SyncAdapter运行动画 - 如何知道SyncAdapter是否正在主动同步

Question

我想在ActionBar中显示ProgressBar,而我的SyncAdapter正在主动与Web同步内容.

我已尝试将SyncStatusObserver与ContentProvider.addStatusChangeListener一起使用.但是,我无法检查SyncAdapter是否正在运行.我只能检查:

1. SyncAdapter正在使用ContentResolver.isSyncPending挂起
2. SyncAdapter正在等待或正在使用ContentResolver.isSyncActive正在工作

可以组合这些标志:!isSyncPending && isSyncActive这样就可以检查SyncAdapter是否正在正常工作,并且没有任何待处理的工作.但是,在某些情况下,SyncAdapter正在正常工作,并有第二个等待它的待处理请求.

看起来很简单,但我无法找到解决这个问题的方法.在SyncAdapter未运行时显示ProgressBar会让用户感觉同步非常慢.让它不显示ProgressBar会让用户认为没有任何事情发生.

代码中的上述解决方案如下所示.我们在activity.onResume中注册观察者:

 int mask = ContentResolver.SYNC_OBSERVER_TYPE_PENDING | ContentResolver.SYNC_OBSERVER_TYPE_ACTIVE;
 syncHandle = ContentResolver.addStatusChangeListener(mask, syncObserver);

syncObserver在这里定义为:

syncObserver = new SyncStatusObserver()
{
    @Override
    public void onStatusChanged(int which)
    {
        Account account = getSomeAccount();
        boolean syncActive = ContentResolver.isSyncActive(account, CONTENT_AUTHORITY);
        boolean syncPending = ContentResolver.isSyncPending(account, CONTENT_AUTHORITY);
        boolean isSynchronizing = syncActive && !syncPending;
        updateRefreshButtonState();
    }
}

Answer 1

我终于找到了问题的解决方案.我们的想法是使用ContentResolver的getCurrentSyncs()或getCurrentSync()方法,无论哪种方法都可用.以下方法将检查同步操作当前是否适用于帐户和权限.它需要API级别8(Froyo = Android 2.2).

private static boolean isSyncActive(Account account, String authority)
{
    if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB)
    {
        return isSyncActiveHoneycomb(account, authority);
    } else
    {
        SyncInfo currentSync = ContentResolver.getCurrentSync();
        return currentSync != null && currentSync.account.equals(account) &&
               currentSync.authority.equals(authority);
    }
}

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
private static boolean isSyncActiveHoneycomb(Account account, String authority)
{
    for(SyncInfo syncInfo : ContentResolver.getCurrentSyncs())
    {
        if(syncInfo.account.equals(account) &&
           syncInfo.authority.equals(authority))
        {
            return true;
        }
    }
    return false;
}

然后,一个Activity注册更新onResume()和注销onDestroy().此外,必须手动更新状态onResume()以赶上当前状态.

这是一个实现这一点的实现.子类应该自己定义

• 什么帐户使用(实施getAccount())
• 什么授权使用(领域CONTENT_AUTHORITY)
• 如何显示同步状态(实现updateState(boolean isSynchronizing))

我希望将来可以帮助某人.

import android.accounts.Account;
import android.annotation.TargetApi;
import android.app.Activity;
import android.content.ContentResolver;
import android.content.SyncInfo;
import android.content.SyncStatusObserver;
import android.os.Build;
import android.os.Bundle;

public abstract class SyncActivity extends Activity
{
    private static final String CONTENT_AUTHORITY = "com.example.authority";
    private Object syncHandle;
    private SyncStatusObserver observer;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);

        observer = new SyncStatusObserver()
        {
            @Override
            public void onStatusChanged(int which)
            {
                runOnUiThread(new Runnable()
                {
                    @Override
                    public void run()
                    {
                        Account account = getAccount();
                        boolean isSynchronizing =
                                isSyncActive(account, CONTENT_AUTHORITY);
                        updateState(isSynchronizing);
                    }
                });
            }
        };
    }

    @Override
    protected void onResume()
    {
        super.onResume();

        // Refresh synchronization status
        observer.onStatusChanged(0);

        // Watch for synchronization status changes
        final int mask = ContentResolver.SYNC_OBSERVER_TYPE_PENDING |
                ContentResolver.SYNC_OBSERVER_TYPE_ACTIVE;
        syncHandle = ContentResolver.addStatusChangeListener(mask, observer);
    }

    @Override
    protected void onPause()
    {
        super.onPause();

        // Remove our synchronization listener if registered
        if (syncHandle != null)
        {
            ContentResolver.removeStatusChangeListener(syncHandle);
            syncHandle = null;
        }
    }

    private static boolean isSyncActive(Account account, String authority)
    {
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB)
        {
            return isSyncActiveHoneycomb(account, authority);
        } else
        {
            SyncInfo currentSync = ContentResolver.getCurrentSync();
            return currentSync != null && currentSync.account.equals(account) 
                    && currentSync.authority.equals(authority);
        }
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    private static boolean isSyncActiveHoneycomb(Account account,
                                                         String authority)
    {
        for(SyncInfo syncInfo : ContentResolver.getCurrentSyncs())
        {
            if(syncInfo.account.equals(account) &&
                    syncInfo.authority.equals(authority))
            {
                return true;
            }
        }
        return false;
    }

    protected abstract Account getAccount();
    protected abstract void updateState(boolean isSynchronizing);
}