我将一些图像导入到 firebase 存储中，并将图像链接添加到名为 images 的文件夹下的实时数据库中。我希望我的应用程序在我更改实时数据库中的链接图像后自动将图像同步给用户。我不太确定如何添加值事件监听器和创建数据库引用。 目前，我正在使用直接链接检索图像，您可以在下面的代码中看到。但是，这不能正常工作，因为我必须更改代码中的链接以更新新内容。谁能帮忙解决这个问题？请分享一些代码，让我了解如何实现这一目标。
图像 Activity .java
package com.example.android.zamcatalog;
import android.net.Uri;
import android.support.annotation.NonNull;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.widget.ImageView;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;
public class gameActivity extends AppCompatActivity {
ViewPager viewPager;
ViewPagerAdapter adapter;
private String[] images = {
"https://firebasestorage.googleapis.com/v0/b/zamcatalog.appspot.com/o/Game%2Fgame1.jpg?alt=media&token=b3917686-090f-43fb-852e-0365ac67dd6e",
"https://firebasestorage.googleapis.com/v0/b/zamcatalog.appspot.com/o/Game%2Fgame2.jpg?alt=media&token=25e4eb76-5361-42a6-9bfd-6e3b1153611f",
"https://firebasestorage.googleapis.com/v0/b/zamcatalog.appspot.com/o/Game%2Fgame3.jpg?alt=media&token=a5d4c8b9-9ecb-4ea1-a095-557955db1d19",
"https://firebasestorage.googleapis.com/v0/b/zamcatalog.appspot.com/o/Game%2Fgame4.jpg?alt=media&token=b4598019-13b3-4600-aa49-86fd0a8c5c64",
"https://firebasestorage.googleapis.com/v0/b/zamcatalog.appspot.com/o/Game%2Fgame5.jpg?alt=media&token=a4991bfe-d3b4-4f1c-be65-55ddfd1de7ba",
"https://firebasestorage.googleapis.com/v0/b/zamcatalog.appspot.com/o/Game%2Fgame6.jpg?alt=media&token=e8b43bb6-c967-495f-b5e2-336f082225b6",
"https://firebasestorage.googleapis.com/v0/b/zamcatalog.appspot.com/o/Game%2Fgame7.jpg?alt=media&token=0f135b82-1a05-4585-a511-bbab35a5613a",
"https://firebasestorage.googleapis.com/v0/b/zamcatalog.appspot.com/o/Game%2Fgame8.jpg?alt=media&token=ab8a9fcf-db2d-4c9c-afd8-969a4db22a8c"
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_game);
viewPager = (ViewPager)findViewById(R.id.viewpager);
adapter = new ViewPagerAdapter(gameActivity.this,images);
viewPager.setAdapter(adapter);
}
}
ViewPagerAdapter.java
package com.example.android.zamcatalog;
import android.app.Activity;
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.DisplayMetrics;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import com.bumptech.glide.Glide;
import com.firebase.ui.storage.images.FirebaseImageLoader;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.storage.FirebaseStorage;
public class ViewPagerAdapter extends PagerAdapter {
Activity activity;
String[] images;
LayoutInflater inflater;
public ViewPagerAdapter(Activity activity, String[] images) {
this.activity = activity;
this.images = images;
}
@Override
public int getCount() {
return images.length;
}
@Override
public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
return view == object;
}
@Override
public Object instantiateItem(@NonNull ViewGroup container, int position) {
inflater = (LayoutInflater) activity.getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View itemview = inflater.inflate(R.layout.viewpager_item, container, false);
ImageView image;
image = (ImageView) itemview.findViewById(R.id.imageView);
DisplayMetrics dis = new DisplayMetrics();
activity.getWindowManager().getDefaultDisplay().getMetrics(dis);
int height = dis.heightPixels;
int width = dis.widthPixels;
image.setMinimumHeight(height);
image.setMinimumWidth(width);
try {
Glide.with(activity.getApplicationContext())
.load(images[position])
.into(image);
} catch (Exception ex) {
}
container.addView(itemview);
return itemview;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
((ViewPager) container).removeView((View) object);
}
}
最佳答案
您应该将这些图像存储在您的数据库中，首先获取它们的链接，然后使用 Glide 检索这些图像或 Picasso .
此代码段将图像保存到存储中并获取其下载 URL:
final StorageReference ref = storageRef.child("images/mountains.jpg");
uploadTask = ref.putFile(file); //your image
Task<Uri> urlTask = uploadTask.continueWithTask(new Continuation<UploadTask.TaskSnapshot, Task<Uri>>() {
@Override
public Task<Uri> then(@NonNull Task<UploadTask.TaskSnapshot> task) throws Exception {
if (!task.isSuccessful()) {
throw task.getException();
}
// Continue with the task to get the download URL
return ref.getDownloadUrl();
}
}).addOnCompleteListener(new OnCompleteListener<Uri>() {
@Override
public void onComplete(@NonNull Task<Uri> task) {
if (task.isSuccessful()) {
Uri downloadUri = task.getResult();
//Here you can write that url to your database like this
yourDatabaseRef.push().child("photo").setValue(downloadUri);
} else {
// Handle failures
// ...
}
}
});
然后您使用 addValueEventListener
检索该链接// Attach a listener to read the data at our posts reference
yourImageRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String photoUrl = dataSnapshot.getValue(String.class);
//Manage picasso or glide to load that url
//Glide example
GlideApp
.with(Context)
.load(photoUrl)
.centerCrop()
.placeholder(R.drawable.loading_spinner)
.into(myImageView);
}
@Override
public void onCancelled(DatabaseError databaseError) {
System.out.println("The read failed: " + databaseError.getCode());
}
});
我们存储图像 URL 以便使用 Picasso 或 Glide 显示它，这是使用 Firebase 加载图像的最简单方法。
关于java - 如何将值事件监听器添加到实时数据库，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/52102584/