JAVA：从Firestore在Android的图像滑块中显示数据

问题描述

我想显示一个图像滑块以从URL中获取图像，为此，我正在使用this Library。，以及此库的github页面上给出的示例代码。我已经通过创建ImageUrls和Description数组添加了图像网址，但是现在我想从Firestore中获取这些图像网址。

如何修改以下代码，请帮助：

public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getName();
    FirebaseFirestore db = FirebaseFirestore.getInstance();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate (savedInstanceState);
        setContentView (R.layout.activity_main);


        //GET DATA FROM FIRESTORE

        db.collection("sliders")
                .get()
                .addOnCompleteListener(new OnCompleteListener<QuerySnapshot> () {
                    @Override
                    public void onComplete(@NonNull Task<QuerySnapshot> task) {

                        if (task.isSuccessful()) {
                            for (QueryDocumentSnapshot document : task.getResult()) {
                                Log.d(TAG,document.getId() + " => " + document.getData());                                
                            }
                        } else {
                            Log.w(TAG,"Error getting documents.",task.getException());
                        }
                    }
                });


        List<SliderItem> mSliderItems = new ArrayList<> ();
        mSliderItems.add(new SliderItem ("test1","https://images.pexels.com/photos/218983/pexels-photo-218983.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=750&w=1260"));
        mSliderItems.add(new SliderItem ("test2","https://images.pexels.com/photos/747964/pexels-photo-747964.jpeg?auto=compress&cs=tinysrgb&h=750&w=1260"));
        mSliderItems.add(new SliderItem ("test3","https://images.pexels.com/photos/929778/pexels-photo-929778.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=750&w=1260"));
        mSliderItems.add(new SliderItem ("test4","https://images.pexels.com/photos/4676400/pexels-photo-4676400.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=750&w=1260"));


        SliderView sliderView = findViewById(R.id.imageSlider);
        SliderAdapterExample adapter = new SliderAdapterExample(this,mSliderItems);
        sliderView.setSliderAdapter(adapter);
        sliderView.setIndicatorAnimation(IndicatorAnimationType.WORM); //set indicator animation by using IndicatorAnimationType. :WORM or THIN_WORM or COLOR or DROP or FILL or NONE or SCALE or SCALE_DOWN or SLIDE and SWAP!!
        sliderView.setSliderTransformAnimation(SliderAnimations.SIMPLETRANSFORMATION);
        sliderView.setAutoCycleDirection(SliderView.AUTO_CYCLE_DIRECTION_BACK_AND_FORTH);
        sliderView.setIndicatorSelectedColor(Color.WHITE);
        sliderView.setIndicatorUnselectedColor(Color.GRAY);
        sliderView.setScrollTimeInSec(4); //set scroll delay in seconds :
        sliderView.startAutoCycle();
    }

}

编辑：

我尝试了以下编辑，但显示上下文错误。

SliderAdapterExample adapter = new SliderAdapterExample(this,mSliderItemList);

在行上方

db.collection("sliders")
        .get()
        .addOnCompleteListener(new OnCompleteListener<QuerySnapshot> () {
            @Override
            public void onComplete(@NonNull Task<QuerySnapshot> task) {
                List<SliderItem> mSliderItemList = new ArrayList<> ();
                if (task.isSuccessful()) {
                    for (QueryDocumentSnapshot document : task.getResult()) {
                        SliderItem slideritem = document.toObject(SliderItem.class);
                        mSliderItemList.add(slideritem);
                        Log.d(TAG,document.getId() + " => " + document.getData());
                    }
                    SliderView sliderView = findViewById(R.id.imageSlider);
                    SliderAdapterExample adapter = new SliderAdapterExample(this,mSliderItemList);
                    sliderView.setSliderAdapter(adapter);
                    sliderView.setIndicatorAnimation(IndicatorAnimationType.WORM); //set indicator animation by using IndicatorAnimationType. :WORM or THIN_WORM or COLOR or DROP or FILL or NONE or SCALE or SCALE_DOWN or SLIDE and SWAP!!
                    sliderView.setSliderTransformAnimation(SliderAnimations.SIMPLETRANSFORMATION);
                    sliderView.setAutoCycleDirection(SliderView.AUTO_CYCLE_DIRECTION_BACK_AND_FORTH);
                    sliderView.setIndicatorSelectedColor(Color.WHITE);
                    sliderView.setIndicatorUnselectedColor(Color.GRAY);
                    sliderView.setScrollTimeInSec(4); //set scroll delay in seconds :
                    sliderView.startAutoCycle();

                } else {
                    Log.w(TAG,task.getException());
                }
            }
        });

解决方法

如果您已将所有图像保存在 Firebase存储中，则可以直接从该文件夹中查询。通过这种方法，您无需将链接添加到您的Cloud Firestore中，从而减少了读取次数。

用于从存储中的文件夹查询。

1. 在存储中创建一个文件夹并上传图像。
2. 现在在项目中添加存储依赖项
3. 为滑块库创建适配器和模型类

现在将以下代码添加到您想要的滑块位置。

FirebaseStorage ST_storage;
SliderView sliderView;

//Code for listing images from storage    
sliderView.setAutoCycle(true);
        sliderView.setScrollTimeInSec(3);
        sliderView.startAutoCycle();
        ST_storage = FirebaseStorage.getInstance().getReference("YOUR_FOLDER_NAME");
        ST_storage.listAll()
                .addOnSuccessListener(listResult -> {
                    for (StorageReference item : listResult.getItems()) {
                        item.getDownloadUrl().addOnCompleteListener(task -> {
                            safetyTips_items.add(new SafetyTips_Item(Objects.requireNonNull(task.getResult()).toString()));
                            safety_tips_adapter.notifyDataSetChanged();
                        });
                    }
                });
        safety_tips_adapter = new SafetyTips_adapter(safetyTips_items);
        sliderView.setSliderAdapter(safety_tips_adapter);

使用此方法，您可以直接列出所有图像，而无需添加URL。