主要讲就是在surfaceview中有 onDraw这个方法，但这个方法surfaceview不会自己去调用，而我们的代码中ondraw也好draw也好，都是我们自己去定义的一个方法， 也就是说我慢把它放在线程中不断的去调用，下面的代码主要是一个对图片操作和按键的处理，那么我们就来看看在代码中是怎么样来实现的吧！
Java代码：
package eoe.demo;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.Log;
import android.view.KeyEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.SurfaceHolder.Callback;
public class MySurfaceView extends SurfaceView implements Callback, Runnable {
private Thread th = new Thread(this);
private SurfaceHolder sfh;
private int SH, SW;
private Canvas canvas;
private Paint p;
private Paint p2;
private Resources res;
private Bitmap bmp;
private int bmp_x = 100, bmp_y = 100;
private boolean UP, DOWN, LEFT, RIGHT;
private int animation_up[] = { 3, 4, 5 };
private int animation_down[] = { 0, 1, 2 };
private int animation_left[] = { 6, 7, 8 };
private int animation_right[] = { 9, 10, 11 };
private int animation_init[] = animation_down;
private int frame_count;
public MySurfaceView(Context context) {
super(context);
this.setKeepScreenOn(true);
res = this.getResources();
bmp = BitmapFactory.decodeResource(res, R.drawable.enemy1);
sfh = this.getHolder();
sfh.addCallback(this);
p = new Paint();
p.setColor(Color.YELLOW);
p2 = new Paint();
p2.setColor(Color.RED);
p.setAntiAlias(true);
setFocusable(true); //备注1
}
public void surfaceCreated(SurfaceHolder holder) {
SH = this.getHeight();
SW = this.getWidth();
th.start();
}
public void draw() {
canvas = sfh.lockCanvas();
canvas.drawRect(0, 0, SW, SH, p); //备注2
canvas.save(); //备注3
canvas.drawText("Himi", bmp_x-2, bmp_y-10, p2);
canvas.clipRect(bmp_x, bmp_y, bmp_x + bmp.getWidth() / 13, bmp_y+bmp.getHeight());
if (animation_init == animation_up) {
canvas.drawBitmap(bmp, bmp_x - animation_up[frame_count] * (bmp.getWidth() / 13), bmp_y, p);
} else if (animation_init == animation_down) {
canvas.drawBitmap(bmp, bmp_x - animation_down[frame_count] * (bmp.getWidth() / 13), bmp_y, p);
} else if (animation_init == animation_left) {
canvas.drawBitmap(bmp, bmp_x - animation_left[frame_count] * (bmp.getWidth() / 13), bmp_y, p);
} else if (animation_init == animation_right) {
canvas.drawBitmap(bmp, bmp_x - animation_right[frame_count] * (bmp.getWidth() / 13), bmp_y, p);
}
canvas.restore(); //备注3
sfh.unlockCanvasAndPost(canvas);
}
public void cycle() {
if (DOWN) {
bmp_y += 5;
} else if (UP) {
bmp_y -= 5;
} else if (LEFT) {
bmp_x -= 5;
} else if (RIGHT) {
bmp_x += 5;
}
if (DOWN || UP || LEFT || RIGHT) {
if (frame_count < 2) {
frame_count++;
} else {
frame_count = 0;
}
}
if (DOWN == false && UP == false && LEFT == false && RIGHT == false) {
frame_count = 0;
}
}
@Override
public boolean onKeyDown(int key, KeyEvent event) {
if (key == KeyEvent.KEYCODE_DPAD_UP) {
if (UP == false) {
animation_init = animation_up;
}
UP = true;
} else if (key == KeyEvent.KEYCODE_DPAD_DOWN) {
if (DOWN == false) {
animation_init = animation_down;
}
DOWN = true;
} else if (key == KeyEvent.KEYCODE_DPAD_LEFT) {
if (LEFT == false) {
animation_init = animation_left;
}
LEFT = true;
} else if (key == KeyEvent.KEYCODE_DPAD_RIGHT) {
if (RIGHT == false) {
animation_init = animation_right;
}
RIGHT = true;
}
return super.onKeyDown(key, event);
}
/* (non-Javadoc)
* @see android.view.View#onKeyUp(int, android.view.KeyEvent)
*/
@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (DOWN) {
DOWN = false;
} else if (UP) {
UP = false;
} else if (LEFT) {
LEFT = false;
} else if (RIGHT) {
RIGHT = false;
}
return super.onKeyUp(keyCode, event);
}
@Override
public void run() {
// TODO Auto-generated method stub
while (true) {
draw();
cycle();
try {
Thread.sleep(100);
} catch (Exception ex) {
}
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
// TODO Auto-generated method stub
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
}
} </STRONG>
备注1
此方法是用来响应按键！如果是自己定义一个继承自View的类,重新实现onKeyDown方法后,只有当该View获得焦点时才会调用 onKeyDown方法,Actvity中的onKeyDown方法是当所有控件均没有处理该按键事件时,才会调用.
备注2
这里也是对屏幕进行刷屏操作，其实这也只是一种，之前文章里我也用到drawRGB的方法同样实现，当然也可以用fillRect等来刷屏。
那么这里我想说下，在继承view中，因为onDraw方法是系统自动调用的，不像在surfaceview这里这样去在run里面自己去不断调 用，在view中我们可以抵用 invalidate()/postInvalidate() 这两种方法实现让系统调用onDraw方法，这里也是和 surfaceview中的不同之一！
备注3
这里canvas.save();和canvas.restore();是两个相互匹配出现的，作用是用来保存画布的状态和取出保存的状态的。这里 稍微解释一下，
当我们对画布进行旋转，缩放，平移等操作的时候其实我们是想对特定的元素进行操作，比如图片，一个矩形等，但是当你用canvas的方法来进行这些 操作的时候，其实是对整个画布进行了操作，那么之后在画布上的元素都会受到影响，所以我们在操作之前调用canvas.save()来保存画布当前的状 态，当操作之后取出之前保存过的状态，这样就不会对其他的元素进行影响
