我是Android和线程新手。
我有一个简单的应用程序，只显示在屏幕边界内弹跳的位图（即如果位图击中屏幕的右边缘，它将反转方向）。
应用程序冻结，当我最小化它，有时需要很长时间加载，当它加载时，我看到一个黑屏。
请尝试运行代码，它只是下面显示的一个文件，我只使用SurfaceView作为布局。在应用程序的功能方面没有什么先进的。 我很困惑为什么我们需要使用SurfaceHolder.Callback匿名类（在嵌套的SurfaceView类中的方法中使用），如果我写的生命周期方法在嵌套的SurfaceView类中称为暂停，恢复和停止由主要活动的onPause，onResume，onStop方法调用。显示整个代码，然后显示app的结构，以查看我所做的概述，因为我没有看到SurfaceHolder.Callback方法的要点所以我的意思是我不知道为什么我们需要使用surfaceCreated， surfaceChanged，surfaceDestroyed，我不知道在surfaceChanged中放入什么。我还有一个onSaveInstanceSate和onRestoreInstance状态方法，只保存位图的x和y坐标。
public class MainActivity extends Activity {
GameView gameView;
Handler myHandler;
int xPos = 0;
int yPos = 0;
int deltaX = 3;
int deltaY = 3;
int iconWidth;
int iconHeight;
static final String STATE_POS_X = "playerPosX";
static final String STATE_POS_Y = "playerPosY";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myHandler = new Handler ();
gameView = new GameView(this);
setContentView(gameView);
}
class GameView extends SurfaceView {
private SurfaceHolder surfaceHolder;
private Bitmap bmpIcon;
private MyThread myThread;
volatile boolean playingGame = true;
public GameView(Context context) {
super(context);
init();
}
public GameView(Context context,
AttributeSet attrs) {
super(context, attrs);
init();
}
public GameView(Context context,
AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init();
}
private void init(){
myThread = new MyThread(this);
surfaceHolder = getHolder();
bmpIcon = BitmapFactory.decodeResource(getResources(),
R.drawable.rubberBall);
iconWidth = bmpIcon.getWidth();
iconHeight = bmpIcon.getHeight();
surfaceHolder.addCallback( new SurfaceHolder.Callback(){
@Override
public void surfaceCreated(SurfaceHolder holder) {
myThread.setRunning(true);
myThread.start();
}
@Override
public void surfaceChanged(SurfaceHolder holder,
int format, int width, int height) {
// What do I enter here???
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
boolean retry = true;
myThread.setRunning(false);
while (retry) {
try {
myThread.join();
retry = false;
} catch (InterruptedException e) {
}
}
}});
}
protected void drawSomething(Canvas canvas) {
canvas.drawColor(Color.BLACK);
canvas.drawBitmap(bmpIcon,
getWidth()/2, getHeight()/2, null);
xPos += deltaX;
if(deltaX > 0){
if(xPos >= getWidth() - iconWidth){
deltaX *= -1;
}
}else{
if(xPos <= 0){
deltaX *= -1;
}
}
yPos += deltaY;
if(deltaY > 0){
if(yPos >= getHeight() - iconHeight){
deltaY *= -1;
}
}else{
if(yPos <= 0){
deltaY *= -1;
}
}
canvas.drawColor(Color.BLACK);
canvas.drawBitmap(bmpIcon,
xPos, yPos, null);
}
public void pause() {
playingGame = false;
try {
myThread.join();
} catch (InterruptedException e) {
}
}
public void resume() {
playingGame = true;
myThread = new MyThread(this);
myThread.start();
}
}//END INNER CLASS: GameView
class MyThread extends Thread {
GameView myView;
private boolean running = false;
public MyThread(GameView view) {
myView = view;
}
public void setRunning(boolean run) {
running = run;
}
@Override
public void run() {
while (running){
Canvas canvas = myView.getHolder().lockCanvas();
if(canvas != null) {
synchronized (myView.getHolder()) {
myView.drawSomething(canvas);
}
myView.getHolder().unlockCanvasAndPost(canvas);
}
try {
this.sleep(30);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}//END WHILE
}
}//END INNER CLASS: MyThread
/**
* BELOW are Main Activity Life Cycle Call Back methods!
*
*/
@Override
protected void onStop() {
super.onStop();
Log.d("onStop", "Main Activity's onStop called");
while (true) {
gameView.pause();
break;
}
this.finish();
}
@Override
protected void onResume() {
super.onResume();
Log.d("onResume", "Main Activity's onResume called");
gameView.resume();
}
@Override
protected void onPause() {
super.onPause();
Log.d("onPause", "Main Activity's onPause called");
gameView.pause();
}
//save and restore state
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
// Always call the superclass so it can save the view hierarchy state
super.onSaveInstanceState(savedInstanceState);
// Save the user's current game state
savedInstanceState.putInt(STATE_POS_X, xPos);
savedInstanceState.putInt(STATE_POS_Y, yPos);
}
public void onRestoreInstanceState(Bundle savedInstanceState) {
// Always call the superclass so it can restore the view hierarchy
super.onRestoreInstanceState(savedInstanceState);
// Restore state members from saved instance
xPos = savedInstanceState.getInt(STATE_POS_X);
yPos = savedInstanceState.getInt(STATE_POS_Y);
}
}//END CLASS: MainActivity
MainActivity life cycle methods
--------------------------------
onCreate:
------------
-links up the layout which is the SurfaceView instance
-initialize variables
onPause:
---------
call the SurfaceView's custom pause method here in addition to calling the
super's onPause
onStop:
------
call the SurfaceView's custom stop method here in addition to calling the
super's onStop
onResume:
---------
call the SurfaceView's custom resume method here in addition to calling the
super's onResume
nested Thread class
------------------------
run method to run SurfaceView
nested class SurfaceView's life cycle methods
-------------------------------------------------------
pause method which pauses the worker thread
---------------------------------------------
stop the worker thread:
stop method which stops the worker thread:
-----------------------------------------
stop the worker thread
resume method which creates a new worker thread:
---------------------------------------------------
make a new worker thread
SurfaceHolder.Callback lifespan methods
***Why do we need to write the methods below if I have pause,
resume stop already that will be called by the Main Activity's
onXXX, respectively????
==========================================
surfaceCreated:
---------------
make a new worker thread
surfaceChanged:
---------------
What do I enter here??
surfaceDestroyed:
-----------------
destroy current worker thread
END of nested SurfaceView class
override onSaveInstanceState method:
------------------------------------
save the bitmap's position (x and y coordinates)
override onRestoreInstanceState method:
-----------------------------------------
restore the bitmap's position (x and y coordinates)
END of MainActivity
答案 0 :(得分：0)
检查非常好的解释，因为与使用自定义视图绘图或使用预定义的图形输入或GUI元素不同，SurfaceView可以更精细地控制图形。
http://blog.infrared5.com/2011/07/android-graphics-and-animation-part-ii-animation/