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Android resource linking failed
xxx/res/layout/login_landscape.xml:2: error: attribute layout_constraintBottom_toBottomOf (aka xxx:layout_constraintBottom_toBottomOf) not found.

ImageButton registerBtn;

registerBtn = (ImageButton)findViewById(R.id.loginBtn) ;

registerBtn.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        Log.d("test","connie");
    }
});

<EditText
    android:id="@+id/editText2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:ems="10"
    android:inputType="textPersonName"
    android:background="@drawable/text_field_bg"
    android:padding="5dp"
    android:hint="請輸入帳號(4-16英數)"/>

File-based resource names must contain only lowercase a-z, 0-9, or underscore

commnet all the things in
public void onBackPressed(){

}

add new andorid library
Gradle
build.gradle(module:app)

compile project(':libraryname');

sync

res/menu/main_activity_actions.xml

del <item> tag