Develop Reference

How to pass a list of custom object through the method View.onSaveInstanceState()?

I have searched the, "custom object passing" issue all over the Internet. There are several solutions but they are all using an Intent to communicate. With Intent, there are methods to facilitate that but what about the method public Parcelable View.onSaveInstanceState()
So, my requirement is saving the state of the view and because it is a custom view, I cannot save the state in the fragment. Rather, I have to override the methods View.onSaveInstanceState() and View.onRestoreInstanceState().
These methods work with Parcelable. I have a view called, BoxDrawingView and a Box class that is contained inside the view.
One more thing - I have tried to Parcelize the Box class.
import android.graphics.PointF;
import android.os.Bundle;
import android.os.Parcel;
import android.os.Parcelable;
/**
* Created by Manish Sharma on 9/6/2016.
*/
public class Box implements Parcelable{
private PointF mOrigin;
private PointF mCurrent;
public Box(PointF origin) {
mOrigin = origin;
mCurrent = origin;
}
public PointF getCurrent() {
return mCurrent;
}
public void setCurrent(PointF current) {
mCurrent = current;
}
public PointF getOrigin() {
return mOrigin;
}
#Override
public int describeContents() {
return 0;
}
public static final Parcelable.Creator<Box> CREATOR
= new Parcelable.Creator<Box>() {
public Box createFromParcel(Parcel in) {
return new Box(in);
}
public Box[] newArray(int size) {
return new Box[size];
}
};
private Box(Parcel in) {
mOrigin = (PointF)in.readValue(ClassLoader.getSystemClassLoader());
mCurrent = (PointF)in.readValue(ClassLoader.getSystemClassLoader());
}
#Override
public void writeToParcel(Parcel out, int flags) {
out.writeValue(mOrigin);
out.writeValue(mCurrent);
}
}
Now, here is the custom view that is supposed to call those 2 lifecycle methods for saving the state:
package com.example.manishsharma.draganddraw;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PointF;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Manish Sharma on 9/5/2016.
*/
public class BoxDrawingView extends View {
private static final String TAG = "BoxDrawingView";
private Box mCurrentBox;
private List<Box> mBoxen = new ArrayList<>();
private Paint mBoxPaint;
private Paint mBackgroundPaint;
// Used when creating the view in code
public BoxDrawingView(Context context) {
this(context, null);
}
// Used when inflating the view from XML
public BoxDrawingView(Context context, AttributeSet attrs) {
super(context, attrs);
// Paint the boxes a nice semitransparent red (ARGB)
mBoxPaint = new Paint();
mBoxPaint.setColor(0x22ff0000);
// Paint the background off-white
mBackgroundPaint = new Paint();
mBackgroundPaint.setColor(0xfff8efe0);
}
#Override
protected void onDraw(Canvas canvas) {
// Fill the background
canvas.drawPaint(mBackgroundPaint);
for (Box box : mBoxen) {
float left = Math.min(box.getOrigin().x, box.getCurrent().x);
float right = Math.max(box.getOrigin().x, box.getCurrent().x);
float top = Math.min(box.getOrigin().y, box.getCurrent().y);
float bottom = Math.max(box.getOrigin().y, box.getCurrent().y);
canvas.drawRect(left, top, right, bottom, mBoxPaint);
}
}
#Override
public boolean onTouchEvent(MotionEvent event) {
PointF current = new PointF(event.getX(), event.getY());
String action = "";
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
action = "ACTION_DOWN";
// Reset drawing state
mCurrentBox = new Box(current);
mBoxen.add(mCurrentBox);
break;
case MotionEvent.ACTION_MOVE:
action = "ACTION_MOVE";
if (mCurrentBox != null) {
mCurrentBox.setCurrent(current);
invalidate();
}
break;
case MotionEvent.ACTION_UP:
action = "ACTION_UP";
mCurrentBox = null;
break;
case MotionEvent.ACTION_CANCEL:
action = "ACTION_CANCEL";
mCurrentBox = null;
break;
}
Log.i(TAG, action + " at x=" + current.x +
", y=" + current.y);
return true;
}
#Override
public Parcelable onSaveInstanceState(){
super.onSaveInstanceState();
//How do I proceed here?
}
}
So finally I have: An arraylist of Parcelable objects that I want to save. How do I do that?
P.S: If I use the method Bundle.putParcelableArrayList(String key, ArrayList<? extends Parcelable> value), it doesn't work because the Box class implements the Parcelable interface not extend it.

save state
#Override
public Parcelable onSaveInstanceState(){
Parcelable superState = super.onSaveInstanceState();
Bundle bundle = new Bundle();
bundle.putParcelable("super", superState);
bundle.putParcelableArrayList("list", mBoxen);
return bundle;
}
and restore
#Override
protected void onRestoreInstanceState(Parcelable state) {
if (state instanceof Bundle) {
super.onRestoreInstanceState(((Bundle) state).getParcelable("super"));
mBoxen = ((Bundle) state).getParcelableArrayList("list");
} else {
super.onRestoreInstanceState(state);
}
}
this should work.
what is the problem with bundle.putParcelableArrayList("list", mBoxen);?

I think you should use:
#Override
protected void onSaveInstanceState(Bundle outState) {}
and putExtra into outState bundle.

pick image from gallery error when setDrawable

I have a null pointer exception when i load an image in my imageview. I have searched in so many topic but i not found a solution. I don't know why this won't work :/ Ahm another small bug, before i made an Imageview parameter in the class i try to use something like ImageView profilPicture = (ImageView) findViewById(R.id.profil_picture); but this produce an "error" android studio tell me to create the method...
So there is the error code :
Caused by: java.lang.NullPointerException
at android.graphics.BitmapShader.<init>(BitmapShader.java:40)
at god.repertoire.RoundImage.<init>(RoundImage.java:30)
at god.repertoire.FragmentNoContact.onActivityResult(FragmentNoContact.java:83)
There is the code of my Fragment :
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
public class FragmentNoContact extends Fragment {
private static int RESULT_LOAD_IMG = 1;
ImageView profilPicture;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// GET FRAGMENT COMPONENT
View myView = inflater.inflate(R.layout.activity_no_contact, container, false);
FloatingActionButton addContact = (FloatingActionButton) myView.findViewById(R.id.button_add);
profilPicture = (ImageView) myView.findViewById(R.id.profil_picture);
// INIT PHOTO DE PROFIL
Bitmap img = SaveLoad.loadFromFile("profil_picture.jpg");
if (img == null)
img = BitmapFactory.decodeResource(getResources(), R.drawable.blank_profile);
RoundImage roundedImage = new RoundImage(img);
profilPicture.setImageDrawable(roundedImage);
// EVENT AU CLIC PHOTO
profilPicture.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent galleryIntent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(galleryIntent, RESULT_LOAD_IMG);
/* an example i used before to test if i can set an another image
ImageView profilPicture = (ImageView) v.findViewById(R.id.profil_picture);
Bitmap img = BitmapFactory.decodeResource(getResources(), R.drawable.me);
RoundImage roundedImage = new RoundImage(img);
profilPicture.setImageDrawable(roundedImage);
*/
}
});
// ACTION BOUTON AJOUTER CONTACT
addContact.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
FragmentAddContact fragment2 = new FragmentAddContact();
transaction.add(R.id.myFrameLayout, fragment2);
transaction.addToBackStack("FragmentAddContact");
transaction.commit();
}
});
return myView;
}
// EVENT IMAGE SELECTED
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == RESULT_LOAD_IMG && resultCode == Activity.RESULT_OK) {
Uri selectedImage = data.getData();
BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 4;//returning null for below statement
Bitmap img = BitmapFactory.decodeFile(selectedImage.toString(), options);
RoundImage roundedImage = new RoundImage(img);
profilPicture.setImageDrawable(roundedImage);
}
}
}
There is the code of the RoundImage class (it's a class to generate a crop circle image in an imageView) :
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.Shader;
import android.graphics.drawable.Drawable;
public class RoundImage extends Drawable {
private final Bitmap mBitmap;
private final Paint mPaint;
private final RectF mRectF;
private final int mBitmapWidth;
private final int mBitmapHeight;
public RoundImage(Bitmap bitmap) {
mBitmap = bitmap;
mRectF = new RectF();
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
final BitmapShader shader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
mPaint.setShader(shader);
mBitmapWidth = mBitmap.getWidth();
mBitmapHeight = mBitmap.getHeight();
}
#Override
public void draw(Canvas canvas) {
canvas.drawOval(mRectF, mPaint);
}
#Override
protected void onBoundsChange(Rect bounds) {
super.onBoundsChange(bounds);
mRectF.set(bounds);
}
#Override
public void setAlpha(int alpha) {
if (mPaint.getAlpha() != alpha) {
mPaint.setAlpha(alpha);
invalidateSelf();
}
}
#Override
public void setColorFilter(ColorFilter cf) {
mPaint.setColorFilter(cf);
}
#Override
public int getOpacity() {
return PixelFormat.TRANSLUCENT;
}
#Override
public int getIntrinsicWidth() {
return mBitmapWidth;
}
#Override
public int getIntrinsicHeight() {
return mBitmapHeight;
}
public void setAntiAlias(boolean aa) {
mPaint.setAntiAlias(aa);
invalidateSelf();
}
#Override
public void setFilterBitmap(boolean filter) {
mPaint.setFilterBitmap(filter);
invalidateSelf();
}
#Override
public void setDither(boolean dither) {
mPaint.setDither(dither);
invalidateSelf();
}
public Bitmap getBitmap() {
return mBitmap;
}
}
And finaly, there is the code xml to create the imageview :
<ImageView
android:id="#+id/profil_picture"
android:layout_width="128dp"
android:layout_height="128dp"
android:scaleType="centerCrop"/>

Try this it may help you.
int id3 = getResources().getIdentifier("com.example.admin:mipmap/status" , null, null);
((ImageView) findViewById(R.id.imageviewstatus)).setImageResource(id3);

Manipulating variables in an activity with a method in another class

I am working on a game and have run into some issues. My architecture is something like this:
class GameView is used to draw bitmaps on my surfaces
class GameLoopThread is used to implement my game loop (if it wasn't obvious...)
class MovementUtils is used to hold all of my utilities related to moving objects
I want to house methods like gravity and movement controls in MovementUtils, but I'm having trouble actually updating the values in GameView. I tried using an intent, to no avail. I'll post my code, and maybe someone can show me what I should do. Also, ignore the Accelerometer lines, that's another problem entirely...
GameView.java
package com.example.connorgame;
import java.util.EventObject;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceHolder.Callback;
import android.view.SurfaceView;
public class GameView extends SurfaceView {
private Bitmap platform;
private Bitmap character;
private Bitmap background;
private SurfaceHolder holder;
private GameLoopThread gameLoopThread;
private MainActivity mainactivity;
private MovementUtils moveutil;
public float charX = 0;
public float charY = 0;
private boolean isFalling = true;
private boolean isJumping = false;
private float initialJumpY = 0;
private int initialFrame;
private int currentFrame;
private int frameDifference;
public GameView(Context context) {
super(context);
gameLoopThread = new GameLoopThread(this);
mainactivity = (MainActivity) context;
moveutil = new MovementUtils();
holder = getHolder();
holder.addCallback(new Callback() {
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
gameLoopThread.setRunning(true);
gameLoopThread.start();
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
}
});
platform = BitmapFactory.decodeResource(getResources(), R.drawable.platform);
character = BitmapFactory.decodeResource(getResources(), R.drawable.character);
background = BitmapFactory.decodeResource(getResources(), R.drawable.background);
}
#Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.BLACK);
canvas.drawBitmap(background, 0, 0, null);
canvas.drawBitmap(platform, 30, 700, null);
canvas.drawBitmap(character, charX, charY, null);
moveutil.gravity(charY, isFalling);
if (charY > getHeight() - character.getHeight()) {
initialFrame = gameLoopThread.numFrames;
initialJumpY = charY;
isFalling = false;
isJumping = true;
}
if (isJumping == true && isFalling == false) {
currentFrame = gameLoopThread.numFrames;
frameDifference = (currentFrame - initialFrame);
charY = charY - 5;
if (charY == initialJumpY - 100) {
isJumping = false;
isFalling = true;
}
}
}
}
MovementUtils.java
package com.example.connorgame;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
public class MovementUtils {
public void gravity (float charY, boolean isFalling) {
if(isFalling == true){
charY = charY + 5;
}
}
}

If I understand what you're doing correctly, you're trying to have charY in the GameView class modified by the gravity function. The issue is that float is a primitive, so it is based by value and only the local copy will be modified. If you passed an object instead, the object would be modified.
One solution is probably to just return the new Y position instead of trying to make gravity() change the Y position.
Another solution is to pass the GameView to MovementUtils and let MovementUtils modify it.
In other words, you would pass the GameView like this new MovementUtils(this);
And the gravity function would call a void setCharY(int y); in GameView.
public class MovementUtils {
private GameView gameView;
public MovementUtils(GameView view) {
this.gameView = view;
}
public void gravity (float charY, boolean isFalling) {
if(isFalling == true){
charY = charY + 5;
gameView.setCharY(charY);
}
}
}

Java only supports passing by value
So when you call moveutil.gravity(charY, isFalling);
and change it within the function, e.g.
public void gravity (float charY, boolean isFalling) {
if(isFalling == true){
charY = charY + 5;
}
Such change only occur in the local copy of the variable charY and does not affect the instance variable charY defined in your GameView class
To solve this, you can define your variables as objects as well as the argument to your functions, e.g.
public void gravity (Float charY, boolean isFalling) {}
And in your GameView class:
private Float charX = 0; // why you define them public !?
private Float charY = 0;
Alternatively, you can pass an instance of your GameView class or create a ValueObject class (similar to Context object in android) and use it to pass arguments

How to clear canvas in a surface view?

I am developing an Android Digital signature app in which user can sign and i have to save this file as image.i am using SurfaceView for drawing. DigitalSignatureActivity has two Buttons Save,Clear.
1.Save Button to save file as image
2.Clear Button to clear surface.
But i am unable to clear the surface.i tried drawingSurface.setBackgroundColor(Color.BLACK); still previous sign is retained and canvas.drawColor(Color.BLACK); has no effect and
i am able to save file but its not storing signature perfectly(Some contents are missing) please help.
My code is:
DigitalSignatureActivity.java
package com.pop.digitalsign;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Bundle;
import android.os.Environment;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;
public class DigitalSignatureActivity extends Activity implements
View.OnTouchListener {
private DrawingSurface drawingSurface;
private DrawingPath currentDrawingPath;
private Paint currentPaint;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setCurrentPaint();
drawingSurface = (DrawingSurface) findViewById(R.id.drawingSurface);
drawingSurface.setOnTouchListener(this);
}
private void setCurrentPaint() {
currentPaint = new Paint();
currentPaint.setDither(true);
currentPaint.setColor(Color.WHITE);
currentPaint.setStyle(Paint.Style.STROKE);
currentPaint.setStrokeJoin(Paint.Join.ROUND);
currentPaint.setStrokeCap(Paint.Cap.ROUND);
currentPaint.setStrokeWidth(2);
}
public boolean onTouch(View view, MotionEvent motionEvent) {
if (motionEvent.getAction() == MotionEvent.ACTION_DOWN) {
drawingSurface.setBackgroundColor(0);
currentDrawingPath = new DrawingPath();
currentDrawingPath.paint = currentPaint;
currentDrawingPath.path = new Path();
currentDrawingPath.path.moveTo(motionEvent.getX(),
motionEvent.getY());
currentDrawingPath.path.lineTo(motionEvent.getX(),
motionEvent.getY());
} else if (motionEvent.getAction() == MotionEvent.ACTION_MOVE) {
currentDrawingPath.path.lineTo(motionEvent.getX(),motionEvent.getY());
drawingSurface.addDrawingPath(currentDrawingPath);
} else if (motionEvent.getAction() == MotionEvent.ACTION_UP) {
currentDrawingPath.path.lineTo(motionEvent.getX(),motionEvent.getY());
}
return true;
}
//To save file as Image
public void saveDrawing(View v) throws IOException {
File mediaStorageDir = new File(
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
"MySignatures");
Bitmap nBitmap = drawingSurface.getBitmap();
try {
if (!mediaStorageDir.exists()) {
mediaStorageDir.mkdirs();
}
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss")
.format(new Date());
File mediaFile = new File(mediaStorageDir.getPath()
+ File.separator + "SIGN_" + timeStamp + ".png");
FileOutputStream out = new FileOutputStream(mediaFile);
nBitmap.compress(Bitmap.CompressFormat.PNG, 90, out);
out.flush();
out.close();
Toast.makeText(this, "Signature saved to " + mediaFile,
Toast.LENGTH_LONG).show();
} catch (Exception e) {
e.printStackTrace();
Toast.makeText(getApplicationContext(), "Not saved",
Toast.LENGTH_SHORT).show();
}
}
//To clear Surface
public void clearScreen(View v) {
//drawingSurface.setBackgroundColor(Color.BLACK);
drawingSurface.clear();
}
}
DrawingSurface.java
package com.pop.digitalsign;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.PorterDuff;
import android.util.AttributeSet;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class DrawingSurface extends SurfaceView implements SurfaceHolder.Callback {
private Boolean _run;
protected DrawThread thread;
private Bitmap mBitmap;
Canvas canvas;
private CommandManager commandManager;
public DrawingSurface(Context context, AttributeSet attrs) {
super(context, attrs);
getHolder().addCallback(this);
commandManager = new CommandManager();
thread = new DrawThread(getHolder());
}
class DrawThread extends Thread{
public SurfaceHolder mSurfaceHolder;
public DrawThread(SurfaceHolder surfaceHolder){
mSurfaceHolder = surfaceHolder;
}
public DrawThread() {
// TODO Auto-generated constructor stub
}
public void setRunning(boolean run) {
_run = run;
}
#Override
public void run() {
canvas = null;
while (_run){
try{
canvas = mSurfaceHolder.lockCanvas(null);
//canvas.drawColor(Color.WHITE);
if(mBitmap == null){
mBitmap = Bitmap.createBitmap (1, 1, Bitmap.Config.ARGB_8888);;
}
final Canvas c = new Canvas (mBitmap);
c.drawColor(0, PorterDuff.Mode.CLEAR);
commandManager.executeAll(c);
canvas.drawBitmap (mBitmap, 0, 0,null);
} finally {
if(canvas!=null){
mSurfaceHolder.unlockCanvasAndPost(canvas);
}
}
}
}
}
public void addDrawingPath (DrawingPath drawingPath){
commandManager.addCommand(drawingPath);
}
public void clear(){
//Here i want to clear surface
canvas.drawColor(Color.BLACK);//it has no effect
}
public boolean hasMoreUndo(){
return commandManager.hasMoreUndo();
}
public Bitmap getBitmap(){
return mBitmap;
}
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
mBitmap = Bitmap.createBitmap (width, height, Bitmap.Config.ARGB_8888);;
}
public void surfaceCreated(SurfaceHolder holder) {
thread.setRunning(true);
thread.start();
}
public void surfaceDestroyed(SurfaceHolder holder) {
boolean retry = true;
thread.setRunning(false);
while (retry) {
try {
thread.join();
retry = false;
} catch (InterruptedException e) {
}
}
}
}
CommandManager.java
package com.pop.digitalsign;
import android.graphics.Canvas;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;
import java.util.ArrayList;
public class CommandManager {
private List<DrawingPath> currentStack;
public CommandManager(){
currentStack = Collections.synchronizedList(new ArrayList<DrawingPath>());
}
public void addCommand(DrawingPath command){
currentStack.add(command);
}
public void undo (){
final int length = currentStackLength();
if ( length > 0) {
final DrawingPath undoCommand = currentStack.get( length - 1 );
currentStack.remove( length - 1 );
undoCommand.undo();
}
}
public int currentStackLength(){
final int length = currentStack.toArray().length;
return length;
}
public void executeAll( Canvas canvas){
if( currentStack != null ){
synchronized( currentStack ) {
final Iterator<?> i = currentStack.iterator();
while ( i.hasNext() ){
final DrawingPath drawingPath = (DrawingPath) i.next();
drawingPath.draw( canvas );
}
}
}
}
public boolean hasMoreUndo(){
return currentStack.toArray().length > 0;
}
}
DrawingPath.java
package com.pop.digitalsign;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
public class DrawingPath {
public Path path;
public Paint paint;
public void draw(Canvas canvas) {
canvas.drawPath( path, paint );
}
public void undo() {
}
}
main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:background="#android:color/white" >
<com.pop.digitalsign.DrawingSurface
android:id="#+id/drawingSurface"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="center" >
<Button
android:id="#+id/saveBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="saveDrawing"
android:text="#string/save" />
<Button
android:id="#+id/clearBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="clearScreen"
android:text="#string/clear" />
</LinearLayout>
</RelativeLayout>

the best suggestion i have is to use this
if (surfaceHolder.getSurface().isValid()) {
Canvas c = surfaceHolder.lockCanvas();
if (first >= 0) {
c.drawARGB(255, 255, 255, 255);
first--;
}
The value of first is 2 you can use what every name you want.
The reason is that the canvas is double buffered so you need to clear both screen by painting it white.
This stops the flickering

canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR)

In DrawingSurface add this method
public void resetCanvas(){ commandManager.clearAllPath(); }
and call this method, when you need to action for clear..
objectNameofDrawingSurefaceClass.resetCanvas();
add the code in CommandManager
public void clearAllPath(){currentStack.clear(); }
ok..

Limit to number of touches on Android?

I have a small test app on Android that is meant to test tracking multitouch input, but I am only ever getting two touches at the same time on my Evo. Does anyone know if this is a limitation to Android or the hardware?
By the way, here's my test class so you can try it out yourself.
import java.util.HashMap;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.view.MotionEvent;
import android.view.View;
public class PressureView extends View
{
private HashMap<Integer, Spot> mSpots = new HashMap<Integer, Spot>();
private final int[] mColors;
private final Paint mPaint;
public PressureView(Context context)
{
super(context);
mPaint = new Paint();
mPaint.setStyle(Style.FILL);
mColors = new int[]{Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW, Color.MAGENTA};
}
#Override
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
canvas.drawColor(Color.WHITE);
for(int id : mSpots.keySet())
{
Spot spot = mSpots.get(id);
mPaint.setColor(spot.Color);
canvas.drawCircle(spot.X, spot.Y, spot.Pressure*500, mPaint);
}
}
#Override
public boolean onTouchEvent(MotionEvent event)
{
System.out.println("************************** " + event.getPointerCount() + " Pointers");
for(int i = 0; i < event.getPointerCount(); i++)
{
int id = event.getPointerId(i);
Spot spot = null;
if(mSpots.containsKey(id))
{
spot = mSpots.get(id);
}
else
{
spot = new Spot();
spot.Color = mColors[mSpots.size()];
}
if(event.getAction() == MotionEvent.ACTION_UP) spot.Pressure = 0;
else spot.Pressure = event.getPressure(id);
spot.X = event.getX(id);
spot.Y = event.getY(id);
mSpots.put(id, spot);
}
invalidate();
return true;
}
private class Spot
{
public float X, Y, Pressure;
public int Color;
}
}

It seems that currently all HTC devices only can 2 finger multi-touch, but the Android SDK supports more fingers. E.g. the Galaxy S i9000 has support for more http://www.youtube.com/watch?v=KRCDRXYJBCY .