我正在尝试使用我的 MVVM 模式登录活动来显示初始屏幕。我的启动画面确实可以正常工作，但是当它尝试完成并启动 LoginActivity 时，应用程序崩溃了。我收到此错误如下。
请帮我解决这个问题。我需要在我的项目中有一个带有 MVVM 模式和用于 LoginActivity 的房间数据库的 slapsh 屏幕。非常欢迎提供解释或代码示例。
我的飞溅活动
public class SplashActivity extends AppCompatActivity {
public void onAttachedToWindow() {
super.onAttachedToWindow();
Window window = getWindow();
window.setFormat(PixelFormat.RGBA_8888);
}
/**
* Called when the activity is first created.
*/
Thread splashTread;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_splash);
StartAnimations();
}
private void StartAnimations() {
Animation anim = AnimationUtils.loadAnimation(this, R.anim.alpha);
anim.reset();
LinearLayout l = findViewById(R.id.splash_layout);
l.clearAnimation();
l.startAnimation(anim);
anim = AnimationUtils.loadAnimation(this, R.anim.translate);
anim.reset();
ImageView iv = findViewById(R.id.splash);
iv.clearAnimation();
iv.startAnimation(anim);
splashTread = new Thread() {
@Override
public void run() {
try {
int waited = 0;
// Splash screen pause time
while (waited < 3500) {
sleep(100);
waited += 100;
}
Intent intent = new Intent(SplashActivity.this,
LoginActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
startActivity(intent);
SplashActivity.this.finish();
} catch (InterruptedException e) {
// do nothing
} finally {
SplashActivity.this.finish();
}
}
};
splashTread.start();
}
}
我的登录活动
public class LoginActivity extends AppCompatActivity {
private LoginViewModel loginViewModel;
private View mProgressView;
private View mLoginFormView;
private ActivityLoginBinding binding;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
mLoginFormView = findViewById(R.id.login_form);
mProgressView = findViewById(R.id.login_progress);
ActivityLoginBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_login);
//get the view model
loginViewModel = ViewModelProviders.of(this).get(LoginViewModel.class);
binding.setUser(loginViewModel);
// The observer updates the UI when Login Operation is successful
loginViewModel.getUser().observe(this, userResponse -> {
if (userResponse != null) {
Toast.makeText(LoginActivity.this, "Login success", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(this, MainActivity.class);
startActivity(intent);
finish();
} else {
Log.d("LoginActivity", "value user is null");
// Show ERROR
}
});
binding.loginButton.setOnClickListener (
(
View view) ->
{
loginViewModel.onBtnLoginClick();
});
}
/**
* Shows the progress UI and hides the login form.
*/
@TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
private void showProgress(final boolean show) {
// On Honeycomb MR2 we have the ViewPropertyAnimator APIs, which allow
// for very easy animations. If available, use these APIs to fade-in
// the progress spinner.
int shortAnimTime = getResources().getInteger(android.R.integer.config_shortAnimTime);
mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
mLoginFormView.animate().setDuration(shortAnimTime).alpha(
show ? 0 : 1).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
}
});
mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
mProgressView.animate().setDuration(shortAnimTime).alpha(
show ? 1 : 0).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
}
});
}
}
我的登录视图模型
public class LoginViewModel extends ViewModel {
private boolean errorMsg = true;
private Validations validations;
// Create a LiveData
private LiveData<User> userResponse;
public static final ObservableField<String> username = new ObservableField<>();
public static final ObservableField<String> password = new ObservableField<>();
public static final ObservableField<String> errorUsername = new ObservableField<>();
public static final ObservableField<String> errorPassword = new ObservableField<>();
private UserRepository userRepository;
public LoginViewModel(Context mContext) {
userRepository = new UserRepository(mContext);
username.set("ccuser");
password.set("67890");
userResponse = userRepository.getUser();
validations=new Validations();
}
public LiveData<User> getUser() {
return userResponse;
}
public void onBtnLoginClick() {
// attemptLogin();
if (validateInputs()) {
userRepository.loginUser(username.get(), password.get());
}
}
@BindingAdapter("error")
public static void setError(EditText editText, Object strOrResId) {
if (strOrResId instanceof Integer) {
editText.setError(
editText.getContext().getString((Integer) strOrResId));
} else {
editText.setError((String) strOrResId);
}
}
@BindingAdapter("onFocus")
public static void bindFocusChange(EditText editText, View.OnFocusChangeListener onFocusChangeListener) {
if (editText.getOnFocusChangeListener() == null) {
editText.setOnFocusChangeListener(onFocusChangeListener);
}
}
//--
public boolean validateInputs() {
boolean isValid = true;
if (username.get() == null || !Validations.isUserNameValid(username.get())) {
errorUsername.set(String.valueOf(R.string.error_invalid_username));
isValid = false;
} else {
errorUsername.set(null);
}
if (password.get() == null || password.get().length() < 8 && !Validations.isPasswordValid(password.get())) {
errorPassword.set(String.valueOf(R.string.error_incorrect_password));
isValid = false;
} else {
errorPassword.set(null);
}
return isValid;
}
}
我得到的错误
E/AndroidRuntime: FATAL EXCEPTION: main Process: com.comcredit.ccui.cclogin, PID: 19969 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.comcredit.ccui.cclogin/com.comcredit.ccui.cclogin.view .LoginActivity}：java.lang.RuntimeException：无法在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2858) 在 android.app.ActivityThread.handleLaunchActivity 创建类 com.comcredit.ccui.cclogin.view_model.LoginViewModel 的实例(ActivityThread.java:2933) 在 android.app.ActivityThread.-wrap11(Unknown Source:0) 在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1612) 在 android.os.Handler.dispatchMessage(Handler. java:105) 在 android.os.Looper.loop(Looper.java:164) 在 android。app.ActivityThread.main(ActivityThread.java:6710) 在 java.lang.reflect.Method.invoke(Native Method) 在 com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 在 com. android.internal.os.ZygoteInit.main(ZygoteInit.java:770) 原因：java.lang.RuntimeException：无法在 android.arch.lifecycle.ViewModelProvider 创建类 com.comcredit.ccui.cclogin.view_model.LoginViewModel 的实例$NewInstanceFactory.create(ViewModelProvider.java:153) 在 android.arch.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:210) 在 android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:134) 在 android。 com.comcredit 上的 arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:102)。ccui.cclogin.view.LoginActivity.onCreate(LoginActivity.java:45) 在 android.app.Activity.performCreate(Activity.java:6980) 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214) 在 android.app .ActivityThread.performLaunchActivity(ActivityThread.java:2811) 在 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2933) 在 android.app.ActivityThread.-wrap11(Unknown Source:0) 在 android.app.ActivityThread$H。 handleMessage(ActivityThread.java:1612) 在 android.os.Handler.dispatchMessage(Handler.java:105) 在 android.os.Looper.loop(Looper.java:164) 在 android.app.ActivityThread.main(ActivityThread.java :6710) 在 java.lang.reflect.Method。com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 处的调用（本机方法） com.android.internal.os.ZygoteInit.main(ZygoteInit.java:770) 引起：java。 lang.InstantiationException：java.lang.Class 在 android.arch 的 android.arch.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:151) 的 java.lang.Class.newInstance(Native Method) 没有零参数构造函数。 lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:210) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:134) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:102) at com .comcredit.ccui.cclogin.view.LoginActivity.onCreate(LoginActivity.java:45) 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2811) 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214) 在 android.app.Activity.performCreate(Activity.java:6980)。 app.ActivityThread.handleLaunchActivity(ActivityThread.java:2933) 在 android.app.ActivityThread.-wrap11(Unknown Source:0) 在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1612) 在 android.os.Handler .dispatchMessage(Handler.java:105) 在 android.os.Looper.loop(Looper.java:164) 在 android.app.ActivityThread.main(ActivityThread.java:6710) 在 java.lang.reflect.Method.invoke(本机方法）在 com.android.internal.os.Zygote$MethodAndArgsCaller。在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:770) 处运行（Zygote.java:240）