根据ActivityManager的getInstalledApplications方法获取手机中所有的应用程序，通过context.createPackageContext得到每个应用的Context对象，循环遍历getCacheDir和getExternalFilesDir中的所有文件 得到缓存文件大小，

 long toatal = 0L;
        final List<ApplicationInfo> packages = packageManager.getInstalledApplications(PackageManager.GET_META_DATA);
        List<AppProcessInfo> list = new ArrayList<>();
        for (ApplicationInfo appInfo : packages) {
            AppProcessInfo processInfo = new AppProcessInfo(appInfo.processName, appInfo.uid, appInfo.uid);
            processInfo.isSystem = (appInfo.flags & ApplicationInfo.FLAG_SYSTEM) != 0;
            Drawable icon = appInfo.loadIcon(packageManager);
            String appName = appInfo.loadLabel(packageManager).toString();
            processInfo.icon = icon;
            processInfo.appName = appName;
            processInfo.packName = appInfo.packageName;
            Context mContext = null;
            try {
                mContext = context.createPackageContext(appInfo.packageName, Context.CONTEXT_IGNORE_SECURITY);
                // Context.getExternalFilesDir() --> SDCard/Android/data/你的应用的包名/files/
                // 目录，一般放一些长时间保存的数据
                // Context.getExternalCacheDir() --> SDCard/Android/data/你的应用包名/cache/
                // 目录，一般存放临时缓存数据
                processInfo.memory = ExternalUtil.getTotalCacheSize(Objects.requireNonNull(mContext));
                list.add(processInfo);

                if(processInfo.memory > 0){
                    String typeName = processInfo.isSystem ? "系统应用" : "本地应用";
                    final String content = typeName + processInfo.appName + "-Cache:" + ExternalUtil.size(processInfo.memory);
                    Log.d("ddd", content);
                    toatal += processInfo.memory;

                    final long finalToatal = toatal;
                    context.runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            textTotal.setText(String.format("缓存总大小为 ： %s", ExternalUtil.size(finalToatal)));
                            sb.append(content).append("\r\n");
                            textLog.setText(sb.toString());
                        }
                    });
                }
            } catch (PackageManager.NameNotFoundException e) {
                e.printStackTrace();
            }
        }

  /**
     * 获取缓存值
     */
    public static long getTotalCacheSize(Context context) {
        long externalCacheSize = 0L;
        long externalFileSize = 0L;
        long internalCacheSize = 0L;
        long internalFileSize = 0L;
        internalCacheSize = getFolderSize(context.getCacheDir());
//        internalFileSize  = getFolderSize(context.getFilesDir());
        if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
            externalCacheSize = getFolderSize(context.getExternalCacheDir());
//            externalFileSize  = getFolderSize(context.getExternalFilesDir(""));
        }
        return internalCacheSize + externalCacheSize + internalFileSize + externalFileSize;
    }

    /**
     * 获取文件
     */
    public static long getFolderSize(File file) {
        long size = 0;
        if (file != null) {
            File[] fileList = file.listFiles();
            if (fileList != null && fileList.length > 0) {
                for (File value : fileList) {
                    // 如果下面还有文件
                    if (value.isDirectory()) {
                        size = size + getFolderSize(value);
                    } else {
                        size = size + value.length();
                    }
                }
            }
        }
        return size;
    }

    /**
     * 将文件大小显示为GB,MB等形式
     */
    public static String size(long size) {
        if (size / (1024 * 1024 * 1024) > 0) {
            float tmpSize = (float) (size) / (float) (1024 * 1024 * 1024);
            DecimalFormat df = new DecimalFormat("#.##");
            return "" + df.format(tmpSize) + "GB";
        } else if (size / (1024 * 1024) > 0) {
            float tmpSize = (float) (size) / (float) (1024 * 1024);
            DecimalFormat df = new DecimalFormat("#.##");
            return "" + df.format(tmpSize) + "MB";
        } else if (size / 1024 > 0) {
            return "" + (size / (1024)) + "KB";
        } else
            return "" + size + "B";

    }