我正在尝试使用新的Saved Games (Snapshot) API
但我一直收到这个错误:
java.lang.NullPointerException: Attempt to invoke interface method 'boolean com.google.android.gms.games.snapshot.Snapshot.writeBytes(byte[])' on a null object reference
这是我正在尝试的代码
Snapshot snapshot = new Snapshot();
snapshot.writeBytes(my_app_state);
// Save the snapshot.
SnapshotMetadataChange metadataChange
= new SnapshotMetadataChange.Builder()
.setDescription("Completed %" + (levelscompleted/totallevels) + " of levels.")
.build();
Games.Snapshots.commitAndClose(getApiClient(), snapshot,
metadataChange);
我正在试图弄清楚如何初始化快照因为= new Snapshot(); 不起作用。
答案 0 :(得分:4)
Snapshot API在您必须执行的操作方面非常具体。以下是快照保存的高级过程:
以下代码来自Google Play Games Snapshot sample,其中介绍了如何在Android和iOS上跨平台使用Snapshots。
首先,您必须打开快照并解决打开时的冲突。
/**
* Prepares saving Snapshot to the user's synchronized storage, conditionally resolves errors,
* and stores the Snapshot.
*/
void saveSnapshot() {
AsyncTask<Void, Void, Snapshots.OpenSnapshotResult> task =
new AsyncTask<Void, Void, Snapshots.OpenSnapshotResult>() {
@Override
protected Snapshots.OpenSnapshotResult doInBackground(Void... params) {
Snapshots.OpenSnapshotResult result = Games.Snapshots.open(getApiClient(),
currentSaveName, true).await();
return result;
}
@Override
protected void onPostExecute(Snapshots.OpenSnapshotResult result) {
Snapshot toWrite = processSnapshotOpenResult(result, 0);
Log.i(TAG, writeSnapshot(toWrite));
}
};
task.execute();
}
接下来,您必须处理冲突解决方案:
/**
* Conflict resolution for when Snapshots are opened.
* @param result The open snapshot result to resolve on open.
* @return The opened Snapshot on success; otherwise, returns null.
*/
Snapshot processSnapshotOpenResult(Snapshots.OpenSnapshotResult result, int retryCount){
Snapshot mResolvedSnapshot = null;
retryCount++;
int status = result.getStatus().getStatusCode();
Log.i(TAG, "Save Result status: " + status);
if (status == GamesStatusCodes.STATUS_OK) {
return result.getSnapshot();
} else if (status == GamesStatusCodes.STATUS_SNAPSHOT_CONTENTS_UNAVAILABLE) {
return result.getSnapshot();
} else if (status == GamesStatusCodes.STATUS_SNAPSHOT_CONFLICT){
Snapshot snapshot = result.getSnapshot();
Snapshot conflictSnapshot = result.getConflictingSnapshot();
// Resolve between conflicts by selecting the newest of the conflicting snapshots.
mResolvedSnapshot = snapshot;
if (snapshot.getMetadata().getLastModifiedTimestamp() <
conflictSnapshot.getMetadata().getLastModifiedTimestamp()){
mResolvedSnapshot = conflictSnapshot;
}
Snapshots.OpenSnapshotResult resolveResult = Games.Snapshots.resolveConflict(
getApiClient(), result.getConflictId(), mResolvedSnapshot)
.await();
if (retryCount < MAX_SNAPSHOT_RESOLVE_RETRIES){
return processSnapshotOpenResult(resolveResult, retryCount);
}else{
String message = "Could not resolve snapshot conflicts";
Log.e(TAG, message);
Toast.makeText(getBaseContext(), message, Toast.LENGTH_LONG);
}
}
// Fail, return null.
return null;
}
以下代码是如何在the Google Play Games Snapshots sample app中完成的:
/**
* Generates metadata, takes a screenshot, and performs the write operation for saving a
* snapshot.
*/
private String writeSnapshot(Snapshot snapshot){
// Set the data payload for the snapshot.
snapshot.writeBytes(mSaveGame.toBytes());
// Save the snapshot.
SnapshotMetadataChange metadataChange = new SnapshotMetadataChange.Builder()
.setCoverImage(getScreenShot())
.setDescription("Modified data at: " + Calendar.getInstance().getTime())
.build();
Games.Snapshots.commitAndClose(getApiClient(), snapshot, metadataChange);
return snapshot.toString();
}
答案 1 :(得分:0)
我认为,而不是显式创建Snapshot对象。它应该在onActivityResult中生成。所以你需要在onActivityResult中处理它。然后你的writeBytes()将执行进一步的操作。
检查文档,其中loadFromSnapshot()包含
Snapshot snapshot = result.getSnapshot();
所以我认为,你的onActivityResult会得到null / false响应。如果没有,则按照loadFromSnapshot()文档中给出的相同步骤进行操作。