我正在编写代码以使用户即使未使用SharedPreference退出应用程序，也可以保持登录状态。我添加了一个Splash类，它将在打开应用程序时运行。
在添加Splash类之前，该应用程序运行正常。
首先，我用以下代码定义了一个类First：
class First
{
static final String PREF_USER_NAME= "username";
static SharedPreferences getSharedPreferences(Context ctx) {
return PreferenceManager.getDefaultSharedPreferences(ctx);
}
public static void setUserName(Context ctx, String userName)
{
SharedPreferences.Editor editor = getSharedPreferences(ctx).edit();
editor.putString(PREF_USER_NAME, userName);
editor.commit();
}
public static String getUserName(Context ctx)
{
return getSharedPreferences(ctx).getString(PREF_USER_NAME, "");
}
}
然后，我想保存用户名，以便它可以保持登录状态。我猜First.setUserName(SignIn.this,Common.currentUser.getName())没有存储它。
这里是登录按钮的监听者：
btnSignIn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
final ProgressDialog mDialog = new ProgressDialog(SignIn.this);
mDialog.setMessage("Please Wait...");
mDialog.show();
table_user.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
//Check if user not exist in database
if(dataSnapshot.child(edtPhone.getText().toString()).exists()) {
//Get User Information
mDialog.dismiss();
User user = dataSnapshot.child(edtPhone.getText().toString()).getValue(User.class);
user.setPhone(edtPhone.getText().toString());
if (user.getPassword().equals(edtPassword.getText().toString())) {
First.setUserName(SignIn.this,Common.currentUser.getName());
//Toast.makeText(SignIn.this, "Sign In Successfully", Toast.LENGTH_SHORT).show();
Intent homeIntent= new Intent(SignIn.this,home.class);
Common.currentUser=user;
startActivity(homeIntent);
finish();
} else {
Toast.makeText(SignIn.this, "Sign In Failed", Toast.LENGTH_SHORT).show();
}
}
else{
mDialog.dismiss();
Toast.makeText(SignIn.this,"User Not Exist in Database",Toast.LENGTH_SHORT).show();
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
});
Splash类代码：
public class Splash extends AppCompatActivity {
@Override
protected void onCreate(Bundle saveInstaceState)
{
super.onCreate(saveInstaceState);
if(First.getUserName(Splash.this).length() == 0)
{
Intent a= new Intent(Splash.this,MainActivity.class);
startActivity(a);
}
else
{
Intent a= new Intent(Splash.this,home.class);
startActivity(a);
}
}
这是logcat：
2019-06-30 11:15:43.104 15040-15040/com.example.nilesh.internapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.nilesh.internapp, PID: 15040
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.nilesh.internapp/com.example.nilesh.internapp.Splash}: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.nilesh.internapp/com.example.nilesh.internapp.MainActivity}; have you declared this activity in your AndroidManifest.xml?
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3260)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3396)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2009)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7319)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:934)
Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.nilesh.internapp/com.example.nilesh.internapp.MainActivity}; have you declared this activity in your AndroidManifest.xml?
at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:2049)
at android.app.Instrumentation.execStartActivity(Instrumentation.java:1709)
at android.app.Activity.startActivityForResult(Activity.java:5173)
at android.support.v4.app.BaseFragmentActivityApi16.startActivityForResult(BaseFragmentActivityApi16.java:54)
at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:67)
at android.app.Activity.startActivityForResult(Activity.java:5131)
at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:720)
at android.app.Activity.startActivity(Activity.java:5502)
at android.app.Activity.startActivity(Activity.java:5470)
at com.example.nilesh.internapp.Splash.onCreate(Splash.java:20)
at android.app.Activity.performCreate(Activity.java:7783)
at android.app.Activity.performCreate(Activity.java:7772)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3235)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3396)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2009)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7319)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:934)