Question

我正在创建此应用程序，我希望用户单击某个按钮photoButton并出现一个新的活动，提示用户输入2个edittext（entry）有价值的信息。在这两种情况下我都遇到错误：

当我尝试启动活动并访问活动中的内容
打开活动结果...时，

我单击一个按钮本质上触发了两个活动。究竟返回一个空值是什么？

尝试使用startactivityforresult方法。

   fun take_pic(){
        val takephotoIntent = Intent(MediaStore.ACTION_IMAGE_CAPTURE)
        if (takephotoIntent.resolveActivity(this.packageManager) != null) {
            startActivityForResult(takephotoIntent, REQUESTCODE)
        } else {
            Toast.makeText(this, "Unable To access Camera... ", Toast.LENGTH_LONG)
                .show()
        }


    }
    fun display_information() {
        /* Connection to firebase       */
        val currentuser = auth.currentUser!!.email


        /* getting the values of the user*/
        val email_of_user = currentuser



        /* Changing the Displayed text                    */
        welcomemessagename.text = email_of_user
        Date.text = "Date:" + date_formatted
    }

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_user_main_hub)
        val storageinfo = FirebaseStorage.getInstance().getReference("/images/")

        auth = FirebaseAuth.getInstance()

        /* displaying basic information for the user comfort.        */
        display_information()

        audioscannerButton.setOnClickListener {
            val action = Intent(this, Recordinit::class.java)
            startActivity(action)
        }

        helpbutton.setOnClickListener {
            val action2 = Intent(this, HelpActivity::class.java)
            startActivity(action2)
        }
        photoButton.setOnClickListener {
            val action3 = Intent(this , nameofphoto::class.java)
            startActivityForResult(action3, REQUESTCODE2 )

        }
    }
    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        if (REQUESTCODE == requestCode && resultCode == Activity.RESULT_OK) {
            //Compressing the bitmap(image) into a byte[] to match the input of the .putbytes method
            val userimage = data?.extras?.get("data") as Bitmap
            val byteoutput = ByteArrayOutputStream()
            userimage.compress(Bitmap.CompressFormat.JPEG,100 , byteoutput)
            val data = byteoutput.toByteArray()
            //ref to the firebase "bucket" database
            val storageinfo = FirebaseStorage.getInstance().getReference("/Images" )
            //extra data that shows who the images belong to (users)


           storageinfo.putBytes(data)


        }else if (requestCode ==REQUESTCODE2) {
            take_pic()

        }
        else {
            super.onActivityResult(requestCode, resultCode, data)
        }
        }



    }

现在的错误：

    Process: com.example.myapplication, PID: 20616
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Class java.lang.Object.getClass()' on a null object reference
        at com.example.myapplication.User_main_hub$onCreate$3.onClick(User_main_hub.kt:82)
        at android.view.View.performClick(View.java:6618)
        at android.view.View.performClickInternal(View.java:6590)
        at android.view.View.access$3100(View.java:781)
        at android.view.View$PerformClick.run(View.java:25950)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:215)
        at android.app.ActivityThread.main(ActivityThread.java:6952)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:870)
I/Process: Sending signal. PID: 20616 SIG: 9
Process 20616 terminated.

Answer 1

我正在阅读两行之间的内容，所以不确定，但是metabtnsubmit似乎不是此Activity R.layout.activity_user_main_hub的布局成员，因此合成的getter找不到它，并且返回null。

也许您正在尝试在下一个活动“ nameofphoto”中设置点击监听器？您无法通过此活动访问其UI元素。

假设这是一个活动，允许用户输入文本并选择照片，那么您需要使用startActivityForResult打开它，将其设置为结果，然后在该活动的{{ 1}}。

Answer 2

NullPointerException发生在onClick内，表达式nameofphoto :: class与其他OnClick方法是不同的，因此，在声明或分配nameofphoto时，在源代码中您不会显示nameofphoto。 / p>

您可以嵌套“ Onclicklisteners”以运行多个活动吗？

2 个答案: