RadioButton使用方法

本文主要是介绍RadioButton使用方法，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

学一点，记一点。

要点

一组Radio Button放到一个Radio Group中；
如果Radio Button很多，就考虑是否Spinner更合适
事件处理有多种方式，如RadioGroup的OnCheckedChangeListener。

示例

效果

功能

选择某一个Radio Button之后，下面一个TextView显示选择结果。

布局文件 my_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical" ><RadioGroupandroid:id="@+id/radio_group"android:layout_width="457dp"android:layout_height="wrap_content"android:orientation="horizontal" ><RadioButtonandroid:id="@+id/radio_first"android:layout_width="wrap_content"android:layout_height="wrap_content"android:checked="true"android:text="@string/first" /><RadioButtonandroid:id="@+id/radio_second"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/second" /><RadioButtonandroid:id="@+id/radio_third"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/third" /></RadioGroup><TextViewandroid:id="@+id/select_result"android:layout_width="match_parent"android:layout_height="wrap_content"/></LinearLayout>

代码

省略掉自动生成的代码。

private RadioGroup radioGroup = null;
private TextView textView = null;@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.my_layout);radioGroup = (RadioGroup) this.findViewById(R.id.radio_group);textView = (TextView) this.findViewById(R.id.select_result);textView.setText(getSelectedInfo());radioGroup.setOnCheckedChangeListener(new OnCheckedChangeListener() {public void onCheckedChanged(RadioGroup group, int checkedId) {textView.setText(getSelectedInfo(checkedId));}});}private String getSelectedInfo() {int checkedId = radioGroup.getCheckedRadioButtonId();return getSelectedInfo(checkedId);
}private String getSelectedInfo(int checkedId) {String selected = "Unknown selection!";switch (checkedId) {case R.id.radio_first:selected = "First was selected.";break;case R.id.radio_second:selected = "Second was selected.";break;case R.id.radio_third:selected = "Third was selected.";break;default:break;}return selected;
}

事件处理

上面的示例是为RadioGroup对象注册OnCheckedChangeListener。此外，还可以直接为每个Radio Button注册listener。接下来详细描述。

RadioButton事件处理

可以为Radio Button注册CompoundButton.OnCheckedChangeListener。

代码一

private RadioButton firstRadio = null;
private RadioButton secondRadio = null;
private RadioButton thirdRadio = null;@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.my_layout);firstRadio = (RadioButton) this.findViewById(R.id.radio_first);secondRadio = (RadioButton) this.findViewById(R.id.radio_second);thirdRadio = (RadioButton) this.findViewById(R.id.radio_third);firstRadio.setOnCheckedChangeListener(new MyListener("First"));secondRadio.setOnCheckedChangeListener(new MyListener("Second"));thirdRadio.setOnCheckedChangeListener(new MyListener("Third"));
}private class MyListener implements CompoundButton.OnCheckedChangeListener {private String radioName = null;public MyListener(String theRadioName) {radioName = theRadioName;}public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) {Toast.makeText(MainActivity.this, radioName + " checked:" + isChecked, Toast.LENGTH_SHORT).show();}
}

实际运行发现，被选中的Radio Button会先处理，显示：xxx checked: true；失去焦点的Radio Button之后处理，显示：xxx checked: false。

注意到，这里通过ctor传入一个标识符，说明当前的事件处理是哪个Radio Button的。显然，这种方式的通用性并不好。

代码二

下面是等价的一种方式：

private RadioButton firstRadio = null;
private RadioButton secondRadio = null;
private RadioButton thirdRadio = null;@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.my_layout);firstRadio = (RadioButton) this.findViewById(R.id.radio_first);secondRadio = (RadioButton) this.findViewById(R.id.radio_second);thirdRadio = (RadioButton) this.findViewById(R.id.radio_third);MyListener listener = new MyListener();firstRadio.setOnCheckedChangeListener(listener);secondRadio.setOnCheckedChangeListener(listener);thirdRadio.setOnCheckedChangeListener(listener);
}private String getRadioName(int id) {switch (id) {case R.id.radio_first: return "First";case R.id.radio_second: return "Second";case R.id.radio_third: return "Third";default: return "Unknown";}
}private class MyListener implements CompoundButton.OnCheckedChangeListener {public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) {String radioName = getRadioName(buttonView.getId());Toast.makeText(MainActivity.this, radioName + " checked:" + isChecked, Toast.LENGTH_SHORT).show();}
}

xml中定义事件

在docs/guide/topics/ui/controls/radiobutton.html中提到在xml中定义Radio Button的事件处理。

xml

在每个RadioButton中增加一个属性：

android:onClick="onRadioButtonClicked"

即变成下面的样子：

<RadioGroupandroid:id="@+id/radio_group"android:layout_width="457dp"android:layout_height="wrap_content"android:orientation="horizontal" ><RadioButtonandroid:id="@+id/radio_first"android:layout_width="wrap_content"android:layout_height="wrap_content"android:checked="true"android:text="@string/first"android:onClick="onRadioButtonClicked" /><RadioButtonandroid:id="@+id/radio_second"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/second"android:onClick="onRadioButtonClicked" /><RadioButtonandroid:id="@+id/radio_third"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/third"android:onClick="onRadioButtonClicked" />
</RadioGroup>

代码

@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.my_layout);
}private String getRadioName(int id) {switch (id) {case R.id.radio_first: return "First";case R.id.radio_second: return "Second";case R.id.radio_third: return "Third";default: return "Unknown";}
}public void onRadioButtonClicked(View view) {boolean checked = ((RadioButton) view).isChecked();String radioName = getRadioName(view.getId());Toast.makeText(this, radioName + " checked:" + checked, Toast.LENGTH_SHORT).show();
}

运行效果

当选中某个Radio Button的时候，会触发事件。失去焦点的不会触发事件，——因为是OnClick类型的事件，而不是OnCheckedChanged。

所以，这种方法比前一种要简洁得多。

在代码中注册OnClickListener

另外一种等价方式就是直接在代码中为RadioButton注册OnClickListener对象。

为此，在xml中删除前面添加的属性，然后代码改成如下的样子：

private RadioButton firstRadio = null;
private RadioButton secondRadio = null;
private RadioButton thirdRadio = null;@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.my_layout);OnClickListener listener = new OnClickListener() {public void onClick(View view) {boolean checked = ((RadioButton) view).isChecked();String radioName = getRadioName(view.getId());Toast.makeText(MainActivity.this, radioName + " checked:" + checked, Toast.LENGTH_SHORT).show();}};firstRadio = (RadioButton) this.findViewById(R.id.radio_first);secondRadio = (RadioButton) this.findViewById(R.id.radio_second);thirdRadio = (RadioButton) this.findViewById(R.id.radio_third);firstRadio.setOnClickListener(listener);secondRadio.setOnClickListener(listener);thirdRadio.setOnClickListener(listener);
}private String getRadioName(int id) {switch (id) {case R.id.radio_first: return "First";case R.id.radio_second: return "Second";case R.id.radio_third: return "Third";default: return "Unknown";}
}