The app is stopped when starting the app in emulator.
I can't find any problems.

Here's The logcat:

```
FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.twy.rsmap/com.twy.rsmap.MainActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1879)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
        at android.app.ActivityThread.access$600(ActivityThread.java:122)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4340)
        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:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at android.app.Activity.findViewById(Activity.java:1794)
        at com.twy.rsmap.MainActivity.<init>(MainActivity.java:173)
        at java.lang.Class.newInstanceImpl(Native Method)
        at java.lang.Class.newInstance(Class.java:1319)
        at android.app.Instrumentation.newActivity(Instrumentation.java:1023)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1870)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
            at android.app.ActivityThread.access$600(ActivityThread.java:122)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4340)
            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:784)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
            at dalvik.system.NativeStart.main(Native Method)

```

How to find out the problem?
(MainActivity.java:173 and MainActivity.java:174)

```
Button[] buttons = new Button[]{(Button)findViewById(R.id.FileToolStripMenuItem),(Button)findViewById(R.id.ImageToolStripMenuItem),(Button)findViewById(R.id.GroundToolStripMenuItem),(Button)findViewById(R.id.SeaToolStripMenuItem),(Button)findViewById(R.id.NailToolStripMenuItem),(Button)findViewById(R.id.RubberToolStripMenuItem),(Button)findViewById(R.id.SpeedboardToolStripMenuItem),(Button)findViewById(R.id.ItemToolStripMenuItem)};
LinearLayout[] lls = new LinearLayout[]{(LinearLayout)findViewById(R.id.FileDrop),(LinearLayout)findViewById(R.id.ImageDrop),(LinearLayout)findViewById(R.id.GroundDrop),(LinearLayout)findViewById(R.id.SeaDrop),(LinearLayout)findViewById(R.id.NailDrop),(LinearLayout)findViewById(R.id.RubberDrop),(LinearLayout)findViewById(R.id.SpeedDrop),(LinearLayout)findViewById(R.id.ItemDrop)};

```

This works properly before, but something happened after doing something.
Maybe related to the version?

The object array is not so well, so after I replaced

```
Button[] buttons = new Button[]{(Button)findViewById(R.id.FileToolStripMenuItem),(Button)findViewById(R.id.ImageToolStripMenuItem),(Button)findViewById(R.id.GroundToolStripMenuItem),(Button)findViewById(R.id.SeaToolStripMenuItem),(Button)findViewById(R.id.NailToolStripMenuItem),(Button)findViewById(R.id.RubberToolStripMenuItem),(Button)findViewById(R.id.SpeedboardToolStripMenuItem),(Button)findViewById(R.id.ItemToolStripMenuItem)};
LinearLayout[] lls = new LinearLayout[]{(LinearLayout)findViewById(R.id.FileDrop),(LinearLayout)findViewById(R.id.ImageDrop),(LinearLayout)findViewById(R.id.GroundDrop),(LinearLayout)findViewById(R.id.SeaDrop),(LinearLayout)findViewById(R.id.NailDrop),(LinearLayout)findViewById(R.id.RubberDrop),(LinearLayout)findViewById(R.id.SpeedDrop),(LinearLayout)findViewById(R.id.ItemDrop)};

```

by

```
int[] idb = {R.id.FileToolStripMenuItem,R.id.ImageToolStripMenuItem,R.id.GroundToolStripMenuItem,R.id.SeaToolStripMenuItem,R.id.NailToolStripMenuItem,R.id.RubberToolStripMenuItem,R.id.SpeedboardToolStripMenuItem,R.id.ItemToolStripMenuItem};
int[] idl = {R.id.FileDrop,R.id.ImageDrop,R.id.GroundDrop,R.id.SeaDrop,R.id.NailDrop,R.id.RubberDrop,R.id.SpeedDrop,R.id.ItemDrop};

```

And replaced the codes with `(Button)findViewById(int[index])`

(From 

```
        int a ;
        for (a=0;a<buttons.length;a++){
            buttons[a].setVisibility(View.VISIBLE);
        }

```

to

```
        int a ;
        for (a=0;a<idb.length;a++){
            Button button1 = (Button)findViewById(idb[a]);
            button1.setVisibility(View.VISIBLE);
        }

```

)

Problem solved.