return true; case INK_MENU_ID: new colorPickerDialog(this,mPaint.getcolor()).show(); //remember the user's last ink choice color so we can revert after eraser //to background color change -- otherwise ink is last bg color inkcolor = mPaint.getcolor(); inkChosen = true; return true; case CLEAR_MENU_ID: mBitmap.erasecolor (bgcolor); return true; case ERASER_MENU_ID: //set pen color to bg color for 'erasing' mPaint.setcolor(bgcolor); return true; case SEND_MENU_ID: /* Todo need to decIDe whether to save image locally * and how to make it available if so. really only need to * save if we want to let users vIEw later,or pick a * prevIoUs message to send again */ // this try-catch block creates a private file and an // inputstream pointing to it for reading fileinputStream ifs; try { fileOutputStream fs = openfileOutput("message_image",Context.MODE_PRIVATE); mBitmap.compress(CompressFormat.PNG,100,fs); ifs = openfileinput("message_image"); } catch (fileNotFoundException e) { // Todo auto-generated catch block e.printstacktrace(); return true; } // inserts file pointed to by ifs into image gallery String url = Images.Media.insertimage(getContentResolver(),BitmapFactory.decodeStream(ifs),"Message image1","Message image"); // alternative: inserts mBitmap into image gallery/* String url = Images.Media.insertimage(getContentResolver(),mBitmap,"Message image");*/ // creates the Intent to open the messaging app // with the image at url attached Intent sendIntent = new Intent(Intent.ACTION_SEND); sendIntent.putExtra("sms_body","Message created using FingerText"); sendIntent.putExtra(Intent.EXTRA_STREAM,Uri.parse(url)); sendIntent.setType("image/png"); startActivity(sendIntent); /* Todo delete the image from the content provIDer * following line deletes the image,but too soon! */// getContentResolver().delete(Uri.parse(url),null); //this resets canvas after send //Could also reset to last user settings w/o var resets bgcolor = 0xFFFFFFFF; //set bg color var back to white inkcolor = 0xFF000000; //set ink color var back to black mBitmap.erasecolor (bgcolor); return true; } return super.onoptionsItemSelected(item);} }
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