Question

我正在尝试构建一个包含两个按钮的MainActivity，一个按钮用于使用相机拍照并将其上传到Firebase Storage，另一个按钮用于从Firebase Storage下载图像并显示在ImageView。

现在，我受制于上传功能。我可以拍照并将其保存到应用程序目录中。我想将保存的图片上传到Firebase存储中。

我的MainActivity.java（基于Firebase开发人员教程）如下：

package com.example.mathi.image;

import android.content.Intent;
import android.net.Uri;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.annotation.NonNull;
import android.support.v4.content.FileProvider;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;
import com.google.firebase.storage.UploadTask;

import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

static final int REQUEST_TAKE_PHOTO = 1;
String mCurrentPhotoPath;

private Button btn_upload;
private Button btn_download;

//Firebase
FirebaseStorage storage;
StorageReference storageReference;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    btn_upload = (Button)findViewById(R.id.btn_upload);
    btn_download = (Button)findViewById(R.id.btn_download);

    btn_upload.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            dispatchTakePictureIntent();



        }
    });

    btn_download.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

        }
    });


}

private void dispatchTakePictureIntent() {
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    // Ensure that there's a camera activity to handle the intent
    if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
        // Create the File where the photo should go
        File photoFile = null;
        try {
            photoFile = createImageFile();
        } catch (IOException ex) {
            // Error occurred while creating the File

        }
        // Continue only if the File was successfully created
        if (photoFile != null) {
            Uri photoURI = FileProvider.getUriForFile(this,
                    "com.example.mathi.image.fileprovider",
                    photoFile);
            takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, photoURI);
            startActivityForResult(takePictureIntent, REQUEST_TAKE_PHOTO);
            upload_photo();
        }
    }
}



private File createImageFile() throws IOException {
    // Create an image file name
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    String imageFileName = "JPEG_" + timeStamp + "_";
    File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
    File image = File.createTempFile(
            imageFileName,  /* prefix */
            ".jpg",         /* suffix */
            storageDir      /* directory */
    );

    // Save a file: path for use with ACTION_VIEW intents
    mCurrentPhotoPath = image.getAbsolutePath();
    return image;
}


private void upload_photo(){
    Uri file = Uri.fromFile(new File(mCurrentPhotoPath));
    UploadTask uploadTask = storageReference.putFile(file);

// Register observers to listen for when the download is done or if 
it fails
    uploadTask.addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception exception) {
            // Handle unsuccessful uploads
        }
    }).addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
        @Override
        public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
            // taskSnapshot.getMetadata() contains file metadata such as size, content-type, etc.
            // ...
        }
    });
}

}

在调试器中，我出现以下错误：

java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'com.google.firebase.storage.UploadTask com.google.firebase.storage.StorageReference.putFile（android.net.Uri）' 在com.example.mathi.image.MainActivity.upload_photo（MainActivity.java:112）

第112行是以下行：

UploadTask uploadTask = storageReference.putFile(file);

当我删除upload()方法时，该文件是在本地目录上创建的。但是，使用upload()方法会使应用程序崩溃。

有人知道我想念什么吗？

Answer 1

尝试此代码

btn_upload.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        CaptureImageFromCamera();
    }
});



private void CaptureImageFromCamera() {
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
        startActivityForResult(takePictureIntent, 200);
    }
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (resultCode == RESULT_OK) {
        try {
            if (requestCode == 200) {
                Uri imageUri = data.getData();
                sendImage(imageUri);
            } 
        }
        catch (Exception e) {

        }
    }else{
        Toast.makeText(this, "Cancelled", Toast.LENGTH_SHORT).show();
    }


}

private void sendImage(Uri imageUri){
UploadTask uploadTask = storageReference.putFile(imageUri);

    uploadTask.addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception exception) {
            // Handle unsuccessful uploads
        }
    }).addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
        @Override
        public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {

        }
    });
}

将照片上传到Firebase存储

1 个答案: