Zi 字媒體

RadioGroup rg1; RadioButton rb1; rg1=(RadioGroup)findViewById(R.id.rg1); rb1=(RadioButton)findViewById(R.id.rb1);   示範 XML xml version="1.0" encoding="utf-8"?> <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity"> <RadioGroup android:id="@+id/rg1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginEnd="8dp" android:layout_marginLeft="8dp" android:layout_marginRight="8dp" android:layout_marginStart="8dp" android:layout_marginTop="8dp" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent"> <RadioButton android:id="@+id/rb1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" /> <RadioButton android:id="@+id/rb2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" /> <RadioButton android:id="@+id/rb3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" /> RadioGroup> <TextView android:id="@+id/t1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginBottom="8dp" android:layout_marginEnd="8dp" android:layout_marginLeft="8dp" android:layout_marginRight="8dp" android:layout_marginStart="8dp" android:layout_marginTop="8dp" android:text="TextView" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toBottomOf="@+id/rg1" /> android.support.constraint.ConstraintLayout> JAVA public class MainActivity extends AppCompatActivity implements RadioGroup.OnCheckedChangeListener { RadioGroup rg1; RadioButton rb1,rb2,rb3; TextView t1; @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN) @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); t1=(TextView)findViewById(R.id.t1); rg1=(RadioGroup)findViewById(R.id.rg1); rb1=(RadioButton)findViewById(R.id.rb1); rb2=(RadioButton)findViewById(R.id.rb2); rb3=(RadioButton)findViewById(R.id.rb3); rb1.setText("R1"); rb2.setText("R2"); rb3.setText("R3"); rg1.setOnCheckedChangeListener(this); } @Override public void onCheckedChanged(RadioGroup group, int checkedId) { switch (checkedId){ case R.id.rb1: t1.setText("R1"); break; case R.id.rb2: t1.setText("R2"); break; case R.id.rb3: t1.setText("R3"); break; } } }   展示