目录
简介
CheckBox是复选按钮，点击选中后再次点击可取消选中。CheckBox继承自CompoundButton(复合按钮)。使用CheckBox需要导入android.widget.CheckBox和android.widget.CompoundButton。
CheckBox的创建
使用xml布局创建
使用xml布局创建CheckBox的核心在于布局文件和findviewById()方法。activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout...>
...
<CheckBox
android:id="@+id/cb_1"
android:width="match_parent"
android:height="wrap_content"
.../>
...
</LinearLayout>
MainActivity.java
import...
import android.widget.CheckBox;
import android.widget.CompoundButton
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//find a CheckBox in xml file
CheckBox cb_1=(CheckBox)findviewById(R.id.cb_1);
...
}
...
}
使用Java代码创建
使用Java代码创建CheckBox的步骤与使用Java代码创建Button一致(以下均以LinearLayout为例)：
①使用构造函数CheckBox(Context context)创建CheckBox对象
CheckBox cb_1=new CheckBox(this);
②为CheckBox对象设置必要属性参数
LinearLayout.LayoutParams params=new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT);
cb_1.setLayoutParams(params);
③将CheckBox对象添加到目标ViewGroup
LinearLayout layout_main=(LinearLayout)findviewById(R.id.layout_main);
layout_main.addView(cb_1);
④在res/values/路径下创建id值资源文件并使用setId()方法为CheckBox对象设置idres/values/cb_id.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<item name="cb_1" type="id"/>
...
</resources>
cb_1.setId(R.id.cb_1);
⑤为CheckBox设置外观、监听器等
cb_1.setText("check1");
cb_1.setBackgroundColor(0x50ff00ff);
...
cb_1.setOnCheckedChangeListener(this);
⑥使用目标ViewGroup对象的removeView()方法从目标ViewGroup移除CheckBox
layout_main.removeView(cb_1);
CheckBox的监听
CheckBox所用的监听器为OnCheckedChangeListener，充当OnCheckedChangeListener的对象类必须实现CompoundButton.OnCheckedChangeListener接口：
public class MyCheckedChangeListener
implements CompoundButton.OnCheckedChangeListener {
...
}
CheckBox设置监听器的方式有：
①当前Activity类实现CompoundButton.OnCheckedChangeListener接口
②内部类实现CompoundButton.OnCheckedChangeListener接口
③匿名内部类实现CompoundButton.OnCheckedChangeListener接口
④外部类实现CompoundButton.OnCheckedChangeListener接口
充当OnCheckedChangeListener的对象类必须重写onCheckedChanged()方法：
public class MyCheckedChangeListener
implements CompoundButton.OnCheckedChangeListener {
...
@Override
public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) {
switch(buttonView.getId()) {
case R.id.cb_1:
if(isChecked) {...}
else {...}
break;
case R.id.cb_2:
if(isChecked) {...}
else {...}
break;
...
}
}
...
}
每点击一次CheckBox按钮就会触发onCheckedChanged()方法。使用buttonView.getId()方法判断响应点击的CheckBox按钮；使用isChecked判断响应点击CheckBox按钮被点击后的选中状态：isChecked为true,响应点击的CheckBox按钮被选中；isChecked为false，响应点击的CheckBox按钮被弃选。
CheckBox的常用属性
①android:checked
CheckBox的当前选中状态。属性值为true/false。为true当前状态为被选中；为false当前状态为未被选中。对应的设置方法为setChecked(boolean checked)。
②android:button
CheckBox左侧按钮的图形或颜色。属性值可以是RGB888或ARGB值，也可以是图形图片资源。对应的设置方法为setButtonDrawable(R.drawable.drawablefile)。
③android:background
CheckBox右侧文字部分的背景。属性值可以是RGB888或ARGB值，也可以是图形图片资源。对应的设置方法为setBackground()和setBackgroundColor()。
④android:gravity
CheckBox文字的内部对齐方式。属性值：top(顶对齐)、bottom(底对齐)、left(左对齐)、right(右对齐)、center(居中)。对应的设置方法为setGravity()。
⑤android:scaleX/android:scaleY
CheckBox的X/Y方向的尺寸缩放。属性值为0~1。对应的设置方法为setScaleX(float scaleX)/setScaleY(float scaleY)。
以下将以实例展示CheckBox的基本用法，代码实现：CheckBox被选中后按钮和文本背景颜色改变；CheckBox被弃选后按钮和文本背景颜色恢复。cb_select.xml
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_checked="true">
<shape android:shape="oval">
<size
android:width="20dp"
android:height="20dp"/>
<solid
android:color="#50ff00ff"/>
<stroke
android:width="3dp"
android:color="#ff000000"/>
</shape>
</item>
<item android:state_checked="false">
<shape android:shape="oval">
<size
android:width="20dp"
android:height="20dp"/>
<solid
android:color="#ffffff"/>
<stroke
android:width="3dp"
android:color="#ff000000"/>
</shape>
</item>
</selector>
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout...>
...
<CheckBox
android:id="@+id/cb_1"
android:width="match_parent"
android:height="wrap_content"
android:text="check1"
android:background="#50005050"
android:button="@drawable/cb_select"/>
<CheckBox
android:id="@+id/cb_2"
android:width="match_parent"
android:height="wrap_content"
android:text="check2"
android:background="#50505000"
android:button="@drawable/cb_select"/>
...
</LinearLayout>
MainActivity.java
import...
import android.widget.CheckBox;
import android.widget.CompoundButton;
public class MainActivity extends Activity
implements CompoundButton.OnCheckedChangeListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
CheckBox cb_1=(CheckBox)findviewById(R.id.cb_1);
CheckBox cb_2=(CheckBox)findviewById(R.id.cb_2);
cb_1.setOnCheckedChangeListener(this);
cb_2.setOnCheckedChangeListener(this);
}
@Override
public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) {
switch(buttonView.getId()) {
case R.id.cb_1:
if(isChecked) {
Toast.makeText(this,"You select check1",Toast.LENGTH_SHORT).show();
}
else {
Toast.makeText(this,"You give up check1",Toast.LENGTH_SHORT).show();
}
break;
case R.id.cb_2:
if(isChecked) {
Toast.makeText(this,"You select check2",Toast.LENGTH_SHORT).show();
}
else {
Toast.makeText(this,"You give up check2",Toast.LENGTH_SHORT).show();
}
break;
}
}
}
CheckBox的继承
自定义CheckBox时会用到CheckBox的继承。AndroidStudio要求使用AppCompatCheckBox代替CheckBox用以自定义CheckBox类的继承。对于开发者而言，自定义CheckBox中最有意义的方法是构造函数和onTouchEvent()。
以下将以简单实例代码展示CheckBox继承的用法。代码实现：选中时CheckBox颜色改变并打印系统提示；弃选后CheckBox颜色恢复并打印系统提示。activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:id="@+id/layout_main"
...>
...
</LinearLayout>
MyCheckBox.java
import...
import androidx.appcompat.widget.AppCompatCheckBox;
public class MyCheckBox extends AppCompatCheckBox {
//context for Toast
private Context context;
//constructors
public MyCheckBox(Context context) {
super(context);
this.context=context;
//use selector file for CheckBox button drawable
this.setButtonDrawable(R.drawable.cb_select);
this.setBackgroundColor(0x50f000f0);
}
public MyCheckBox(Context context, AttributeSet attrs) {
super(context, attrs);
this.context=context;
//use selector file for CheckBox button drawable
this.setButtonDrawable(R.drawable.cb_select);
this.setBackgroundColor(0x50f000f0);
}
public MyCheckBox(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
this.context=context;
//use selector file for CheckBox button drawable
this.setButtonDrawable(R.drawable.cb_select);
this.setBackgroundColor(0x50f000f0);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if(event.getAction()==MotionEvent.ACTION_DOWN) {
Toast.makeText(context,"You pressed",Toast.LENGTH_SHORT).show();
}
else if(event.getAction()==MotionEvent.ACTION_UP){
Toast.makeText(context,"You complete press",Toast.LENGTH_SHORT).show();
}
//must return super.onTouchEvent(event),or onCheckedChanged() method will not reach
return super.onTouchEvent(event);
}
}
MainActivity.java
public class MainActivity extends Activity
implements CompoundButton.OnCheckedChangeListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//find ViewGroup in xml file
LinearLayout layout_main=(LinearLayout)findviewById(R.id.layout_main);
//create a MyCheckBox
MyCheckBox cb_1=new MyCheckBox(this);
LinearLayout.LayoutParams params=new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT);
cb_1.setLayoutParams(params);
//add cb_1 to target ViewGroup
layout_main.addView(cb_1);
//set cb_1
cb_1.setText("check1");
//this id is in res/values/cb_id file
cb_1.setId(R.id.cb_1);
cb_1.setOnCheckedChangeListener(this);
}
@Override
public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) {
if(buttonView.getId==R.id.cb_1) {
if(isChecked) {
Toast.makeText(this,"You select check1",Toast.LENGTH_SHORT).show();
}
else {
Toast.makeText(this,"You give up check1",Toast.LENGTH_SHORT).show();
}
}
}
}
欢迎指正