我正在为我的学校项目创建一个应用程序,我的编码不是那么先进,所以我提前为我的错误编码道歉。所以我正在尝试获取下载 Uri,所以一旦用户完成带有图片的表单,我就可以将详细信息上传到实时数据库,以便在我的应用程序的其他部分中使用。
//I use this code below, I got it from the Firebase documents//
ref.getDownloadUrl().addOnSuccessListener(new OnSuccessListener<Uri>() {
@Override
public void onSuccess(Uri uri) {
// picUri is a globally declared string and I use it to set my database values,
picUri=(uri.toString());
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception exception) {
// Handle any errors
}
});
我相信这与 Firebase 方法是异步的事实有关吗?所以 uri.toString() 没有被解析成全局字符串变量?因为我一直在玩,我意识到当我执行 .setValue(object) 将我的对象写入实时数据库时,uri 确实被捕获了,但这太混乱了,然后我将无法捕获另一个值。我已经读到我需要写一个回调,那里有很多指南,我在这里真的很困惑。
有人可以将我引导到有关如何理解回调和实现回调以获取此值的指南或 youtube 教程,或者是我做错了什么,请提供建议,谢谢。
照片和其他参数正在成功记录,只有我无法捕获图片的uri。 (我暂时用 picUri 替换了 categoryinput 以更轻松地运行测试)
我是新用户所以我不能上传图片但是数据库和布局的图片是: https://i.ibb.co/YbdSzwB/databasestack.png
https://i.ibb.co/SVG2zxL/stackoverflow.png
我将输入我的整个代码仅供参考
package com.example.giventake;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.View;
import android.widget.*;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.OnProgressListener;
import com.google.firebase.storage.StorageReference;
import com.google.firebase.storage.UploadTask;
import java.io.IOException;
public class ListPage extends AppCompatActivity {
/*Declare all variables I'll be using*/
private EditText title, category, description;
private ImageView image, image2, image3;
private FirebaseAuth mAuth;
private FirebaseStorage storage;
private StorageReference storageReference;
private FirebaseDatabase rootNode;
private DatabaseReference referenceItems;
private Uri filePath;
private Uri filePath2;
private Uri filePath3;
private final int PICK_IMAGE_REQUEST = 1;
private final int PICK_IMAGE2_REQUEST = 2;
private final int PICK_IMAGE3_REQUEST = 3;
String picUri;
/*Declare all variables I'll be using*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list);
/*Initialise all instances of variables*/
title = (EditText) findViewById(R.id.editTextItemTitle);
category = (EditText) findViewById(R.id.editTextItemCategory);
description = (EditText) findViewById(R.id.editTextItemDescription);
image = (ImageView) findViewById(R.id.imgViewPic);
image2 = (ImageView) findViewById(R.id.imgViewPic2);
image3 = (ImageView) findViewById(R.id.imgViewPic3);
image.setImageResource(R.drawable.ic_baseline_list_24);
image2.setImageResource(R.drawable.ic_baseline_list_24);
image3.setImageResource(R.drawable.ic_baseline_list_24);
storage = FirebaseStorage.getInstance();
storageReference = storage.getReference();
mAuth = FirebaseAuth.getInstance();
rootNode = FirebaseDatabase.getInstance();
referenceItems = rootNode.getReference("Items");
/*Initialise all instances of variables*/
}
/*This is to upload images from your phones direction*/
public void onFirstPicClick(View view) {
Intent i = new Intent();
i.setType("image/*");
i.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(Intent.createChooser(i, "Select Picture"), PICK_IMAGE_REQUEST);
}
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == PICK_IMAGE_REQUEST && resultCode == RESULT_OK
&& data != null && data.getData() != null) {
filePath = data.getData();
try {
Bitmap bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), filePath);
image.setImageBitmap(bitmap);
} catch (IOException e) {
e.printStackTrace();
}
}
}
/*This is to upload images from your phones direction*/
public void onSubmitClicked(View view) {
//Fetching data
String titleInput = title.getText().toString().trim();
//String categoryInput = category.getText().toString().trim();
String descriptionInput = description.getText().toString().trim();
String itemId = referenceItems.child(mAuth.getCurrentUser().getUid()).push().getKey();
referenceItems = referenceItems.child(mAuth.getCurrentUser().getUid()).child(itemId);
if (filePath != null) {
StorageReference ref = storageReference.child("Images").child(mAuth.getCurrentUser().getUid()).child(itemId).child("Pic1");
ref.putFile(filePath)
.addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
@Override
public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
// Toast.makeText(ListPage.this, "Uploaded", Toast.LENGTH_SHORT).show();
}
})
.addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
Toast.makeText(ListPage.this, "Picture upload failed" + e.getMessage(), Toast.LENGTH_SHORT).show();
}
})
.addOnProgressListener(new OnProgressListener<UploadTask.TaskSnapshot>() {
@Override
public void onProgress(UploadTask.TaskSnapshot taskSnapshot) {
double progress = (100.0 * taskSnapshot.getBytesTransferred() / taskSnapshot
.getTotalByteCount());
}
});
ref.getDownloadUrl().addOnSuccessListener(new OnSuccessListener<Uri>() {
@Override
public void onSuccess(Uri uri) {
// Got the download URL for 'users/me/profile.png'
picUri=(uri.toString());
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception exception) {
// Handle any errors
}
});
}
//ItemsHelperClass item = new ItemsHelperClass(titleInput, categoryInput, descriptionInput, itemId);
ItemsHelperClass item = new ItemsHelperClass(titleInput,picUri,descriptionInput,itemId);
referenceItems.setValue(item).addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
if (task.isSuccessful()) {
Intent i = new Intent(ListPage.this, MainActivity.class);
startActivity(i);
finish();
// getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new HomeFragment()).commit();
} else {
//If it fails to add
Toast.makeText(ListPage.this, "Something went wrong, please try again", Toast.LENGTH_LONG).show();
}
}
}
);
}
}
答案 0 :(得分:1)
Java Firebase Android SDK 大量使用 Task
对象(类似于 JavaScript Promise
对象),您可以将需要与异步 API 交互的多个操作链接在一起。
一个 Task
对象,有很多方法来附加监听器,你会遇到的主要有:
addOnSuccessListener
- 任务成功完成后,运行给定的代码。addOnFailureListener
- 当任务失败时,运行给定的代码。addOnCompleteListener
- 当任务完成(成功或失败)时,运行给定的代码。onSuccessTask
- 任务成功完成后,开始另一个任务。continueWith
- 当任务完成(成功或失败)时,开始另一个任务。有时,如果您一次处理多个任务,则需要使用 Tasks
实用程序类中的方法。
对于您要执行的操作,以下是用户单击提交按钮后需要执行的步骤列表:
DatabaseReference
和一个StorageReference
由于这是一个学校项目,我不会再深入研究。研究上面的链接,您应该能够将这些知识与这些步骤结合起来找到解决方案。
但是,我会指出这个会让你陷入困境的错误:
String itemId = referenceItems.child(mAuth.getCurrentUser().getUid()).push().getKey();
referenceItems = referenceItems.child(mAuth.getCurrentUser().getUid()).child(itemId);
您在此处分配给 referenceItems
,这会在您下次点击提交时弄乱您的代码,并很快使您的数据库看起来像:
{
"Items": {
"-MYu4i_5q-GUETw4WV1i": {
"title": "my first image",
"uri": "https://firebasestorage.googleapis.com/...",
"description": "some description",
"category": "some category",
"-MYu5jNs2MMJJGB2L7jJ": {
"title": "my second image",
"uri": "https://firebasestorage.googleapis.com/...",
"description": "some description",
"category": "some category",
"-MYu72gLxsi4M6J9aBAr": {
"title": "my third image",
"uri": "https://firebasestorage.googleapis.com/...",
"description": "some description",
"category": "some category",
"-MYu78gFeoWhV6OSiF9I": ...
}
}
}
}
}
或者,如果您遇到语法错误而不是成功上传,您可能会得到:
{
"Items": {
"-MYu4i_5q-GUETw4WV1i": {
"-MYu5jNs2MMJJGB2L7jJ": {
"-MYu72gLxsi4M6J9aBAr": {
"title": "my first image",
"uri": "https://firebasestorage.googleapis.com/...",
"description": "some description",
"category": "some category"
}
}
}
}
}
相反,保存并使用 push()
返回的引用:
DatabaseReference itemDataRef = referenceItems.child(mAuth.getCurrentUser().getUid()).push();
String itemId = itemDataRef.getKey();
/* ... */
StorageReference itemStorageRef = storageReference.child("Images").child(mAuth.getCurrentUser().getUid()).child(itemId).child("Pic1");