Android WearのButtonでsetOnClickListenerはonLayoutInflatedの中でやらなければならない

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ずっとonCreateに書いてクラッシュし続けてたら間違ってたのでメモ。


setOnClickListenerはonCreateに書いてはならない

下記のようなエラーでクラッシュします。


terminal

E/AndroidRuntime: FATAL EXCEPTION: main

Process: net.furusin.www.whereiswear, PID: 25720
java.lang.RuntimeException: Unable to start activity ComponentInfo{net.furusin.www.whereiswear/net.furusin.www.whereiswear.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5422)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at net.furusin.www.whereiswear.MainActivity.onCreate(MainActivity.java:31)
at android.app.Activity.performCreate(Activity.java:6251)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5422) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 


対処方法

onLayoutInflatedの中でやらなければならない。


MainActivity.java

        stub.setOnLayoutInflatedListener(new WatchViewStub.OnLayoutInflatedListener() {

@Override
public void onLayoutInflated(WatchViewStub stub) {
Button button = (Button) stub.findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// do something.
}
});
}
});

以上。