android-mcp-server

Instructions

Implementation Reference

• src/index.ts:360-406 (handler)

  The handler and registration for 'scroll_to_element' tool. It checks the UI tree for the element using the provided criteria and performs scrolls if not found.

  server.tool(
    "scroll_to_element",
    "Scroll down repeatedly until an element matching the given criteria is visible",
    {
      by: z.enum(["resource-id", "text", "content-desc"]).describe("How to find the element"),
      value: z.string().describe("Value to match"),
      max_scrolls: z.number().optional().default(10).describe("Maximum scroll attempts (default 10)"),
      device_id: z.string().optional().describe("Device ID (optional if only one device)"),
    },
    async ({ by, value, max_scrolls, device_id }) => {
      const finder: Record<string, (el: { resourceId: string; text: string; contentDesc: string }) => boolean> = {
        "resource-id": (el) => el.resourceId === value || el.resourceId.endsWith(`:id/${value}`),
        text: (el) => el.text.toLowerCase().includes(value.toLowerCase()),
        "content-desc": (el) => el.contentDesc.toLowerCase().includes(value.toLowerCase()),
      };
  
      const info = await adb.getDeviceInfo(device_id);
      const [w, h] = info.screenSize.split("x").map(Number);
      const centerX = Math.round(w / 2);
      const fromY = Math.round(h * 0.7);
      const toY = Math.round(h * 0.3);
  
      for (let i = 0; i < max_scrolls; i++) {
        const elements = await adb.getUiTree(device_id);
        const found = elements.find(finder[by]);
        if (found) {
          return {
            content: [
              {
                type: "text",
                text: `Found "${value}" after ${i} scrolls at (${found.center.x},${found.center.y})`,
              },
            ],
          };
        }
        await adb.swipe(centerX, fromY, centerX, toY, 500, device_id);
        await new Promise((r) => setTimeout(r, 500));
      }
  
      return {
        content: [
          { type: "text", text: `Element "${by}=${value}" not found after ${max_scrolls} scrolls` },
        ],
        isError: true,
      };
    },
  );