我的过渡时遇到问题。希望有人可以帮助我。
首先，启动画面活动的代码。
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_splash);
/****** Create Thread that will sleep for 5 seconds *************/
Thread background = new Thread()
{
public void run()
{
try
{
// Thread will sleep for 5 seconds
sleep(5*1000);
// After 5 seconds redirect to another intent
if(SharedPreferences.getUserName(getApplication()) != null && SharedPreferences.getUserName(getApplication()).length() == 0)
{
Intent i = new Intent(getBaseContext(), LoginActivity.class);
startActivity(i);
}
else
{
Intent i = new Intent(getBaseContext(), MainActivity.class);
startActivity(i);
}
//Remove activity
finish();
}
catch (Exception e)
{
e.printStackTrace();
}
}
};
// start thread
background.start();
}
接下来，登录活动的代码：
公共类LoginActivity扩展了FragmentActivity {
public static String user_id = "";
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.i("LoginActivity", "Start Login Activity");
int titleId = getResources().getIdentifier("title_activity_login", "id", "android");
TextView abTitle = (TextView) findViewById(titleId);
abTitle.setTextColor(Color.WHITE);
}
然后，登录活动开始时启动的片段：
public static class CardSectionFragment extends Fragment
{
/**
* The fragment argument representing the section number for this
* fragment.
*/
public static final String ARG_SECTION_NUMBER = "section_number";
Button registerBtn, toggleBtn;
EditText useridET;
EditText passwordET;
EditText dobET;
Spinner daySpin, mthSpin, yrSpin;
LinearLayout dobLayout;
public CardSectionFragment()
{
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
recLifeCycle_with_savedInstanceState(savedInstanceState);
View rootView = inflater.inflate(R.layout.fragment_register,
container, false);
registerBtn = (Button) rootView.findViewById(R.id.registerBtn);
toggleBtn = (Button) rootView.findViewById(R.id.toggleBtn);
useridET = (EditText) rootView.findViewById(R.id.useridET);
passwordET = (EditText) rootView.findViewById(R.id.passwordET);
dobLayout = (LinearLayout) rootView.findViewById(R.id.dobLayout);
daySpin = (Spinner) rootView.findViewById(R.id.daySpin);
mthSpin = (Spinner) rootView.findViewById(R.id.mthSpin);
yrSpin = (Spinner) rootView.findViewById(R.id.yrSpin);
ArrayAdapter<String> dayAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_spinner_item, R.array.date_spin);
dayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
ArrayAdapter<String> mthAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_spinner_item, R.array.mnth_spin);
mthAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
ArrayAdapter<String> yrAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_spinner_item, R.array.year_spin);
yrAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
daySpin.setAdapter(dayAdapter);
mthSpin.setAdapter(mthAdapter);
yrSpin.setAdapter(yrAdapter);
registerBtn.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
((MainActivity) getActivity()).hideSoftKeyboard();
// TODO Auto-generated method stub
// ((MainActivity) getActivity()).registerSuccess("");
if (registerBtn.getText().toString().equals("Sign Up"))
{
String dob = daySpin.getSelectedItem().toString() + "-" + mthSpin.getSelectedItem().toString() + "-" + yrSpin.getSelectedItem().toString().substring(Math.max(yrSpin.getSelectedItem().toString().length() - 2, 0));
new RegisterUserAsyncTask((LoginActivity) getActivity()).execute(useridET.getText().toString(), passwordET.getText().toString(), dob);
}
else
{
if (registerBtn.getText().toString().equals("Login"))
{
user_id = useridET.getText().toString();
new LoginUserAsyncTask((LoginActivity) getActivity()).execute(useridET.getText().toString(),passwordET.getText().toString());
}
}
}
});
toggleBtn.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
// TODO Auto-generated method stub
if (registerBtn.getText().toString().equals("Sign Up"))
{
dobLayout.setVisibility(View.GONE);
registerBtn.setText("Login");
toggleBtn.setText("Do not have an account? Register here.");
}
else
{
dobLayout.setVisibility(View.VISIBLE);
registerBtn.setText("Sign Up");
toggleBtn.setText("To begin, login with your account");
}
}
});
return rootView;
}
public void recLifeCycle() {
String className = getClass().getSimpleName();
StackTraceElement[] s = Thread.currentThread().getStackTrace();
String methodName = s[3].getMethodName();
String msg = className + "." + methodName;
// Toast.makeText(getActivity(),
// msg, Toast.LENGTH_SHORT).show();
Log.i("MYTAG", msg);
}
public void recLifeCycle(String note) {
String className = getClass().getSimpleName();
StackTraceElement[] s = Thread.currentThread().getStackTrace();
String methodName = s[3].getMethodName();
String msg = className + "." + methodName;
// Toast.makeText(getActivity(),
// msg, Toast.LENGTH_SHORT).show();
Log.i("MYTAG", msg + " / " + note);
}
public void recLifeCycle_with_savedInstanceState(Bundle state) {
String stateMsg;
if (state == null) {
stateMsg = "savedInstanceState == null";
} else {
stateMsg = "savedInstanceState != null";
}
String className = getClass().getSimpleName();
StackTraceElement[] s = Thread.currentThread().getStackTrace();
String methodName = s[3].getMethodName();
String msg = className + "." + methodName + " / " + stateMsg;
// Toast.makeText(getActivity(),
// msg, Toast.LENGTH_SHORT).show();
Log.i("MYTAG", msg);
}
@Override
public void onResume() {
// TODO Auto-generated method stub
recLifeCycle();
super.onResume();
}
@Override
public void onDestroy() {
// TODO Auto-generated method stub
recLifeCycle();
super.onDestroy();
}
@Override
public void onDestroyView() {
// TODO Auto-generated method stub
recLifeCycle();
super.onDestroyView();
}
@Override
public void onDetach() {
// TODO Auto-generated method stub
recLifeCycle();
super.onDetach();
}
@Override
public void onPause() {
// TODO Auto-generated method stub
recLifeCycle();
super.onPause();
}
@Override
public void onStart() {
// TODO Auto-generated method stub
recLifeCycle();
super.onStart();
}
@Override
public void onStop() {
// TODO Auto-generated method stub
recLifeCycle();
super.onStop();
}
}
而且，这是错误:(我能找到的最接近错误的东西）
10-09 17:17:01.642: I/LoginActivity(12487): Start Login Activity
10-09 17:17:01.652: D/AndroidRuntime(12487): Shutting down VM
10-09 17:17:01.652: W/dalvikvm(12487): threadid=1: thread exiting with uncaught exception (group=0x42f00500)
10-09 17:17:01.662: E/AndroidRuntime(12487): FATAL EXCEPTION: main
10-09 17:17:01.662: E/AndroidRuntime(12487): java.lang.RuntimeException: Unable to start activity ComponentInfo{nyp.edu.sg.alumnigo/nyp.edu.sg.alumnigo.LoginActivity}: java.lang.NullPointerException
10-09 17:17:01.662: E/AndroidRuntime(12487): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2342)
10-09 17:17:01.662: E/AndroidRuntime(12487): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417)
10-09 17:17:01.662: E/AndroidRuntime(12487): at android.app.ActivityThread.access$600(ActivityThread.java:148)
10-09 17:17:01.662: E/AndroidRuntime(12487): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1355)
10-09 17:17:01.662: E/AndroidRuntime(12487): at android.os.Handler.dispatchMessage(Handler.java:99)
10-09 17:17:01.662: E/AndroidRuntime(12487): at android.os.Looper.loop(Looper.java:150)
10-09 17:17:01.662: E/AndroidRuntime(12487): at android.app.ActivityThread.main(ActivityThread.java:5406)
10-09 17:17:01.662: E/AndroidRuntime(12487): at java.lang.reflect.Method.invokeNative(Native Method)
10-09 17:17:01.662: E/AndroidRuntime(12487): at java.lang.reflect.Method.invoke(Method.java:525)
10-09 17:17:01.662: E/AndroidRuntime(12487): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-09 17:17:01.662: E/AndroidRuntime(12487): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-09 17:17:01.662: E/AndroidRuntime(12487): at dalvik.system.NativeStart.main(Native Method)
10-09 17:17:01.662: E/AndroidRuntime(12487): Caused by: java.lang.NullPointerException
10-09 17:17:01.662: E/AndroidRuntime(12487): at nyp.edu.sg.alumnigo.LoginActivity.onCreate(LoginActivity.java:42)
10-09 17:17:01.662: E/AndroidRuntime(12487): at android.app.Activity.performCreate(Activity.java:5303)
10-09 17:17:01.662: E/AndroidRuntime(12487): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
10-09 17:17:01.662: E/AndroidRuntime(12487): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2296)
10-09 17:17:01.662: E/AndroidRuntime(12487): ... 11 more
我不知道为什么它有一个空指针，请帮忙。 第42行是abTitle.setTextColor（Color.WHITE）;在登录活动中btw。
编辑：
这是我的activity_main.xml
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" />
答案 0 :(得分：0)
如果您确定view-id，请尝试替换此行：
TextView abTitle = (TextView) findViewById(titleId);
使用：
TextView abTitle = (TextView) getWindow().getDecorView().getRootView().findViewById(titleId);
如果你想改变android标准ActionBar的标题，请使用：
getActionBar().setTitle("your title");
答案 1 :(得分：0)
找到答案： 我应该使用action_bar_title而不是使用title_activity_login。 我假设它是@string资源ID。因此，无法找到它。对带来的麻烦表示抱歉。