有没有更好的方法来制作可拖动的背景？
我正在开始一个新项目，到目前为止，我已经制作了一个简单的应用程序，其中有一个绘制在 Canvas 上的图像，您可以用手指在屏幕上拖动该图像。这个想法是在游戏的 Canvas 上绘制大量内容。然而，拖动速度非常缓慢，用手指拖动时，屏幕可能每秒更新图像 2-3 次。它的速度非常慢，所以我假设我做错了（我使用的是 Nexus S）。
我只有应用程序的基本框架，只有一个 SurfaceView，其中包含一个线程，用于使用这一张图像更新 Canvas。这是代码：
// In GameThread
private void doDraw(Canvas c) {
if(canvasInit){
Bitmap background = BitmapFactory.decodeResource(mContext.getResources(), R.drawable.bg);
c.drawBitmap(background, offsetX, offsetY, null);
}
}
public boolean doTouchDown(MotionEvent event) {
if(drag == false){
//initialize drag
startX = event.getX();
startY = event.getY();
drag = true;
}else{
//caluclate new position
offsetX = Math.max(Math.min(0, offsetX + (event.getX() - startX)), mCanvasWidth - BACKGROUND_WIDTH);
offsetY = Math.max(Math.min(0, offsetY + (event.getY() - startY)), mCanvasHeight- BACKGROUND_HEIGHT);
startX = event.getX();
startY = event.getY();
}
return true;
}
public boolean doTouchUp(MotionEvent event){
drag = false;
return true;
}
I'm starting out a new project, and thus far I've made a simple app that has an image which is drawn onto a Canvas, which you can drag around the screen with your finger. The idea is to draw lots of stuff onto this Canvas for a game. However the dragging is extremely laggy, while dragging with my finger the screen updates the image maybe 2-3 times a second. It's very noticeably slow, so I'm assuming I'm doing it very wrong (I'm on a Nexus S).
I only have the very barebones of the app, just a SurfaceView containing a thread to update the Canvas with this one image. Here's the code:
// In GameThread
private void doDraw(Canvas c) {
if(canvasInit){
Bitmap background = BitmapFactory.decodeResource(mContext.getResources(), R.drawable.bg);
c.drawBitmap(background, offsetX, offsetY, null);
}
}
public boolean doTouchDown(MotionEvent event) {
if(drag == false){
//initialize drag
startX = event.getX();
startY = event.getY();
drag = true;
}else{
//caluclate new position
offsetX = Math.max(Math.min(0, offsetX + (event.getX() - startX)), mCanvasWidth - BACKGROUND_WIDTH);
offsetY = Math.max(Math.min(0, offsetY + (event.getY() - startY)), mCanvasHeight- BACKGROUND_HEIGHT);
startX = event.getX();
startY = event.getY();
}
return true;
}
public boolean doTouchUp(MotionEvent event){
drag = false;
return true;
}
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评论（2）
您似乎每次绘制时都会加载位图。您可以尝试将资源加载移动到某种初始化方法/ SurfaceView 构造函数并比较性能？
You seem to be loading the Bitmap every time you draw. You can try moving the resource loading to some kind of initialisation method/ SurfaceView constructor and compare the performance?
我认为问题出在
doDraw方法中，您每次Draw创建一个新的位图，尝试在构造函数中加载此Bitmapcode> 然后在 doDraw 方法中获取它的引用，并使用您的 x 和 y 绘制它。I Think the problem is in
doDrawmethod, your creating a new Bitmap everyDraw, try to load thisBitmapinConstructorthen get it reference indoDrawmethod, and draw it using your x and y.