我真的不知道我哪里错了。根据文档，我正在做的一切正确。我怀疑它是否正在发生只因为我使用TabbedActivity并处理碎片，但我仍然不知道它是怎么回事。 请查看代码并帮助我。我一直在努力实现从FIREBASE检索和显示数据的任务。 作为初学者，我很难弄明白。
MainActivity.Java
package com.example.souravkumar.sqaurewallpapers;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.GridView;
import android.widget.Toast;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;
import com.google.firebase.storage.UploadTask;
public class MainActivity extends AppCompatActivity {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
int count=0;
public FloatingActionButton mAddImage;
private StorageReference mStorage;
public DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
String stringUri;
Long date;
private static final int GALLERY_INTENT = 2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
mStorage = FirebaseStorage.getInstance().getReference();
mAddImage = (FloatingActionButton) findViewById(R.id.addImage);
mAddImage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(Intent.ACTION_PICK);
intent.setType("image/*");
startActivityForResult(intent, GALLERY_INTENT);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == GALLERY_INTENT && resultCode == RESULT_OK) {
Uri uri = data.getData();
StorageReference filePath = mStorage.child("Wallpapers").child(uri.getLastPathSegment());
filePath.putFile(uri).addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
@Override
public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
Toast.makeText(MainActivity.this, "Upload Successful", Toast.LENGTH_LONG).show();
Uri downloadUrl = taskSnapshot.getDownloadUrl();
//Adding image to the database
stringUri= downloadUrl.toString();
date = System.currentTimeMillis();
addImageToDatabase (stringUri, date);
}
});
}
}
private void addImageToDatabase(String downloadUrl, Long date){
image_details id= new image_details(downloadUrl, date);
String key = mDatabase.push().getKey();
mDatabase.child(key).child("URL").setValue(id.getUrl());
mDatabase.child(key).child("Date").setValue(id.getDate());
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
public PlaceholderFragment() {
}
/**
* Returns a new instance of this fragment for the given section
* number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
GridView gridView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (getArguments().getInt(ARG_SECTION_NUMBER) == 1) {
View rootView = inflater.inflate(R.layout.fragment_popular, container, false);
return rootView;
} else if (getArguments().getInt(ARG_SECTION_NUMBER) == 2) {
View rootView = inflater.inflate(R.layout.fragment_recent, container, false);
return rootView;
} else
return inflater.inflate(R.layout.fragment_main, container, false);
}
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return PlaceholderFragment.newInstance(position + 1);
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "POPULAR";
case 1:
return "RECENT";
case 2:
return "PROFILES";
}
return null;
}
}
}
Popular.Java
package com.example.souravkumar.sqaurewallpapers;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.FragmentActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.squareup.picasso.Picasso;
/**
* Created by Sourav Kumar on 11/3/2017.
*/
public class popular extends FragmentActivity {
private RecyclerView recyclerView;
private DatabaseReference myRef;
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
myRef = FirebaseDatabase.getInstance().getReference();
FirebaseRecyclerAdapter<image_details,BlogViewHolder> recyclerAdapter=new FirebaseRecyclerAdapter<image_details,BlogViewHolder>(
image_details.class,
R.layout.individual_row,
BlogViewHolder.class,
myRef
) {
@Override
protected void populateViewHolder(BlogViewHolder viewHolder, image_details model, int position) {
viewHolder.setUrl(model.getUrl());
viewHolder.setDate(model.getDate());
}
};
recyclerView.setAdapter(recyclerAdapter);
}
public static class BlogViewHolder extends RecyclerView.ViewHolder {
View mView;
TextView textView;
ImageView imageView;
public BlogViewHolder(View itemView) {
super(itemView);
mView=itemView;
textView = (TextView)itemView.findViewById(R.id.date);
imageView = (ImageView)itemView.findViewById(R.id.imageView);
}
public void setDate(Long date) {
textView.setText(date.toString());
}
public void setUrl(String url) {
Picasso.with(mView.getContext())
.load(url)
.resize(50, 50)
.centerCrop()
.into(imageView);
}
}
}
image_details.Java
package com.example.souravkumar.sqaurewallpapers;
/**
* Created by Sourav Kumar on 10/29/2017.
*/
public class image_details {
String url;
Long date;
image_details(){}
public image_details(String url, Long date){
this.url = url;
this.date = date;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public Long getDate() {
return date;
}
public void setDate(Long date) {
this.date = date;
}
}
fragment_popular.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.souravkumar.sqaurewallpapers.popular">
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/recyclerView">
</android.support.v7.widget.RecyclerView>
</RelativeLayout>
individual_row.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<ImageView
android:layout_width="150dp"
android:layout_height="280dp"
android:id="@+id/imageView"
android:src="@mipmap/ic_launcher"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Date"
android:id="@+id/date"/>
</LinearLayout>
</android.support.v7.widget.CardView>