Wie wird das Ereignis onclick beim Verschieben von Objekten in Canvas festgelegt?

Question

Wie wird ein Klickereignis in einem bewegten Objekt im Canvas festgelegt? Auch, wie man das Objekt unten nach oben in canvas.I bewegen bin neu in Javascript ich werde das Beispiel zu entwickeln, wie wenn die Seite geöffnet, Objekte wie Quadrat und Kreis kommen zufällig von der Unterseite der Seite und nach oben automatisch verschieben.

Answer 1

Sie müssen ein Array einrichten, in dem sich Ihre beweglichen Objekte befinden. Wenn der onclick-Handler ausgelöst wird, überprüfen Sie, ob sich die Koordinaten des Klicks in einem der Objekte im Array befinden.

Verschieben Sie in jedem Animationsframe Ihre Objekte, indem Sie einige der y-Koordinaten von jedem Objekt subtrahieren.

//width and height of canvas... 
 
var rW = 400; 
 
var rH = 500; 
 

 
var coinImage = getCoinImage(); 
 
var coinsOnScreen = []; 
 
var risingSpeed = 100; //pixels per second... 
 
var coinSize = 75; 
 

 
var lastAnimationTime = 0; 
 
var howLongUntilNextCoin = 1000; 
 
var nextCoinOnScreen = 0; 
 

 
function doDraw() { 
 
    var can = document.getElementById("myCanvas"); 
 
    can.width = rW; 
 
    can.height = rH; 
 
    var context = can.getContext("2d"); 
 

 
    //Erase the canvas 
 
    context.fillStyle = "#FFFFFF"; 
 
    context.fillRect(0, 0, rW, rH); 
 

 
    if (new Date().getTime() - nextCoinOnScreen > 0) { 
 

 
    var newX = Math.floor(Math.random() * rW) + 1; 
 
    var newY = rH + 50; 
 

 
    var newCoin = { 
 
     x: newX, 
 
     y: newY 
 
    }; 
 
    coinsOnScreen.push(newCoin); 
 
    nextCoinOnScreen = new Date().getTime() + howLongUntilNextCoin; 
 
    } 
 

 
    //Now draw the coins 
 
    if (lastAnimationTime != 0) { 
 

 
    var deltaTime = new Date().getTime() - lastAnimationTime; 
 
    var coinRisePixels = Math.floor((deltaTime * risingSpeed)/1000); 
 

 
    var survivingCoins = []; 
 
    for (var i = 0; i < coinsOnScreen.length; i++) { 
 
     var coin = coinsOnScreen[i]; 
 
     coin.y = coin.y - coinRisePixels; 
 
     //the stl variable controlls the alpha of the image    
 
     if (coin.y + 50 > 0) { 
 
     context.drawImage(coinImage, coin.x, coin.y); 
 
     //this coin is still on the screen, so promote it to the new array... 
 
     survivingCoins.push(coin); 
 
     } 
 
    } 
 
    coinsOnScreen = survivingCoins; 
 
    } 
 
    lastAnimationTime = new Date().getTime(); 
 
    //Wait, and then call this function again to animate: 
 
    setTimeout(function() { 
 
    doDraw(); 
 
    }, 30); 
 
} 
 

 
function setupClickHandler() { 
 
    var can = document.getElementById("myCanvas"); 
 
    //Here is the onclick handler 
 
    can.onclick = function(e) { 
 
    var x = e.clientX; 
 
    var y = e.clientY; 
 
    var survivingCoins = []; 
 
    for (var i = 0; i < coinsOnScreen.length; i++) { 
 
     var coin = coinsOnScreen[i]; 
 
     //check to see if this coin has been clicked... 
 
     if (x > coin.x && x < coin.x + coinSize && y > coin.y && y < coin.y + coinSize) { 
 
     //ths coin will disappear because it is not inserted into the new array... 
 
     console.log("Coin was clicked!! " + x + " " + y); 
 
     } else { 
 
     survivingCoins.push(coin); 
 
     } 
 

 
    } 
 
    coinsOnScreen = survivingCoins; 
 
    }; 
 

 
} 
 

 

 
doDraw(); 
 
setupClickHandler(); 
 

 
function getCoinImage() { 
 
    var image = new Image(50, 50); 
 
    image.src = 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TECEECUeASRbP4zaILaPUC+EZCtDmQD27oMvDhMBeWsh0BH3QTSF4BuOwBkX4LFCSO2RW5EeAQgwACQYpcXuHTdswAAAABJRU5ErkJggg=="; 
 
    return image; 
 
}

<canvas id="myCanvas"></canvas>