增加xapk安装，未成功

app/src/main/java/com/example/mir4updater/utils/JsonUtils.java

@@ -0,0 +1,39 @@
+package com.example.mir4updater.utils;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+
+public class JsonUtils {
+    /**
+     * 读取json文件，返回json串
+     * @param fileName
+     * @return
+     */
+    public static String readJsonFile(String fileName) {
+        String jsonStr = "";
+        try {
+            File jsonFile = new File(fileName);
+            FileReader fileReader = new FileReader(jsonFile);
+
+            Reader reader = new InputStreamReader(new FileInputStream(jsonFile), StandardCharsets.UTF_8);
+            int ch = 0;
+            StringBuffer sb = new StringBuffer();
+            while ((ch = reader.read()) != -1) {
+                sb.append((char) ch);
+            }
+            fileReader.close();
+            reader.close();
+            jsonStr = sb.toString();
+            return jsonStr;
+        } catch (IOException e) {
+            e.printStackTrace();
+            return null;
+        }
+    }
+
+}