android中的触摸和拖拽图片
android中的触摸和拖拽图片
提问于 2010-11-23 20:09:37
我正在做一些例子，在这些例子中，我想在Android中拖动与触摸相对应的图像。有谁知道我该怎么做吗？
回答 2
Stack Overflow用户
回答已采纳
发布于 2010-11-23 21:18:37
public class TouchBall extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
int w=getWindowManager().getDefaultDisplay().getWidth()-25;
int h=getWindowManager().getDefaultDisplay().getHeight()-25;
BallView ballView=new BallView(this,w,h);
setContentView(ballView);
}
}
public class BallView extends SurfaceView implements SurfaceHolder.Callback {
private Bitmap bitmap ;
private MyThread thread;
private int x=20,y=20;int width,height;
public BallView(Context context,int w,int h) {
super(context);
width=w;
height=h;
thread=new MyThread(getHolder(),this);
getHolder().addCallback(this);
setFocusable(true);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
bitmap =BitmapFactory.decodeResource(getResources(), R.drawable.ball_green);
canvas.drawColor(Color.BLUE);//To make background
canvas.drawBitmap(bitmap,x-(bitmap.getWidth()/2),y-(bitmap.getHeight()/2),null);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
x=(int)event.getX();
y=(int)event.getY();
if(x<25)
x=25;
if(x> width)
x=width;
if(y <25)
y=25;
if(y > 405)
y=405;
return true;
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {
// TODO Auto-generated method stub
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
thread.startrun(true);
thread.start();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
thread.startrun(false);
thread.stop();
}
}线程：
public class MyThread extends Thread {
private SurfaceHolder msurfaceHolder;
private BallView mballView;
private boolean mrun =false;
public MyThread(SurfaceHolder holder, BallView ballView) {
msurfaceHolder = holder;
mballView=ballView;
}
public void startrun(boolean run) {
mrun=run;
}
@Override
public void run() {
super.run();
Canvas canvas;
while (mrun) {
canvas=null;
try {
canvas = msurfaceHolder.lockCanvas(null);
synchronized (msurfaceHolder) {
mballView.onDraw(canvas);
}
} finally {
if (canvas != null) {
msurfaceHolder.unlockCanvasAndPost(canvas);
}
}
}
}
}Stack Overflow用户
发布于 2011-01-06 04:15:01
作为对TouchBall答案的一个细微修改--如果你真的没有游戏循环--换句话说，屏幕的唯一变化是直接由用户输入引起的--那么省略线程可能更有意义。否则，它只是不断地循环和重新绘制，即使没有任何变化。所以：
public class TouchBall extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
int w=getWindowManager().getDefaultDisplay().getWidth()-25;
int h=getWindowManager().getDefaultDisplay().getHeight()-25;
BallView ballView=new BallView(this,w,h);
setContentView(ballView);
}
}
public class BallView extends SurfaceView implements SurfaceHolder.Callback {
private Bitmap bitmap ;
private int x=20,y=20;int width,height;
public BallView(Context context,int w,int h) {
super(context);
width=w;
height=h;
getHolder().addCallback(this);
setFocusable(true);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
bitmap =BitmapFactory.decodeResource(getResources(), R.drawable.ball_green);
canvas.drawColor(Color.BLUE);//To make background
canvas.drawBitmap(bitmap,x-(bitmap.getWidth()/2),y-(bitmap.getHeight()/2),null);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
x=(int)event.getX();
y=(int)event.getY();
if(x<25)
x=25;
if(x> width)
x=width;
if(y <25)
y=25;
if(y > 405)
y=405;
updateBall();
return true;
}
@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
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
}
private void updateBall() {
Canvas canvas = null;
try {
canvas = getHolder().lockCanvas(null);
synchronized (getHolder()) {
this.onDraw(canvas);
}
}
finally {
if (canvas != null) {
getHolder().unlockCanvasAndPost(canvas);
}
}
}
}诚然，我是Android开发的新手，所以我可能在这里遗漏了一些东西。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/4255859
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