Question

我写了一个简单的代码到即时相机图像捕获并将其上传到android firebase 来自Referance Here

尝试将完整代码编写为android studio文档。但是在logcat中我们可以显示此代码出现错误 uri.getLastPathSegment（）。如何解决这个错误？

错误Logcat：
--------- beginning of crash 05-23 14:52:06.627 12364-12364/com.example.hasib_pc.firebasetest E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.hasib_pc.firebasetest, PID: 12364 java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=3, result=-1, data=Intent { }} to activity {com.example.hasib_pc.firebasetest/com.example.hasib_pc.firebasetest.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.net.Uri.getLastPathSegment()' on a null object reference at android.app.ActivityThread.deliverResults(ActivityThread.java:4268) at android.app.ActivityThread.handleSendResult(ActivityThread.java:4312) at android.app.ActivityThread.-wrap19(Unknown Source:0) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1644) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:164) at android.app.ActivityThread.main(ActivityThread.java:6494) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.net.Uri.getLastPathSegment()' on a null object reference

MainActivity完整代码：

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";
    public static final int IMAGE_CAPTURE_CODE = 3;
    private Button uploadBtn;
    private ImageView showImage;
    private StorageReference mStorage;
    private ProgressDialog progressDialog;

    String mCurrentPhotoPath;

    private File createImageFile() throws IOException {
        Log.d(TAG, "createImageFile: start.");
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        String imageFileName = "JPEG_" + timeStamp + "_";
        File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
        File image = File.createTempFile(
                imageFileName,
                ".jpg",
                storageDir
        );

        mCurrentPhotoPath = image.getAbsolutePath();
        Log.d(TAG, "createImageFile: End.");
        return image;
    }

    private void takePictureIntent() {
        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        if (intent.resolveActivity(getPackageManager()) != null) {
            // Create the File where the photo should go
            File photoFile = null;
            try {
                photoFile = createImageFile();
            } catch (IOException ex) {
                Log.e(TAG, "takePictureIntent: IOException: "+ex.getMessage(),ex);
            }
            if (photoFile != null) {
                Uri photoURI = FileProvider.getUriForFile(this,
                        "com.example.android.fileprovider",
                        photoFile);
                intent.putExtra(MediaStore.EXTRA_OUTPUT, photoURI);
                startActivityForResult(intent, IMAGE_CAPTURE_CODE);
                Log.d(TAG, "takePictureIntent: End.");
            }
        }
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mStorage = FirebaseStorage.getInstance().getReference();

        uploadBtn = findViewById(R.id.uploadBtnId);
        showImage = findViewById(R.id.imageShowId);

        progressDialog = new ProgressDialog(this);

        uploadBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                takePictureIntent();
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        Log.d(TAG, "onActivityResult: Started.");
        if(requestCode == IMAGE_CAPTURE_CODE && resultCode == RESULT_OK){
            Log.d(TAG, "onActivityResult: start uploading");
            progressDialog.setMessage("Uploading...");
            progressDialog.show();
            Uri uri = data.getData();

            Log.d(TAG, "onActivityResult: set filepath");
            StorageReference filepath = mStorage.child("Photos").child(uri.getLastPathSegment());
            Log.d(TAG, "onActivityResult: try to putFile");
            filepath.putFile(uri).addOnSuccessListener(new    OnSuccessListener<UploadTask.TaskSnapshot>() {
                @Override
                public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
                    Log.d(TAG, "onSuccess: started.");
                    Toast.makeText(MainActivity.this, "Upload Successful!",    Toast.LENGTH_SHORT).show();
                    progressDialog.dismiss();
                }
            }).addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    Toast.makeText(MainActivity.this, "Upload Failed!", Toast.LENGTH_SHORT).show();
                }
            });
        }
    }
}

Answer 1

这是我的错。我找到了解决方案。创建一个Uri instantce veriable。 private Uri photoURI;

然后用Intent putExtra方法发送这个Uri。

photoURI = FileProvider.getUriForFile(this,
                        "com.example.android.fileprovider",
                        photoFile);
intent.putExtra(MediaStore.EXTRA_OUTPUT, photoURI);

并通过StorageReference putFile方法传递uri对象 filepath.putFile(photoURI)

我在 onCreate 方法中调用了Uri photoURI，这个方法是Class实例可靠的，这就是为什么得到NullPointerException。

拍照并上传到Android Firebase错误

1 个答案: