public class MainActivity extends ActionBarActivity {    private Button btn = null;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        btn = (Button) this.findViewById(R.id.btnChoose);        btn.setOnClickListener(new View.OnClickListener() {  // 定义了一个按钮，然后点显示日期组件            @Override            public void onClick(View v) {                new DatePickerDialog(MainActivity.this, new DatePickerDialog.OnDateSetListener() {                    @Override                    public void onDateSet(DatePicker view, int year, int month, int dayOfMonth) {  // 当日期选择的时候                        String date = String.format("%d-%d-%d", year, month, dayOfMonth);                        btn.setText(date);       // 改变按钮的text                        System.out.print(date);  // 打印                    }                }, 2016, 1, 1).show();            }        });        System.out.println("onCreate");    }}

public class MainActivity extends ActionBarActivity {    private Button btn = null;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        btn = (Button) this.findViewById(R.id.btnChoose);        btn.setOnClickListener(new View.OnClickListener() {  // 定义了一个按钮，然后点显示时间控件            @Override            public void onClick(View v) {                // 创建一个时间控件               new TimePickerDialog(MainActivity.this, new TimePickerDialog.OnTimeSetListener() {                   @Override                   public void onTimeSet(TimePicker view, int hourOfDay, int minute) {  // 选择时间市，相应                       String s = String.format("%d:%d", hourOfDay, minute);                       btn.setText(s);                   }               }, 0, 0, true).show();            }        });        System.out.println("onCreate");    }    }

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical" android:layout_width="match_parent"    android:layout_height="match_parent">    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="世界上最大的洋?"        android:textAppearance="?android:attr/textAppearanceLarge"        android:id="@+id/textView2" />    <!-- 单选组，单选按钮必须要放一个RadioGroup -->    <RadioGroup        android:layout_width="wrap_content"        android:layout_height="wrap_content">        <RadioButton            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="A.大西洋"            android:id="@+id/rbA" />        <RadioButton            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="B.太平洋"            android:id="@+id/rbB" />        <RadioButton            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="C.印度洋"            android:id="@+id/rbC" />    </RadioGroup>    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="提交"        android:id="@+id/btnChoose" /></LinearLayout>

public class MainActivity extends ActionBarActivity {    private Button btn = null;    private RadioButton rbA = null;   // 单选按钮A    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        btn = (Button) this.findViewById(R.id.btnChoose);        rbA = (RadioButton) this.findViewById(R.id.rbA);        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                if(rbA.isChecked()) {   // 当选择是正确的                    // 提示                    Toast.makeText(MainActivity.this, "所选是正确的", Toast.LENGTH_SHORT).show();                } else {                    Toast.makeText(MainActivity.this, "所选是错误的", Toast.LENGTH_SHORT).show();                }            }        });        System.out.println("onCreate");    }}