SeekBar выпадает в java.lang.NullPointerException

Создаю простейший сикбар и одно текстовое поле. При изменении сикбара должно происходить изменение значения в поле. Но студия не компилирует код и вылетает в ошибку java.lang.NullPointerException. Поиски ошибки не увенчались успехом. Прошу помощи.
import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.widget.SeekBar; import android.widget.TextView; public class MainActivity extends AppCompatActivity implements SeekBar.OnSeekBarChangeListener { SeekBar sb1; TextView tv1; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); TextView tv1 = (TextView)findViewById(R.id.tv1); tv1.setText(""); SeekBar sb1 = (SeekBar)findViewById(R.id.sb1); sb1.setOnSeekBarChangeListener(this); } @Override public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) { tv1.setText(String.valueOf(progress)); } @Override public void onStartTrackingTouch(SeekBar seekBar) { } @Override public void onStopTrackingTouch(SeekBar seekBar) { } }
Exeption FATAL EXCEPTION: main Process: com.example.ivanvovk.linearlayout, PID: 21145 java.lang.NullPointerException at com.example.ivanvovk.linearlayout.MainActivity.onProgressChanged(MainActivity.java:38) at android.widget.SeekBar.onProgressRefresh(SeekBar.java:91) at android.widget.ProgressBar.doRefreshProgress(ProgressBar.java:655) at android.widget.ProgressBar.refreshProgress(ProgressBar.java:667) at android.widget.ProgressBar.setProgress(ProgressBar.java:714) at android.widget.AbsSeekBar.trackTouchEvent(AbsSeekBar.java:451) at android.widget.AbsSeekBar.onTouchEvent(AbsSeekBar.java:372) at android.view.View.dispatchTouchEvent(View.java:7765) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2068) at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1515) at android.app.Activity.dispatchTouchEvent(Activity.java:2458) at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:60) at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2016) at android.view.View.dispatchPointerEvent(View.java:7945) at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:3961) at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3840) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3406) at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3456) at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3425) at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3532) at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3433) at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3589) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3406) at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3456) at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3425) at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3433) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3406) at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5609) at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5589) at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5560) at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5689) at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185) at android.os.MessageQueue.nativePollOnce(Native Method) at android.os.MessageQueue.next(MessageQueue.java:138) at android.os.Looper.loop(Looper.java:123) at android.app.ActivityThread.main(ActivityThread.java:5021) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:515) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:827) at com.android.internal.os.ZygoteInit.main

Ответ

У вас seekBar и textView объявлены два раза. Исправьте на это:
SeekBar sb1; TextView tv1; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); tv1 = (TextView)findViewById(R.id.tv1); tv1.setText(""); sb1 = (SeekBar)findViewById(R.id.sb1); sb1.setOnSeekBarChangeListener(this); }