如何访问库活动的方法

Question

抱歉我的英语。
我用editetextview和按钮创建我的自定义DatePicker，当我点击按钮我显示DatePickerDialog时，在设置按钮后点击我在我的editetextview中设置日期。这工作正常，但是当我在库中创建一些方法时，我无法从活动中访问这些方法。这是我的图书馆

public class PickerView extends FrameLayout implements OnClickListener{

DatePickerDialog.OnDateSetListener date;
Calendar myCalendar;
EditText pickerText;
String dateformat;



public PickerView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    TypedArray a = context.obtainStyledAttributes(attrs,R.styleable.custom_keyboard);
    dateformat = a.getString(R.styleable.custom_keyboard_mydateformat);
    if (dateformat == null) {
        dateformat="dd.MM.yyyy";
    }
    a.recycle();
    if(!isInEditMode())
        init(context);

    Log.d("PickerView", dateformat);
    // TODO Auto-generated constructor stub
}

public PickerView(Context context) {
    super(context);

    if(!isInEditMode())
        init(context);
    // TODO Auto-generated constructor stub
}

public PickerView(Context context, AttributeSet attrs) {
    super(context);
    TypedArray a = context.obtainStyledAttributes(attrs,R.styleable.custom_keyboard);
    dateformat = a.getString(R.styleable.custom_keyboard_mydateformat);
    if (dateformat == null) {
        dateformat="dd.MM.yyyy";
    }
    a.recycle();
    if(!isInEditMode())
        init(context);


    Log.d("PickerView", dateformat);

    // TODO Auto-generated constructor stub
}

void init(Context context){
    LayoutInflater  mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View picker=mInflater.inflate(R.layout.picker_layout, this, true);

    myCalendar = Calendar.getInstance();
    date = new DatePickerDialog.OnDateSetListener() {

        @Override
        public void onDateSet(DatePicker view, int year, int monthOfYear,
                int dayOfMonth) {
                myCalendar.set(Calendar.YEAR, year);
                myCalendar.set(Calendar.MONTH, monthOfYear);
                myCalendar.set(Calendar.DAY_OF_MONTH, dayOfMonth);

                updateLabel();
        }

    };

    Button button=(Button)picker.findViewById(R.id.editPicker1);
    button.setOnClickListener(this);

    pickerText=(EditText)picker.findViewById(R.id.picker1Text);
}

@Override
public void onClick(View v) {
    if(pickerText.getText().length()==0)
    {
        new DatePickerDialog(getContext(), date, myCalendar
                .get(Calendar.YEAR), myCalendar.get(Calendar.MONTH),
                myCalendar.get(Calendar.DAY_OF_MONTH)).show();
    }
    else
    {
        try {
            java.util.Date dateF=new SimpleDateFormat( dateformat )
            .parse( pickerText.getText().toString() );
            myCalendar.setTime(dateF);
            new DatePickerDialog(getContext(), date, myCalendar
                .get(Calendar.YEAR), myCalendar.get(Calendar.MONTH),
                myCalendar.get(Calendar.DAY_OF_MONTH)).show();
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

private void updateLabel() {
    SimpleDateFormat sdf = new SimpleDateFormat(dateformat, Locale.US);
    pickerText.setText(sdf.format(myCalendar.getTime()));
}

public void setDateformat(String dateformat) {
    //this.dateformat = dateformat;
    //updateLabel();
}

我的活动

public class MainActivity extends Activity {
PickerView picker;
EditText editText;
Button bt;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    picker=(PickerView)findViewById(R.id.pickerView1);
    editText=(EditText)findViewById(R.id.editeDateF);
    bt=(Button)findViewById(R.id.buttonCl1);
    bt.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            picker.setDateformat("dd/MM/yyyy");
            //there i get error
        }
    });
}

activity_main.xml中

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:custom="http://schemas.android.com/apk/res-auto" 
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >



<com.gevorg89.PickerView.PickerView
    android:id="@+id/pickerView1"
    android:layout_width="match_parent"      
    android:layout_height="wrap_content" 
    custom:mydateformat="dd.MM.yyyy"
    >
</com.gevorg89.PickerView.PickerView>

<EditText
    android:id="@+id/editeDateF"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:ems="10"
    android:text="dd|MM|yyyy"
    android:inputType="date" >
</EditText>

<Button
    android:id="@+id/buttonCl1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Button" />
 </LinearLayout>

错误日志

12-15 19:38:50.923: E/AndroidRuntime(631): FATAL EXCEPTION: main
12-15 19:38:50.923: E/AndroidRuntime(631): java.lang.NullPointerException
12-15 19:38:50.923: E/AndroidRuntime(631):  at         com.example.customview.MainActivity$1.onClick(MainActivity.java:28)
12-15 19:38:50.923: E/AndroidRuntime(631):  at    android.view.View.performClick(View.java:3511)
12-15 19:38:50.923: E/AndroidRuntime(631):  at android.view.View$PerformClick.run(View.java:14105)
12-15 19:38:50.923: E/AndroidRuntime(631):  at android.os.Handler.handleCallback(Handler.java:605)
12-15 19:38:50.923: E/AndroidRuntime(631):  at android.os.Handler.dispatchMessage(Handler.java:92)
12-15 19:38:50.923: E/AndroidRuntime(631):  at android.os.Looper.loop(Looper.java:137)
12-15 19:38:50.923: E/AndroidRuntime(631):  at android.app.ActivityThread.main(ActivityThread.java:4424)
12-15 19:38:50.923: E/AndroidRuntime(631):  at java.lang.reflect.Method.invokeNative(Native Method)
12-15 19:38:50.923: E/AndroidRuntime(631):  at java.lang.reflect.Method.invoke(Method.java:511)
12-15 19:38:50.923: E/AndroidRuntime(631):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
12-15 19:38:50.923: E/AndroidRuntime(631):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
12-15 19:38:50.923: E/AndroidRuntime(631):  at dalvik.system.NativeStart.main(Native Method)