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POHow to perform Undo and Redo operation on canvas in android
 

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  1. POHow to perform Undo and Redo operation on canvas in android
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    <p>How can I perform the Undo/Redo operation on canvas . And my code is blow and i am not performing the these two operation .In the main class paint is performing by this reason am not perform the undo redo operation.</p> <pre><code>public class MainActivity extends Activity implements OnClickListener{ MyView mView; private Path mPath; Button btnUndo,btnRedo; FrameLayout frmLayout; private Paint mPaint; private MaskFilter mEmboss; Bitmap mBitmap; int bckcolor=0xffffffff; final Context context = this; ArrayList&lt;Path&gt; paths = new ArrayList&lt;Path&gt;(); ArrayList&lt;Path&gt; undonePaths = new ArrayList&lt;Path&gt;(); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mView = new MyView(this); setContentView(R.layout.activity_main); btnUndo=(Button)findViewById(R.id.Undo); btnRedo=(Button)findViewById(R.id.Redo); btnUndo.setOnClickListener(this); btnRedo.setOnClickListener(this); frmLayout=(FrameLayout)findViewById(R.id.frameLayout); frmLayout.addView(mView,LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT); mPaint = new Paint(); mPath=new Path(); mPaint.setAntiAlias(true); mPaint.setDither(true); mPaint.setColor(0xFF000000); mPaint.setStyle(Paint.Style.STROKE); mPaint.setStrokeJoin(Paint.Join.ROUND); mPaint.setStrokeCap(Paint.Cap.ROUND); mPaint.setStrokeWidth(5); new Canvas(); paths.add(mPath); mEmboss = new EmbossMaskFilter(new float[] { 1, 1, 1 },0.4f, 6, 3.5f); new BlurMaskFilter(8, BlurMaskFilter.Blur.NORMAL); } @Override public void onClick(View v) { // TODO Auto-generated method stub switch (v.getId()) { case R.id.Undo: if (paths.size()&gt;0) { undonePaths.add(paths.remove(paths.size()-1)); mView.invalidate(); Toast.makeText(getApplicationContext(), "Undo", 1000).show(); } mView.undo(); break; case R.id.Redo: mView.redo(); break; default: break; } } public class MyView extends View { private float posX = 105; private float posY = 105; Mode mode; private Bitmap mBitmap; private Canvas mCanvas; private Path mPath; private Paint mBitmapPaint; ArrayList&lt;Path&gt; paths = new ArrayList&lt;Path&gt;(); ArrayList&lt;Path&gt; undonePaths = new ArrayList&lt;Path&gt;(); BlurMaskFilter blurMaskFilter = new BlurMaskFilter(10, BlurMaskFilter.Blur.OUTER); int screenWidth; int screenHeight; /** */ public MyView(Context c) { super(c); mBitmap=BitmapFactory.decodeResource(getResources(), R.drawable.e); mBitmap = Bitmap.createBitmap(800, 800, Bitmap.Config.ARGB_8888); mCanvas = new Canvas(mBitmap); mPath = new Path(); mBitmapPaint = new Paint(Paint.DITHER_FLAG); mCanvas.drawColor(0xFFFFFFFF); paths.add(mPath); } public void redo() { // TODO Auto-generated method stub if (undonePaths.size()&gt;0) { paths.add(undonePaths.remove(undonePaths.size()-1)); invalidate(); } else { } } public void undo() { // TODO Auto-generated method stub Toast.makeText(getApplicationContext(), "Hello", 1000).show(); if (paths.size()&gt;0) { undonePaths.add(paths.remove(paths.size()-1)); mView.invalidate(); Toast.makeText(getApplicationContext(), "Undo", 1000).show(); } else { Toast.makeText(getApplicationContext(), "Not", 1000).show(); } } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); } /** */ @Override protected void onDraw(Canvas canvas) { canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint); for(Path p:paths) { canvas.drawPath(p, 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 &gt;= TOUCH_TOLERANCE || dy &gt;= TOUCH_TOLERANCE) { mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2); mX = x; mY = y; } } private void touch_up() { mPath.lineTo(mX, mY); mCanvas.drawPath(mPath, mPaint); paths.add(mPath); 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; } public void drawImage (int resourceId) { Bitmap _scratch = BitmapFactory.decodeResource(getResources(), resourceId); mCanvas.drawBitmap(_scratch, 0, 0, null); } } } </code></pre>
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