Eclipse：“ ClassCastException”，并且GUI不在图形布局中显示

Question

I have created a custom component. Here is the code

html_5_spinner.xml

 <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal" >

        <EditText
            android:id="@+id/spinText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:paddingBottom="5dp"
            android:paddingTop="5dp" >

            <requestFocus />
        </EditText>

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical" >

            <Button
                android:id="@+id/upBtn"
                android:layout_width="25dp"
                android:layout_height="15dp"
                android:background="@android:drawable/arrow_up_float" />

            <Button
                android:id="@+id/downBtn"
                android:layout_width="25dp"
                android:layout_height="15dp"
                android:background="@android:drawable/arrow_down_float" />

        </LinearLayout>

    </LinearLayout>

HTML5Spinner.java

import android.app.Activity;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.Toast;

public class HTML5Spinner extends LinearLayout {

    private EditText spinText;
    private Button upBtn, downBtn;

    public HTML5Spinner(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
    }

    @Override
    protected void onFinishInflate()
    {
        super.onFinishInflate();
        ((Activity)getContext()).getLayoutInflater().inflate(R.layout.html5_spinner, this);

        setupViewItems();
    }

    private void setupViewItems()
    {
        spinText = (EditText)findViewById(R.id.spinText);
        upBtn = (Button)findViewById(R.id.upBtn);
        downBtn = (Button)findViewById(R.id.downBtn);


        //Register Listeners
        upBtn.setOnClickListener(new UpButtonAction());
    }

    private class UpButtonAction implements OnClickListener
    {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            Log.d("workn", "It is running");
        }

    }

}

Main activity is using the above cusom component. It just has a XML, no business logic or GUI rendering Java code

activity_main.xml

    <ScrollView
        android:id="@+id/scroller"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        >

        <TableLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:stretchColumns="*" >

            <TableRow
                android:id="@+id/tableRow1"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content" >

                <RadioButton
                    android:id="@+id/radioButton1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textAppearance="?android:attr/textAppearanceMedium"
                    android:drawablePadding="5dp"
                    android:text="RadioButton" />

                <com.nFlate.nflate.HTML5Spinner
                    android:id="@+id/aasaas"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    ></com.nFlate.nflate.HTML5Spinner>



            </TableRow>

            <TableRow
                android:id="@+id/tableRow2"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" >

                <RadioButton
                    android:id="@+id/radioButton1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textAppearance="?android:attr/textAppearanceMedium"
                    android:drawablePadding="5dp"
                    android:text="RadioButton" />

                 <com.nFlate.nflate.HTML5Spinner
                    android:id="@+id/aasaas"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    ></com.nFlate.nflate.HTML5Spinner>

            </TableRow>

            <TableRow
                android:id="@+id/tableRow3"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" >
            </TableRow>

            <TableRow
                android:id="@+id/tableRow4"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" >
            </TableRow>
        </TableLayout>

    </ScrollView>



</RelativeLayout>

This gives no error when running. But eclipse shows errors in "Graphical Layout" of activity_main.xml

Below is the error

Exception raised during rendering: com.android.layoutlib.bridge.android.BridgeContext cannot be cast to android.app.Activity
Exception details are logged in Window > Show View > Error Log

java.lang.ClassCastException: com.android.layoutlib.bridge.android.BridgeContext cannot be cast to android.app.Activity
    at com.xxx.xxx.HTML5Spinner.onFinishInflate(HTML5Spinner.java:27)
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:754)
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:64)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:718)
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:749)
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:64)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:718)
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:749)
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:64)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:718)
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:749)
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:64)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:718)
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:749)
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:64)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:718)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:372)

Below is the place where this error is displayed.

Because of this error, the GUI is not getting displayed in eclipse Graphical Layout . Why is this?

Answer 1

In your onFinishInflate there's this problematic cast:

((Activity)getContext())

Eclipse Graphical Layout renders views with a Context that is not an Activity . You shouldn't need this cast here anyway.

Answer 2

You are missing the library which renders the spinner. Include that library in your project. Please import library into the workspace in order to work properly and mark this library in the android option of the project properties. The main problem for this is not including the library properly.

Answer 3

如果在清单文件中将HTML5Spinner.java注册为活动，则它必须扩展“活动”类型才能继续进行，但是此处使用的LinearLayout不会启动，因此xml GUI也为ClassCastException给出了错误。