just to save works

app/src/main/assets/sample/画图/函数图像.js

@@ -0,0 +1,24 @@
+"ui";
+ui.layout(
+    <frame>
+        <canvas id="graphic" w="*" h="*"/>
+    </frame>
+);
+
+var f = function(x){
+    return x * x + 3 * x - 4;
+}
+
+var paint = new Paint();
+paint.setStrokeWidth(2);
+var start = -5;
+var end = 5;
+
+ui.graphic.on("draw", function(canvas){
+    var w = canvas.getWidth();
+    for (var i = 0; i < w; i++) {
+        var x = (end - start) / w * i + start;
+        var y = f(x);
+        canvas.drawPoint(x, y, paint);
+    }
+});