I have 2 activities, MainActivity and Advanced ..... I want to open Advanced when Swiping from Right to left and Advanced to Main on swiping from Left to right.... The problem is, using the following code...
import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.view.Menu; import android.view.View; import android.widget.RelativeLayout; public class Advanced extends Activity implements SwipeInterface { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_advanced); ActivitySwipeDetector swipe = new ActivitySwipeDetector(null, this); RelativeLayout swipe_layout = (RelativeLayout) findViewById(R.layout.activity_advanced); swipe_layout.setOnTouchListener(swipe); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.advanced, menu); return true; } @Override public void onLeftToRight(View v) { // TODO Auto-generated method stub Intent intent = new Intent(this, MainActivity.class); startActivity(intent); } @Override public void onRightToLeft(View v) { // TODO Auto-generated method stub } } This is the coding I gave to the Advanced activity ..... I gave similar code in the main activity
My Class code is ...
import android.content.Context; import android.util.DisplayMetrics; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.view.ViewConfiguration; public class ActivitySwipeDetector implements View.OnTouchListener { static final String logTag = "ActivitySwipeDetector"; private SwipeInterface activity; private float downX, downY; private long timeDown; private final float MIN_DISTANCE; private final int VELOCITY; private final float MAX_OFF_PATH; public ActivitySwipeDetector(Context context, SwipeInterface activity){ this.activity = activity; final ViewConfiguration vc = ViewConfiguration.get(context); DisplayMetrics dm = context.getResources().getDisplayMetrics(); MIN_DISTANCE = vc.getScaledPagingTouchSlop() * dm.density; VELOCITY = vc.getScaledMinimumFlingVelocity(); MAX_OFF_PATH = MIN_DISTANCE * 2; } public void onRightToLeftSwipe(View v){ Log.i(logTag, "RightToLeftSwipe!"); activity.onRightToLeft(v); } public void onLeftToRightSwipe(View v){ Log.i(logTag, "LeftToRightSwipe!"); activity.onLeftToRight(v); } public boolean onTouch(View v, MotionEvent event) { switch(event.getAction()){ case MotionEvent.ACTION_DOWN: { Log.d("onTouch", "ACTION_DOWN"); timeDown = System.currentTimeMillis(); downX = event.getX(); downY = event.getY(); return true; } case MotionEvent.ACTION_UP: { Log.d("onTouch", "ACTION_UP"); long timeUp = System.currentTimeMillis(); float upX = event.getX(); float upY = event.getY(); float deltaX = downX - upX; float absDeltaX = Math.abs(deltaX); float deltaY = downY - upY; float absDeltaY = Math.abs(deltaY); long time = timeUp - timeDown; if (absDeltaY > MAX_OFF_PATH) { Log.i(logTag, String.format("absDeltaY=%.2f, MAX_OFF_PATH=%.2f", absDeltaY, MAX_OFF_PATH)); return v.performClick(); } final long M_SEC = 1000; if (absDeltaX > MIN_DISTANCE && absDeltaX > time * VELOCITY / M_SEC) { if(deltaX < 0) { this.onLeftToRightSwipe(v); return true; } if(deltaX > 0) { this.onRightToLeftSwipe(v); return true; } } else { Log.i(logTag, String.format("absDeltaX=%.2f, MIN_DISTANCE=%.2f, absDeltaX > MIN_DISTANCE=%b", absDeltaX, MIN_DISTANCE, (absDeltaX > MIN_DISTANCE))); Log.i(logTag, String.format("absDeltaX=%.2f, time=%d, VELOCITY=%d, time*VELOCITY/M_SEC=%d, absDeltaX > time * VELOCITY / M_SEC=%b", absDeltaX, time, VELOCITY, time * VELOCITY / M_SEC, (absDeltaX > time * VELOCITY / M_SEC))); } } } return false; } }
My Interface contains
import android.view.View; public interface SwipeInterface { public void onLeftToRight(View v); public void onRightToLeft(View v); }
The problem is that the app terminates without opening..... The message comes ... Unfortunately, MyApp has stopped...
Please help me fix the problem.. There are no errors which arise in the code...
My Logcat display is as follows:
02-16 15:58:55.842: E/Trace(25383): error opening trace file: No such file or directory (2) 02-16 15:58:55.843: D/jdwp(25383): sendBufferedRequest : len=0x39 02-16 15:58:55.864: D/dalvikvm(25383): open_cached_dex_file : /data/app/com.Candy.teacher-1.apk /data/dalvik-cache/data@[email protected]@classes.dex 02-16 15:58:55.875: D/ActivityThread(25383): BIND_APPLICATION handled : 0 / AppBindData {appInfo=ApplicationInfo{41fada00 com.Candy.teacher}} 02-16 15:58:55.958: D/AndroidRuntime(25383): Shutting down VM 02-16 15:58:55.958: W/dalvikvm(25383): threadid=1: thread exiting with uncaught exception (group=0x4179d908) 02-16 15:58:55.970: E/AndroidRuntime(25383): FATAL EXCEPTION: main 02-16 15:58:55.970: E/AndroidRuntime(25383): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.Candy.teacher/com.Candy.teacher.MainActivity}: java.lang.NullPointerException 02-16 15:58:55.970: E/AndroidRuntime(25383): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184) 02-16 15:58:55.970: E/AndroidRuntime(25383): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2211) 02-16 15:58:55.970: E/AndroidRuntime(25383): at android.app.ActivityThread.access$600(ActivityThread.java:149) 02-16 15:58:55.970: E/AndroidRuntime(25383): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1300) 02-16 15:58:55.970: E/AndroidRuntime(25383): at android.os.Handler.dispatchMessage(Handler.java:99) 02-16 15:58:55.970: E/AndroidRuntime(25383): at android.os.Looper.loop(Looper.java:153) 02-16 15:58:55.970: E/AndroidRuntime(25383): at android.app.ActivityThread.main(ActivityThread.java:4994) 02-16 15:58:55.970: E/AndroidRuntime(25383): at java.lang.reflect.Method.invokeNative(Native Method) 02-16 15:58:55.970: E/AndroidRuntime(25383): at java.lang.reflect.Method.invoke(Method.java:511) 02-16 15:58:55.970: E/AndroidRuntime(25383): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:821) 02-16 15:58:55.970: E/AndroidRuntime(25383): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584) 02-16 15:58:55.970: E/AndroidRuntime(25383): at dalvik.system.NativeStart.main(Native Method) 02-16 15:58:55.970: E/AndroidRuntime(25383): Caused by: java.lang.NullPointerException 02-16 15:58:55.970: E/AndroidRuntime(25383): at com.Candy.teacher.MainActivity.onCreate(MainActivity.java:20) 02-16 15:58:55.970: E/AndroidRuntime(25383): at android.app.Activity.performCreate(Activity.java:5023) 02-16 15:58:55.970: E/AndroidRuntime(25383): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 02-16 15:58:55.970: E/AndroidRuntime(25383): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148) 02-16 15:58:55.970: E/AndroidRuntime(25383): ... 11 more 02-16 15:58:58.325: I/Process(25383): Sending signal. PID: 25383 SIG: 9 
