android活动的唯一ID

Question

我需要获取一个android活动实例的唯一ID.我想把活动管理器在日志中写入的字符串(例如:ActivityManager:HistoryRecord的活动暂停超时{ 450495a0 ...}),但我不知道如何获取它.

有人知道我怎么能得到这个字符串？或者每个活动实例还有另一个唯一ID吗？

Answer 1

也许你可以使用Activity的hashCode.

Answer 2

正如另一个答案中正确指出的那样，活动可以由操作系统重新创建，因此使用Activity.hashCode()不是一个可靠的解决方案。此外，整个应用程序进程可以重新创建（例如，在权限更改之后），这意味着任何运行时/非持久 ID 都不能被信任。正确的解决方案是在 期间手动生成唯一 ID onCreate(Bundle)（或从 读取savedInstanceState，如果存在）并在 期间保存onSaveInstanceState(Bundle)。

另一个问题是生成真正唯一的 ID。最简单、最可靠的解决方案也是保留一个静态计数器，但由于应用程序进程可能会终止，因此需要多加小心。

为了将样板代码降至最低，我组合了一个专门的类：

public class ActivityUUID {

    private static final String INSTANCE_DATA_ID = "BwsKCwYBDg8GAQ4LBAgAAA"; // NOTE Any globally unique ID
    private static final String UUID_NODE_ID = "a";
    private static final long INVALID_UUID = 0;

    private static long _lastActivityUUID = INVALID_UUID; // NOTE All activity callbacks are guaranteed to be made from UI thread, so no synchronization is required
    private static SharedPreferences _persistentData;

    private final long _uuid;

    public ActivityUUID(Context context, Bundle savedInstanceState) {
        _uuid = readUUID(context, savedInstanceState);
    }

    public long get() {
        return _uuid;
    }

    public void onSaveInstanceState(Bundle outState) {
        outState.putLong(INSTANCE_DATA_ID, _uuid);
    }

    private static long readUUID(Context context, Bundle savedInstanceState) {
        long result = (savedInstanceState != null) ? savedInstanceState.getLong(INSTANCE_DATA_ID, INVALID_UUID) : INVALID_UUID;
        return (result != INVALID_UUID) ? result : generateUUID(context);
    }

    private static long generateUUID(Context context) {
        if (_persistentData == null) {
            _persistentData = context.getSharedPreferences(INSTANCE_DATA_ID, Context.MODE_PRIVATE);
            _lastActivityUUID = _persistentData.getLong(UUID_NODE_ID, INVALID_UUID);
        }

        long result = ++_lastActivityUUID;
        if (result != INVALID_UUID) {
            _persistentData.edit().putLong(UUID_NODE_ID, result).apply();
        } else {
            throw new RuntimeException("You have somehow managed to create a total of 9223372036854775807 activities during lifetime of your app! =)");
        }
        return result;
    }

}

用法非常简单：

private ActivityUUID _activityUUID;

@Override
public final void onCreate(Bundle savedInstanceState) {
    _activityUUID = new ActivityUUID(this, savedInstanceState);
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    _activityUUID.onSaveInstanceState(outState);
}

// ...somewhere else in the code
long activityUUID = _activityUUID.get();