Develop Reference

ACTION_UP case is not triggering

Desired Outcome
I want to draw a red circle at the position the screen is touched then remove it when the touch is released.
Current Outcome
Whenever I touch the screen the red circle appears in the touched location, however when I release the touch the circle stays on the screen.
Extra Help
I am pretty new to coding for android and if a quick gloss over my code shows that I'm using anything unnecessary I would love to be told so I can improve.
My Code
package com.mr.mwood.thumbinput;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class MainActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new SampleView(this));
}
class SampleView extends SurfaceView {
private final SurfaceHolder surfaceHolder;
private final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
// CONSTRUCTOR
public SampleView(Context context) {
super(context);
surfaceHolder = getHolder();
paint.setColor(Color.RED);
paint.setStyle(Style.FILL);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
Canvas canvas = surfaceHolder.lockCanvas();
switch (event.getActionMasked()) {
case (MotionEvent.ACTION_DOWN):
canvas.drawColor(Color.BLACK);
canvas.drawCircle(event.getX(), event.getY(), 50, paint);
break;
case (MotionEvent.ACTION_UP):
canvas.drawColor(Color.BLACK);
break;
}
surfaceHolder.unlockCanvasAndPost(canvas);
return false;
}
}
}

SurfaceView showing blank white screen

I am trying to draw an oval to the screen but all I am getting is a blank white canvas. Not only am I unsure whether I am drawing the oval correctly, but also am getting nothing to the screen. Does anyone know why this is happening, I think the problem is that it isnt getting to the drawing section of the thread...
package hidden;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.PorterDuff;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.shapes.OvalShape;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.view.View.OnTouchListener;
public class Surface extends Activity implements OnTouchListener
{
SurfaceView v;
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_main);
setRequestedOrientation(1);
v = new SView(this);
v.setOnTouchListener(this);
v.setZOrderOnTop(true);
setContentView(v);
}
public class SView extends SurfaceView implements Runnable
{
Thread t1 = null;
SurfaceHolder holder;
boolean isItOk = false;
public SView(Context context)
{
super(context);
holder = getHolder();
holder.setFormat(PixelFormat.TRANSPARENT);
}
public void run()
{
while(isItOk)
{
if(!holder.getSurface().isValid())
{
continue;
}
Canvas c = holder.lockCanvas();
Paint p = new Paint();
p.setColor(Color.BLUE);
//OvalShape oval = new OvalShape();
//oval.draw(c, p);
Paint paint = new Paint();
paint.setColor(Color.GREEN);
paint.setStyle(Paint.Style.STROKE);
float leftx = 20;
float topy = 20;
float rightx = 50;
float bottomy = 100;
RectF ovalBounds = new RectF(leftx, topy, rightx, bottomy);
c.drawOval(ovalBounds, paint);
holder.unlockCanvasAndPost(c);
}
}
public void pause()
{
isItOk = false;
while(true)
{
try
{
t1.join();
}
catch(InterruptedException e)
{
e.printStackTrace();
}
break;
}
t1 = null;
}
public void resume()
{
isItOk = true;
t1 = new Thread(this);
t1.start();
}
}
public boolean onTouch(View arg0, MotionEvent arg1)
{
return false;
}
}

Increase speed to redraw the Android Screen

I am new to Android.My application requires to redraw a canvas circle over and over again. However, the speed of redraw is less than what I want. How may I increase the same.
My code is as follows:
--> ImagePracActivity.java
package com.pkg.ImagPrac;
import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
public class ImagePracActivity extends Activity {
//DrawView drawView;
movement mv;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Set full screen view
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
requestWindowFeature(Window.FEATURE_NO_TITLE);
mv=new movement(getApplicationContext());
setContentView(mv);
mv.requestFocus();
}
}
--> movement.java
package com.pkg.ImagPrac;
import android.content.Context;
import android.content.Intent;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.Log;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.WindowManager;
public class movement extends View implements OnTouchListener{
Display display;
float x=0,y=0;
Paint paint=new Paint();
private boolean flag;
public movement(Context context) {
super(context);
setFocusable(true);
setFocusableInTouchMode(true);
this.setOnTouchListener(this);
paint.setColor(Color.BLUE);
paint.setAntiAlias(true);
display = ((WindowManager)
context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
x = 0;
y = display.getHeight();
}
#Override
protected void onDraw(Canvas canvas) {
if(x<(display.getWidth()/2))
{
canvas.drawCircle(x++, y--, 5, paint);
}
else if(x<(display.getWidth()))
{
canvas.drawCircle(x++, y++, 5, paint);
}
this.invalidate();
}
public boolean onTouch(View arg0, MotionEvent arg1) {
// TODO Auto-generated method stub
return false;
}
}

A would advice you to use SurfaceView class instead of View, because SurfaceView faster and allows you to have all drawing logic in separate thread. Read more about SurfaceView : http://developer.android.com/guide/topics/graphics/2d-graphics.html

try this
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(Color.BLUE);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(5);

Problem with SurfaceView and its holder

Hi All
I tried to use SurfaceView, but the view appeared black and nothing painted
Here My code
package com.samples;
import android.app.Activity;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.BlurMaskFilter;
import android.graphics.BlurMaskFilter.Blur;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.graphics.Region;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceHolder.Callback;
import android.view.SurfaceView;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.ImageView;
public class Galary 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 GalaryView(this));
}
private static class GalaryView extends SurfaceView implements Callback {
private SurfaceHolder surfaceHolder;
public GalaryView(Context context) {
super(context);
surfaceHolder = getHolder();
surfaceHolder.addCallback(this);
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
Effects effects= new Effects(surfaceHolder, this);
effects.start();
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
}
}
}
and the second file
package com.samples;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;
import android.graphics.Region;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class Effects extends Thread {
private SurfaceView surfaceView;
private SurfaceHolder surfaceHolder;
private Bitmap bitmap1;
private Path mPath;
private Bitmap bitmap2;
private Paint paint;
public Effects(SurfaceHolder surfaceHolder, SurfaceView surfaceView) {
this.surfaceView = surfaceView;
this.surfaceHolder = surfaceHolder;
this.mPath = new Path();
bitmap1 = BitmapFactory.decodeResource(surfaceView.getContext()
.getResources(), R.drawable.qina1);
bitmap2 = BitmapFactory.decodeResource(surfaceView.getContext()
.getResources(), R.drawable.qina2);
paint= new Paint();
}
#Override
public void run() {
Canvas canvas = surfaceHolder.lockCanvas();
canvas.drawColor(Color.WHITE);
for (int i = 1; i < 100; i++) {
canvas.drawBitmap(bitmap1, 0, 0, null);
canvas.save();
canvas.translate(0, 0);
mPath.reset();
canvas.clipPath(mPath);
int ovalWidth = (int) (surfaceView.getWidth() * (i / 100.0));
int ovalHeight = (int) (surfaceView.getHeight() * (i / 100.0));
int ovalX = (surfaceView.getWidth() - ovalWidth) / 2;
int ovalY = (surfaceView.getHeight() - ovalHeight) / 2;
mPath.addOval(new RectF(ovalX, ovalY, ovalWidth + ovalX, ovalHeight
+ ovalY), Path.Direction.CCW);
canvas.clipPath(mPath, Region.Op.REPLACE);
canvas.drawBitmap(bitmap2, 0, 0, paint);
canvas.restore();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
Please could you tell me what is the problem?
Thanks a lot

Have a onDraw() inside the class "GalaryView" and draw your graphics there. From the run() of the thread call the onDraw(). This post has some sample code Android:Crash: Binary XML file line : Error inflating class (using SurfaceView) . Hope this helps !

Android On Touch

I have been trying to make a program draw circles as I touch the screen with no luck, can anyone please tell me how I can do this? or GOOD tutorial that shows me how... I keep getting errors in my code
import android.content.Context;
import android.content.Intent;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.text.format.Time;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import java.lang.Math;
public class GameView extends View{
private final float x;
private final float y;
private final int r;
private final Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
public GameView(Context context, float x, float y, int r) {
super(context);
setFocusable(true);
mPaint.setColor(0xFFFF0000);
this.x = x;
this.y = y;
this.r = r;
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawCircle(x, y, r, mPaint);
}
}
GameActivity.java
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.FrameLayout;
public class GameActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
FrameLayout main = (FrameLayout) findViewById(R.id.my_view);
main.setOnTouchListener(new View.OnTouchListener() {
public boolean onTouch(final View v, MotionEvent e) {
final float x = e.getX();
final float y = e.getY();
final Handler handler = new Handler()
{
public void handleMessage(Message msg) {
}
};
Thread graphicThread = new Thread()
{
public void run() {
try {
//Do the drop
FrameLayout flView = (FrameLayout) v;
GameView gm = new GameView(getParent(), x,y,25);
flView.addView(gm);
Thread.sleep(1000);
handler.sendMessage(handler.obtainMessage());
}
catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
boolean isRunning=true;
graphicThread.start();
return true;
}
});
}
}

You shouldn't be using getParent() in your activity if it's not a child Activity.
Use this instead:
GameView gm = new GameView(this, x, y, 25);

As the NPE question is already answered, I want to provide an answer for the tutorial question. I have written a series (which is partly updated) which you can find here: I have written a tutorial about 2d graphics for a game. Read this: http://www.droidnova.com/2d-tutorial-series