SecurityException even after giving uses-permission tag for vibration

Question

I am trying to make an Android app which starts vibration on button click.

below is the code related to vibration, I have added uses-permission tag in Android manifest file, still the app terminates giving SecurityException

public class MainActivity extends AppCompatActivity {

    private Vibrator v;
    TimerTask timerTask;
    int n=0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        v = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
    }

    public void startTimer(View view) {

        final Handler handler = new Handler();
        Timer mTimer = new Timer();
        v.vibrate(2000);

        timerTask = new TimerTask() {
            @Override
            public void run() {
                boolean post = handler.post(new Runnable() {
                    @Override
                    public void run() {

                        TextView timer = (TextView) findViewById(R.id.timer);
                        timer.setText(n);
                        n++;
                    }
                });
            }
        };
        mTimer.schedule(timerTask, 0, 100);
    }

logcat:

06-17 03:41:12.962    8851-8851/com.neuroapp.ojas.neuroapp W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x40c3ba68)
06-17 03:41:13.022    8851-8851/com.neuroapp.ojas.neuroapp E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.IllegalStateException: Could not execute method of the activity
            at android.view.View$1.onClick(View.java:3099)
            at android.view.View.performClick(View.java:3571)
            at android.view.View$PerformClick.run(View.java:14247)
            at android.os.Handler.handleCallback(Handler.java:605)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4517)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.reflect.InvocationTargetException
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at android.view.View$1.onClick(View.java:3094)
            at android.view.View.performClick(View.java:3571)
            at android.view.View$PerformClick.run(View.java:14247)
            at android.os.Handler.handleCallback(Handler.java:605)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4517)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.SecurityException: Requires VIBRATE permission
            at android.os.Parcel.readException(Parcel.java:1327)
            at android.os.Parcel.readException(Parcel.java:1281)
            at android.os.IVibratorService$Stub$Proxy.vibrateMagnitude(IVibratorService.java:290)
            at android.os.Vibrator.vibrate(Vibrator.java:88)
            at android.os.Vibrator.vibrate(Vibrator.java:57)
            at com.neuroapp.ojas.neuroapp.MainActivity.startTimer(MainActivity.java:48)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at android.view.View$1.onClick(View.java:3094)
            at android.view.View.performClick(View.java:3571)
            at android.view.View$PerformClick.run(View.java:14247)
            at android.os.Handler.handleCallback(Handler.java:605)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4517)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
            at dalvik.system.NativeStart.main(Native Method)