边做游戏边学android—7（塔防②创建目标）

创建目标类、代码如下：

package com.example.object;


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 com.example.tafang.R;

public class Target {

    private Resources resources;
    private Bitmap target;
    private float object_x;
    private float object_y;
    private float object_width;
    private float object_height;
    private float middle_x;
    private float middle_y;
    private Paint paint;
    private float screen_width;
    private float screen_height;

    public Target(Resources resources){
        this.resources = resources;
        initBitmap();
        this.paint = new Paint();
        paint.setColor(Color.BLACK);
        object_x = 20;
        object_y = 20;
    }

    public void getScreenWH(float screen_width,float screen_height){
        this.screen_width = screen_width;
        this.screen_height = screen_height;
        object_x = this.screen_width/2;

    }

    private void initBitmap(){
        target = BitmapFactory.decodeResource(resources, R.drawable.enemy);
        object_width = target.getWidth();
        object_height = target.getHeight();
        middle_x = object_x + object_width/2;
        middle_y = object_y + object_height/2;
    }

    public void drawSelf(Canvas canvas){
        if(object_y < screen_width){
            canvas.save();
            canvas.rotate(90, object_x, object_y);
            canvas.clipRect(object_x, object_y, object_x + object_width , object_y + object_height);
            canvas.drawBitmap(target, object_x, object_y, paint);

            canvas.restore();
        }

    }

    public float getMiddle_x() {
        return middle_x;
    }

    public void setMiddle_x(float middle_x) {
        this.middle_x = middle_x;
        this.object_x = middle_x - this.object_width/2;
    }

    public float getMiddle_y() {
        return middle_y;
    }

    public void setMiddle_y(float middle_y) {
        this.middle_y = middle_y;
        this.object_y = middle_y - this.object_height/2;
    }




}

创建gameview类

package com.example.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.view.SurfaceHolder;
import android.view.SurfaceHolder.Callback;
import android.view.SurfaceView;

import com.example.object.Target;
import com.example.tafang.MainActivity;

public class GameView extends SurfaceView implements SurfaceHolder.Callback,Runnable {

    private Target target;
    private Thread thread;
    private float screen_width;
    private float screen_height;
    private Canvas canvas;
    private MainActivity main;
    private SurfaceHolder sfh;

    public GameView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        this.main = (MainActivity)context;
        sfh = this.getHolder();
        target = new Target(getResources());
        sfh.addCallback(this);
        thread = new Thread(this);
    }

    public void initObject(){

    }

    public void drawSelf(){
        try{
            canvas = sfh.lockCanvas();
            canvas.drawColor(Color.WHITE);
            target.drawSelf(canvas);
        } finally{
            if(canvas != null){
                sfh.unlockCanvasAndPost(canvas);
            }
        }


    }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        int i=0;
        while (true) {
            if(i == 3){
                initObject();
                i=0;
            }
            drawSelf();
            target.setMiddle_y(target.getMiddle_y() + 10);
            if(target.getMiddle_y()>screen_height){
                target.setMiddle_y(0);
            }
            i ++;
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

    }

    @Override
    public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
        // TODO Auto-generated method stub

    }

    @Override
    public void surfaceCreated(SurfaceHolder arg0) {
        // TODO Auto-generated method stub
        screen_height = this.getHeight();
        screen_width = this.getWidth();
        target.getScreenWH(screen_width, screen_height);
        if(thread.isAlive()){
            thread.start();
        } else {
            thread = new Thread(this);
            thread.start();
        }

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder arg0) {
        // TODO Auto-generated method stub

    }

}

运行结果如下：