Question

我试图在活动开始时显示listView，其中条目位于firebase中，但是活动没有显示任何内容，当我点击屏幕上的某个地方时onItemClickListener正常工作

我的问题是因为onDataChange仅适用于数据库中的更改

在布局中，可见性全部设置为true，因此它与可见性

无关

public class ViewUploads extends AppCompatActivity{

    //the listview
    ListView listView;

    //database reference to get uploads data
    DatabaseReference mDatabaseReference;

    //list to store uploads data
    List<Upload> uploadList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_view_uploads);

        uploadList = new ArrayList<>();
        listView = (ListView) findViewById(R.id.listView);





        //adding a clicklistener on listview
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                //getting the upload
                Upload upload = uploadList.get(i);

                //Opening the upload file in browser using the upload url
                Intent intent = new Intent(Intent.ACTION_VIEW);
                intent.setData(Uri.parse(upload.getUrl()));
                startActivity(intent);
            }
        });


        //getting the database reference
        mDatabaseReference = FirebaseDatabase.getInstance().getReference(Constants.DATABASE_PATH_UPLOADS);

        //retrieving upload data from firebase database
        mDatabaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                    Upload upload = postSnapshot.getValue(Upload.class);
                    uploadList.add(upload);
                }

                String[] uploads = new String[uploadList.size()];

                for (int i = 0; i < uploads.length; i++) {
                    uploads[i] = uploadList.get(i).getName();
                }

                //displaying it to list
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, uploads);
                listView.setAdapter(adapter);
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });


    }



}

Answer 1

只需在String data = upload.getData();

下面添加Upload upload = postSnapshot.getValue(Upload.class);即可

这里是getData（）; method表示firebase中节点的getter方法....只需用自己的方法替换getData

Firebase未在onCreate中显示

1 个答案: