我上课了
public class DialogUtils
{
private Context context;
@Inject
public DialogUtils(Context context)
{
this.context = context;
}
}
在我的活动类中我已经做了但是我在dialogUtils实例上得到空指针异常.
public class LoginActivity extends Activity{
@Inject DialogUtils dialogUtils;
}
我知道如何通过模块和组件注入依赖,但不知道如何使用构造注入.任何帮助深表感谢.
解决方法
如果您没有保留活动级别组件,并且您没有使用组件依赖关系或子组件继承超级作用域(应用程序级组件),那么它是以下内容
// unscoped
public class DialogUtils {
private final Context context;
@Inject
public DialogUtils(Context context) {
this.context = context;
}
}
然后
@Module
public class ActivityModule {
private final Context context;
public ActivityModule (Context context) {
this.context = context;
}
@Provides //scope is not necessary for parameters stored within the module
public Context context() {
return context;
}
}
@Component(modules={ActivityModule.class})
@Singleton
public interface ActivityComponent {
Context context();
DialogUtils dialogUtils();
void inject(MainActivity mainActivity);
}
然后
@Inject
DialogUtils dialogUtils;
...
ActivityComponent activityComponent = DaggerMainActivityComponent.builder()
.activityModule(new ActivityModule(MainActivity.this))
.build();
activityComponent.inject(this); // activityComponent.dialogUtils() also works
