Question

I have made an android application in which there is a text and button in first activity when I click on button it should go to second activity and view the images in grid view but its not doing that it gives the message it has stopped unexpectedly. Here is the code.

mainactivity:

package com.karan.myjigsaw;

import android.os.Bundle;
import android.app.Activity;
import android.view.View;
import android.content.Intent;

public class MainActivity extends Activity {

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

}
public void playGame(View view) {
    Intent intent = new Intent(this, GameActivity.class);
    startActivity(intent);

}

}

main.xml

RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">

<TextView
    android:layout_margin="120dip"
    android:layout_width="200dp"
    android:layout_height="150dp"
    android:text="@string/welcome_note"
    android:layout_centerHorizontal="true"
    tools:context=".MainActivity" />

<Button 
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/button_play"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:onClick = "playGame" />


   </RelativeLayout> 

gameactivity:

 public class GameActivity extends Activity {

ImageView image;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Intent intent = getIntent();

    //create grid view
    GridView gridView = new GridView(this);
    gridView = (GridView)findViewById(R.id.grid_view);   

    // Instance of ImageAdapter Class
   gridView.setAdapter(new ImageAdapter(this));
}

}

gameactivity.xml:

 <?xml version="1.0" encoding="utf-8"?>

<GridView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/grid_view"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:numColumns="auto_fit"
android:columnWidth="90dp"
android:horizontalSpacing="10dp"
android:verticalSpacing="10dp"
android:gravity="center"
android:stretchMode="columnWidth" > 

</GridView>

image view adapter class

public class ImageAdapter extends BaseAdapter{
 private Context mContext;

// references to our images
    private Integer[] mThumbIds = {R.drawable.imagesl_01,R.drawable.imagesl_02,
               R.drawable.imagesl_03,R.drawable.imagesl_04,R.drawable.imagesl_05,
             R.drawable.imagesl_06,R.drawable.imagesl_07,R.drawable.imagesl_8,
            R.drawable.imagesl_9};

    public ImageAdapter(Context c) {
        mContext = c;
    }

    public int getCount() {
        return mThumbIds.length;
    }

    public Object getItem(int position) {
        return null;
    }

    public long getItemId(int position) {
        return 0;
    }

    // create a new ImageView for each item referenced by the Adapter
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;

        if (convertView == null) {  // if it's not recycled, initialize some attributes
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(8, 8, 8, 8);
       } else {
           imageView = (ImageView) convertView;
        }

        imageView.setImageResource(mThumbIds[position]);
        return imageView;
    }

    }

logcat:

08-02 00:24:30.160: D/AndroidRuntime(286): Shutting down VM
08-02 00:24:30.160: W/dalvikvm(286): threadid=1: thread exiting with uncaught     exception (group=0x4001d800)
08-02 00:24:30.190: E/AndroidRuntime(286): FATAL EXCEPTION: main
08-02 00:24:30.190: E/AndroidRuntime(286): java.lang.RuntimeException: Unable to start activity         ComponentInfo{com.bellurbis.karan.myjigsaw/com.bellurbis.karan.myjigsaw.GameActivity}: java.lang.NullPointerException
08-02 00:24:30.190: E/AndroidRuntime(286):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
08-02 00:24:30.190: E/AndroidRuntime(286):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
08-02 00:24:30.190: E/AndroidRuntime(286):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
08-02 00:24:30.190: E/AndroidRuntime(286):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
08-02 00:24:30.190: E/AndroidRuntime(286):  at android.os.Handler.dispatchMessage(Handler.java:99)
08-02 00:24:30.190: E/AndroidRuntime(286):  at android.os.Looper.loop(Looper.java:123)
08-02 00:24:30.190: E/AndroidRuntime(286):  at android.app.ActivityThread.main(ActivityThread.java:4627)
08-02 00:24:30.190: E/AndroidRuntime(286):  at java.lang.reflect.Method.invokeNative(Native Method)
08-02 00:24:30.190: E/AndroidRuntime(286):  at java.lang.reflect.Method.invoke(Method.java:521)
08-02 00:24:30.190: E/AndroidRuntime(286):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
08-02 00:24:30.190: E/AndroidRuntime(286):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-02 00:24:30.190: E/AndroidRuntime(286):  at dalvik.system.NativeStart.main(Native Method)
08-02 00:24:30.190: E/AndroidRuntime(286): Caused by: java.lang.NullPointerException
08-02 00:24:30.190: E/AndroidRuntime(286):  at com.bellurbis.karan.myjigsaw.GameActivity.onCreate(GameActivity.java:20)
08-02 00:24:30.190: E/AndroidRuntime(286):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-02 00:24:30.190: E/AndroidRuntime(286):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
08-02 00:24:30.190: E/AndroidRuntime(286):  ... 11 more

Answer 1

Error:U must setContentView(R.layout.gameactivity) firstly,and secondly to use findViewById(R.id.grid_view)!