NPE尝试调用虚拟方法'android.content.res.XmlResourceParser android.content.pm.ProviderInfo.loadXmlMetaData

Question

我正在尝试从对话框片段中启动ACTION_IMAGE_CAPTURE活动，并在单击相关按钮以启动它时获得NPE。

我检查了清单权限，并验证了我的片段中的权限字符串具有与清单相同的“ .fileprovider”。

private static final int REQUEST_CODE = 123;
private EditText etUsername, etPassword;
private Button btnSignup;
private TextView tvGoback;
private String username, password;
private OnSignupFragmentListener listener;
private ImageView selfiImage;
private String photoPath;

public void setUsername(String username) {
    this.username = username;
}

public void setPassword(String password) {
    this.password = password;
}

public void setListener(OnSignupFragmentListener listener) {
    this.listener = listener;
}

@Override
public void onStart() {
    super.onStart();
    Objects.requireNonNull(getDialog().getWindow()).setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_HIDDEN);
}

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    getDialog().setTitle("Sign-up");
    getDialog().getWindow().setBackgroundDrawableResource(R.drawable.signup_background);
    View view = inflater.inflate(R.layout.fragment_signup, container, false);
    etUsername = view.findViewById(R.id.etUsername);
    etPassword = view.findViewById(R.id.etPassword);
    btnSignup = view.findViewById(R.id.btnSignup);
    tvGoback = view.findViewById(R.id.tvGobacktologin);
    selfiImage = view.findViewById(R.id.ivSelfi);
    btnSignup.setOnClickListener(this);
    tvGoback.setOnClickListener(this);
    selfiImage.setOnClickListener(this);
    if (username != null) {
        etUsername.setText(username);
    }
    if (password != null) {
        etPassword.setText(password);
    }
    return view;
}

@Override
public void onClick(View view) {
    switch (view.getId()){
        case R.id.btnSignup:
            signup();
            break;
        case R.id.tvGoBack:
            dismiss();
            break;
        case R.id.ivSelfi:
            Intent takePhotoIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
            if(takePhotoIntent.resolveActivity(getContext().getPackageManager()) != null) {
                File file = createImageFile();
                Uri photoUri = FileProvider.getUriForFile(getContext(), "com.example.alon.a2018_17_12_userloginexhomework.fileprovider", file);
                takePhotoIntent.putExtra(MediaStore.EXTRA_OUTPUT, photoUri);
                startActivityForResult(takePhotoIntent, REQUEST_CODE);
            }
            break;
    }
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_CODE && resultCode == LoginActivity.RESULT_OK){
        setPic();
    }
}

private void setPic(){
    int imageWidth = selfiImage.getWidth();
    int imageHeight = selfiImage.getHeight();
    BitmapFactory.Options bitmapOptions = new BitmapFactory.Options();
    bitmapOptions.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(photoPath, bitmapOptions);
    int photoWidth = bitmapOptions.outWidth;
    int photoHeight = bitmapOptions.outHeight;
    int scaleFactor = Math.min(photoWidth / imageWidth, photoHeight / imageHeight);
    bitmapOptions.inJustDecodeBounds = false;
    bitmapOptions.inSampleSize = scaleFactor;


    Bitmap bitmap = BitmapFactory.decodeFile(photoPath, bitmapOptions);
    selfiImage.setImageBitmap(bitmap);

}

private void signup() {
    String userName = etUsername.getText().toString();
    String password = etPassword.getText().toString();
    if (userName.isEmpty() || password.isEmpty()) {
        Toast.makeText(getContext(), "username and password are required", Toast.LENGTH_SHORT).show();
        return;
    }
    if (listener != null)
        listener.onSignup(userName, password);
    dismiss();
}

private File createImageFile(){

    File storageDir = getActivity().getExternalFilesDir(Environment.DIRECTORY_PICTURES);
    File file = new File(storageDir, "photo.jpg");
    photoPath = file.getAbsolutePath();
    return file;
}

public interface OnSignupFragmentListener {
    void onSignup(String username, String password);
}

s

单击ivSelfi按钮时，我得到以下NPE-

java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.XmlResourceParser android.content.pm.ProviderInfo.loadXmlMetaData(android.content.pm.PackageManager, java.lang.String)' on a null object reference
        at android.support.v4.content.FileProvider.parsePathStrategy(FileProvider.java:605)
        at android.support.v4.content.FileProvider.getPathStrategy(FileProvider.java:579)
        at android.support.v4.content.FileProvider.getUriForFile(FileProvider.java:417)
        at com.example.alon.a2018_17_12_userloginexhomework.SignupFragment.onClick(SignupFragment.java:92)


<?xml version="1.0" encoding="utf-8"?>

<uses-permission android:name="android.permission.INTERNET"/>
<uses-feature android:name="android.hardware.camera" android:required="true"/>

我的清单文件：

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="false"
    android:theme="@style/AppTheme">

    <provider
        android:name="android.support.v4.content.FileProvider"
        android:authorities="${applicationId}.camera.fileprovider"
        android:exported="false"
        android:grantUriPermissions="true">
        <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/file_paths">
        </meta-data>
    </provider>
    <activity android:name=".GameActivity"></activity>
    <activity android:name=".LoginActivity"
        android:windowSoftInputMode="stateHidden">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name=".UserDetailsActivity" />
</application>

我的file_paths.xml文件-

<paths>
<external-path
    name="my_images"
    path="Android/data/com.example.alon.a2018_17_12_userloginexhomework/files/Pictures" />

Answer 1

好的，所以我想出了解决方案-我写的软件包名称不正确。该项目是：

android:authorities="com.example.alon.a2018_17_12_userloginexhomework.fileprovider"