Android用Kotlin查看id

Question

我正在使用Nav抽屉的项目。

<android.support.design.widget.NavigationView
        ...
        app:headerLayout="@layout/home_nav_header" />

标题布局包含一个TextView和一个将保存用户名和用户pic的ImageView。 home_nav_header文件如下所示：

<LinearLayout ...>

    <ImageView
        android:id="@+id/nav_drawer_user_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/nav_header_vertical_spacing"
        app:srcCompat="@mipmap/ic_launcher_round" />

    <TextView
        android:id="@+id/nav_drawer_user_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/nav_header_vertical_spacing"
        android:textAppearance="@style/TextAppearance.AppCompat.Body1" />

</LinearLayout>

在我的HomeActivity中，我以这种方式设置数据：

import kotlinx.android.synthetic.main.home_content.*
import kotlinx.android.synthetic.main.home_nav_header.*
/...
override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_home)
        mPresenter = HomePresenter(this)

        //Fill user name
        mUser = intent.getParcelableExtra(LoginActivity.INTENT_USER)
        val userName: String = mUser.firstName + " " + mUser.lastName
        nav_drawer_user_name.text = userName

        //Fill user image
        val decodedString = Base64.decode(mUser.photoUrl, Base64.DEFAULT)
        val decodedByte = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.size)
        val userImageDrawable = BitmapDrawable(getResources(), decodedByte)
        nav_drawer_user_name.background = userImageDrawable
    }

我检查了userName和userImageDrawable都不为null。

问题是，当我尝试在TextView和ImageView中填充数据时，应用程序崩溃时出现以下错误：

java.lang.IllegalStateException：findViewById（R.id.nav_drawer_user_name）不能为null

我的代码中缺少什么？

Answer 1

我认为kotlin android插件存在问题，我在onCreate，onStart和onResume上尝试了同样的错误但是如果我设置文本onClick的东西，它正常工作。如果您仍然想要setText（或该视图的任何其他方法），您可以通过传统方式进行

    val textView  = nav_view.getHeaderView(0).findViewById<TextView>(R.id.nav_drawer_user_name)
    textView.text= "new Text"

Answer 2

您必须先获取视图，然后才能为其指定值。

   import kotlinx.android.synthetic.main.home_content.*
   import kotlinx.android.synthetic.main.home_nav_header.*

    override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_home)
            mPresenter = HomePresenter(this)

            //Fill user name
            mUser = intent.getParcelableExtra(LoginActivity.INTENT_USER)
            val userName: String = mUser.firstName + " " + mUser.lastName
            val nav_drawer_user_name = findViewById<TextView>(R.id.nav_drawer_user_name)
            nav_drawer_user_name.text = userName

            //Fill user image
            val decodedString = Base64.decode(mUser.photoUrl, Base64.DEFAULT)
            val decodedByte = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.size)
            val userImageDrawable = BitmapDrawable(getResources(), decodedByte)
            nav_drawer_user_name.background = userImageDrawable
        }

注意val nav_drawer_user_name = findViewById<TextView(R.id.nav_drawer_user_name)