All geek questions in one place

A finger draw line deletes a previously drawn image

I work with painting. when drawing a line, it is perfectly drawn. when I draw a new line, the previously drawn line is removed from the view, I do not know why this is happening. Does anyone know please help me.

public class DrawView extends View implements OnTouchListener {// custom view private Canvas mCanvas; private Path mPath; private ArrayList<Pair<Path, Paint>> paths = new ArrayList<Pair<Path, Paint>>(); private ArrayList<Pair<Path, Paint>> undonePaths = new ArrayList<Pair<Path, Paint>>(); public DrawView(Context context) { super(context); setFocusable(true); setFocusableInTouchMode(true); this.setOnTouchListener(this); mCanvas = new Canvas(); mPath = new Path(); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); //do as user want } @Override protected void onDraw(Canvas canvas) { //onDraw method //DRAWING LINE................................ linearray[0]=stupx; linearray[1]=stupy; linearray[2]=upx; linearray[3]=upy; canvas.drawLines(linearray, mPaint); Log.d("METHOD", "ONDRAW LINE FIRED "+stupx+" "+stupy+""+upx+" "+upy); } private float mX, mY; private static final float TOUCH_TOLERANCE = 4; private void touch_start(float x, float y) { undonePaths.clear(); 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 touchline() { // TODO Auto-generated method stub Log.d("METHOD", "TOUCHLINE FIRED "); mPath.lineTo(mX, mY); // commit the path to our offscreen mCanvas.drawPath(mPath, mPaint); // kill this so we don't double draw newShapePaint = new Paint(mPaint); // Clones the mPaint object paths.add(new Pair<Path, Paint>(mPath, newShapePaint)); Log.d("TOUCH UP", "METHOD FIRED WITHOUT COLOR CHANGE"+_color); mPath = new Path(); } }

// onTouch event

  @Override public boolean onTouch(View arg0, MotionEvent event) { x = event.getX(); y = event.getY(); upx=0f; upy=0f; switch (event.getAction()) { case MotionEvent.ACTION_DOWN: stupx=event.getX(); stupy=event.getY(); touch_start(x, y); invalidate(); break; case MotionEvent.ACTION_MOVE: touch_move(x, y); invalidate(); break; case MotionEvent.ACTION_UP: Log.d("method", "touch up fired"); upx=event.getX(); upy=event.getY(); touchline(); //call after remove finger invalidate(); break; } return true; } }
+4
source share
1 answer

When you call invalidate without any parameters, it invalidates the full screen (redraws the full rectangle of the screen), thereby deleting your previous line. Try calling invalidate with the appropriate parameter.

Below is the code for fingerPaint. I took this from apidemos :) (apidemos-graphics-fingerpaint):

 /* * Copyright (C) 2007 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.example.android.apis.graphics; import android.content.Context; import android.graphics.*; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import android.view.MotionEvent; import android.view.View; public class FingerPaint extends GraphicsActivity implements ColorPickerDialog.OnColorChangedListener { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(new MyView(this)); mPaint = new Paint(); mPaint.setAntiAlias(true); mPaint.setDither(true); mPaint.setColor(0xFFFF0000); mPaint.setStyle(Paint.Style.STROKE); mPaint.setStrokeJoin(Paint.Join.ROUND); mPaint.setStrokeCap(Paint.Cap.ROUND); mPaint.setStrokeWidth(12); mEmboss = new EmbossMaskFilter(new float[] { 1, 1, 1 }, 0.4f, 6, 3.5f); mBlur = new BlurMaskFilter(8, BlurMaskFilter.Blur.NORMAL); } private Paint mPaint; private MaskFilter mEmboss; private MaskFilter mBlur; public void colorChanged(int color) { mPaint.setColor(color); } public class MyView extends View { private static final float MINP = 0.25f; private static final float MAXP = 0.75f; private Bitmap mBitmap; private Canvas mCanvas; private Path mPath; private Paint mBitmapPaint; public MyView(Context c) { super(c); 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); mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888); mCanvas = new Canvas(mBitmap); } @Override protected void onDraw(Canvas canvas) { canvas.drawColor(0xFFAAAAAA); canvas.drawBitmap(mBitmap, 0, 0, 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 COLOR_MENU_ID = Menu.FIRST; private static final int EMBOSS_MENU_ID = Menu.FIRST + 1; private static final int BLUR_MENU_ID = Menu.FIRST + 2; private static final int ERASE_MENU_ID = Menu.FIRST + 3; private static final int SRCATOP_MENU_ID = Menu.FIRST + 4; @Override public boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu); menu.add(0, COLOR_MENU_ID, 0, "Color").setShortcut('3', 'c'); menu.add(0, EMBOSS_MENU_ID, 0, "Emboss").setShortcut('4', 's'); menu.add(0, BLUR_MENU_ID, 0, "Blur").setShortcut('5', 'z'); menu.add(0, ERASE_MENU_ID, 0, "Erase").setShortcut('5', 'z'); menu.add(0, SRCATOP_MENU_ID, 0, "SrcATop").setShortcut('5', 'z'); /**** 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, 0, new ComponentName(this, NotesList.class), null, intent, 0, null); *****/ return true; } @Override public boolean onPrepareOptionsMenu(Menu menu) { super.onPrepareOptionsMenu(menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { mPaint.setXfermode(null); mPaint.setAlpha(0xFF); switch (item.getItemId()) { case COLOR_MENU_ID: new ColorPickerDialog(this, this, mPaint.getColor()).show(); return true; case EMBOSS_MENU_ID: if (mPaint.getMaskFilter() != mEmboss) { mPaint.setMaskFilter(mEmboss); } else { mPaint.setMaskFilter(null); } return true; case BLUR_MENU_ID: if (mPaint.getMaskFilter() != mBlur) { mPaint.setMaskFilter(mBlur); } else { mPaint.setMaskFilter(null); } return true; case ERASE_MENU_ID: mPaint.setXfermode(new PorterDuffXfermode( PorterDuff.Mode.CLEAR)); return true; case SRCATOP_MENU_ID: mPaint.setXfermode(new PorterDuffXfermode( PorterDuff.Mode.SRC_ATOP)); mPaint.setAlpha(0x80); return true; } return super.onOptionsItemSelected(item); } }
0
source

Source: https://habr.com/ru/post/1497964/

More articles:


All Articles