借助于Bitmap的createBitmap()方法可以“挖取”源位图的其中一块，这样可以在程序中通过定时器控制不断地“挖取”源位图不同位置的块，从而给用户看到背景移动“假象”。
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
public class MoveBack extends Activity{
@Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new MyView(this));
}
class MyView extends View{
//记录背景位图的实际高度
final int BACK_HEIGHT = 1700;
//背景图片
private Bitmap back;
private Bitmap plane;
//背景图片的开始位置
final int WIDTG = 320;
final int HEIGHT = 440;
private int startY = BACK_HEIGHT - HEIGHT;
public MyView(Context context) {
super(context);
back = BitmapFactory.decodeResource(context.getResources(), R.drawable.back_img);
plane = BitmapFactory.decodeResource(context.getResources(), R.drawable.plane);
final Handler handler = new Handler(){
@Override
public void handleMessage(Message msg) {
if(msg.what == 0x123){
//重新开始移动
if(startY <= 0){
startY = BACK_HEIGHT - HEIGHT;
}else{
startY -= 3;
}
}
invalidate();
}
};
new Timer().schedule(new TimerTask() {
@Override
public void run() {
handler.sendEmptyMessage(0x123);
}
}, 0, 100);
}
@Override
protected void onDraw(Canvas canvas) {
// 根据原始位图和Matrix创建新图片
Bitmap bitmap2 = Bitmap.createBitmap(back, 0, startY, WIDTG, HEIGHT);
//绘制新位图
canvas.drawBitmap(bitmap2, 0, 0 , null);
//绘制飞机
canvas.drawBitmap(plane, 160, 380, null);
}
}
}