Android 不明故障读取json？

我的应用程序崩溃了，我不明白为什么。问题似乎出现在json读取器块中。自从我修改了一些我不记得的东西后，它就开始工作了。请帮我检索错误

public class Home extends ActionBarActivity implements OnTaskComplete {

    LinearLayout wrapper = null;
    Context context = this;

    public Bitmap imageHandler;

    @Override
    public void callBackFunction(Bitmap image) {

        imageHandler = image;

    }

    public class Post{

        String id;
        String title;
        String description;
        String release;

        public String getTitle() {
            return title;
        }

        public String getDescription() {
            return description;
        }

        public String getRelease() {
            return release;
        }

        public void setTitle(String title) {
            this.title = title;
        }

        public void setDescription(String description) {
            this.description = description;
        }

        public void setRelease(String release) {
            this.release = release;
        }

        public void setId(String id) {
            this.id = id;
        }

        public String getId() {

            return id;
        }

    }

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


        //OUTER
        RelativeLayout outer = (RelativeLayout)findViewById(R.id.outer);

        //SCROLLER
        Scroller scroller = new Scroller(this);
        scroller.setLayoutParams(new RelativeLayout.LayoutParams(
                RelativeLayout.LayoutParams.FILL_PARENT, RelativeLayout.LayoutParams.FILL_PARENT));

        //WRAPPER
        wrapper = new LinearLayout(this);
        wrapper.setOrientation(LinearLayout.VERTICAL);

        outer.addView(scroller);
        scroller.addView(wrapper);


        String result = null;
        ArrayList<Post> focusOn = new ArrayList<Post>();


        try {
            URL address = new URL("http://www.youth-stories.com/api/all.php");
            URLDataReader reader = new URLDataReader(context);
            result = reader.execute(address).get();

        }catch (IOException e){
            e.printStackTrace();
        } catch(InterruptedException e){
            e.printStackTrace();
        } catch (ExecutionException e){
            e.printStackTrace();
        }
            try {
            JSONObject obj = new JSONObject(result);
            String success = (String) obj.getString("success");
            JSONArray records = obj.getJSONArray("records");

            for(int i = 0; i < records.length(); i++) {
                Post tmp = new Post();
                tmp.setId(records.getJSONObject(i).getString("id"));
                tmp.setTitle(records.getJSONObject(i).getString("title"));
                tmp.setDescription(records.getJSONObject(i).getString("contents"));
                tmp.setRelease(records.getJSONObject(i).getString("data_post"));
                focusOn.add(tmp);
            }

        }catch (JSONException e){
            e.printStackTrace();
        }

        //wrapper
        LinearLayout container = wrapper;

        ProgressDialog dialog = new ProgressDialog(context);
        dialog.setMessage("loading contents, please wait..");
        dialog.setCancelable(false);
        dialog.show();

        for(int i = 0; i < focusOn.size(); i++) {
            //item
            LinearLayout item = new LinearLayout(getApplicationContext());
            String select = focusOn.get(i).getId();
            item.setId(new Integer(select));
            item.setClickable(true);

            //setUp new activity
            final Intent intent = new Intent(getApplicationContext(),HomeOnSelect.class);
            Bundle bundle = new Bundle();
            int id = item.getId();
            String strid = new Integer(id).toString();
            bundle.putString("id",  strid);
            bundle.putString("title",   focusOn.get(i).getTitle());
            bundle.putString("contents", focusOn.get(i).getDescription());
            bundle.putString("release", focusOn.get(i).getRelease());
            intent.putExtras(bundle);

            item.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    startActivity(intent);
                }
            });
            container.addView(item);
            item.setOrientation(LinearLayout.HORIZONTAL);
            item.setPadding(0, 40, 0, 40);
            item.setGravity(Gravity.CENTER_VERTICAL);
            item.setBackgroundResource(R.drawable.postlayout);

            //image
            ImageView asset = new ImageView(getApplicationContext());
            URL address = null;

            try {

                address = new URL("http://www.youth-stories.com/public/admin/CH_FocusOn/images/" + focusOn.get(i).getId() + "_thumb2.jpg");
                URLImageReader reader = new URLImageReader(this, this, asset, dialog, i, focusOn.size());
                reader.execute(address);

            } catch (MalformedURLException e) {
                e.printStackTrace();
            }

            item.addView(asset);

            LinearLayout.LayoutParams imgSettings = new LinearLayout.LayoutParams(300, 300);

            asset.setLayoutParams(imgSettings);
            asset.setPadding(50,0,0,0);

            //inside
            LinearLayout contents = new LinearLayout(getApplicationContext());
            contents.setOrientation(LinearLayout.VERTICAL);
            contents.setPadding(55, 0, 100, 0);
            item.addView(contents);
            //title
            TextView title = new TextView(getApplicationContext());
            title.setText(focusOn.get(i).getTitle());
            title.setTextAppearance(this, R.style.title);
            contents.addView(title);
            //description
            TextView description = new TextView(getApplicationContext());
            description.setText(focusOn.get(i).getDescription());
            description.setTextAppearance(this, R.style.description);
            contents.addView(description);
            //date
            TextView date = new TextView(getApplicationContext());
            date.setText(focusOn.get(i).getRelease());
            date.setTextAppearance(this, R.style.description);
            contents.addView(date);
            //div
            LinearLayout div = new LinearLayout(getApplicationContext());
            div.setLayoutParams(new LinearLayout.LayoutParams(200, 40));
            div.setBackgroundColor(Color.parseColor("#00000000"));
            container.addView(div);
        }
    }

}

公共类Home扩展了ActionBarActivity实现了OnTaskComplete{
LinearLayout包装器=null；
上下文=这个；
公共位图图像处理器；
@凌驾
公共无效调用函数（位图图像）{
imageHandler=图像；
}
公营职位{
字符串id；
字符串标题；
字符串描述；
释放管柱；
公共字符串getTitle（）{
返回标题；
}
公共字符串getDescription（）{
返回说明；
}
公共字符串getRelease（）{
返回释放；
}
公共无效集合标题（字符串标题）{
this.title=标题；
}
公共void集合描述（字符串描述）{
this.description=描述；
}
公共void setRelease（字符串释放）{
这个。释放=释放；
}
公共无效集合id（字符串id）{
this.id=id；
}
公共字符串getId（）{
返回id；
}
}
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_home）；
//外
RelativeLayout outer=（RelativeLayout）findViewById（R.id.outer）；
//卷轴
Scroller Scroller=新的滚动条（此）；
scroller.setLayoutParams（新的RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.FILL_父级，RelativeLayout.LayoutParams.FILL_父级）；
//包装纸
包装器=新的线性布局（此）；
包装器。设置方向（线性布局。垂直）；
outer.addView（滚动条）；
scroller.addView（包装器）；
字符串结果=null；
ArrayList focusOn=新的ArrayList（）；
试一试{
URL地址=新URL（“http://www.youth-stories.com/api/all.php");
URLDataReader=新的URLDataReader（上下文）；
结果=reader.execute（address.get（）；
}捕获（IOE异常）{
e、 printStackTrace（）；
}捕捉（中断异常e）{
e、 printStackTrace（）；
}捕获（执行例外）{
e、 printStackTrace（）；
}
试一试{
JSONObject obj=新JSONObject（结果）；
String success=（String）obj.getString（“success”）；
JSONArray记录=obj.getJSONArray（“记录”）；
for（int i=0；i03-05 12:23:03.276  25591-25591/youth_stories.com.youth_stories E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: youth_stories.com.youth_stories, PID: 25591
    java.lang.RuntimeException: Unable to start activity ComponentInfo{youth_stories.com.youth_stories/youth_stories.com.youth_stories.Home}: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
            at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
            at org.json.JSONTokener.nextValue(JSONTokener.java:94)
            at org.json.JSONObject.<init>(JSONObject.java:156)
            at org.json.JSONObject.<init>(JSONObject.java:173)
            at youth_stories.com.youth_stories.Home.onCreate(Home.java:129)
            at android.app.Activity.performCreate(Activity.java:5933)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)