【Android原创】自定义SurfaceViews实现地图移动

屏幕显示地图指定的位置，并且流程滚动。

黑色框代表屏幕大小

红色框代表地图大小

。。。

想想原理是这样的，但是通过代码怎么实现呢？

忽然想起createBitmap可以截取某一片区域

于是乎准备自定义SurfaceView

因为SurfaceView是独立线程，所以优先考虑

package com.ask.jilun.view;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.WindowManager;

import com.ask.jilun.R;

/**
 */

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

    private SurfaceHolder surfaceHolder;
    private Context context;
    private int windowWidth;//屏幕宽高
    private int windowHeight;
    private boolean isRunning;
    private Paint paint;
    private Bitmap mapBitmap;//地图
    private int mapBitmapWidth;//地图的宽高
    private int mapBitmapHeight;
    private Bitmap nowBitmap;//现在显示的部分
    private Thread thread;
    private int startX,startY;//开始剪裁的位置

  
    public MapsView(Context context,int startX ,int startY) {
        super(context);
        this.context = context;
        surfaceHolder = getHolder();
        surfaceHolder.addCallback(this);
        WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
        windowWidth = wm.getDefaultDisplay().getWidth();
        windowHeight = wm.getDefaultDisplay().getHeight();
        this.startX = startX;
        this.startY = startY;
        paint = new Paint();
        mapBitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.mapfengyuegu);
        mapBitmapWidth = mapBitmap.getWidth();
        mapBitmapHeight = mapBitmap.getHeight();
        isRunning = true;
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        thread = new Thread(this);
        thread.start();
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        isRunning = false;
        thread.destroy();//销毁线程
    }

    @Override
    public void run() {
        Canvas canvas = null;
        while (isRunning){
            synchronized (surfaceHolder) {
                canvas = surfaceHolder.lockCanvas(null);
                doDraw(canvas,startX,startY);
                try {
                    Thread.sleep(10);//刷新频率
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }finally {
                    surfaceHolder.unlockCanvasAndPost(canvas);
                }
            }
            startX += 10;
            startY += 10;
        }
    }

    /**
     * 根据移动的距离在地图中剪裁对应的位置
     * @param canvas
     * @param startX 开始的X
     * @param startY 开的的Y
     *
     *               注意：开始剪裁的X+WindowX Y+WindowY 不能大于mapBitmap
     */
    private void doDraw(Canvas canvas ,int startX , int startY) {
        if(startX+windowWidth <= mapBitmapWidth && startY+windowHeight <= mapBitmapHeight){
            nowBitmap = Bitmap.createBitmap(mapBitmap,startX,startY,windowWidth,windowHeight);
            canvas.drawBitmap(nowBitmap,this.startX,this.startY,paint);
        }else{
            isRunning = false;
        }
    }
}

这是地图的原图，是不是比屏幕要大的多了