我正在使用Android-Image-Cropper库进行裁剪。我选择图像并显示菜单项（＆＃34;裁剪＆＃34;）see here
。我想在此Crop项目上添加一个监听器。它（截图）是我在清单文件中添加的Android-Image-Cropper库中的内置活动。我试图在该菜单项上添加监听器，但它给出了错误。
FATAL EXCEPTION: main
Process: com.theartofdev.cropimage, PID: 11439
java.lang.NullPointerException: Attempt to invoke interface method 'android.view.MenuItem android.view.MenuItem.
setOnMenuItemClickListener(android.view.MenuItem$OnMenuItemClickListener)' on a null object reference
atcom.theartofdev.cropimage.MainActivity.onCreateOptionsMenu(MainActivity.java:57)at android.app.Activity.onCreatePanelMenu(Activity.java:2845)
at android.support.v4.app.FragmentActivity.onCreatePanelMenu(FragmentActivity.java:341)...
public class MainActivity extends AppCompatActivity {
private CropImageView mCropImageView;
private Uri mCropImageUri;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mCropImageView = (CropImageView) findViewById(R.id.CropImageView);
}
/**
* On load image button click, start pick image chooser activity.
*/
public void onLoadImageClick(View view) {
startActivityForResult(getPickImageChooserIntent(), 200);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuItem item = menu.findItem(R.id.crop_image_menu_crop);
item.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
@Override
public boolean onMenuItemClick(MenuItem item) {
Log.e("crop","i am clicked");
Bitmap cropped = mCropImageView.getCroppedImage(500, 500);
if (cropped != null) mCropImageView.setImageBitmap(cropped);
return true;
}
});
return true;
}
/**
* Crop the image and set it back to the cropping view.
*/
@Override
@SuppressLint("NewApi")
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// handle result of pick image chooser
if (resultCode == Activity.RESULT_OK) {
Uri imageUri = CropImage.getPickImageResultUri(this, data);
// For API >= 23 we need to check specifically that we have permissions to read external storage.
boolean requirePermissions = false;
if (CropImage.isReadExternalStoragePermissionsRequired(this, imageUri)) {
// request permissions and handle the result in onRequestPermissionsResult()
requirePermissions = true;
mCropImageUri = imageUri;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, CropImage.PICK_IMAGE_PERMISSIONS_REQUEST_CODE);
}
} else {
// no permissions required or already grunted, can start crop image activity
CropImage.activity(imageUri).start(this);
}
}
}
@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
if (mCropImageUri != null && grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
mCropImageView.setImageUriAsync(mCropImageUri);
} else {
Toast.makeText(this, "Required permissions are not granted", Toast.LENGTH_LONG).show();
}
}
/**
* Create a chooser intent to select the source to get image from.<br/>
* The source can be camera's (ACTION_IMAGE_CAPTURE) or gallery's (ACTION_GET_CONTENT).<br/>
* All possible sources are added to the intent chooser.
*/
public Intent getPickImageChooserIntent() {
// Determine Uri of camera image to save.
Uri outputFileUri = getCaptureImageOutputUri();
List<Intent> allIntents = new ArrayList<>();
PackageManager packageManager = getPackageManager();
// collect all camera intents
Intent captureIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
List<ResolveInfo> listCam = packageManager.queryIntentActivities(captureIntent, 0);
for (ResolveInfo res : listCam) {
Intent intent = new Intent(captureIntent);
intent.setComponent(new ComponentName(res.activityInfo.packageName, res.activityInfo.name));
intent.setPackage(res.activityInfo.packageName);
if (outputFileUri != null) {
intent.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri);
}
allIntents.add(intent);
}
// collect all gallery intents
Intent galleryIntent = new Intent(Intent.ACTION_GET_CONTENT);
galleryIntent.setType("image/*");
List<ResolveInfo> listGallery = packageManager.queryIntentActivities(galleryIntent, 0);
for (ResolveInfo res : listGallery) {
Intent intent = new Intent(galleryIntent);
intent.setComponent(new ComponentName(res.activityInfo.packageName, res.activityInfo.name));
intent.setPackage(res.activityInfo.packageName);
allIntents.add(intent);
}
// the main intent is the last in the list (fucking android) so pickup the useless one
Intent mainIntent = allIntents.get(allIntents.size() - 1);
for (Intent intent : allIntents) {
if (intent.getComponent().getClassName().equals("com.android.documentsui.DocumentsActivity")) {
mainIntent = intent;
break;
}
}
allIntents.remove(mainIntent);
// Create a chooser from the main intent
Intent chooserIntent = Intent.createChooser(mainIntent, "Select source");
// Add all other intents
chooserIntent.putExtra(Intent.EXTRA_INITIAL_INTENTS, allIntents.toArray(new Parcelable[allIntents.size()]));
return chooserIntent;
}
/**
* Get URI to image received from capture by camera.
*/
private Uri getCaptureImageOutputUri() {
Uri outputFileUri = null;
File getImage = getExternalCacheDir();
if (getImage != null) {
outputFileUri = Uri.fromFile(new File(getImage.getPath(), "pickImageResult.jpeg"));
}
return outputFileUri;
}
/**
* Get the URI of the selected image from {@link #getPickImageChooserIntent()}.<br/>
* Will return the correct URI for camera and gallery image.
*
* @param data the returned data of the activity result
*/
public Uri getPickImageResultUri(Intent data) {
boolean isCamera = true;
if (data != null && data.getData() != null) {
String action = data.getAction();
isCamera = action != null && action.equals(MediaStore.ACTION_IMAGE_CAPTURE);
}
return isCamera ? getCaptureImageOutputUri() : data.getData();
}
/**
* Test if we can open the given Android URI to test if permission required error is thrown.<br>
*/
public boolean isUriRequiresPermissions(Uri uri) {
try {
ContentResolver resolver = getContentResolver();
InputStream stream = resolver.openInputStream(uri);
stream.close();
return false;
} catch (FileNotFoundException e) {
if (e.getCause() instanceof ErrnoException) {
return true;
}
} catch (Exception e) {
}
return false;
}
}
答案 0 :(得分：0)
我想你忘了给菜单充气：
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuItem item = menu.findItem(R.id.crop_image_menu_crop);
item.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener()
...
}
MenuItem时返回的 findItem为空，我相信，这会为您提供NullPointerException
你可能需要在这里添加菜单通胀：
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.your_menu_res, menu);
MenuItem item = menu.findItem(R.id.crop_image_menu_crop);
item.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener()
...
}