[英]Null pointer Exception on file- URI?
In my app a capture button is there to capture an image using device camera,so I have used a method captureImage() on the click event of that button.When I click the button a null pointer exception is thrown.I could not understand how this happens Can anyone help?在我的应用程序中,有一个捕获按钮可以使用设备相机捕获图像,所以我在该按钮的单击事件上使用了一个方法 captureImage()。当我单击按钮时,会抛出一个空指针异常。我不明白是怎么回事发生这种情况有人可以帮忙吗? Thanks in advance!提前致谢!
capture button on on Create () method Create () 方法上的捕获按钮
photoButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
/*
Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(cameraIntent, CAMERA_REQUEST);*/
captureImage();
}
});
captureImage() method captureImage() 方法
private void captureImage() {
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);
intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);
// start the image capture Intent
startActivityForResult(intent, CAMERA_REQUEST);
}
Null pointer exception on this method此方法的空指针异常
public Uri getOutputMediaFileUri(int type) {
return Uri.fromFile(getOutputMediaFile(type));
}
/**
* returning image / video
*/
private static File getOutputMediaFile(int type) {
// External sdcard location
File mediaStorageDir = new File(
Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
Config.IMAGE_DIRECTORY_NAME);
// Create the storage directory if it does not exist
if (!mediaStorageDir.exists()) {
if (!mediaStorageDir.mkdirs()) {
Log.d(TAG, "Oops! Failed create "
+ Config.IMAGE_DIRECTORY_NAME + " directory");
return null;
}
}
// Create a media file name
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss",
Locale.getDefault()).format(new Date());
File mediaFile;
if (type == MEDIA_TYPE_IMAGE) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "IMG_" + timeStamp + ".jpg");
} else {
return null;
}
return mediaFile;
}
Logcat逻辑猫
java.lang.NullPointerException: file
at android.net.Uri.fromFile(Uri.java:447)
at com.riafy.user.imagegallerydemo.MainActivity.getOutputMediaFileUri(MainActivity.java:235)
at com.riafy.user.imagegallerydemo.MainActivity.captureImage(MainActivity.java:97)
at com.riafy.user.imagegallerydemo.MainActivity.access$100(MainActivity.java:29)
at com.riafy.user.imagegallerydemo.MainActivity$2.onClick(MainActivity.java:68)
at android.view.View.performClick(View.java:4761)
at android.view.View$PerformClick.run(View.java:19767)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
getOutputMediaFile(type) returns null. getOutputMediaFile(type) 返回 null。
public Uri getOutputMediaFileUri(int type) {
return Uri.fromFile(getOutputMediaFile(type));
}
You are returning here:你回到这里:
// Create the storage directory if it does not exist
if (!mediaStorageDir.exists()) {
if (!mediaStorageDir.mkdirs()) {
Log.d(TAG, "Oops! Failed create "
+ Config.IMAGE_DIRECTORY_NAME + " directory");
return null;
}
}
Have you added the following permission您是否添加了以下权限
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
to your manifest?到你的清单?
My solution was simple.我的解决方案很简单。
Realised the error.意识到错误。 Android Manifest had put a maxSDKVersion to 18 on the permission to write to storage. Android Manifest 已将 maxSDKVersion 设置为 18 写入存储的权限。 After removing that, it was working perfectly.删除后,它完美地工作。
File mediaStorageDir = new File(
Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
Config.IMAGE_DIRECTORY_NAME);
I directly copied to code from Android getting started page.我直接从Android入门页面复制到代码。 My problem was I was running it on emulator.我的问题是我在模拟器上运行它。 Therefore I think the code above that I used could not assess my file system.因此,我认为我使用的上述代码无法评估我的文件系统。
In my case, I found out SDK version 23 and up might need runtime permission for writing external storage.就我而言,我发现 SDK 版本 23 及更高版本可能需要运行时权限才能写入外部存储。 So I solved like this:所以我是这样解决的:
public Uri getOutputMediaFileUri(int type) {
requestRuntimePermission();
return Uri.fromFile(getOutputMediaFile(type));
}
public void requestRuntimePermission() {
if (Build.VERSION.SDK_INT >= 23) {
if (ContextCompat.checkSelfPermission(context,android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
!= PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(activity,
new String[]{android.Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
}
}
}
Note: You might put this
instead of context
and activity
above if applicable注意:您可以把this
,而不是context
和activity
以上(如果适用)
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