我的应用程序中有一个列表视图。如何更改所选项目的文本颜色?
例如,我选择一些列表项。其文本颜色应从黑色更改为灰色。 然后,我选择另一个项目。其文字颜色也应从黑色更改为灰色,但第一个元素的文字颜色应再次变为黑色。
我尝试了以下代码,但出现异常:
试图在空对象引用上调用虚拟方法'
void android.widget.TextView.setText(java.lang.CharSequence)
'
QuestionActivity.kt:
var answersList = arrayOf("about", "against", "for", "by")
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_question)
val selection= findViewById<TextView>(R.id.options)
val lv = findViewById<ListView>(R.id.variants)
val prodAdapter = ArrayAdapter<String>(this, R.layout.mytextview, answersList)
lv.adapter = prodAdapter
lv.setOnItemClickListener { parent, view, position, id ->
val selectedItem = parent.getItemAtPosition(position).toString()
selection.setText(selectedItem)
selection.setTextColor(Color.DKGRAY)
}}
activity_question.xml:
<?xml version="1.0" encoding="utf-8"?>
<ListView
android:id="@+id/variants"
android:divider="#FFFFFF"
android:layout_width="347dp"
android:layout_height="254dp" tools:ignore="MissingConstraints"
app:layout_constraintStart_toStartOf="parent" android:layout_marginLeft="32dp"
android:layout_marginStart="32dp" app:layout_constraintEnd_toEndOf="parent" android:layout_marginEnd="32dp"
android:layout_marginRight="32dp" android:layout_marginTop="8dp"
app:layout_constraintTop_toBottomOf="@+id/appBarLayout" android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="@+id/button4"
/>
</android.support.constraint.ConstraintLayout>
和 mytextview.xml:
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/options"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceListItemSmall"
android:gravity="center_vertical"
android:minHeight="?android:attr/listPreferredItemHeightSmall"
android:textSize="20dp"
android:textColor="#000000"
/>
请帮助我解决此问题
答案 0 :(得分:0)
您必须使用选择器。像这样:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:color ="@color/selected_color" android:state_selected="true"/>
<item android:color ="@color/pressed_color" android:state_pressed="true"/>
<item android:color ="@color/default_color"/>
</selector>
然后在项目XML文件中使用选择器:
android:textColor="@color/text_selector"
您可以获取更多信息here