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Javascript を使用して HTML5 Canvas アニメーションのコードを書いています。そのために使っrequestAnimFrameています。アニメーションはポイントに対して正常に機能しています。requestAnimFrameしかし、 orを使用している関数にループ (for または while) を追加するとsetTimeout、アニメーションが機能しません。ループを追加することは私にとって重要です。それを可能にするための提案はありますか？

function animate(lastTime) {
            var date = new Date();
            var time = date.getTime();
            var timeDiff = time - lastTime;
            var linearSpeed = 100;
            var linearDistEachFrame = linearSpeed * timeDiff / 1000;
            var currentX = LINE.x;              
            var currentY = LINE.y;
                var newY = currentY + linearDistEachFrame;
                var newX = currentX + linearDistEachFrame;
                context.beginPath();
                context.moveTo(LINE.x, LINE.y);
                lastTime = time;

                var Xindex=LINE.arrayX.indexOf(newX);

                //here am getting error..if i replace this with 'if' its working fine..and even if there is not a single LOC it doesnt work
                 while(Xindex!=-1) {
                                        //processes the loop
                 }

                context.lineTo(LINE.x, LINE.y);
                context.fillStyle = "red";
                context.fill();
                context.lineWidth = LINE.borderWidth;
                context.strokeStyle = "red";
                context.stroke();
            // request new frame

            requestAnimFrame(function() {
                animate(lastTime);
            });
        }
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Try adding a break statement in the loop and see if that fixes it. If it does, it means that the condition has been met, and the code will be stuck in the loop forever unless you break out, or change Xindex to -1.

You need to narrow down exactly where the code is failing. One way to do this is by printing out debug statements at key parts of the code, so you know for sure they were executed, and what the value of important variables was.

You can use console.log("test"); for example, to write to Chrome's JavaScript console, or Firebug, or similar.

One trouble you'll face with debug output for a working animation program is the screeds of output. You might want to log only in certain interesting circumstances or you'll be drowning in a stream. Of data.

于 2012-04-16T11:59:24.950 に答える