Android:将主类扩展到Actionbar活动时发生错误（java.lang.RuntimeException:无法启动活动组件信息）

我在主类中编写了代码，将其扩展到活动类，因为我的最小sdk级别为8，所以我无法使用actionbar，因此在编写所有代码后，我将扩展类更改为ActionBarActivity类替换活动类。除了导入ActionBarActivity类之外，我没有收到任何错误。但是我在运行时出错了。请帮我解决这个问题

MainActivity.java

package com.vibrator;

import android.annotation.SuppressLint;
import android.os.Bundle;
import android.os.Vibrator;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.View;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.ToggleButton;

@SuppressLint("ShowToast")
public class MainActivity extends ActionBarActivity 
       implements OnCheckedChangeListener, OnSeekBarChangeListener{

    ToggleButton tbutton;
    Vibrator v;
    int i;
    int j;
    TextView txt;
    SeekBar sb;
    TextView txt1;
    SeekBar sb1;


    protected void onCreate(Bundle savedInstanceState) {

        //creating instance for vibrator
         v=(Vibrator) getSystemService(VIBRATOR_SERVICE);        
         //checking if the device has vibrator or not        
        if(v!=null){

            setContentView(R.layout.activity_main);
        }
        else {
            setContentView(R.layout.secound);
        }
            //Log.e("vibrate", "setcontentview");


        //creating instance of toggle buttton and setting listener
        tbutton=(ToggleButton) findViewById(R.id.tb1);
        tbutton.setOnCheckedChangeListener(this);
        super.onCreate(savedInstanceState);
    }
    @Override
    public void onCheckedChanged(CompoundButton arg0, boolean arg1) {
        Log.d("real status", ""+arg1);
        //if vibrator is ON
        if(arg1)
        {
            Log.d("vibrate", "if loop");
            Toast.makeText(this,"status: "+arg1, Toast.LENGTH_LONG).show();
            //creating instance of seekbar and textview
            sb=(SeekBar) findViewById(R.id.seekbar);
            txt=(TextView) findViewById(R.id.txt12);
            sb1=(SeekBar) findViewById(R.id.seekbar1);
            txt1=(TextView) findViewById(R.id.txt11);
            //changing visibility
            txt.setVisibility(View.VISIBLE);
            sb.setVisibility(View.VISIBLE);
            txt1.setVisibility(View.VISIBLE);
            sb1.setVisibility(View.VISIBLE);

            sb1.setOnSeekBarChangeListener(this);       
            sb.setOnSeekBarChangeListener(this);
            // Start without a delay
            // Vibrate for 100 j milliseconds
            // Sleep for 1000  (i) milliseconds         
            long[] pattern = {0, j, i};
            // The '0' here means to repeat indefinitely
            // '-1' would play the vibration once                       
            v.vibrate(pattern, 0);          
        }

        else {
            sb.setVisibility(View.INVISIBLE);
            txt.setVisibility(View.INVISIBLE);
            sb1.setVisibility(View.INVISIBLE);
            txt1.setVisibility(View.INVISIBLE);
            Log.d("vibrate", "else loop");
            Toast.makeText(this,"status: "+arg1, Toast.LENGTH_LONG).show();
            v.cancel();         
        }       
    }

    @Override
    public void onProgressChanged(SeekBar s, int v, boolean b) {
        switch (s.getId()) {
        case R.id.seekbar:
            i=v;
            break;

        case R.id.seekbar1:
            j=v;
            break;

        }       
        txt.setText("Vibrator OFF time: "+i);
        txt1.setText("Vibrator ON time: "+j);

    }
    @Override
    public void onStartTrackingTouch(SeekBar arg0) {        
    }
    @Override
    public void onStopTrackingTouch(SeekBar arg0) {     
    }
}

日志：

07-28 01:10:41.306: D/AndroidRuntime(381): Shutting down VM
07-28 01:10:41.306: W/dalvikvm(381): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
07-28 01:10:41.326: E/AndroidRuntime(381): FATAL EXCEPTION: main
07-28 01:10:41.326: E/AndroidRuntime(381): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.vibrator/com.vibrator.MainActivity}: java.lang.NullPointerException
07-28 01:10:41.326: E/AndroidRuntime(381):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
07-28 01:10:41.326: E/AndroidRuntime(381):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
07-28 01:10:41.326: E/AndroidRuntime(381):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
07-28 01:10:41.326: E/AndroidRuntime(381):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
07-28 01:10:41.326: E/AndroidRuntime(381):  at android.os.Handler.dispatchMessage(Handler.java:99)
07-28 01:10:41.326: E/AndroidRuntime(381):  at android.os.Looper.loop(Looper.java:123)
07-28 01:10:41.326: E/AndroidRuntime(381):  at android.app.ActivityThread.main(ActivityThread.java:4627)
07-28 01:10:41.326: E/AndroidRuntime(381):  at java.lang.reflect.Method.invokeNative(Native Method)
07-28 01:10:41.326: E/AndroidRuntime(381):  at java.lang.reflect.Method.invoke(Method.java:521)
07-28 01:10:41.326: E/AndroidRuntime(381):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
07-28 01:10:41.326: E/AndroidRuntime(381):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
07-28 01:10:41.326: E/AndroidRuntime(381):  at dalvik.system.NativeStart.main(Native Method)
07-28 01:10:41.326: E/AndroidRuntime(381): Caused by: java.lang.NullPointerException
07-28 01:10:41.326: E/AndroidRuntime(381):  at android.support.v7.app.ActionBarActivity.setContentView(ActionBarActivity.java:76)
07-28 01:10:41.326: E/AndroidRuntime(381):  at com.vibrator.MainActivity.onCreate(MainActivity.java:37)
07-28 01:10:41.326: E/AndroidRuntime(381):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-28 01:10:41.326: E/AndroidRuntime(381):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
07-28 01:10:41.326: E/AndroidRuntime(381):  ... 11 more
07-28 01:15:41.356: I/Process(381): Sending signal. PID: 381 SIG: 9

---

您将获得

NullPointerException

，因为

ActionBarActivity

要求在设置内容视图之前调用

super.onCreate（savedInstanceState）

方法

尝试将

super.onCreate（savedInstanceState）

移动到

onCreate

方法的第一行

希望有帮助