Button
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textView4"
android:layout_centerHorizontal="true"
android:layout_marginTop="112dp"
android:text="Click Button" />
<EditText
android:id="@+id/editText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/textView2"
android:layout_alignBottom="@+id/textView2"
android:layout_alignParentEnd="true"
android:layout_alignParentRight="true"
android:layout_marginEnd="21dp"
android:layout_marginRight="21dp"
android:ems="10"
android:inputType="textPersonName"
android:text="" />
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/editText"
android:layout_alignStart="@+id/editText"
android:layout_alignTop="@+id/textView3"
android:textSize="16sp"
android:text="TextView" />
为按钮添加事件，当EditText控件的内容不为空时将TextView的内容设为EditText的内容。
button.setOnClickListener(){
val inputValue: String = editText.text.toString()
if (inputValue == null || inputValue.trim()==""){
Toast.makeText(this,"please input data, edit text cannot be blank",Toast.LENGTH_LONG).show()
}else{
textView.setText(inputValue).toString()
}
}
为按钮控件添加点击事的方法:
- 匿名内部类:
override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) bt_click.setOnClickListener { Toast.makeText(this,"点击了",Toast.LENGTH_SHORT).show(); } } - Activity实现全局OnClickListener接口:
class MainActivity : AppCompatActivity(), View.OnClickListener {
override fun onClick(v: View?) {
when (v?.id) {
R.id.bt_click ->
Toast.makeText(this, "点击了", Toast.LENGTH_SHORT).show()
}
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
bt_click.setOnClickListener(this)
}
}
- 指定xml的onClick属性:
<Button
android:id="@+id/bt_click"
android:layout_width="match_parent"
android:layout_height="50dp"
android:onClick="click"
android:text="点击" />
fun click(v: View?) {
when (v?.id) {
R.id.bt_click ->
Toast.makeText(this, "点击了", Toast.LENGTH_SHORT).show()
}
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
TextView
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/editText"
android:layout_alignStart="@+id/editText"
android:layout_alignTop="@+id/textView3"
android:textSize="16sp"
android:text="TextView" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignEnd="@+id/editText"
android:layout_alignRight="@+id/editText"
android:layout_centerVertical="true"
android:text="reset output text" />
textView2.setOnClickListener(){
if (textView1.text.toString() == null || textView1.text.toString().trim()==""){
Toast.makeText(this,"clicked on reset textView,\n output textView already reset",Toast.LENGTH_LONG).show()
}else{
textView1.setText("").toString()
}
}
EditText
为EditText控件添加内容变更触发事件。控件定义代码如下：
<EditText
android:id="@+id/editText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/textView2"
android:layout_alignBottom="@+id/textView2"
android:layout_alignParentEnd="true"
android:layout_alignParentRight="true"
android:layout_marginEnd="21dp"
android:layout_marginRight="21dp"
android:ems="10"
android:inputType="textPersonName"
android:text="" />
实现代码如下：
editText.addTextChangedListener(object: TextWatcher{
override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
// TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
Toast.makeText(applicationContext,"executed before making any change over EditText",Toast.LENGTH_SHORT).show()
} //事件：变更前触发。
override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
// TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
Toast.makeText(applicationContext,"executed while making any change over EditText",Toast.LENGTH_SHORT).show()
} //事件：变更时触发。
override fun afterTextChanged(p0: Editable?) {
// TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
Toast.makeText(applicationContext,"executed after change made over EditText",Toast.LENGTH_SHORT).show()
} //事件：变更后触发。
})
