Android应用从Firebase Storage、Realtime Database加载图片不显示问题

问题根因 #

你当前写法错误是因为新版Firebase Storage SDK中，getDownloadUrl()返回的是异步Task<Uri>对象，而非直接返回下载链接。你直接调用toString()存储的是Task实例的描述信息，并非可访问的图片地址，所以存入数据库的url无效，无法加载图片。你手动替换为Storage真实访问链接可正常加载，也验证了这个问题。

修改方案 #

你需要监听getDownloadUrl()的异步返回结果，拿到真实Uri后再写入Realtime Database，修改代码如下：

需替换的核心代码段 #

将原来的错误代码：

Upload upload = new Upload(productName.getText().toString().trim(), productDesc.getText().toString().trim(), taskSnapshot.getMetadata().
                        getReference().getDownloadUrl().toString());

String uploadId = mDatabaseRef.push().getKey();
mDatabaseRef.child(uploadId).setValue(upload);

替换为：

// 异步获取真实下载地址
taskSnapshot.getStorage().getDownloadUrl().addOnSuccessListener(new OnSuccessListener<Uri>() {
    @Override
    public void onSuccess(Uri uri) {
        String realImageUrl = uri.toString();
        Upload upload = new Upload(productName.getText().toString().trim(), productDesc.getText().toString().trim(), realImageUrl);
        String uploadId = mDatabaseRef.push().getKey();
        mDatabaseRef.child(uploadId).setValue(upload);
    }
});

完整修改后的uploadFile方法 #

private void uploadFile() {
    if(mImageUri != null){
        StorageReference fileReference = mStorageRef.child(System.currentTimeMillis() + "." + getFileExtension(mImageUri));
        mUploadTask = fileReference.putFile(mImageUri)
        .addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
            @Override
            public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
                Handler handler = new Handler();
                handler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        uploadProgress.setProgress(0);
                    }
                }, 1000);
                Toast.makeText(AddItemForSale.this, "Upload successful", Toast.LENGTH_LONG).show();
                // 异步获取下载链接后再写入数据库
                taskSnapshot.getStorage().getDownloadUrl().addOnSuccessListener(new OnSuccessListener<Uri>() {
                    @Override
                    public void onSuccess(Uri uri) {
                        String realImageUrl = uri.toString();
                        Upload upload = new Upload(productName.getText().toString().trim(), productDesc.getText().toString().trim(), realImageUrl);
                        String uploadId = mDatabaseRef.push().getKey();
                        mDatabaseRef.child(uploadId).setValue(upload);
                    }
                });
            }
        })
        .addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Toast.makeText(AddItemForSale.this, e.getMessage(), Toast.LENGTH_SHORT).show();
            }
        })
        .addOnProgressListener(new OnProgressListener<UploadTask.TaskSnapshot>() {
            @Override
            public void onProgress(@NonNull UploadTask.TaskSnapshot snapshot) {
                double progress = (100.0 * snapshot.getBytesTransferred() / snapshot.getTotalByteCount());
                uploadProgress.setProgress((int) progress);
            }
        });
    }else {
        Toast.makeText(this, "No file selected", Toast.LENGTH_SHORT).show();
    }
}

如果你的项目支持Java 8+ lambda表达式，可自行简化匿名内部类的写法。

内容的提问来源于stack exchange，提问作者Ranko Koturic