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  1. PO
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    <p>I am not sure if this is the best way for undo and redo. However the below worked on my device (Samsung galaxy s3). The Draw seems to be fast and the undo works fine. I do think the below can be modified to further enhance performance.</p> <pre><code>public class MainActivity extends Activity { MyView mv; LinearLayout ll; private ArrayList&lt;Path&gt; undonePaths = new ArrayList&lt;Path&gt;(); private ArrayList&lt;Path&gt; paths = new ArrayList&lt;Path&gt;(); Button b; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mv= new MyView(this); mv.setDrawingCacheEnabled(true); ll= (LinearLayout) findViewById(R.id.ll); ll.addView(mv); b= (Button) findViewById(R.id.button1); b.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub if (paths.size() &gt; 0) { undonePaths.add(paths .remove(paths.size()-2)); mv.invalidate(); } } }); } public class MyView extends View implements OnTouchListener { private Canvas mCanvas; private Path mPath; private Paint mPaint; // private ArrayList&lt;Path&gt; undonePaths = new ArrayList&lt;Path&gt;(); private float xleft, xright, xtop, xbottom; public MyView(Context context) { super(context); setFocusable(true); setFocusableInTouchMode(true); this.setOnTouchListener(this); mPaint = new Paint(); mPaint.setAntiAlias(true); mPaint.setColor(Color.RED); mPaint.setStyle(Paint.Style.STROKE); mPaint.setStrokeJoin(Paint.Join.ROUND); mPaint.setStrokeCap(Paint.Cap.ROUND); mPaint.setStrokeWidth(6); mCanvas = new Canvas(); mPath = new Path(); paths.add(mPath); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); } @Override protected void onDraw(Canvas canvas) { for (Path p : paths) { canvas.drawPath(p, mPaint); } } private float mX, mY; private static final float TOUCH_TOLERANCE = 0; 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); // commit the path to our offscreen mCanvas.drawPath(mPath, mPaint); // kill this so we don't double draw mPath = new Path(); paths.add(mPath); } @Override public boolean onTouch(View arg0, 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; } } } </code></pre> <p>activity_main.xml</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" &gt; &lt;LinearLayout android:id="@+id/ll" android:layout_width="match_parent" android:layout_height="fill_parent" android:layout_weight="1" android:orientation="vertical" &gt; &lt;/LinearLayout&gt; &lt;Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:text="Undo" /&gt; &lt;/LinearLayout&gt; </code></pre>
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    1. POAndroid Drawing View is very slow
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      1. PTQuestion
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    1. USRaghunandan
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    1. COThis is still has the same performance problem described in my question. But thanks anyways.
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      1. USAmjad Abu Saa
    2. CO@AmjadAbuSaa on what device do you test?
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      1. USRaghunandan
    3. COS3, Note 10.1, and the emulator S3 is the fastest as you stated, but still we should consider slower devices while making apps, shouldn't we?
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      1. USAmjad Abu Saa
 

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