技術標籤：android

報錯log

	E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.hgfenis.radiogroupdemo01, PID: 7180
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.hgfenis.radiogroupdemo01/com.hgfenis.radiogroupdemo01.RadioGroupActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RadioGroup.setOnCheckedChangeListener(android.widget.RadioGroup$OnCheckedChangeListener)'
 
 on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2668)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2729)
        at android.app.ActivityThread.-wrap12(ActivityThread.java)
        at android.app.ActivityThread$H.
 
handleMessage(ActivityThread.java:1480)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6198)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.
 
internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:891)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:781)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RadioGroup.setOnCheckedChangeListener(android.widget.RadioGroup$OnCheckedChangeListener)' on a null object reference
        at com.hgfenis.radiogroupdemo01.RadioGroupActivity.onCreate(RadioGroupActivity.java:31)
        at android.app.Activity.performCreate(Activity.java:6692)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2621)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2729) 
        at android.app.ActivityThread.-wrap12(ActivityThread.java) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1480) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6198) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:891) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:781) 

報錯行程式碼

radiogroup.setOnCheckedChangeListener(this);

報錯原因：
對 ButterKnife.bind(this); 的使用不熟練
解決辦法：
使用普通控制元件繫結方法即解決問題

public class RadioGroupActivity extends AppCompatActivity implements RadioGroup.OnCheckedChangeListener {

    private String TAG = RadioGroupActivity.class.getSimpleName();

    /*@BindView(R.id.activity_main_radiogroup)
    RadioGroup radiogroup;

    @BindView(R.id.activity_main_radiobutton_home)
    RadioButton activity_main_radiobutton_home;*/
    private RadioGroup radiogroup;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_radio_group);

        /*ButterKnife.bind(this);*/
        radiogroup = (RadioGroup)findViewById(R.id.activity_main_radiogroup);
        radiogroup.setOnCheckedChangeListener(this);

    }

    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        switch (checkedId) {
            case R.id.activity_main_radiobutton_home:
                Log.i(TAG,"首頁");
                break;
            case R.id.activity_main_radiobutton_classification:
                Log.i(TAG,"商品");
                break;
            case R.id.activity_main_radiobutton_activity:
                Log.i(TAG,"分類");
                break;
            case R.id.activity_main_radiobutton_mine:
                Log.i(TAG,"我的");
                break;
            default:
                break;
        }
    }
}