Develop Reference

Android: unresponsive thread when a new activity for result is started

I am new to Android so I am making a coloring book app just to get myself acquainted to android programming. I have looked up my problem extensively and implemented the solutions but still no progress.
I have an activity 'ColoringActivity' which calls a class 'PaintView' which extends surfaceview. I am trying to update the canvas in a separate thread. I also have a button in the layout which takes the user to another activity for picking colors. The problem is that when the user returns after choosing the color, the canvas becomes empty and I cant draw on the canvas anymore. I think i somehow loose the thread in between activities and although the thread is running in the background, I have no access to it.
I read on this forum that I must implement pause() and resume() methods in the thread class and basically kill the thread when I go to another activity and restart it when I return. Also I read I have to override onPause() and onResume() method in activity class and construct the surfaceview in onResume() so that it is constructed every time user returns to this activity.
I am sorry if it doesnt make much sense because I am lost as well.
My 'ColoringActivity':
package com.ali.coloryourself;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;
public class ColoringActivity extends Activity {
private static final int COLOR_REQUEST_CODE = 100;
public static String file;
public static Bitmap bitmap;
BitmapFactory.Options options;
PaintView paintView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_draw);
Intent intent = getIntent();
file = intent.getStringExtra("fileName");
// paintView = (PaintView) findViewById(R.id.drawingSurface);
}
#Override
protected void onResume() {
paintView = (PaintView) findViewById(R.id.drawingSurface);
paintView.getThread().resume();
super.onResume();
}
#Override
protected void onPause() {
paintView.getThread().pause();
super.onPause();
}
public void pickColor(View v) {
paintView.getThread().pause();
Intent colorIntent = new Intent(this, ColorPickerActivity.class);
startActivityForResult(colorIntent, COLOR_REQUEST_CODE);
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode != RESULT_CANCELED) {
if (requestCode == COLOR_REQUEST_CODE) {
int color = data.getIntExtra("Color", -1);
// paintView.getPaint().setColor(color);
}
}
}
}
My 'PaintView' class:
package com.ali.coloryourself;
import android.R.color;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
class PaintView extends SurfaceView implements SurfaceHolder.Callback {
private Paint paint = new Paint();
private Canvas canvas;
private PaintThread thread;
private Path path = new Path();
private Bitmap bitmap;
public PaintView(Context context, AttributeSet attrs) {
super(context, attrs);
SurfaceHolder holder = getHolder();
holder.addCallback(this);
paint.setColor(Color.WHITE);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeCap(Paint.Cap.ROUND);
paint.setStrokeWidth(3);
setThread(new PaintThread(holder));
}
class PaintThread extends Thread {
private boolean mRun;
private SurfaceHolder mSurfaceHolder;
private int mMode;
public static final int STATE_PAUSE = 2;
public static final int STATE_RUNNING = 4;
public PaintThread(SurfaceHolder surfaceHolder) {
mSurfaceHolder = surfaceHolder;
}
#Override
public void run() {
while (mRun) {
try {
canvas = mSurfaceHolder.lockCanvas(null);
if (mMode == STATE_RUNNING) {
if (bitmap == null) {
bitmap = Bitmap.createBitmap(1, 1,
Bitmap.Config.ARGB_8888);
}
}
doDraw(canvas);
canvas.drawBitmap(bitmap, 0, 0, null);
} catch (Exception e) {
e.printStackTrace();
} finally {
if (canvas != null) {
mSurfaceHolder.unlockCanvasAndPost(canvas);
}
}
}
}
private void doDraw(Canvas canvas) {
canvas.drawPath(path, paint);
}
public void setRunning(boolean b) {
mRun = b;
}
public void pause() {
if (mMode == STATE_RUNNING)
setState(STATE_PAUSE);
}
public void resume() {
setState(STATE_RUNNING);
}
public void setState(int mode) {
synchronized (mSurfaceHolder) {
mMode = mode;
}
}
}
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
// Log.d("Touch", "I am touching");
float eventX = event.getX();
float eventY = event.getY();
int action = event.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
path.moveTo(eventX, eventY);
return true;
case MotionEvent.ACTION_MOVE:
path.lineTo(eventX, eventY);
break;
case MotionEvent.ACTION_UP:
// nothing to do
break;
default:
return false;
}
return true;
}
public void surfaceCreated(SurfaceHolder holder) {
if (getThread().getState() == Thread.State.NEW) {
getThread().setRunning(true);
getThread().start();
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
boolean retry = true;
getThread().setRunning(false);
getThread().resume();
while (retry) {
try {
getThread().join();
retry = false;
} catch (InterruptedException e) {
}
}
}
public Paint getPaint() {
return paint;
}
public void setPaint(int color) {
this.paint.setColor(color);
}
public PaintThread getThread() {
return thread;
}
public void setThread(PaintThread thread) {
this.thread = thread;
}
}
my 'activity_draw.xml'
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="10dp"
android:onClick="pickColor"
android:text="Pick Color" />
<com.ali.coloryourself.PaintView
android:id="#+id/drawingSurface"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#+id/button1"
android:layout_marginTop="10dp"/>
</RelativeLayout>
I know I am missing some very basic thread concept. I need to allow the user to pick color and return and be able to continue drawing. I will be extremely grateful for your help.

I think I have found an answer although I am not sure if it is a good programming practice. I found out that my surface view and thread were created once 'ColoringActivity' was created and destroyed every time 'ColoringActivity' went to background. But once 'ColoringActivity' was restarted and resumed, surface view and thread were not recreated. So i moved the following line
setContentView(R.layout.activity_draw);
to onResume() method and now I can draw on the canvas every time. Now I just need to save the canvas and re load it when the activity comes back on to start off the coloring where the user left it.

How to calculate direction and speed from roll and pitch (tilt)?

I'm learning Android programming.
So I managed to implement a simple app that rolls a ball over the screen if you tilt yout phone. But right now it is as simple as:
if roll > 0 then xpos++ else xpos-- end and the same for ypos.
So I want to calculate a more exact direction and also I would like the ball to roll faster the more the phone is tilting.
So if I know the tilt in the roll direction and the pitch direction, how do I calculate the direction and speed of the ball?

Here is how:
package benyamephrem.tiltball;
import android.graphics.Point;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import java.util.Timer;
import java.util.TimerTask;
import android.app.Activity;
import android.os.Handler;
import android.view.Display;
import android.view.Window;
import android.view.WindowManager.LayoutParams;
import android.widget.FrameLayout;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorManager;
import android.content.Context;
import android.content.res.Configuration;
import android.hardware.SensorEventListener;
import android.widget.Toast;
public class TiltBall extends ActionBarActivity {
BallView mBallView = null;
Handler RedrawHandler = new Handler(); //so redraw occurs in main thread
Timer mTmr = null;
TimerTask mTsk = null;
int mScrWidth, mScrHeight;
android.graphics.PointF mBallPos, mBallSpd;
#Override
protected void onCreate(Bundle savedInstanceState) {
requestWindowFeature(Window.FEATURE_NO_TITLE); //hide title bar
//set app to full screen and keep screen on
getWindow().setFlags(0xFFFFFFFF, LayoutParams.FLAG_FULLSCREEN | LayoutParams.FLAG_KEEP_SCREEN_ON);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tilt_ball);
//create pointer to main screen
final FrameLayout mainView = (android.widget.FrameLayout) findViewById(R.id.main_view);
//get screen dimensions
Display display = getWindowManager().getDefaultDisplay();
mScrWidth = display.getWidth();
mScrHeight = display.getHeight();
mBallPos = new android.graphics.PointF();
mBallSpd = new android.graphics.PointF();
//create variables for ball position and speed
mBallPos.x = mScrWidth / 2;
mBallPos.y = mScrHeight / 5;
mBallSpd.x = 0;
mBallSpd.y = 0;
//create initial ball
mBallView = new BallView(this, mBallPos.x, mBallPos.y, 75);
mainView.addView(mBallView); //add ball to main screen
mBallView.invalidate(); //call onDraw in BallView
//listener for accelerometer, use anonymous class for simplicity
((SensorManager) getSystemService(Context.SENSOR_SERVICE)).registerListener(
new SensorEventListener() {
#Override
public void onSensorChanged(SensorEvent event) {
//set ball speed based on phone tilt (ignore Z axis)
//***Change speed here by multiplying event values by bigger numbers***
mBallSpd.x = -event.values[0] * (30/10);
mBallSpd.y = event.values[1] * (30/10);
//timer event will redraw ball
}
#Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
} //ignore
},
((SensorManager) getSystemService(Context.SENSOR_SERVICE))
.getSensorList(Sensor.TYPE_ACCELEROMETER).get(0),
SensorManager.SENSOR_DELAY_NORMAL);
//listener for touch event
mainView.setOnTouchListener(new android.view.View.OnTouchListener() {
public boolean onTouch(android.view.View v, android.view.MotionEvent e) {
//set ball position based on screen touch
mBallPos.x = e.getX();
mBallPos.y = e.getY();
//timer event will redraw ball
return true;
}
});
} //OnCreate
//listener for menu button on phone
#Override
public boolean onCreateOptionsMenu(Menu menu) {
menu.add("Exit"); //only one menu item
return super.onCreateOptionsMenu(menu);
}
//listener for menu item clicked
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
if (item.getTitle() == "Exit") //user clicked Exit
finish(); //will call onPause
return super.onOptionsItemSelected(item);
}
//For state flow see http://developer.android.com/reference/android/app/Activity.html
#Override
public void onPause() //app moved to background, stop background threads
{
mTmr.cancel(); //kill\release timer (our only background thread)
mTmr = null;
mTsk = null;
super.onPause();
}
#Override
public void onResume() //app moved to foreground (also occurs at app startup)
{
//create timer to move ball to new position
mTmr = new Timer();
mTsk = new TimerTask() {
public void run() {
//if debugging with external device,
// a log cat viewer will be needed on the device
Log.d("TiltBall", "Timer Hit - " + mBallPos.x + ":" + mBallPos.y);
//move ball based on current speed
mBallPos.x += mBallSpd.x;
mBallPos.y += mBallSpd.y;
//if ball goes off screen, reposition to opposite side of screen
if (mBallPos.x > mScrWidth) mBallPos.x = 0;
if (mBallPos.y > mScrHeight) mBallPos.y = 0;
if (mBallPos.x < 0) mBallPos.x = mScrWidth;
if (mBallPos.y < 0) mBallPos.y = mScrHeight;
//update ball class instance
mBallView.x = mBallPos.x;
mBallView.y = mBallPos.y;
//redraw ball. Must run in background thread to prevent thread lock.
RedrawHandler.post(new Runnable() {
public void run() {
mBallView.invalidate();
}
});
}
}; // TimerTask
mTmr.schedule(mTsk, 10, 10); //start timer
super.onResume();
} // onResume
#Override
public void onDestroy() //main thread stopped
{
super.onDestroy();
//wait for threads to exit before clearing app
System.runFinalizersOnExit(true);
//remove app from memory
android.os.Process.killProcess(android.os.Process.myPid());
}
//listener for config change.
//This is called when user tilts phone enough to trigger landscape view
// we want our app to stay in portrait view, so bypass event
#Override
public void onConfigurationChanged(Configuration newConfig)
{
super.onConfigurationChanged(newConfig);
}
} //TiltBallActivity
Here is the BallView class;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.View;
public class BallView extends View {
public float x;
public float y;
private final int r;
private final Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
//construct new ball object
public BallView(Context context, float x, float y, int r) {
super(context);
//color hex is [transparncy][red][green][blue]
mPaint.setColor(0xFF1325E0); //not transparent. color is blue
this.x = x;
this.y = y;
this.r = r; //radius
}
//qcalled by invalidate()
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawCircle(x, y, r, mPaint);
}
public int getRadius(){
return r;
}
}
This is not my code but I forgot its source so credits to whoever made it. I am using it for a current project I'm working on.

How to appear and disappear an object on screen using game loop for every five second

I am trying to learn game development in android. First I am trying to appear and disappear an object on screen using game loop for every five second. But I did not get succeed. I have read different tutorials and forums. I applied all things as in tutorials but still object is drawing continuously. It is not disappearing. I a not getting what I am missing? Please guide me.
The complete code is here:
MainGameActivity.java
package com.example.showandhideobject;
import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
public class MainGameActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(new MainGamePanel(this));
}
}
MainGamePanel .java
package com.example.showandhideobject;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class MainGamePanel extends SurfaceView implements
SurfaceHolder.Callback {
private MainGameThread thread;
private ImageObject image;
// private long gameStartTime;
public MainGamePanel(Context context) {
super(context);
// adding the callback (this) to the surface holder to intercept events
getHolder().addCallback(this);
// create the game loop thread
thread = new MainGameThread(getHolder(), this);
Bitmap imageBitMap = BitmapFactory.decodeResource(getResources(),
R.drawable.rose);
image = new ImageObject(imageBitMap, 100, 150);
image.setAppeared(false);
image.setDisappearTime(System.currentTimeMillis());
// make the GamePanel focusable so it can handle events
setFocusable(true);
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
// at this point the surface is created and
// we can safely start the game loop
thread.setRunning(true);
thread.start();
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
}
public void update() {
Log.i("Image Status::::::::::::: ",
Boolean.valueOf(image.isAppeared()).toString());
if (!image.isAppeared()
&& System.currentTimeMillis() - image.getDisappearTime() >= 5000) {
Log.i("Image Object::::::: ", "Showing");
image.setAppeared(true);
image.setAppearTime(System.currentTimeMillis());
}
if (image.isAppeared()
&& (System.currentTimeMillis() - image.getAppearTime() >= 5000)) {
Log.i("Image Object::::::: ", "Not Showing");
image.setAppeared(false);
image.setDisappearTime(System.currentTimeMillis());
}
}
public void render(Canvas canvas) {
if (image.isAppeared()) {
image.draw(canvas);
}
}
}
MainGameThread.java
package com.example.showandhideobject;
import android.graphics.Canvas;
import android.util.Log;
import android.view.SurfaceHolder;
public class MainGameThread extends Thread {
// Surface holder that can access the physical surface
private SurfaceHolder surfaceHolder;
// The actual view that handles inputs
// and draws to the surface
private MainGamePanel gamePanel;
// flag to hold game state
private boolean running;
public boolean isRunning() {
return running;
}
public void setRunning(boolean running) {
this.running = running;
}
public MainGameThread(SurfaceHolder surfaceHolder, MainGamePanel gamePanel) {
super();
this.surfaceHolder = surfaceHolder;
this.gamePanel = gamePanel;
}
#Override
public void run() {
Canvas canvas;
while (isRunning()) {
canvas = null;
// try locking the canvas for exclusive pixel editing
// in the surface
try {
canvas = this.surfaceHolder.lockCanvas();
synchronized (surfaceHolder) {
Log.i("With in :::::::::", "Game Loop");
// update game state
gamePanel.update();
// render state to the screen and draw the canvas on the
// panel
gamePanel.render(canvas);
// gamePanel.onDraw(canvas);
}
} finally {
// in case of an exception the surface is not left in an
// inconsistent state
if (canvas != null) {
surfaceHolder.unlockCanvasAndPost(canvas);
}
} // end finally
}
}
}
ImageObject.java
package com.example.showandhideobject;
import android.graphics.Bitmap;
import android.graphics.Canvas;
public class ImageObject {
private Bitmap bitmap; // the actual bitmap
private int x; // the X coordinate
private int y; // the Y coordinate
private boolean isAppeared;
private long appearTime;
private long disappearTime;
// Constructor for this class
public ImageObject(Bitmap bitmap, int x, int y) {
this.bitmap = bitmap;
this.x = x;
this.y = y;
}
public Bitmap getBitmap() {
return bitmap;
}
public void setBitmap(Bitmap bitmap) {
this.bitmap = bitmap;
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
public boolean isAppeared() {
return isAppeared;
}
public void setAppeared(boolean isAppeared) {
this.isAppeared = isAppeared;
}
public long getAppearTime() {
return appearTime;
}
public void setAppearTime(long appearTime) {
this.appearTime = appearTime;
}
public long getDisappearTime() {
return disappearTime;
}
public void setDisappearTime(long disappearTime) {
this.disappearTime = disappearTime;
}
/* Method to draw images on Canvas */
public void draw(Canvas canvas) {
canvas.drawBitmap(bitmap, x - (bitmap.getWidth() / 2),
y - (bitmap.getHeight() / 2), null);
}
}

in this part
if (image.isAppeared()) {
image.draw(canvas);
}
you never clear your canvas. What you are doing is actually drawing your image over and over on the same spot.
You probably need to redraw a background in cas isAppeared() is false
Edit
you can also use canvas.save() before drawing the image, and canvas.restore() when you don't want the image anymore.

Don't try to optimise too early, game rendering is usually inefficient as almost always most of the screen is expected to change.
Loop should be:
always draw the background to canvas
always draw all game objects to the canvas, let them decide if they are visible or not which will simplify the MainGamePanel class
finally always display canvas (by copying to the image as you are doing)
To expand on point 2:
/* Method to draw images on Canvas */
public void draw(Canvas canvas) {
if(!isAppeared) return; //let the object decide when it should be drawn
canvas.drawBitmap(bitmap, x - (bitmap.getWidth() / 2),
y - (bitmap.getHeight() / 2), null);
}

Change the method render in MainGamePanel.java to
if (image.isAppeared() && canvas != null) {
image.draw(canvas);
}

Scroll Background Like Lunar Lander or Ninja Jump Game - Android

I'm developing a 2d Game using Canvas/Surfaceview and have a problem with scrolling my background image.
Check out the game - http://youtu.be/4Gi5rRqzZ3M
In the NinJump game, the character Ninja is just jumping in X coordinates and Background image is scrolling at a very high speed, making Ninja look like it is actually running.
I have created the basic setup, created the Ninja, added jump functionality, added background. Now I want to repeat the same background over and over again. How can I accomplish that?
Below are my source files - Main Activity Class
package com.abc.apps;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.Window;
import android.view.WindowManager;
public class LadderActivity extends Activity {
private static final String TAG = LadderActivity.class.getSimpleName();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// requesting to turn the title OFF
requestWindowFeature(Window.FEATURE_NO_TITLE);
// making it full screen
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
// set our MainGamePanel as the View
setContentView(new MainGameBoard(this));
Log.d(TAG, "View added");
}
#Override
protected void onDestroy() {
Log.d(TAG, "Destroying...");
super.onDestroy();
}
#Override
protected void onStop() {
Log.d(TAG, "Stopping...");
super.onStop();
}
}
Game Board extends SurfaceView
package com.abc.apps;
import android.app.Activity;
import android.content.Context;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.util.Log;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class MainGameBoard extends SurfaceView implements SurfaceHolder.Callback{
private MainGameLoop thread;
private Monkey monkey;
private static final String TAG = MainGameLoop.class.getSimpleName();
int currentX, currentY;
public MainGameBoard(Context context) {
super(context);
// TODO Auto-generated constructor stub
// adding the callback (this) to the surface holder to intercept events
//This line sets the current class (MainGamePanel) as the handler for the events happening on the actual surface
getHolder().addCallback(this);
// create monkey and load bitmap INITIALIZE AT LEFT
monkey = new Monkey(BitmapFactory.decodeResource(getResources(), R.drawable.actor),60, 340);
// create the game loop thread
thread = new MainGameLoop(getHolder(), this);
// make the GamePanel focusable so it can handle events.
setFocusable(true);
}
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
}
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
thread.setRunning(true);
thread.start();
}
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
// tell the thread to shut down and wait for it to finish
// this is a clean shutdown
boolean retry = true;
while (retry) {
try {
thread.join();
retry = false;
}
catch (InterruptedException e) {
// try again shutting down the thread
}
}
}
#Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
//For jumping Left
if (event.getX() < (getWidth()/2 - 32)) {
// Log.d(TAG, "Coords: x=" + event.getX() + ",y=" + event.getY());
//Log.d(TAG, "Jump Left");
// Sleep so that the main thread doesn't get flooded with UI events.
try {
Thread.sleep(32);
monkey.setX((getWidth()/2 - 60));
monkey.setY(monkey.getY()-70);
} catch (InterruptedException e) {
// No big deal if this sleep is interrupted.
}
}
//For Jumping Right
if (event.getX() > (getWidth()/2 + 32)) {
//Log.d(TAG, "Coords: x=" + event.getX() + ",y=" + event.getY());
//Log.d(TAG, "Jump Right");
// Sleep so that the main thread doesn't get flooded with UI events.
try {
Thread.sleep(32);
monkey.setX((getWidth()/2 + 60));
monkey.setY(monkey.getY()-70);
} catch (InterruptedException e) {
// No big deal if this sleep is interrupted.
}
}
/* //Middle Portion
if (event.getX() > (getWidth()/2 - 32) && event.getX() < (getWidth()/2 +32)) {
//thread.setRunning(false);
//((Activity)getContext()).finish();
}*/
}
return true;
}
public void render(Canvas canvas) {
canvas.drawBitmap(BitmapFactory.decodeResource(getResources(), R.drawable.monkey_sc), 0, 0,null);
monkey.draw(canvas);
}
/* #Override
protected void onDraw(Canvas canvas){
canvas.drawBitmap(BitmapFactory.decodeResource(getResources(), R.drawable.monkey_scene), 0, 0,null);
monkey.draw(canvas);
}*/
}
Main Game Loop
package com.abc.apps;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.util.Log;
import android.view.SurfaceHolder;
public class MainGameLoop extends Thread {
private SurfaceHolder surfaceHolder;
private MainGameBoard gameBoard;
private Monkey monkey;
private static final String TAG = MainGameLoop.class.getSimpleName();
// flag to hold game state
private boolean running = true;
public void setRunning(boolean running) {
this.running = running;
}
#Override
public void run() {
Canvas canvas;
Log.d(TAG, "Starting game loop");
while (running) {
canvas = null;
// try locking the canvas for exclusive pixel editing on the surface
try {
canvas = surfaceHolder.lockCanvas();
synchronized (surfaceHolder) {
// update game state
// render state to the screen
// draws the canvas on the panel
gameBoard.render(canvas);
}
}
finally {
// in case of an exception the surface is not left in
// an inconsistent state
if (canvas != null) {
surfaceHolder.unlockCanvasAndPost(canvas);
}
} // end finally
}
}
public MainGameLoop(SurfaceHolder surfaceHolder, MainGameBoard gameBoard) {
super();
this.surfaceHolder = surfaceHolder;
this.gameBoard = gameBoard;
}
}//MainThread
Monkey Class
package com.abc.apps;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.MotionEvent;
public class Monkey {
private Bitmap bitmap; // the actual bitmap
private int x; // the X coordinate
private int y; // the Y coordinate
private boolean touched; // if monkey is touched
public Monkey(Bitmap bitmap, int x, int y) {
this.bitmap = bitmap;
this.x = x;
this.y = y;
}
public Bitmap getBitmap() {
return bitmap;
}
public void setBitmap(Bitmap bitmap) {
this.bitmap = bitmap;
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
public boolean isTouched() {
return touched;
}
public void setTouched(boolean touched) {
this.touched = touched;
}
public void draw(Canvas canvas) {
Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setFilterBitmap(true);
paint.setDither(true);
canvas.drawBitmap(bitmap, x - (bitmap.getWidth() / 2), y, paint);
}
}

It looks like you are drawing your background in your MainGameBoard class in the render method.
public void render(Canvas canvas) {
canvas.drawBitmap(BitmapFactory.decodeResource(getResources(), R.drawable.monkey_sc), 0, 0,null);
monkey.draw(canvas);
}
You should just need 2 drawBitmap calls instead of 1 there.
canvas.drawBitmap(BitmapFactory.decodeResource(getResources(), R.drawable.monkey_sc), 0, y_offset1,null);
canvas.drawBitmap(BitmapFactory.decodeResource(getResources(), R.drawable.monkey_sc), 0, y_offset2,null);
I'm making an assumption that each background image has the same height or greater than the screen height; if it is less than the screen height you would need more than 2 instances.
Then you start 1 image at y_offset1 = 0 and the other at y_offset2 = -image_height.
Each draw you would increase y_offset1 and y_offset2 by the same amount. You would then need to do a check for both offsets to see if either has an amount greater than the screen height. If it does then the y_offset that is now "below screen" should be reset to the other y_offset minus the image_height. This will create a scroll image that loops indefinitely.
When using this type of technique it is important to think about your image edges; the image should be designed such that they tile seamlessly, otherwise at the looping point there is a noticeable visual artifact along the edge.

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..