Question

正确实现了来自PackageInfo列表数据的appName和appVersion的值，但我希望将Package Info数据与数据库数据相匹配。

面临的问题：
如果我将db数据与for循环中的Package Info数据匹配，那么循环无限运行，如果我在循环外得到Package info数据，那么Package info只显示一个值。

那么如何在for循环之外获取所有的PackageInfo数据，以便它可以在循环外匹配？

代码段：

    Cursor cursor = dbHandler.getDeviceApkData();
    String dbName = null;
    String dbVersion = null;
        if (cursor.getCount() !=0) {

            if (cursor.moveToFirst()) {
                do {
                dbName = cursor.getString(1);
                dbVersion = cursor.getString(2);
           } while (cursor.moveToNext());
        }
    }
List<PackageInfo> pInfo=getPackageManager().getInstalledPackages(0);
    String appNameInfo = null;
    String versionInfo = null;
        for (PackageInfo packageInfo : pInfo) {
        appNameInfo = (String) getPackageManager().getApplicationLabel(packageInfo.applicationInfo);
        versionInfo = packageInfo.versionName;

    }

if (dbName.equals(appNameInfo) && dbVersion.equals(versionInfo)) {
// do something here
}
else{
// do something here
}

Answer 1

您需要将代码划分为多种方法，其中每种方法只执行一项特定作业。

首先，移动以下内容以获取appNameInfo和versionInfo方法：

List<PackageInfo> pInfo=getPackageManager().getInstalledPackages(0);
String appNameInfo = null;
String versionInfo = null;
for (PackageInfo packageInfo : pInfo) {
   appNameInfo = (String) getPackageManager().getApplicationLabel(packageInfo.applicationInfo);
   versionInfo = packageInfo.versionName;
}

我们可以看到您的代码产生了两个值：appNameInfo和versionInfo这两个值。因此，我们可以使用配对。我们还需要为每个packageInfo创建一个Pair列表。我们可以通过以下方法实现它：

private List<Pair<String, String>> getPackageInfos() {
  List<Pair<String, String>> pairs = new ArrayList<>();

  List<PackageInfo> pInfo=getPackageManager().getInstalledPackages(0);

  for (PackageInfo packageInfo : pInfo) {
     String appNameInfo = (String) getPackageManager().getApplicationLabel(packageInfo.applicationInfo);
     String versionInfo = packageInfo.versionName;
     pairs.add(new Pair<>(appNameInfo, versionInfo));
  }

  return pairs;
}

第二，您需要使数据库查询代码创建数据列表。因此，您需要更改以下代码：

Cursor cursor = dbHandler.getDeviceApkData();
String dbName = null;
String dbVersion = null;
    if (cursor.getCount() !=0) {

        if (cursor.moveToFirst()) {
            do {
            dbName = cursor.getString(1);
            dbVersion = cursor.getString(2);
       } while (cursor.moveToNext());
    }
}

这样的事情：

List<Pair<String, String>> dbNameVersions = new ArrayList<>();
Cursor cursor = dbHandler.getDeviceApkData();
String dbName = null;
String dbVersion = null;
    if (cursor.getCount() !=0) {

        if (cursor.moveToFirst()) {
            do {
            dbName = cursor.getString(1);
            dbVersion = cursor.getString(2);
            dbNameVersions.add(new Pair<>(dbName, dbVersion));
       } while (cursor.moveToNext());
    }
}

我们也使用配对：

List<Pair<String, String>> dbNameVersions = new ArrayList<>();

所以我们可以将数据与包信息数据进行比较。

第三次，我们可以根据dbNameVersions和getPackageInfos执行某些操作，方法是检查包信息中是否存在匹配的dbName和dbVersion，如下所示：

packageInfos.contains(dbNameVersion)

这是完整的代码（我没有这个）：

private List<Pair<String, String>> getPackageInfos() {
  List<Pair<String, String>> pairs = new ArrayList<>();

  List<PackageInfo> pInfo=getPackageManager().getInstalledPackages(0);

  for (PackageInfo packageInfo : pInfo) {
     String appNameInfo = (String) getPackageManager().getApplicationLabel(packageInfo.applicationInfo);
     String versionInfo = packageInfo.versionName;
     pairs.add(new Pair<>(appNameInfo, versionInfo));
  }

  return pairs;
}

private void checkData() {
  List<Pair<String, String>> dbNameVersions = new ArrayList<>();
  Cursor cursor = dbHandler.getDeviceApkData();
  String dbName = null;
  String dbVersion = null;

  if (cursor.getCount() !=0) {

     if (cursor.moveToFirst()) {
        do {
            dbName = cursor.getString(1);
            dbVersion = cursor.getString(2);
            dbNameVersions.add(new Pair<>(dbName, dbVersion));
        } while (cursor.moveToNext());
     }
  }

  List<Pair<String, String>> packageInfos = getPackageInfos();

  for(Pair<String,String> dbNameVersion: dbNameVersions) {
    if(packageInfos.contains(dbNameVersion)) {
      // found matching dbName and dbVersion in packageInfo.
      // do something
    } else {
      // do something when not found.
    }
  }
}

Answer 2

是否可以将for循环移入while循环？

 Cursor cursor = dbHandler.getDeviceApkData();
    String dbName = null;
    String dbVersion = null;
    if (cursor.getCount() != 0) {

        if (cursor.moveToFirst()) {
            do {
                dbName = cursor.getString(1);
                dbVersion = cursor.getString(2);

                List<PackageInfo> pInfo = getPackageManager().getInstalledPackages(0);
                String appNameInfo = null;
                String versionInfo = null;
                for (PackageInfo packageInfo : pInfo) {
                    appNameInfo = (String) getPackageManager().getApplicationLabel(packageInfo.applicationInfo);
                    versionInfo = packageInfo.versionName;

                    if (dbName.equals(appNameInfo) && dbVersion.equals(versionInfo)) {
                    // do something here
                    } else {
                        // do something here
                    }
                }

            } while (cursor.moveToNext());
        }
    }

如何在for循环外访问循环变量？

2 个答案: