SurfaceView for Android Development

I. Basic Knowledge:

SurfaceView is inherited from the View. The View is responsible for updating the animation in the main thread, while the SurfaceView is used to update the animation in a new thread.

Main Methods of SurfaceView class:

// Called when SurfaceView is created

Pubilic abstract void surfaceCreated (SurfaceHolder holder)

// Called when SurfaceView changes

Pubilic abstract void surfaceChanged (SurfaceHolder holder, int format, int width, int height)

// Called when SurfaceView is destroyed

Pubilic abstract void surfaceDestroyed (SurfaceHolder holder)

// Draw a SurfaceView Image

Protected void onDraw (Canvas canvas)

(The canvas parameter is the paint brush of the SurfaceView. This method is called for every screen change in the SurfaceView)

II. Implementation results:

First, a pair of images start to move from the lower left corner of the screen to the upper right corner. When the image and the cell phone screen collide, the horizontal speed and direction of the image remain unchanged, and the vertical speed remains unchanged,

In the opposite direction; after the current collision, the same effect will remain until the image is flying out of the screen. Then, the screen gradually displays an image.

Iii. Programming implementation:

1. Edit the interface (reslayoutmain. xml ):

[Java]

　　

Android: orientation = "vertical"

Android: layout_width = "fill_parent"

Android: layout_height = "fill_parent"

>

　　

Android: layout_width = "fill_parent"

Android: layout_height = "wrap_content"

Android: text = "@ string/hello"

/>

　　

　　

Android: orientation = "vertical"

Android: layout_width = "fill_parent"

Android: layout_height = "fill_parent"

>

　　

Android: layout_width = "fill_parent"

Android: layout_height = "wrap_content"

Android: text = "@ string/hello"

/>

　　

2. Edit the Code:

(SrcwyfzclMyActivity. java)

[Java]

Package wyf. zcl;

/*

* This example demonstrates how to draw a simple scenario in surfaceView.

* MyActivity. java is the main Activity of the program.

* MySurfaceView. java is the SurfaceView class of the program.

* Constant. java Constant class, which writes all constants in this class

* The OnDrawThread. java class is used to refresh the onDraw from time to time and repaint the image.

* PicRunThread. java: This class controls the motion of duke images.

**/

Import android. app. Activity; // introduce related packages

Import android. content. pm. ActivityInfo; // introduce the related package

Import android. OS. Bundle; // introduce related packages

Import android. view. Window; // introduce related packages

Import android. view. WindowManager; // introduce related packages

Public class MyActivity extends Activity {

/** Called when the activity is first created .*/

Private MySurfaceView msv; // get surfaceView reference

@ Override

Public void onCreate (Bundle savedInstanceState) {// Life Cycle Function of the Activity, called during Program Creation

Super. onCreate (savedInstanceState );

Msv = new MySurfaceView (MyActivity. this); // instantiate the object of MySurfaceView

RequestWindowFeature (Window. FEATURE_NO_TITLE); // you can specify whether the title bar is displayed on the screen.

GetWindow (). setFlags (WindowManager. LayoutParams. FLAG_FULLSCREEN,

WindowManager. LayoutParams. FLAG_FULLSCREEN); // set full screen

// Set to allow only landscape screens

This. setRequestedOrientation (ActivityInfo. SCREEN_ORIENTATION_LANDSCAPE );

SetContentView (msv); // set the content displayed in the Activity to msv

}

}

Package wyf. zcl;

/*

* This example demonstrates how to draw a simple scenario in surfaceView.

* MyActivity. java is the main Activity of the program.

* MySurfaceView. java is the SurfaceView class of the program.

* Constant. java Constant class, which writes all constants in this class

* The OnDrawThread. java class is used to refresh the onDraw from time to time and repaint the image.

* PicRunThread. java: This class controls the motion of duke images.

**/

Import android. app. Activity; // introduce related packages

Import android. content. pm. ActivityInfo; // introduce the related package

Import android. OS. Bundle; // introduce related packages

Import android. view. Window; // introduce related packages

Import android. view. WindowManager; // introduce related packages

Public class MyActivity extends Activity {

/** Called when the activity is first created .*/

Private MySurfaceView msv; // get surfaceView reference

@ Override

Public void onCreate (Bundle savedInstanceState) {// Life Cycle Function of the Activity, called during Program Creation

Super. onCreate (savedInstanceState );

Msv = new MySurfaceView (MyActivity. this); // instantiate the object of MySurfaceView

RequestWindowFeature (Window. FEATURE_NO_TITLE); // you can specify whether the title bar is displayed on the screen.

GetWindow (). setFlags (WindowManager. LayoutParams. FLAG_FULLSCREEN,

WindowManager. LayoutParams. FLAG_FULLSCREEN); // set full screen

// Set to allow only landscape screens

This. setRequestedOrientation (ActivityInfo. SCREEN_ORIENTATION_LANDSCAPE );

SetContentView (msv); // set the content displayed in the Activity to msv

}

}

(SrcwyfzclConstant. java)

[Java]

Package wyf. zcl;

Import android. view. Display;

// Constant. java Constant class, which writes all constants in this class

Public class Constant {

Public static int SCREENWIDTH = 480; // screen width (this program is a horizontal screen)

Public static int SCREENHEIGHT = 320; // screen height

Public static int PICWIDTH = 64; // The image width.

Public static int PICHEIGHT = 64; // Image Height

Public static int ONDRAWSPEED = 30; // draw interval of the onDraw Thread class

Public static float PICXSPEED = 1.5f; // horizontal movement speed of the image

Public static float PICYSPEED = 2; // vertical image movement speed

Public static int PICRUNSPEED = 30; // refresh speed of the motion thread of the image

Public static int PICALPHASPEED = 20; // The image fades in to demonstrate the refreshing speed.

}

Package wyf. zcl;

Import android. view. Display;

// Constant. java Constant class, which writes all constants in this class

Public class Constant {

Public static int SCREENWIDTH = 480; // screen width (this program is a horizontal screen)

Public static int SCREENHEIGHT = 320; // screen height

Public static int PICWIDTH = 64; // The image width.

Public static int PICHEIGHT = 64; // Image Height

Public static int ONDRAWSPEED = 30; // draw interval of the onDraw Thread class

Public static float PICXSPEED = 1.5f; // horizontal movement speed of the image

Public static float PICYSPEED = 2; // vertical image movement speed

Public static int PICRUNSPEED = 30; // refresh speed of the motion thread of the image

Public static int PICALPHASPEED = 20; // The image fades in to demonstrate the refreshing speed.

}

(SrcwyfzclMySurfaceView. java)

[Java]

Package wyf. zcl;

Import android. content. Context; // introduce related packages

Import android. graphics. Bitmap; // introduce related packages

Import android. graphics. BitmapFactory; // introduce related packages

Import android. graphics. Canvas; // introduce related packages

Import android. graphics. Color; // introduce related packages

Import android. graphics. Paint; // introduce related packages

Import android. view. Display; // introduce related packages

Import android. view. SurfaceHolder; // introduce related packages

Import android. view. SurfaceView; // introduce related packages

Public class MySurfaceView extends SurfaceView

Implements SurfaceHolder. Callback {

// SurfaceHolder. Callback interface is implemented here to add the lifecycle Callback function for surfaceView

Int dy = Display. DEFAULT_DISPLAY;

MyActivity ma; // get reference of MyActivity

Paint paint; // Paint brush reference

OnDrawThread odt; // OnDrawThread class reference

PicRunThread prt; // Thread class reference for Image Motion

Private float picX = 0; // x coordinate of the image

Private float picY = 0; // y coordinate of the image

Boolean picAlphaFlag = false; // indicates the dimmed image. If the value is false, the image is not displayed. If the value is true, the image is displayed.

Int picAlphaNum = 0; // The alpha value of the paint brush in the dimmed image.

Public MySurfaceView (Context context ){

Super (context );

This. ma = (MyActivity) context;

// Point the reference of ma to the object that calls the Surfaceview constructor method. In this example, MyActivity

This. getHolder (). addCallback (this); // registers the callback Interface

Paint = new Paint (); // instantiate the paint brush

Odt = new OnDrawThread (this); // instantiate the OnDrawThread class

Prt = new PicRunThread (this); // instantiate the PicRunThread class

Prt. start ();

}

Public void setPicX (float picX) {// set the image x coordinate

This. picX = picX;

}

Public void setPicY (float picY) {// set the y coordinate of the image

This. picY = picY;

}

Public void setPicAlphaNum (int picAlphaNum) {// sets the alpha parameter for image darkening.

This. picAlphaNum = picAlphaNum;

}

@ Override

Protected void onDraw (Canvas canvas) {// onDraw method, which is used to draw images and images.

Super. onDraw (canvas );

Paint. setColor (Color. WHITE); // set the paint brush to WHITE.

Canvas. drawRect (0, 0, Constant. SCREENWIDTH, Constant. SCREENHEIGHT, paint );

// A white full-screen rectangle is drawn to set the background to white and clear the background each time the screen is re-painted.

// Perform a flat map

Bitmap bitmapDuke = BitmapFactory. decodeResource (ma. getResources (), R. drawable. duke );

Canvas. drawBitmap (bitmapDuke, picX, picY, paint );

// Fades in the image

If (picAlphaFlag ){

Bitmap bitmapBG = BitmapFactory. decodeResource (ma. getResources (), R.drawable.jpg 1 );

Paint. setAlpha (picAlphaNum );

Canvas. drawBitmap (bitmapBG, 0, 0, paint );

}

}

@ Override

Public void surfaceChanged (SurfaceHolder holder, int format, int width,

Int height) {// this method is called when surfaceView changes, such as the screen size.

}

@ Override

Public void surfaceCreated (SurfaceHolder holder) {// this method is called when surfaceView is created

Odt. start (); // start the onDraw draw thread

}

@ Override

Public void surfaceDestroyed (SurfaceHolder holder) {// this method is called before the surfaceView is destroyed.

}

}

Package wyf. zcl;

Import android. content. Context; // introduce related packages

Import android. graphics. Bitmap; // introduce related packages

Import android. graphics. BitmapFactory; // introduce related packages

Import android. graphics. Canvas; // introduce related packages

Import android. graphics. Color; // introduce related packages

Import android. graphics. Paint; // introduce related packages

Import android. view. Display; // introduce related packages

Import android. view. SurfaceHolder; // introduce related packages

Import android. view. SurfaceView; // introduce related packages

Public class MySurfaceView extends SurfaceView

Implements SurfaceHolder. Callback {

// SurfaceHolder. Callback interface is implemented here to add the lifecycle Callback function for surfaceView

Int dy = Display. DEFAULT_DISPLAY;

MyActivity ma; // get reference of MyActivity

Paint paint; // Paint brush reference

OnDrawThread odt; // OnDrawThread class reference

PicRunThread prt; // Thread class reference for Image Motion

Private float picX = 0; // x coordinate of the image

Private float picY = 0; // y coordinate of the image

Boolean picAlphaFlag = false; // indicates the dimmed image. If the value is false, the image is not displayed. If the value is true, the image is displayed.

Int picAlphaNum = 0; // The alpha value of the paint brush in the dimmed image.

Public MySurfaceView (Context context ){

Super (context );

This. ma = (MyActivity) context;

// Point the reference of ma to the object that calls the Surfaceview constructor method. In this example, MyActivity

This. getHolder (). addCallback (this); // registers the callback Interface

Paint = new Paint (); // instantiate the paint brush

Odt = new OnDrawThread (this); // instantiate the OnDrawThread class

Prt = new PicRunThread (this); // instantiate the PicRunThread class

Prt. start ();

}

Public void setPicX (float picX) {// set the image x coordinate

This. picX = picX;

}

Public void setPicY (float picY) {// set the y coordinate of the image

This. picY = picY;

}

Public void setPicAlphaNum (int picAlphaNum) {// sets the alpha parameter for image darkening.

This. picAlphaNum = picAlphaNum;

}

@ Override

Protected void onDraw (Canvas canvas) {// onDraw method, which is used to draw images and images.

Super. onDraw (canvas );

Paint. setColor (Color. WHITE); // set the paint brush to WHITE.

Canvas. drawRect (0, 0, Constant. SCREENWIDTH, Constant. SCREENHEIGHT, paint );

// A white full-screen rectangle is drawn to set the background to white and clear the background each time the screen is re-painted.

// Perform a flat map

Bitmap bitmapDuke = BitmapFactory. decodeResource (ma. getResources (), R. drawable. duke );

Canvas. drawBitmap (bitmapDuke, picX, picY, paint );

// Fades in the image

If (picAlphaFlag ){

Bitmap bitmapBG = BitmapFactory. decodeResource (ma. getResources (), R.drawable.jpg 1 );

Paint. setAlpha (picAlphaNum );

Canvas. drawBitmap (bitmapBG, 0, 0, paint );

}

}

@ Override

Public void surfaceChanged (SurfaceHolder holder, int format, int width,

Int height) {// this method is called when surfaceView changes, such as the screen size.

}

@ Override

Public void surfaceCreated (SurfaceHolder holder) {// this method is called when surfaceView is created

Odt. start (); // start the onDraw draw thread

}

@ Override

Public void surfaceDestroyed (SurfaceHolder holder) {// this method is called before the surfaceView is destroyed.

}

}

(SrcwyfzclOnDrawThread. java)

[Java]

Package wyf. zcl;

Import android. graphics. Canvas; // introduce related packages

Import android. view. SurfaceHolder; // introduce related packages

// This class is used to refresh the onDraw from time to time and redraw the screen.

Public class OnDrawThread extends Thread {

MySurfaceView msv; // get the reference of MySurfaceView

SurfaceHolder sh; // SurfaceHolder reference

Public OnDrawThread (MySurfaceView msv ){

Super ();

This. msv = msv; // In the constructor, point the msv reference to the object that calls the MySurfaceView class.

Sh = msv. getHolder ();

}

@ Override

Public void run (){

Super. run ();

Canvas canvas = null; // Canvas reference

While (true ){

Try {

Canvas = sh. lockCanvas (null); // point the canvas reference to the canvas object of surfaceView.

Synchronized (this. sh) {// The Painting Process may cause synchronization problems, locking

If (canvas! = Null ){

Msv. onDraw (canvas );

}

}

} Finally {

Try {

If (sh! = Null ){

Sh. unlockCanvasAndPost (canvas); // unlock after painting

}

} Catch (Exception e) {e. printStackTrace ();}

}

Try {

Thread. sleep (Constant. ONDRAWSPEED); // rest for 1 second

} Catch (Exception e) {e. printStackTrace ();}

}

}

}

Package wyf. zcl;

Import android. graphics. Canvas; // introduce related packages

Import android. view. SurfaceHolder; // introduce related packages

// This class is used to refresh the onDraw from time to time and redraw the screen.

Public class OnDrawThread extends Thread {

MySurfaceView msv; // get the reference of MySurfaceView

SurfaceHolder sh; // SurfaceHolder reference

Public OnDrawThread (MySurfaceView msv ){

Super ();

This. msv = msv; // In the constructor, point the msv reference to the object that calls the MySurfaceView class.

Sh = msv. getHolder ();

}

@ Override

Public void run (){

Super. run ();

Canvas canvas = null; // Canvas reference

While (true ){

Try {

Canvas = sh. lockCanvas (null); // point the canvas reference to the canvas object of surfaceView.

Synchronized (this. sh) {// The Painting Process may cause synchronization problems, locking

If (canvas! = Null ){

Msv. onDraw (canvas );

}

}

} Finally {

Try {

If (sh! = Null ){

Sh. unlockCanvasAndPost (canvas); // unlock after painting

}

} Catch (Exception e) {e. printStackTrace ();}

}

Try {

Thread. sleep (Constant. ONDRAWSPEED); // rest for 1 second

} Catch (Exception e) {e. printStackTrace ();}

}

}

}

(SrcwyfzclPicRunThread. java)

[Java]

Package wyf. zcl;

// This class controls the motion of duke Images

Public class PicRunThread extends Thread {

MySurfaceView msv; // reference of MySurfaceView

Private float picX = 0; // x coordinate of the image

Private float picY = Constant. SCREENHEIGHT-Constant.PICHEIGHT; // picture y coordinate

Boolean yRunFlag = false; // The motion mark in the y direction. If it is false, y = y + speed. If it is true, y = y-speed.

Int picAlphaNum = 0; // The alpha value of the paint brush in the dimmed image.

Public PicRunThread (MySurfaceView msv ){

Super ();

This. msv = msv; // point the reference of this thread class to the object that calls its MySurfaceView

}

@ Override

Public void run (){

Super. run ();

While (true ){

// Control the motion of the duke Image

While (this. picX

Msv. setPicX (picX );

Msv. setPicY (picY );

PicX = picX + Constant. PICXSPEED;

If (yRunFlag) {// It should be upward, auto-minus

PicY = picY-Constant.PICYSPEED;

} Else {// downward movement, auto-Increment

PicY = picY + Constant. PICYSPEED;

}

If (picY <= 0) {// arrive at the top of the screen

YRunFlag = false;

} Else if (picY> Constant. SCREENHEIGHT-Constant.PICHEIGHT) {// arrive at the bottom of the screen

YRunFlag = true;

}

Try {

Thread. sleep (Constant. PICRUNSPEED );

} Catch (Exception e) {e. printStackTrace ();}

}

// Demo of the dimmed Image

Msv. picAlphaFlag = true; // enable the dimmed image.

For (picAlphaNum = 0; picAlphaNum <= 255; picAlphaNum ++ ){

If (picAlphaNum = 255 ){

Msv. picAlphaFlag = false; // when the image fades out, mark the reset

PicX = 0; // x coordinate of the image

PicY = Constant. SCREENHEIGHT-Constant.PICHEIGHT; // picture y coordinate

System. out. println (msv. picAlphaFlag + "picX:" + picX + "picY:" + picY );

}

Msv. setPicAlphaNum (picAlphaNum );

Try {

Thread. sleep (Constant. PICALPHASPEED );

} Catch (Exception e) {e. printStackTrace ();}

}

}

}

}

Package wyf. zcl;

// This class controls the motion of duke Images

Public class PicRunThread extends Thread {

MySurfaceView msv; // reference of MySurfaceView

Private float picX = 0; // x coordinate of the image

Private float picY = Constant. SCREENHEIGHT-Constant.PICHEIGHT; // picture y coordinate

Boolean yRunFlag = false; // The motion mark in the y direction. If it is false, y = y + speed. If it is true, y = y-speed.

Int picAlphaNum = 0; // The alpha value of the paint brush in the dimmed image.

Public PicRunThread (MySurfaceView msv ){

Super ();

This. msv = msv; // point the reference of this thread class to the object that calls its MySurfaceView

}

@ Override

Public void run (){

Super. run ();

While (true ){

// Control the motion of the duke Image

While (this. picX

Msv. setPicX (picX );

Msv. setPicY (picY );

PicX = picX + Constant. PICXSPEED;

If (yRunFlag) {// It should be upward, auto-minus

PicY = picY-Constant.PICYSPEED;

} Else {// downward movement, auto-Increment

PicY = picY + Constant. PICYSPEED;

}

If (picY <= 0) {// arrive at the top of the screen

YRunFlag = false;

} Else if (picY> Constant. SCREENHEIGHT-Constant.PICHEIGHT) {// arrive at the bottom of the screen

YRunFlag = true;

}

Try {

Thread. sleep (Constant. PICRUNSPEED );

} Catch (Exception e) {e. printStackTrace ();}

}

// Demo of the dimmed Image

Msv. picAlphaFlag = true; // enable the dimmed image.

For (picAlphaNum = 0; picAlphaNum <= 255; picAlphaNum ++ ){

If (picAlphaNum = 255 ){

Msv. picAlphaFlag = false; // when the image fades out, mark the reset

PicX = 0; // x coordinate of the image

PicY = Constant. SCREENHEIGHT-Constant.PICHEIGHT; // picture y coordinate

System. out. println (msv. picAlphaFlag + "picX:" + picX + "picY:" + picY );

}

Msv. setPicAlphaNum (picAlphaNum );

Try {

Thread. sleep (Constant. PICALPHASPEED );

} Catch (Exception e) {e. printStackTrace ();}

}

}

}

}

This part of the code is hard for me, a beginner of java, but I tried to figure out the framework after two days.

The Code involves some basic java knowledge. I made some notes as follows:

[Extends]:

A class uses the keyword extends to inherit other classes. The keyword extends appears after the class name when the class is declared,

Extends is followed by the name of the class to be inherited, and extends implements inheritance. Only one class can be inherited in Java.

[Super]:

B inherits the method A and B wants to call the method A, so you can use the method super.. In Chinese, super is an alias of the parent class.

[Implements]:

Implements is a key word used by a class to implement an interface,

It is used to implement the abstract methods defined in interfaces.

. For example, people is an interface with the say method.

Public interface people ()

{

Public say ();

}

However, the interface does not have a method body.

Only one specific class can be used to implement the method body.

For example, the chinese class implements the people interface.

Public class chinese implements extends El {

Public say ()

{System. out. println ("Hello! ");}

}

[Differences between extends and implements]:

[Plain]

Extends inherits the parent class, as long as the class is not declared as final or defined as abstract, it can inherit,

JAVA does not support multiple inheritance, but can be implemented using interfaces. In this case, implements must be used to inherit only one class,

However, implements can implement multiple interfaces, which can be separated by commas.

For example

Class A extends B implements C, D, E

Extends inherits the parent class, as long as the class is not declared as final or defined as abstract, it can inherit,

JAVA does not support multiple inheritance, but can be implemented using interfaces. In this case, implements must be used to inherit only one class,

However, implements can implement multiple interfaces, which can be separated by commas.

For example

Class A extends B implements C, D, E