经过彻底的调试后，我得出结论，我的GridView未显示任何图片的原因是因为OnSuccessListeners和getData()中的getImage()来自何时我从Firebase存储中获取缩略图和标题尚未成功。
我在getData()方法中执行了所有操作，我在用户选择onActivityResult中的Google地方信息后调用此方法。该方法应该实例化一个新的ImageItem（位图，字符串），但由于ImageItem尚未成功，因此返回空onSucessListeners。有任何想法吗？
private void getData() {
imageItems = new ArrayList<>();
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.child((String) p.getName()).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
Iterator<DataSnapshot> iter = dataSnapshot.getChildren().iterator();
FirebaseStorage storage = FirebaseStorage.getInstance();
StorageReference httpsReference = storage.getReferenceFromUrl(myUrl);
while (iter.hasNext()) {
hasImage = false;
hasTitle = false;
HashMap<String, String> m = (HashMap<String, String>) iter.next().getValue();
String v = m.get("url");
Log.d("url", v);
String bu = m.get("bucket");
Log.d("bucket", bu);
b = getImage(bu, v);
StorageReference iR = httpsReference.child(bu).child("thumb");
httpsReference.child(bu).getMetadata().addOnSuccessListener(new OnSuccessListener<StorageMetadata>() {
@Override
public void onSuccess(StorageMetadata storageMetadata) {
// Metadata now contains the metadata for 'images/forest.jpg'
t = storageMetadata.getCustomMetadata("title");
hasTitle = true;
Log.d("title", t);
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception exception) {
Log.d("error", "ERROr");
// Uh-oh, an error occurred!
}
});
gridAdapter.data.add(new ImageItem(b, t, bu, v));
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
public Bitmap getImage(String bx, String vu) {
FirebaseStorage storage = FirebaseStorage.getInstance();
StorageReference httpsReference = storage.getReferenceFromUrl(myUrl);
String v = vu;
Log.d("url", v);
String bu = bx;
Log.d("bucket", bu);
StorageReference iR = httpsReference.child(bu).child("thumb");
final long ONE_MEGABYTE = 1024 * 1024;
iR.getBytes(ONE_MEGABYTE).addOnSuccessListener(new OnSuccessListener<byte[]>() {
@Override
public void onSuccess(byte[] bytes) {
// Data for "images/island.jpg" is returns, use this as needed
b = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
hasImage = true;
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception exception) {
// Handle any errors
}
});
return b;
}
}
****************更新1/7/2017 *********************
private void getData() {
imageItems = new ArrayList<>();
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.child((String) p.getName()).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
Iterator<DataSnapshot> iter = dataSnapshot.getChildren().iterator();
FirebaseStorage storage = FirebaseStorage.getInstance();
final StorageReference httpsReference = storage.getReferenceFromUrl("gs://socialnetwork-4b0c9.appspot.com");
while (iter.hasNext()) {
hasImage = false;
hasTitle = false;
HashMap<String, String> m = (HashMap<String, String>) iter.next().getValue();
final String v = m.get("url");
Log.d("url", v);
final String bu = m.get("bucket");
Log.d("bucket", bu);
StorageReference iR = httpsReference.child(bu).child("thumb");
final long ONE_MEGABYTE = 1024 * 1024;
iR.getBytes(ONE_MEGABYTE).addOnSuccessListener(new OnSuccessListener<byte[]>() {
@Override
public void onSuccess(byte[] bytes) {
// Data for "images/island.jpg" is returns, use this as needed
b = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
httpsReference.child(bu).getMetadata().addOnSuccessListener(new OnSuccessListener<StorageMetadata>() {
@Override
public void onSuccess(StorageMetadata storageMetadata) {
// Metadata now contains the metadata for 'images/forest.jpg'
t = storageMetadata.getCustomMetadata("title");
hasTitle = true;
gridAdapter.data.add(new ImageItem(b, t, bu, v));
Log.d("title", t);
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception exception) {
Log.d("error", "ERROr");
// Uh-oh, an error occurred!
}
});
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception exception) {
// Handle any errors
}
});
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
************************用于网格和网格的方法*********
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == PLACE_AUTOCOMPLETE_REQUEST_CODE) {
if (resultCode == RESULT_OK) {
Place place = PlaceAutocomplete.getPlace(this, data);
p = place;
gridView = (GridView) findViewById(R.id.grid_View);
gridAdapter = new GridViewAdapter(this, R.layout.grid_item_layout);
getData();
gridView.setAdapter(gridAdapter);
gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
ImageItem item = (ImageItem) parent.getItemAtPosition(position);
//Create intent
Intent intent = new Intent(PlaceActivity.this, VideoActivity.class);
intent.putExtra("bucket", item.getBucket());
intent.putExtra("dUrl", item.getdUrl());
//Start details activity
startActivity(intent);
}
});
} else if (resultCode == PlaceAutocomplete.RESULT_ERROR) {
Status status = PlaceAutocomplete.getStatus(this, data);
// TODO: Handle the error.
} else if (resultCode == RESULT_CANCELED) {
// The user canceled the operation.
}
}
}
答案 0 :(得分：0)
这是一个经典的异步编程问题：
var a = 1;
incrementAsync(function() {
a = 2;
});
console.log(a); // prints 1 because the function hasn't returned yet
您需要在异步函数中执行操作：
var a = 1;
incrementAsync(function() {
a = 2;
console.log(a); // prints 2 now
});
所以我将你的功能重写为：
FirebaseDatabase mDatabase = FirebaseDatabase.getInstance();
FirebaseStorage mStorage = FirebaseStorage.getInstance();
mDatabase.getReference("...").addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String previousChildName) {
ModelObject modelObject = storage.getValue(ModelObject.class);
// Or just download the object here...
mStorage.getReferenceFromUrl(modelObject.getUrl()).getMetadata().addOnSuccessListener(new OnSuccessListener<StorageMetadata>() {
@Override
public void onSuccess(StorageMetadata storageMetadata) {
String title = storageMetadata.getCustomMetadata("title");
gridAdapter.data.add(...);
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception exception) {
// Uh-oh, an error occurred!
}
});
}
...
});