[您好，我仍在学习Android Studio的基础知识，每次运行我的应用程序并按“添加”按钮将我带到另一页，它显示“应用程序已停止”时，我遇到了错误。我在日志中遇到了错误，我不知道这是什么意思？
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.sliteproj.productsGroups.AddProductGroupActivity.onCreate(AddProductGroupActivity.java:72)
这是我的导致错误的.java代码：
package com.example.sliteproj.productsGroups;
import android.Manifest;
import android.app.ProgressDialog;
import android.content.ContentValues;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import com.example.sliteproj.R;
import com.theartofdev.edmodo.cropper.CropImage;
import com.theartofdev.edmodo.cropper.CropImageView;
public class AddProductGroupActivity extends AppCompatActivity {
private ImageView pImageView;
private EditText pNameEt, pSelectableDateEt;
Button saveInfoBut;
ActionBar actionBar;
ProgressDialog pd;
private static final int CAMERA_REQUEST_CODE = 100;
private static final int STORAGE_REQUEST_CODE = 101;
private static final int IMAGE_PICK_CAMERA_CODE = 102;
private static final int IMAGE_PICK_GALLERY_CODE = 103;
private String[] cameraPermissions;
private String[] storagePermissions;
private Uri imageUri;
private String name, selectableDate;
private ProductsGroupDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_group);
pd = new ProgressDialog(AddProductGroupActivity.this);
pNameEt = findViewById(R.id.productGroup);
pSelectableDateEt = findViewById(R.id.selectableDays);
saveInfoBut = findViewById(R.id.addGroupInfoBtn);
dbHelper = new ProductsGroupDatabaseHelper(this);
cameraPermissions = new String[]{Manifest.permission.CAMERA, Manifest.permission.WRITE_EXTERNAL_STORAGE};
storagePermissions = new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE};
pImageView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
imagePickDialog();
}
});
saveInfoBut.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
pd.setTitle("Adding");
pd.setMessage("Please wait...");
pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);
pd.show();
getData();
startActivity(new Intent(AddProductGroupActivity.this, productGroupActivity.class));
Toast.makeText(AddProductGroupActivity.this, "Information Added Successfully!", Toast.LENGTH_SHORT).show();
}
});
}
private void getData() {
name = ""+pNameEt.getText().toString().trim();
selectableDate = ""+pSelectableDateEt.getText().toString().trim();
dbHelper.insertInfo(
""+imageUri,
""+name,
""+selectableDate
);
}
private void imagePickDialog() {
String[] options = {"Camera", "Gallery"};
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Pick Image From");
builder.setItems(options, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if (which == 0) {
if (!checkCameraPermission()) {
requestCameraPermission();
}
else {
pickFromCamera();
}
}
else if (which == 1) {
if (!checkStoragePermission()) {
requestStoragePermission();
}
else {
pickFromGallery();
}
}
}
});
builder.create().show();
}
private void pickFromGallery() {
Intent galleryIntent = new Intent(Intent.ACTION_PICK);
galleryIntent.setType("image/*");
startActivityForResult(galleryIntent, IMAGE_PICK_GALLERY_CODE);
}
private void pickFromCamera() {
ContentValues values = new ContentValues();
values.put(MediaStore.Images.Media.TITLE, "Image title");
values.put(MediaStore.Images.Media.DESCRIPTION, "Image description");
imageUri = getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values);
Intent cameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
startActivityForResult(cameraIntent, IMAGE_PICK_CAMERA_CODE);
}
private boolean checkStoragePermission() {
boolean result = ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
== (PackageManager.PERMISSION_GRANTED);
return result;
}
private void requestStoragePermission() {
ActivityCompat.requestPermissions(this, storagePermissions, STORAGE_REQUEST_CODE);
}
private boolean checkCameraPermission() {
boolean result = ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
== (PackageManager.PERMISSION_GRANTED);
boolean result1 = ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
== (PackageManager.PERMISSION_GRANTED);
return result && result1;
}
private void requestCameraPermission() {
ActivityCompat.requestPermissions(this, cameraPermissions, CAMERA_REQUEST_CODE);
}
@Override
public boolean onSupportNavigateUp() {
onBackPressed();
return super.onSupportNavigateUp();
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
switch (requestCode) {
case CAMERA_REQUEST_CODE: {
if (grantResults.length>0) {
boolean cameraAccepted = grantResults[0] == PackageManager.PERMISSION_GRANTED;
boolean storageAccepted = grantResults[1] == PackageManager.PERMISSION_GRANTED;
if (cameraAccepted && storageAccepted) {
pickFromCamera();
}
else {
Toast.makeText(this, "Camera permission required!", Toast.LENGTH_SHORT).show();
}
}
}
break;
case STORAGE_REQUEST_CODE:{
if (grantResults.length>0) {
boolean storageAccepted = grantResults[0] == PackageManager.PERMISSION_GRANTED;
if (storageAccepted) {
pickFromGallery();
}
else {
Toast.makeText(this, "Storage permission required!", Toast.LENGTH_SHORT).show();
}
}
}
break;
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
if (resultCode == RESULT_OK) {
if (requestCode == IMAGE_PICK_GALLERY_CODE) {
CropImage.activity(data.getData())
.setGuidelines(CropImageView.Guidelines.ON)
.setAspectRatio(1, 1)
.start(this);
}
else if (requestCode == IMAGE_PICK_CAMERA_CODE) {
CropImage.activity(imageUri)
.setGuidelines(CropImageView.Guidelines.ON)
.setAspectRatio(1, 1)
.start(this);
}
else if (requestCode == CropImage.CROP_IMAGE_ACTIVITY_REQUEST_CODE) {
CropImage.ActivityResult result = CropImage.getActivityResult(data);
if (resultCode == RESULT_OK) {
Uri resultUri = result.getUri();
imageUri = resultUri;
pImageView.setImageURI(resultUri);
}
else if (resultCode == CropImage.CROP_IMAGE_ACTIVITY_RESULT_ERROR_CODE) {
Exception error = result.getError();
Toast.makeText(this, ""+error, Toast.LENGTH_SHORT).show();
}
}
}
super.onActivityResult(requestCode, resultCode, data);
}
}
非常感谢您对我的问题的任何帮助或解决方案！抱歉给您带来的不便
您忘记初始化