[英]CameraX PreviewView to Bitmap instead of a File
我知道還有其他問題已經回答了很多次,我試圖找到答案,但我最不明白。 我想讓相機拍照,但不是制作物理圖像文件,而是希望它直接將其制作成位圖並從不同的活動中將其顯示在 ImageView 中,但是我不斷地Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
,那是因為viewFinder.bitmap
是一個 null 並決定創建一個單獨的函數getBitmap(): Bitmap?
. 我不知道它希望我誠實地做什么或由此產生任何線索,我想要做的就是將照片作為位圖直接發送到 ImageView。 先感謝您。
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.camerax5, PID: 5472
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.camerax5/com.example.camerax5.VirtualPreview}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3141)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3284)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1972)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7179)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:975)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:164)
at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:157)
at android.content.Context.obtainStyledAttributes(Context.java:677)
at androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor(AppCompatDelegateImpl.java:842)
at androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor(AppCompatDelegateImpl.java:809)
at androidx.appcompat.app.AppCompatDelegateImpl.findViewById(AppCompatDelegateImpl.java:633)
at androidx.appcompat.app.AppCompatActivity.findViewById(AppCompatActivity.java:259)
at com.example.camerax5.MainActivity.getBitmap(MainActivity.kt:118)
at com.example.camerax5.VirtualPreview.onCreate(VirtualPreview.kt:19)
at android.app.Activity.performCreate(Activity.java:7335)
at android.app.Activity.performCreate(Activity.java:7326)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1275)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3121)
所以問題出現在這一行:
viewFinder = findViewById(R.id.previewView)
這是我試圖做的完整代碼:
MainActivity.kt 和 MainActivity 代碼下面是另一個具有另一個活動的類,用於在 ImageView 中顯示位圖,我添加這種方式是因為我不想將它們分開並使它們變得混亂:
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
viewFinder = findViewById(R.id.previewView)
//Permissions
if (allPermissions()) {
startCamera()
} else {
ActivityCompat.requestPermissions(this, REQUIRED_PERMISSIONS, REQUEST_CODE_PERMISSIONS)
}
//Capture button
val captureBtn: Button = findViewById(R.id.captureButton)
captureBtn.setOnClickListener {
takePhoto()
}
outputDirectory = outputDirectoryFolder()
cameraExecutor = Executors.newSingleThreadExecutor()
}
private fun takePhoto() {
Toast.makeText(baseContext, "Processing ..", Toast.LENGTH_SHORT).show()
//Directly to open the new Activity
val intent = Intent(this, VirtualPreview::class.java)
startActivity(intent)
}
fun getBitmap(): Bitmap? {
//Preview to Bitmap
viewFinder = findViewById(R.id.previewView)
val source = viewFinder.bitmap
val newWidth = 200
val newHeight = 200
val bitmapWidth = source?.width
val bitmapHeight = source?.height
//Matrix
val matrix = Matrix()
val scaleWidth = newWidth.toFloat() / bitmapWidth!!
val scaleHeight = newHeight.toFloat() / bitmapHeight!!
matrix.postScale(scaleWidth, scaleHeight)
return Bitmap.createBitmap(source, 0, 0, newWidth, newHeight, matrix, true)
}
}
class VirtualPreview : AppCompatActivity() {
private lateinit var acceptButton: Button
private lateinit var denyButton: Button
private lateinit var imageView: ImageView
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_virtual_preview)
val bitmapPreview = MainActivity().getBitmap()
val drawableBitmap = BitmapDrawable(resources, bitmapPreview)
imageView = findViewById(R.id.imagePreview)
imageView.setImageDrawable(drawableBitmap)
acceptButton = findViewById(R.id.acceptButton)
acceptButton.setOnClickListener {
}
denyButton = findViewById(R.id.denyButton)
denyButton.setOnClickListener {
//delete the matrix and returns to the main activity
finish()
}
}
}
val bitmapPreview = MainActivity().getBitmap()
- 這樣你就創建了一個MainActivity
的新實例,新實例在預覽視圖中沒有任何東西,也不推薦這種方法。 更好地將位圖存儲在 MainActivity 中,然后將該位圖傳遞給構造函數中的VirtualPreview
活動(在捆綁中它不起作用)。 對於您的情況,這不會成為問題,因為您將位圖縮放到 200x200。 對於大位圖,存儲在文件中,並使用該文件。 對於您的情況,您可以在 mainactivity 中創建另一個 imageview 並在該 imageview 中顯示位圖,而不是創建另一個活動。
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